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[Git][ghc/ghc][wip/dcoutts/issue-27105-stopTicker] 4 commits: Fix for RTS stopTicker not being synchronous
by Duncan Coutts (＠dcoutts) 13 May '26

13 May '26

Duncan Coutts pushed to branch wip/dcoutts/issue-27105-stopTicker at Glasgow Haskell Compiler / GHC Commits: cbe1f682 by Duncan Coutts at 2026-05-13T10:59:14+01:00 Fix for RTS stopTicker not being synchronous Fixes issue #27105. The stopTicker() action was asynchronous (on both posix and win32) but it was being used in several places as if it were synchronous. It turns out there are two uses for stopTicker: 1. for concurrency safety: to avoid the tick handler running concurrently with some other critical section. 2. for efficiency: to reduce CPU wakeups when the RTS goes idle. The first case is where it relies on the stopTicker() being synchronous (which it wasn't), while the second case can be asynchronous for performance. In fact it _must_ be asynchronous because it is called within the tick handler itself, and it cannot wait on itself. So in this patch we deprecate stopTicker/startTicker and replace it with two pairs: block/unblockTicker for case 1, and pause/unpauseTicker for case 2. We update all calls of stop/startTicker with the appropriate replacement. In the posix implementation, we take care to keep the tick action cheap. Since block/unblock are used very infrequently, we make them more expensive and complicated to allow the normal hot path in the tick action to be cheap. We avoid locks and atomic memory ops in the hot path. We use message passing via an eventfd or pipe. In the win32 implementation, we continue to use the TimerQueue API, and we make use of its ability to delete timers synchronously or asynchronously. Add a changelog entry. - - - - - 72ca45e3 by Duncan Coutts at 2026-05-13T10:59:14+01:00 Make win32 ticker wait interval for initial tick too There is no need to tick immediately. This is consistent with the posix implementation. - - - - - c459d69f by Duncan Coutts at 2026-05-13T10:59:15+01:00 Remove now-unnecessary layer of RTS ticker block/unblocking There was an atomic variable used to block *part* of the actions of the tick handler. This still did not make stopTimer synchronous, even for the part of the the handle_tick actions it covered. It also added a more expensive (sequentuially consistent) atomic operation in the hot path for the handle_tick action, whereas our new design requires no atomic ops at all. Now that we have a proper synchronous solution, we don't need this not-quite-working-anyway atomic protocol. - - - - - 8a1787a7 by Duncan Coutts at 2026-05-13T10:59:15+01:00 Add TODOs about issue #27250: too much being done from handle_tick The handle_tick should not perform I/O, block, perform long-running operations or call arbitrary user code. Unfortunately, everything to do with the eventlog (at the moment) falls into all those categories. - - - - - 11 changed files: - + changelog.d/T27105 - rts/Capability.c - rts/RtsStartup.c - rts/Schedule.c - rts/Ticker.h - rts/Timer.c - rts/Timer.h - rts/include/rts/Timer.h - rts/include/stg/SMP.h - rts/posix/Ticker.c - rts/win32/Ticker.c Changes: ===================================== changelog.d/T27105 ===================================== @@ -0,0 +1,13 @@ +section: rts +issues: #27105 +mrs: !16023 +synopsis: RTS stopTicker is asynchronous, but is used relying on it being synchronous. +description: { + As a result of the fix, the exported RTS APIs `stopTimer` and `startTimer` + are now no-ops and are deprecated. They were called at least by the process + and unix libraries. No replacement is needed. + + They were used by libraries to temporarily block the RTS's use of the timer + signal. These functions no longer have a purpose since the RTS interval + timer no longer uses signals. +} ===================================== rts/Capability.c ===================================== @@ -31,6 +31,7 @@ #include "sm/OSMem.h" #include "sm/BlockAlloc.h" // for countBlocks() #include "IOManager.h" +#include "Timer.h" #include <string.h> @@ -448,7 +449,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS) // as we free it. The alternative would be to protect the capabilities // array with a lock but this seems more expensive than necessary. // See #17289. - stopTimer(); + blockTimer(); if (to == 1) { // THREADED_RTS must work on builds that don't have a mutable @@ -471,7 +472,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS) debugTrace(DEBUG_sched, "allocated %d more capabilities", to - from); - startTimer(); + unblockTimer(); #endif } ===================================== rts/RtsStartup.c ===================================== @@ -415,8 +415,8 @@ hs_init_ghc(int *argc, char **argv[], RtsConfig rts_config) traceInitEvent(dumpIPEToEventLog); initHeapProfiling(); - /* start the virtual timer 'subsystem'. */ - startTimer(); + /* start the timer (after initTimer above) */ + unblockTimer(); #if defined(RTS_USER_SIGNALS) if (RtsFlags.MiscFlags.install_signal_handlers) { @@ -512,14 +512,12 @@ hs_exit_(bool wait_foreign) } #endif - /* stop the ticker */ - stopTimer(); - /* - * it is quite important that we wait here as some timer implementations - * (e.g. pthread) may fire even after we exit, which may segfault as we've - * already freed the capabilities. + /* We rely on the guarantee that exitTimer stops the timer synchronously, + * which ensures the timer handler does not get run again after this point. + * We are about to start freeing resources used by the timer handler (like + * the capabilities, eventlog and profiling data structures). */ - exitTimer(true); + exitTimer(); /* * Dump the ticky counter definitions ===================================== rts/Schedule.c ===================================== @@ -454,7 +454,7 @@ run_thread: prev = setRecentActivity(ACTIVITY_YES); if (prev == ACTIVITY_DONE_GC) { #if !defined(PROFILING) - startTimer(); + unpauseTimer(); #endif } break; @@ -1935,7 +1935,7 @@ delete_threads_and_gc: // it will get re-enabled if we run any threads after the GC. setRecentActivity(ACTIVITY_DONE_GC); #if !defined(PROFILING) - stopTimer(); + pauseTimer(); #endif break; } @@ -2100,7 +2100,7 @@ forkProcess(HsStablePtr *entry ACQUIRE_LOCK(&all_tasks_mutex); #endif - stopTimer(); // See #4074 + blockTimer(); // See #4074 #if defined(TRACING) flushAllCapsEventsBufs(); // so that child won't inherit dirty file buffers @@ -2110,7 +2110,7 @@ forkProcess(HsStablePtr *entry if (pid) { // parent - startTimer(); // #4074 + unblockTimer(); // #4074 RELEASE_LOCK(&sched_mutex); RELEASE_LOCK(&sm_mutex); @@ -2224,8 +2224,9 @@ forkProcess(HsStablePtr *entry generations[g].threads = END_TSO_QUEUE; } - // On Unix, all timers are reset in the child, so we need to start - // the timer again. + // The timer thread is not present in the child process, so we need + // to initialise the timer again. Note that the timer is in a blocked + // state when we re-init, and this is permitted. initTimer(); // TODO: need to trace various other things in the child @@ -2236,7 +2237,7 @@ forkProcess(HsStablePtr *entry // start timer after the IOManager is initialized // (the idle GC may wake up the IOManager) - startTimer(); + unblockTimer(); // Install toplevel exception handlers, so interruption // signal will be sent to the main thread. @@ -2307,7 +2308,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS) // N.B. We must stop the interval timer while we are changing the // capabilities array lest handle_tick may try to context switch // an old capability. See #17289. - stopTimer(); + blockTimer(); stopAllCapabilities(&cap, task); @@ -2394,7 +2395,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS) // Notify IO manager that the number of capabilities has changed. notifyIOManagerCapabilitiesChanged(&cap); - startTimer(); + unblockTimer(); rts_unlock(cap); ===================================== rts/Ticker.h ===================================== @@ -12,9 +12,59 @@ typedef void (*TickProc)(int); -void initTicker (Time interval, TickProc handle_tick); -void startTicker (void); -void stopTicker (void); -void exitTicker (bool wait); +/* The ticker is initialised in a blocked state. Use unblockTicker to start. */ +void initTicker(Time interval, TickProc handle_tick); + +/* Stop and terminate the ticker. It does not need to be stopped first. */ +void exitTicker(void); + +/* Block and unblock the ticker handle_tick action. + * + * The blockTicker action is *synchronous*. When it returns the caller is + * guaranteed that the tick action is blocked. The unblockTicker may be + * asynchronous. + * + * These should be used for the purpose of *concurrency safety*: to prevent + * the tick action from running concurrently with some other critical section. + * + * The blockTicker action is moderately expensive (because it is synchronous) + * and the implementation is optimised on the assumption that this action is + * infrequent (e.g. compared to tick frequency). + * + * It is *not* safe to call these functions from within the tick handler itself. + * + * It is safe to use these functions concurrently from multiple threads. They + * are *not* idempotent however: each thread must pair up each blockTicker call + * with exactly one corresponding unblockTicker. Additionally, initTicker acts + * like blockTicker and also must be matched by a corresponding unblockTicker. + */ +void blockTicker(void); +void unblockTicker(void); + +/* Pause and unpause (resume) the ticker. + * + * The pauseTicker and unpauseTicker actions are *asynchronous*. After calling + * pauseTicker, the ticker will pause eventually, but there may be another tick + * action before it does pause (and theoretically there could be several but + * in practice this is unlikely). Similarly, after calling unpauseTicker the + * ticker will start up again eventually, but there is an unspecified delay + * between the unpause and the next tick action (but in practice it is short). + * + * This should be used for the purpose of *efficiency*: to avoid unnecessary + * OS thread wakeups caused by the ticker. + * + * The pairing of unpauseTicker and the handle_tick action form a + * synchonises-with relation: values written before unpauseTicker can be + * read from the resulting handle_tick action. + * + * It *is* safe to call these functions from within the tick handler itself. + * + * It is safe to use these functions concurrently from multiple threads, but + * note that they *are* idempotent. This means it is not appropriate to use + * paired pause/unpause calls concurrently. They can be used by threads based + * on consistent use of some shared state or observation. + */ +void pauseTicker(void); +void unpauseTicker(void); #include "EndPrivate.h" ===================================== rts/Timer.c ===================================== @@ -33,15 +33,6 @@ #define HAVE_PREEMPTION #endif -// This global counter is used to allow multiple threads to stop the -// timer temporarily with a stopTimer()/startTimer() pair. If -// timer_enabled == 0 timer is enabled -// timer_disabled == N, N > 0 timer is disabled by N threads -// When timer_enabled makes a transition to 0, we enable the timer, -// and when it makes a transition to non-0 we disable it. - -static StgWord timer_disabled; - /* ticks left before next pre-emptive context switch */ static int ticks_to_ctxt_switch = 0; @@ -112,9 +103,9 @@ static void handle_tick(int unused STG_UNUSED) { - handleProfTick(); - if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0 - && SEQ_CST_LOAD_ALWAYS(&timer_disabled) == 0) + handleProfTick(); // Bad or worse: see issue #27250. + + if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) { ticks_to_ctxt_switch--; if (ticks_to_ctxt_switch <= 0) { @@ -128,7 +119,7 @@ handle_tick(int unused STG_UNUSED) ticks_to_eventlog_flush--; if (ticks_to_eventlog_flush <= 0) { ticks_to_eventlog_flush = RtsFlags.TraceFlags.eventlogFlushTicks; - flushEventLog(NULL); + flushEventLog(NULL); // Bad or worse: see issue #27250. } } #endif @@ -153,7 +144,7 @@ handle_tick(int unused STG_UNUSED) RtsFlags.MiscFlags.tickInterval; #if defined(THREADED_RTS) wakeUpRts(); - // The scheduler will call stopTimer() when it has done + // The scheduler will call pauseTimer() when it has done // the GC. #endif } else { @@ -165,10 +156,10 @@ handle_tick(int unused STG_UNUSED) #if defined(PROFILING) if (!(RtsFlags.ProfFlags.doHeapProfile || RtsFlags.CcFlags.doCostCentres)) { - stopTimer(); + pauseTimer(); } #else - stopTimer(); + pauseTimer(); #endif } } else { @@ -181,48 +172,71 @@ handle_tick(int unused STG_UNUSED) } } -void -initTimer(void) +void initTimer(void) { #if defined(HAVE_PREEMPTION) initProfTimer(); if (RtsFlags.MiscFlags.tickInterval != 0) { initTicker(RtsFlags.MiscFlags.tickInterval, handle_tick); } - SEQ_CST_STORE_ALWAYS(&timer_disabled, 1); #endif } -void -startTimer(void) +/* Deprecated exported functions. Now no-ops. + * Historically they were used by the process and unix libraries to disable + * the signal-based interval timer, since otherwise the timer signal would + * keep going off in the child process and confusing everything. The interval + * timer no longer uses signals, so there is no need any more for libraries to + * disable the timer. Also, the timer internal API has changed. + */ +void stopTimer(void) { /* no-op */ } +void startTimer(void) { /* no-op */ } + +/* We allow multiple threads to block the timer temporarily with a + * blockTimer()/unblockTimer() pair. The counting for this is done by + * the ticker implementation when using blockTicker()/unblockTicker(). + */ +void unblockTimer(void) { #if defined(HAVE_PREEMPTION) - if (SEQ_CST_SUB_ALWAYS(&timer_disabled, 1) == 0) { - if (RtsFlags.MiscFlags.tickInterval != 0) { - startTicker(); - } + if (RtsFlags.MiscFlags.tickInterval != 0) { + unblockTicker(); } #endif } -void -stopTimer(void) +void blockTimer(void) { #if defined(HAVE_PREEMPTION) - if (SEQ_CST_ADD_ALWAYS(&timer_disabled, 1) == 1) { - if (RtsFlags.MiscFlags.tickInterval != 0) { - stopTicker(); - } + if (RtsFlags.MiscFlags.tickInterval != 0) { + blockTicker(); } #endif } -void -exitTimer (bool wait) +void pauseTimer(void) +{ +#if defined(HAVE_PREEMPTION) + if (RtsFlags.MiscFlags.tickInterval != 0) { + pauseTicker(); + } +#endif +} + +void unpauseTimer(void) +{ +#if defined(HAVE_PREEMPTION) + if (RtsFlags.MiscFlags.tickInterval != 0) { + unpauseTicker(); + } +#endif +} + +void exitTimer (void) { #if defined(HAVE_PREEMPTION) if (RtsFlags.MiscFlags.tickInterval != 0) { - exitTicker(wait); + exitTicker(); } #endif } ===================================== rts/Timer.h ===================================== @@ -8,5 +8,15 @@ #pragma once -RTS_PRIVATE void initTimer (void); -RTS_PRIVATE void exitTimer (bool wait); +#include "BeginPrivate.h" + +void initTimer(void); +void exitTimer(void); + +void blockTimer(void); +void unblockTimer(void); + +void pauseTimer(void); +void unpauseTimer(void); + +#include "EndPrivate.h" ===================================== rts/include/rts/Timer.h ===================================== @@ -13,6 +13,6 @@ #pragma once -void startTimer (void); -void stopTimer (void); +void startTimer (void); // Deprecated: see issue #27086 +void stopTimer (void); // Deprecated: see issue #27086 int rtsTimerSignal (void); // Deprecated: see issue #27073 ===================================== rts/include/stg/SMP.h ===================================== @@ -29,6 +29,8 @@ void arm_atomic_spin_unlock(void); // Acquire/release atomic operations #define ACQUIRE_LOAD_ALWAYS(ptr) __atomic_load_n(ptr, __ATOMIC_ACQUIRE) #define RELEASE_STORE_ALWAYS(ptr,val) __atomic_store_n(ptr, val, __ATOMIC_RELEASE) +#define RELEASE_ADD_ALWAYS(ptr,val) __atomic_add_fetch(ptr, val, __ATOMIC_RELEASE) +#define RELEASE_SUB_ALWAYS(ptr,val) __atomic_sub_fetch(ptr, val, __ATOMIC_RELEASE) // Sequentially consistent atomic operations #define SEQ_CST_LOAD_ALWAYS(ptr) __atomic_load_n(ptr, __ATOMIC_SEQ_CST) ===================================== rts/posix/Ticker.c ===================================== @@ -103,120 +103,212 @@ #include <unistd.h> #include <fcntl.h> -static Time itimer_interval = DEFAULT_TICK_INTERVAL; - -// Should we be firing ticks? -// Writers to this must hold the mutex below. -static bool stopped = false; - -// should the ticker thread exit? -// This can be set without holding the mutex. -static bool exited = true; +static Time ticker_interval = DEFAULT_TICK_INTERVAL; + +// Atomic variable used by client threads to communicate their request to the +// ticker thread to block the ticks. +static int block_request_count; + +// Condition, mutex and cond var to communicate confirmation that the ticker is +// indeed blocked. +static bool block_confirmed; // must hold the mutex to get/set +static Mutex block_confirmed_mutex; +static Condition block_confirmed_cond; + +// Atomic variable used by client threads to communicate that they want the +// ticker thread to pause. This communication is one-way, with no +// acknowledgement. +static bool pause_request; + +// Atomic variable used by other threads to communicate that they want the +// ticker thread to exit. +static bool exit_request; +// Used to wait for the ticker thread to terminate after asking it to exit. +static OSThreadId ticker_thread_id; + +// Fds used with sendFdWakeup to notify the ticker thread that any of the +// *_request variables above have been set. +static int notifyfd_r = -1, notifyfd_w = -1; + + +// Synchronous, request and confirm. Not idempotent. +// Request the ticker to stop ticking, and wait until it confirms +// this. This guarantees no more ticks after this returns. +void blockTicker(void) +{ + // Request + // atomic increment with release memory order + RELEASE_ADD_ALWAYS(&block_request_count, 1); + + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + if (!block_confirmed) { + // Avoid notifying if it's not necessary. This always happens during + // rts startup, since initTicker starts in the blocked state and then + // moreCapabilities() uses block/unblockTicker. + sendFdWakeup(notifyfd_w); + } + // Wait for confirmation + while (!block_confirmed) { + waitCondition(&block_confirmed_cond, &block_confirmed_mutex); + } + OS_RELEASE_LOCK(&block_confirmed_mutex); +} -// Signaled when we want to (re)start the timer -static Condition start_cond; -static Mutex mutex; -static OSThreadId thread; +// Asynchronous request. Not idempotent. +void unblockTicker(void) +{ + // Request + RELEASE_SUB_ALWAYS(&block_request_count, 1); + sendFdWakeup(notifyfd_w); +} -// fds for interrupting the ticker -static int interruptfd_r = -1, interruptfd_w = -1; +// Asynchronous request. Idempotent. +void pauseTicker(void) +{ + RELEASE_STORE_ALWAYS(&pause_request, true); + sendFdWakeup(notifyfd_w); +} -static void *itimer_thread_func(void *_handle_tick) +// Asynchronous request. Idempotent. +void unpauseTicker(void) { - TickProc handle_tick = _handle_tick; + RELEASE_STORE_ALWAYS(&pause_request, false); + sendFdWakeup(notifyfd_w); +} -#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 - struct pollfd pollfds[1]; +// Synchronous. Not idempotent. +// The ticker is guaranteed stopped after this. +void exitTicker(void) +{ + ASSERT(!RELAXED_LOAD_ALWAYS(&exit_request)); + RELEASE_STORE_ALWAYS(&exit_request, true); + sendFdWakeup(notifyfd_w); - pollfds[0].fd = interruptfd_r; - pollfds[0].events = POLLIN; + // wait for ticker thread to terminate + if (pthread_join(ticker_thread_id, NULL)) { + sysErrorBelch("Ticker: Failed to join: %s", strerror(errno)); + } + closeFdWakeup(notifyfd_r, notifyfd_w); + closeMutex(&block_confirmed_mutex); + closeCondition(&block_confirmed_cond); +} - struct timespec ts = { .tv_sec = TimeToSeconds(itimer_interval) - , .tv_nsec = TimeToNS(itimer_interval) % 1000000000 - }; +#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 +typedef struct timespec timeout; // for ppoll() +typedef struct { struct pollfd pollfds[1]; } fdset; #else - fd_set selectfds; - FD_ZERO(&selectfds); - FD_SET(interruptfd_r, &selectfds); - - struct timeval tv = { .tv_sec = TimeToSeconds(itimer_interval) - /* convert remainder time in nanoseconds - to microseconds, rounding up: */ - , .tv_usec = ((TimeToNS(itimer_interval) % 1000000000) - + 999) / 1000 - }; +typedef struct timeval timeout; // for select() +typedef struct { int fd; fd_set selectfds; } fdset; // need to stash fd #endif - // Relaxed is sufficient: If we don't see that exited was set in one iteration we will - // see it next time. - while (!RELAXED_LOAD_ALWAYS(&exited)) { +// local helpers, to hide the difference between ppoll() and select() +static void poll_init_timeout(timeout *tv, Time t); +static void poll_init_fdset(fdset *fds, int fd); // single fd only +// These two return: >0 if fd ready, ==0 if timeout, <0 if error +static int poll_no_timeout(fdset *fdset); +static int poll_with_timeout(fdset *fdset, timeout *t); -#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 - int nfds = 1; - int nready = ppoll(pollfds, nfds, &ts, NULL); -#else - struct timeval tv_tmp = tv; // copy since select may change this value. - int nfds = interruptfd_r+1; - int nready = select(nfds, &selectfds, NULL, NULL, &tv_tmp); -#endif - // In either case (ppoll or select), the result nready is the number - // of fds that are ready. - if (RTS_LIKELY(nready == 0)) { - // Timer expired, not interrupted, continue. - } else if (nready > 0) { - // We only monitor one fd (the interruptfd_r), so we know - // it is that fd that is ready without any further checks. - collectFdWakeup(interruptfd_r); - // No further action needed, continue on to handling the final tick - // and then stop. - - // Note that we rely on sendFdWakeup and select/poll to provide the - // happens-before relation. So if 'exited' was set before calling - // sendFdWakeup, then we should be able to reliably read it after. - // And thus reading 'exited' in the while loop guard is ok. +static void *ticker_thread_func(void *_handle_tick) +{ + TickProc handle_tick = _handle_tick; + + // Thread-local view of our state. We compare these with the corresponding + // atomic shared variables used to request state changes. + bool blocked = true; // compare to atomic shared var block_request_count + bool paused = false; // updated from atomic shared var pause_request + bool exit = false; // updated from atomic shared var exit_request + + timeout timeout; + fdset fdset; + poll_init_timeout(&timeout, ticker_interval); + poll_init_fdset(&fdset, notifyfd_r); + + while (!exit) { + + int notify; + if (blocked || paused) { + notify = poll_no_timeout(&fdset); } else { - // While the RTS attempts to mask signals, some foreign libraries - // that rely on signal delivery may unmask them. Consequently we - // may see EINTR. See #24610. - if (errno != EINTR) { - sysErrorBelch("Ticker: poll failed: %s", strerror(errno)); - } + notify = poll_with_timeout(&fdset, &timeout); } - // first try a cheap test - if (RELAXED_LOAD_ALWAYS(&stopped)) { - OS_ACQUIRE_LOCK(&mutex); - // should we really stop? - if (stopped) { - waitCondition(&start_cond, &mutex); - } - OS_RELEASE_LOCK(&mutex); - } else { + if (RTS_LIKELY(notify == 0)) { + // The time expired, no state change notification. handle_tick(0); + + } else if (notify > 0) { + // State change notification, check the request variables. + + // We rely on sendFdWakeup and select/poll to provide the + // happens-before relation. So if the request variables are set + // before calling sendFdWakeup, then we should be able to reliably + // read them here afterwards. + collectFdWakeup(notifyfd_r); + + paused = ACQUIRE_LOAD_ALWAYS(&pause_request); + exit = RELAXED_LOAD_ALWAYS(&exit_request); + int block_request_count_snapshot = + ACQUIRE_LOAD_ALWAYS(&block_request_count); + + if (block_request_count_snapshot > 0 && !blocked) { + // State change: !blocked -> blocked + blocked = true; // local state + + // confirm to requesting thread(s) + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + block_confirmed = true; + // Must use broadcastCondition not signalCondition since there + // could be concurrent requesting threads. + broadcastCondition(&block_confirmed_cond); + OS_RELEASE_LOCK(&block_confirmed_mutex); + + } else if (block_request_count_snapshot == 0 && blocked) { + // State change: blocked -> !blocked + blocked = false; // local state + + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + block_confirmed = false; + OS_RELEASE_LOCK(&block_confirmed_mutex); + } + + } else if (errno != EINTR) { + // While the RTS attempts to mask signals, some foreign libraries + // that rely on signal delivery may unmask them. Consequently we + // may see EINTR. See #24610. + sysErrorBelch("Ticker: poll failed: %s", strerror(errno)); } } return NULL; } +/* Initialise the ticker on startup or re-initialise the ticker after a fork(). + * In the fork case, the thread will not be present, but fds are inherited. + * + * The ticker is started in the blocked state. A single unblockTicker should + * be used to unblock. + */ void initTicker (Time interval, TickProc handle_tick) { - itimer_interval = interval; - stopped = true; - exited = false; + ticker_interval = interval; + block_request_count = 1; + pause_request = false; + exit_request = false; + #if defined(HAVE_SIGNAL_H) sigset_t mask, omask; int sigret; #endif int ret; - initCondition(&start_cond); - initMutex(&mutex); + block_confirmed = true; + initMutex(&block_confirmed_mutex); + initCondition(&block_confirmed_cond); /* Open the interrupt fd synchronously. * - * We used to do it in itimer_thread_func (i.e. in the timer thread) but it + * We used to do it in ticker_thread_func (i.e. in the timer thread) but it * meant that some user code could run before it and get confused by the * allocation of the timerfd. * @@ -226,11 +318,11 @@ initTicker (Time interval, TickProc handle_tick) * descriptor closed by the first call! (see #20618) */ - if (interruptfd_r != -1) { + if (notifyfd_r != -1) { // don't leak the old file descriptors after a fork (#25280) - closeFdWakeup(interruptfd_r, interruptfd_w); + closeFdWakeup(notifyfd_r, notifyfd_w); } - newFdWakeup(&interruptfd_r, &interruptfd_w); + newFdWakeup(&notifyfd_r, &notifyfd_w); /* * Create the thread with all blockable signals blocked, leaving signal @@ -242,7 +334,7 @@ initTicker (Time interval, TickProc handle_tick) sigfillset(&mask); sigret = pthread_sigmask(SIG_SETMASK, &mask, &omask); #endif - ret = createAttachedOSThread(&thread, "ghc_ticker", itimer_thread_func, (void*)handle_tick); + ret = createAttachedOSThread(&ticker_thread_id, "ghc_ticker", ticker_thread_func, (void*)handle_tick); #if defined(HAVE_SIGNAL_H) if (sigret == 0) pthread_sigmask(SIG_SETMASK, &omask, NULL); @@ -253,47 +345,65 @@ initTicker (Time interval, TickProc handle_tick) } } -void -startTicker(void) +/* Implementation of the local helpers, to hide the difference between ppoll() + * and select(). + */ +#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 +static void poll_init_timeout(timeout *tv, Time t) { - OS_ACQUIRE_LOCK(&mutex); - RELAXED_STORE(&stopped, false); - signalCondition(&start_cond); - OS_RELEASE_LOCK(&mutex); + tv->tv_sec = TimeToSeconds(t); + tv->tv_nsec = TimeToNS(t) % 1000000000; } -/* There may be at most one additional tick fired after a call to this */ -void -stopTicker(void) +static void poll_init_fdset(fdset *fds, int fd) { - OS_ACQUIRE_LOCK(&mutex); - RELAXED_STORE(&stopped, true); - OS_RELEASE_LOCK(&mutex); + fds->pollfds[0].fd = fd; + fds->pollfds[0].events = POLLIN; } -/* There may be at most one additional tick fired after a call to this */ -void -exitTicker (bool wait) +static int poll_no_timeout(fdset *fds) { - ASSERT(!SEQ_CST_LOAD(&exited)); - SEQ_CST_STORE(&exited, true); - // ensure that ticker wakes up if stopped - startTicker(); - sendFdWakeup(interruptfd_w); - - // wait for ticker to terminate if necessary - if (wait) { - if (pthread_join(thread, NULL)) { - sysErrorBelch("Ticker: Failed to join: %s", strerror(errno)); - } - closeFdWakeup(interruptfd_r, interruptfd_w); - closeMutex(&mutex); - closeCondition(&start_cond); - } else { - pthread_detach(thread); - } + int nfds = 1; + return ppoll(fds->pollfds, nfds, NULL, NULL); +} + +static int poll_with_timeout(fdset *fds, timeout *ts) +{ + int nfds = 1; + return ppoll(fds->pollfds, nfds, ts, NULL); +} + +#else // select() + +static void poll_init_timeout(timeout *tv, Time t) +{ + tv->tv_sec = TimeToSeconds(t); + /* convert remainder time in nanoseconds to microseconds, rounding up: */ + tv->tv_usec = ((TimeToNS(t) % 1000000000) + 999) / 1000; +} + +static void poll_init_fdset(fdset *fds, int fd) +{ + FD_ZERO(&fds->selectfds); + FD_SET(fd, &fds->selectfds); + fds->fd = fd; +} + +static int poll_no_timeout(fdset *fds) +{ + int nfds = fds->fd+1; + return select(nfds, &fds->selectfds, NULL, NULL, NULL); } +static int poll_with_timeout(fdset *fds, timeout *tv) +{ + struct timeval tv_tmp = *tv; // copy since select may change this value. + int nfds = fds->fd+1; + return select(nfds, &fds->selectfds, NULL, NULL, &tv_tmp); +} +#endif + +/* This is obsolete, but is used in the unix package for now */ int rtsTimerSignal(void) { ===================================== rts/win32/Ticker.c ===================================== @@ -9,10 +9,14 @@ #include <stdio.h> #include <process.h> +static Time tick_interval = 0; static TickProc tick_proc = NULL; + +static Mutex lock; // To protect the timer and state vars below static HANDLE timer_queue = NULL; static HANDLE timer = NULL; -static Time tick_interval = 0; +static int blocked_count; +static bool paused; static VOID CALLBACK tick_callback( PVOID lpParameter STG_UNUSED, @@ -39,9 +43,13 @@ static VOID CALLBACK tick_callback( void initTicker (Time interval, TickProc handle_tick) { + ASSERT(timer_queue == NULL); tick_interval = interval; tick_proc = handle_tick; + OS_INIT_LOCK(&lock); + blocked_count = 1; // starts blocked + paused = false; timer_queue = CreateTimerQueue(); if (timer_queue == NULL) { sysErrorBelch("CreateTimerQueue"); @@ -49,39 +57,94 @@ initTicker (Time interval, TickProc handle_tick) } } -void -startTicker(void) -{ - BOOL r; - - r = CreateTimerQueueTimer(&timer, - timer_queue, - tick_callback, - 0, - 0, - TimeToMS(tick_interval), // ms - WT_EXECUTEINTIMERTHREAD); +static void startTicker(void) { + ASSERT(timer_queue != NULL && timer == NULL); + DWORD interval = TimeToMS(tick_interval); // ms + BOOL r = CreateTimerQueueTimer(&timer, + timer_queue, + tick_callback, + NULL, // callback param + interval, // inital interval + interval, // recurrant interval + WT_EXECUTEINTIMERTHREAD); + //TODO: using WT_EXECUTEINTIMERTHREAD is fine for context switching, and + // plausibly also ok for profile sampling but is way out for eventlog + // flushing. The eventlog flush does a global synchronisation of all + // capabilities and I/O! And with eventlog providers, it calls arbitrary + // user code. This is not ok! See issue #27250. if (r == 0) { sysErrorBelch("CreateTimerQueueTimer"); stg_exit(EXIT_FAILURE); } + ASSERT(timer != NULL); } -void -stopTicker(void) +static void stopTicker(bool synchronous) { + ASSERT(timer_queue != NULL && timer != NULL); + // From the docs for DeleteTimerQueueTimer + // If this parameter is INVALID_HANDLE_VALUE, the function waits for any + // running timer callback functions to complete before returning. + HANDLE completion = synchronous ? INVALID_HANDLE_VALUE : NULL; + DeleteTimerQueueTimer(timer_queue, timer, completion); + timer = NULL; +} + +// Synchronous. Not idempotent. +void blockTicker(void) { - if (timer_queue != NULL && timer != NULL) { - DeleteTimerQueueTimer(timer_queue, timer, NULL); - timer = NULL; + OS_ACQUIRE_LOCK(&lock); + if (blocked_count == 0 && !paused) { + stopTicker(true /* synchronous */); } + blocked_count++; + OS_RELEASE_LOCK(&lock); } -void -exitTicker (bool wait) +// Asynchronous. Not idempotent. +void unblockTicker(void) { - stopTicker(); - if (timer_queue != NULL) { - DeleteTimerQueueEx(timer_queue, wait ? INVALID_HANDLE_VALUE : NULL); - timer_queue = NULL; + OS_ACQUIRE_LOCK(&lock); + if (blocked_count == 1 && !paused) { + startTicker(); } + blocked_count--; + OS_RELEASE_LOCK(&lock); +} + +// Asynchronous. Idempotent. +void pauseTicker(void) +{ + OS_ACQUIRE_LOCK(&lock); + if (!paused && blocked_count == 0) { + /* pauseTicker is called from within the handle_tick, so stopping + * the ticker here /must/ be asynchronous or we will deadlock! */ + stopTicker(false /* asynchronous */); + } + paused = true; + OS_RELEASE_LOCK(&lock); +} + +// Asynchronous. Idempotent. +void unpauseTicker(void) +{ + OS_ACQUIRE_LOCK(&lock); + if (paused && blocked_count == 0) { + startTicker(); + } + paused = false; + OS_RELEASE_LOCK(&lock); +} + +void exitTicker(void) +{ + ASSERT(timer_queue != NULL); + blockTicker(); + // From the docs for DeleteTimerQueueEx: + // If this parameter is INVALID_HANDLE_VALUE, the function waits + // for all callback functions to complete before returning. + // This is a belt-and-braces approach to ensuring exitTicker is synchronous, + // since blockTicker() is already synchronous and there's only one timer. + HANDLE completion = INVALID_HANDLE_VALUE; + DeleteTimerQueueEx(timer_queue, completion); + timer_queue = NULL; } View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/5d283c9b59b8a7bf39adccf785f819… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/5d283c9b59b8a7bf39adccf785f819… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/T26989] Major refactor of the Simplifier
by Simon Peyton Jones (＠simonpj) 13 May '26

13 May '26

Simon Peyton Jones pushed to branch wip/T26989 at Glasgow Haskell Compiler / GHC Commits: 710a4f21 by Simon Peyton Jones at 2026-05-13T11:48:30+01:00 Major refactor of the Simplifier The main payload of this patch is to refactor the Simplifer to avoid repeated simplification when using Plan (AFTER) for rule rewrites. The need for this was shown up by #26989. See Note [Avoid repeated simplification] in GHC.Core.Opt.Simplify.Iteration. Related refactoring: * Refactor the two fields `sc_dup` and `sc_env` in `ApplyToVal` into one, `sc_env`. Reason: the envt is irrelevant in the "simplified" case, so the data type describes the possiblitiies much more accurately now. * Some refactoring in `knownCon` to split off `wrapDataConFloats`. * Refactor `lookupRule` and its auxiliary functions to return `RuleMatch`, a new data type. See Note [data RuleMatch] in GHC.Core. Ditto for BuiltinRule. This RuleMatch returns fragments of the target in rm_args and rm_floats, leaving `rm_rhs` to be the stuff from the RULE itself. Doing this has routine consequences in GHC.Core.Opt.ConstantFold. Many changes there but all routine. * When doing occurrence analysis on RULEs, make the occ-info on the rule binders relate just to the RHS, not the LHS. See (OUR1) in Note Note [OccInfo in unfoldings and rules] This means that Lint must not complain about the fact that the patterns in the RULE mentions binders that are marked dead. See Note [Dead occurrences] in GHC.Core.Lint. I changed the Core pretty-printer so that it didn't suppress dead binders, else I can't see those binders in RULEs. That led to quite a lot of testsuite wibbles. * Refactor FloatBinds, so that it is used both by `exprIsConApp_mabye` and by `lookupRule` * Move the definition of FloatBinds out of GHc.Core.Make, into GHC.Core. * Add FloatTick as an extra constructor. * Refactor `lookupRule` to use `FloatBinds` instead of `BindWrapper`. This refactor just shares more code. (Rename GHC.Core.Opt.FloatOut.FloatBinds to FloatLets, to avoid gratuitious name clash with GHC.Core.FloatBinds.) Corecion optimisation * In simpleOpt, when composing coercions, call new function `optTransCo`. This is much lighter weight than full blown coercion optimisation. * Make `GHC.Core.Opt.Arity.pushCoValArg` and `pushCoTyArg` return the coercionLKind of the coercion. This saves recomputing that coercionLKind at the key call sites in GHC.Core.Opt.Simplify.Iteration.pushCast. * Rename `addCoerce` in GHC.Core.Simplify.Iteration to become `pushCast`. * In the `ApplyToVal` case of `pushCast` we had a very unsavoury call to `simplArg`. I eliminated it by adding a field `sc_cast` to `ApplyToVal` that records any pending casts. Much nicer now. See Note [The sc_cast field of ApplyToVal]. * Don't optimise coercions if the type-substitution is empty. See Note [Optimising coercions] in GHC.Core.Opt.Simplify.Iteration. The fix for #26838 is dramatic. For the test in perf/compiler/T26839 we have Compiler allocs: Before: 7,363M After: 688M Compile time goes down generally. Here are compiler-alloc changes over 0.5%: CoOpt_Read(normal) 729,184,920 -0.7% CoOpt_Singletons(normal) 666,916,960 -4.6% GOOD LargeRecord(normal) 1,227,056,876 +1.1% T12227(normal) 256,827,604 -4.6% GOOD T12425(optasm) 76,879,410 -0.8% T12545(normal) 787,826,918 -10.8% GOOD T12707(normal) 775,186,464 -0.9% T13253(normal) 318,599,596 -0.8% T14766(normal) 685,857,320 -1.0% T15304(normal) 1,123,333,422 -2.2% T15630(normal) 123,142,330 -2.6% T15630a(normal) 123,092,100 -2.6% T15703(normal) 299,751,682 -2.9% GOOD T17516(normal) 964,072,280 +1.0% T18223(normal) 367,016,820 -6.2% GOOD T18730(optasm) 130,643,770 -3.3% GOOD T20261(normal) 535,608,584 -0.7% T21839c(normal) 340,340,436 -0.9% T24984(normal) 85,568,392 -1.9% T3064(normal) 174,631,992 -1.2% T3294(normal) 1,215,886,432 -0.7% T5030(normal) 141,449,704 -17.2% GOOD T5321Fun(normal) 258,484,744 -1.9% T8095(normal) 770,532,232 -2.7% T9630(normal) 858,423,408 -14.5% GOOD T9872c(normal) 1,591,709,448 +0.7% info_table_map_perf(normal) 19,700,614,458 -1.3% geo. mean -0.7% minimum -17.2% maximum +1.1% Metric Decrease: CoOpt_Singletons T12227 T12545 T15703 T18223 T18730 T21839c T5030 T9630 - - - - - 55 changed files: - compiler/GHC/Core.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion/Opt.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Make.hs - compiler/GHC/Core/Opt/Arity.hs - compiler/GHC/Core/Opt/ConstantFold.hs - compiler/GHC/Core/Opt/FloatIn.hs - compiler/GHC/Core/Opt/FloatOut.hs - compiler/GHC/Core/Opt/OccurAnal.hs - compiler/GHC/Core/Opt/Simplify/Env.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - compiler/GHC/Core/Opt/SpecConstr.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Ppr.hs - compiler/GHC/Core/Rules.hs - compiler/GHC/Core/SimpleOpt.hs - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Data/List/SetOps.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Types/Id/Make.hs - testsuite/tests/codeGen/should_compile/T25177.stderr - testsuite/tests/deSugar/should_compile/T13208.stdout - testsuite/tests/linters/notes.stdout - testsuite/tests/numeric/should_compile/T15547.stderr - testsuite/tests/numeric/should_compile/T20347.stderr - testsuite/tests/numeric/should_compile/T20374.stderr - testsuite/tests/numeric/should_compile/T20376.stderr - + testsuite/tests/perf/compiler/T26989.hs - + testsuite/tests/perf/compiler/T26989a.hs - testsuite/tests/perf/compiler/all.T - testsuite/tests/printer/T18052a.stderr - testsuite/tests/simplCore/should_compile/DsSpecPragmas.stderr - testsuite/tests/simplCore/should_compile/RewriteHigherOrderPatterns.stderr - testsuite/tests/simplCore/should_compile/T15205.stderr - testsuite/tests/simplCore/should_compile/T18668.stderr - testsuite/tests/simplCore/should_compile/T19246.stderr - testsuite/tests/simplCore/should_compile/T19599.stderr - testsuite/tests/simplCore/should_compile/T19599a.stderr - testsuite/tests/simplCore/should_compile/T21917.stderr - testsuite/tests/simplCore/should_compile/T23074.stderr - testsuite/tests/simplCore/should_compile/T24359a.stderr - testsuite/tests/simplCore/should_compile/T25160.stderr - testsuite/tests/simplCore/should_compile/T25718c.stderr-ws-32 - testsuite/tests/simplCore/should_compile/T25718c.stderr-ws-64 - testsuite/tests/simplCore/should_compile/T26051.stderr - testsuite/tests/simplCore/should_compile/T26116.stderr - testsuite/tests/simplCore/should_compile/T8331.stderr - testsuite/tests/simplCore/should_compile/T8848a.stderr - testsuite/tests/simplCore/should_compile/spec004.stderr - testsuite/tests/typecheck/should_compile/T13032.stderr The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/710a4f21b994c26970ff7b817124fc3… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/710a4f21b994c26970ff7b817124fc3… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/27162/remove-hadrian-so-symlinks] 117 commits: compiler: Warn when -finfo-table-map is used with -fllvm
by David Eichmann (＠DavidEichmann) 13 May '26

13 May '26

David Eichmann pushed to branch wip/27162/remove-hadrian-so-symlinks at Glasgow Haskell Compiler / GHC Commits: 7fe84ea5 by Zubin Duggal at 2026-04-07T19:11:52+05:30 compiler: Warn when -finfo-table-map is used with -fllvm These are currently not supported together. Fixes #26435 - - - - - 4a45a7da by Matthew Pickering at 2026-04-08T04:37:29-04:00 packaging: correctly propagate build/host/target to bindist configure script At the moment the host and target which we will produce a compiler for is fixed at the initial configure time. Therefore we need to persist the choice made at this time into the installation bindist as well so we look for the right tools, with the right prefixes at install time. In the future, we want to provide a bit more control about what kind of bindist we produce so the logic about what the host/target will have to be written by hadrian rather than persisted by the configure script. In particular with cross compilers we want to either build a normal stage 2 cross bindist or a stage 3 bindist, which creates a bindist which has a native compiler for the target platform. Fixes #21970 Co-authored-by: Sven Tennie <sven.tennie(a)gmail.com> - - - - - b0950df6 by Sven Tennie at 2026-04-08T04:37:29-04:00 Cross --host and --target no longer required for cross (#21970) We set sane defaults in the configure script. Thus, these paramenters aren't required any longer. - - - - - fef35216 by Sven Tennie at 2026-04-08T04:37:30-04:00 ci: Define USER_CONF_CC_OPTS_STAGE2 for aarch64/mingw ghc-toolchain doesn't see $CONF_CC_OPTS_STAGE2 when the bindist gets configured. So, the hack to override the compiler gets lost. - - - - - 8dd6f453 by Cheng Shao at 2026-04-08T04:38:11-04:00 ghci: use ShortByteString for LookupSymbol/LookupSymbolInDLL/LookupClosure messages This patch refactors ghci to use `ShortByteString` for `LookupSymbol`/`LookupSymbolInDLL`/`LookupClosure` messages as the first part of #27147. Co-authored-by: Codex <codex(a)openai.com> - - - - - 371ef200 by Cheng Shao at 2026-04-08T04:38:11-04:00 ghci: use ShortByteString for MkCostCentres message This patch refactors ghci to use `ShortByteString` for `MkCostCentres` messages as a first part of #27147. This also considerably lowers the memory overhead of breakpoints when cost center profiling is enabled. ------------------------- Metric Decrease: interpreter_steplocal ------------------------- Co-authored-by: Codex <codex(a)openai.com> - - - - - 4a122bb6 by Phil Hazelden at 2026-04-08T20:49:42-04:00 Implement modifiers syntax. The `%m` syntax of linear types is now accepted in more places, to allow use by future extensions, though so far linear types is still the only consumer. This may break existing code where it * Uses -XLinearTypes. * Has code of the form `a %m -> b`, where `m` can't be inferred to be kind Multiplicity. The code can be fixed either by adding a kind annotation, or by setting `-XLinearTypes -XNoModifiers`. Proposal: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0370-m… - - - - - 07267f79 by Zubin Duggal at 2026-04-08T20:50:25-04:00 hadrian: Don't include the package hash in the haddock directory Since GHC 9.8 and hash_unit_ids, haddock urls have looked like`ghc-9.10.3/doc/html/libraries/base-4.20.2.0-39f9/**/*.html` The inclusion of the hash makes it hard for downstream non-boot packages to properly link to these files, as the hash is not part of a standard cabal substitution. Since we only build one version of each package, we don't need the hash to disambiguate anything, we can just remove it. Fixes #26635 - - - - - 0a83b95b by ARATA Mizuki at 2026-04-08T20:51:18-04:00 testsuite: Allow multiple ways to be run by setting multiple command-line options This patch allows multiple `--test-way`s to take effect, like: $ hadrian/build test --test-way=normal --test-way=llvm Previously, only one way was run if the test speed was 'normal' or 'fast'. Closes #26926 Co-authored-by: sheaf <sam.derbyshire(a)gmail.com> - - - - - e841931c by Teo Camarasu at 2026-04-08T20:52:00-04:00 doc: improve eventlog-flush-interval flag documentation We mention the performance cost and how this flag can be turned off. Resolves #27056 - - - - - e332db25 by Teo Camarasu at 2026-04-08T20:52:01-04:00 docs/user_guide: fix typo - - - - - 5b82080a by Simon Jakobi at 2026-04-08T20:52:44-04:00 Fix -dsuppress-uniques for free variables in demand signatures Before: Str=b{sXyZ->S} With this patch: Str=b{S} T13143.stderr is updated accordingly. Fixes #27106. - - - - - b7a084cc by Simon Jakobi at 2026-04-08T20:53:27-04:00 Documentation fixes for demand signature notation Fixes #27115. - - - - - 59391132 by Simon Jakobi at 2026-04-08T20:54:08-04:00 Use upsert for non-deleting map updates Some compiler functions were using `alter`, despite never removing any entries: they only update an existing entry or insert a new one. These functions are converted to using `upsert`: alter :: (Maybe a -> Maybe a) -> Key -> Map a -> Map a upsert :: (Maybe a -> a) -> Key -> Map a -> Map a `upsert` variants are also added to APIs of the various Word64Map wrapper types. The precedent for this `upsert` operation is in the containers library: see https://github.com/haskell/containers/pull/1145 Metrics: compile_time/bytes allocated ------------------------------------- geo. mean: -0.1% minimum: -0.5% maximum: +0.0% Resolves #27140. - - - - - da7e82f4 by Cheng Shao at 2026-04-08T20:54:49-04:00 testsuite: fix testsuite run for +ipe again This patch makes the +ipe flavour transformer pass the entire testsuite again by dropping stdout/stderr checks of certain tests that are sensitive to stack layout changes with `+ipe`. Related: #26799. - - - - - b135a87d by Zubin Duggal at 2026-04-09T19:36:50+05:30 Bump directory submodule to 1.3.11.0 (unreleased) - - - - - 3a291d07 by Zubin Duggal at 2026-04-09T19:36:50+05:30 Bump file-io submodule to 0.2.0 - - - - - e0ab606d by Zubin Duggal at 2026-04-10T18:40:20+05:30 Release notes for GHC 10.0 - - - - - e08b9b34 by Zubin Duggal at 2026-04-10T18:40:20+05:30 Bump ghc-prim version to 0.14.0 - - - - - a92aac6e by Zubin Duggal at 2026-04-10T18:40:20+05:30 Bump template-haskell to 2.25.0.0; update submodule exceptions for TH 2.25 - - - - - f254d9e8 by Zubin Duggal at 2026-04-10T18:40:20+05:30 Bump GHC version to 10.0 - - - - - 6ce0368a by Zubin Duggal at 2026-04-10T18:40:28+05:30 Bump base to 4.23.0.0; update submodules for base 4.24 upper bound - - - - - 702fb8a5 by Zubin Duggal at 2026-04-10T18:40:28+05:30 Bump GHC version to 10.1; update submodules template-haskell-lift and template-haskell-quasiquoter for ghc-internal 10.200 - - - - - 75df1ca4 by Zubin Duggal at 2026-04-10T18:40:28+05:30 Use changelog.d for release notes (#26002) GHC now uses a fragment-based changelog workflow using a custom script adapted from https://codeberg.org/fgaz/changelog-d. Contributors add a file in changelog.d/ for each user-facing change. At release time, these are assembled into release notes for sphinx (in RST) format, using the tool. New hadrian `changelog` target to generate changelogs CI job to validate changelog entries for MRs unless skipped with ~"no-changelog" label Teach sphinx about ghc-mr: extlink to link to MRs Remove `ghc-package-list` from sphinx, and implement it in changelog-d instead (Fixes #26476). (cherry picked from commit 989c07249978f418dfde1353abfad453f024d61a) - - - - - 585d7450 by Luite Stegeman at 2026-04-11T02:17:13-04:00 tc: discard warnings in tcUserStmt Plan C We typecheck let_stmt twice, but we don't want the warnings twice! see #26233 - - - - - 2df604e9 by Sylvain Henry at 2026-04-11T02:19:30-04:00 Introduce TargetInt to represent target's Int (#15973) GHC was using host 'Int' in several places to represent values that live in the target machine's 'Int' type. This is silently wrong when cross-compiling from a 32-bit host to a 64-bit target: the host Int is 32 bits while the target Int is 64 bits. See Note [TargetInt] in GHC.Platform. Also used the opportunity to make DynTag = Word8. Fixes #15973 Co-Authored-By: Claude Sonnet 4.6 <noreply(a)anthropic.com> - - - - - d419e972 by Luite Stegeman at 2026-04-13T15:16:04-04:00 Suppress desugaring warnings in the pattern match checker Avoid duplicating warnings from the actual desugaring pass. fixes #25996 - - - - - c5b80dd0 by Phil de Joux at 2026-04-13T15:16:51-04:00 Typo ~/ghc/arch-os-version/environments - - - - - 71462fff by Luite Stegeman at 2026-04-13T15:17:38-04:00 add changelog entry for #26233 - - - - - d1ddfd4b by Rodrigo Mesquita at 2026-04-14T18:41:12-04:00 Add test for #25636 The existing test behaviour of "T23146_liftedeq" changed because the simplifier now does a bit more inlining. We can restore the previous bad behavior by using an OPAQUE pragma. This test doubles as a test for #25636 when run in ghci, so we add it as such. - - - - - b9df40ee by Rodrigo Mesquita at 2026-04-14T18:41:12-04:00 refactor: protoBCOName is always a Name Simplifies the code by removing the unnecessary type argument to ProtoBCO which was always 'Name' - - - - - 5c2a179e by Rodrigo Mesquita at 2026-04-14T18:41:12-04:00 Allocate static constructors for bytecode This commit adds support for static constructors when compiling and linking ByteCode objects. Top-level StgRhsCon get lowered to ProtoStaticCons rather than to ProtoBCOs. A ProtoStaticCon gets allocated directly as a data con application on the heap (using the new primop newConApp#). Previously, we would allocate a ProtoBCO which, when evaluated, would PACK and return the constructor. A few more details are given in Note [Static constructors in Bytecode]. Secondly, this commit also fixes issue #25636 which was caused by linking *unlifted* constructors in BCO instructions as - (1) a thunk indexing the array of BCOs in a module - (2) which evaluated to a BCO which still had to be evaluated to return the unlifted constructor proper. The (2) issue has been resolved by allocating the static constructors directly. The (1) issue can be resolved by ensuring that we allocate all unlifted top-level constructors eagerly, and leave the knot-tying for the lifted BCOs and top-level constructors only. The top-level unlifted constructors are never mutually recursive, so we can allocate them all in one go as long as we do it in topological order. Lifted fields of unlifted constructors can still be filled by the knot-tied lifted variables since in those fields it is fine to keep those thunks. See Note [Tying the knot in createBCOs] for more details. Fixes #25636 ------------------------- Metric Decrease: LinkableUsage01 ------------------------- - - - - - cde47053 by Rodrigo Mesquita at 2026-04-14T18:41:12-04:00 Revert "StgToByteCode: Assert that PUSH_G'd values are lifted" This reverts commit ec26c54d818e0cd328276196930313f66b780905. Ever since f7a22c0f4e9ae0dc767115d4c53fddbd8372b777, we now do support and will link top-level unlifted constructors into evaluated and properly tagged values which we can reference with PUSH_G. This assertion is no longer true and triggered a failure in T25636 - - - - - c7a7e5b8 by Rodrigo Mesquita at 2026-04-14T18:41:12-04:00 refactor: Tag more remote Ptrs as RemotePtr Pure refactor which improves the API of - GHC.ByteCode.Linker - GHC.Runtime.Interpreter - GHC.Runtime.Interpreter.Types.SymbolCache by using `RemotePtr` for more functions which used to return `Ptr`s that could potentially be in a foreign process. E.g. `lookupIE`, `lookupStaticPtr`, etc... - - - - - fc59494c by Rodrigo Mesquita at 2026-04-14T18:41:12-04:00 Add float# and subword tests for #25636 These tests cover that static constructors in bytecode work correctly for Float# and subword values (Word8#, Word16#) - - - - - 477f521b by Rodrigo Mesquita at 2026-04-14T18:41:12-04:00 test: Validate topoSort logic in createBCOs This test validates that the topological sorting and ordering of the unlifted constructors and lifted constructors in `createBCOs` is correct. See `Note [Tying the knot in createBCOs]` for why tying the knot for the created BCOs is slightly difficult and why the topological sorting is necessary. This test fails when `let topoSortedObjs = topSortObjs objs` is substituted by `let topoSortedObjs = zip [0..] objs`, thus witnessing the toposort logic is correct and necessary. The test calls the ghci `createBCOs` directly because it is currently impossible to construct in Source Haskell a situation where a top-level static unlifted constructor depends on another (we don't have top-level unlifted constructors except for nullary constructors like `Leaf :: (UTree :: UnliftedType)`). This is another test for fix for #25636 - - - - - 2d9c30be by Simon Jakobi at 2026-04-14T18:42:00-04:00 Improve tests for `elem` ...in order to simplify the work on #27096. * Improve T17752 by including the Core output in golden files, checking both -O1 and -O2. * Add tests for fusion and no-fusion cases. Fixes #27101. - - - - - 2dadf3b0 by sheaf at 2026-04-16T13:28:39-04:00 Simplify mkTick This commit simplifies 'GHC.Core.Utils.mkTick', removing the accumulating parameter 'rest' which was suspiciously treating a bunch of different ticks as a group, and moving the group as a whole around the AST, ignoring that the ticks in the group might have different placement properties. The most important change is that we revert the logic (added in 85b0aae2) that allowed ticks to be placed around coercions, which caused serious issues (e.g. #27121). It was just a mistake, as it doesn't make sense to put a tick around a coercion. Also adds Note [Pushing SCCs inwards] which clarifies the logic for pushing SCCs into lambdas, constructor applications, and dropping SCCs around non-function variables (in particular the treatment of splittable ticks). A few other changes are also implemented: - simplify 'can_split' predicate (no functional change) - combine profiling ticks into one when possible Fixes #26878, #26941 and #27121 Co-authored-by: simonpj <simon.peytonjones(a)gmail.com> - - - - - a0d6f1f4 by Simon Jakobi at 2026-04-16T13:29:28-04:00 Add regression test for #9074 Closes #9074. - - - - - d178ee89 by Sylvain Henry at 2026-04-16T13:30:25-04:00 Add changelog for #15973 - - - - - e8a196c6 by sheaf at 2026-04-16T13:31:19-04:00 Deal with 'noSpec' in 'coreExprToPmLit' This commit makes two separate changes relating to 'GHC.HsToCore.Pmc.Solver.Types.coreExprAsPmLit': 1. Commit 7124e4ad mistakenly marked deferred errors as non-canonical, which led to the introduction of 'nospec' wrappers in the generated Core. This reverts that accident by declaring deferred errors as being canonical, avoiding spurious 'nospec' wrapping. 2. Look through magic identity-like Ids such as 'nospec', 'inline' and 'lazy' in 'coreExprAsPmLit', just like Core Prep does. There might genuinely be incoherent evidence, but that shouldn't obstruct the pattern match checker. See test T27124a. Fixes #25926 #27124 ------------------------- Metric Decrease: T3294 ------------------------- - - - - - 8cb99552 by Sylvain Henry at 2026-04-16T19:22:43-04:00 hadrian: warn when package index is missing (#16484) Since cabal-install 3.0 we can query the path of remote-repo-cache and check if hackage package index is present. Fixes #16484 - - - - - d6ce7477 by Richard Eisenberg at 2026-04-16T19:23:25-04:00 Teach hadrian to --skip-test. Fixes #27188. This adds the --skip-test flag to `hadrian build`, as documented in the patch. - - - - - 7666f4a9 by Fendor at 2026-04-17T22:29:51-04:00 Migrate `ghc-pkg` to use `OsPath` and `file-io` `ghc-pkg` should use UNC paths as much as possible to avoid MAX_PATH issues on windows. `file-io` uses UNC Paths by default on windows, ensuring we use the correct APIs and that we finally are no longer plagued by MAX_PATH issues in CI and private machines. On top of it, the higher correctness of `OsPath` is appreciated in this small codebase. Also, we improve memory usage very slightly, due to the more efficient memory representation of `OsPath` over `FilePath` Adds `ghc-pkg` regression test for MAX_PATH on windows Make sure `ghc-pkg` behaves as expected when long paths (> 255) are involved on windows. Let's generate a testcase where we can actually observe that `ghc-pkg` behaves as epxected. See the documentation for windows on Maximum Path Length Limitation: * `https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation` Adds changelog entry for long path support in ghc-pkg. - - - - - 78434e8c by Simon Peyton Jones at 2026-04-17T22:30:38-04:00 Kill off the substitution in Lint Now that we have invariant (NoTypeShadowing) we no longer need Lint to carry an ambient substitution. This makes it simpler and faster. A really worthwhile refactor. There are some knock-on effects * Linting join points after worker/wrapper. See Note [Join points and beta redexes] * Running a type substitution after the desugarer. See Note [Substituting type-lets] in the new module GHC.Core.SubstTypeLets Implements #27078 Most perf tests don't use Lint so we won't see a perf incresae. But T1969, which uses -O0 and Lint, gets 1.3% worse because it has to run the SubstTypeLets pass which is a somewhat expensive no-op Overall though compile-time allocations are down 0.1%. Metric Increase: T1969 - - - - - 86ca6c2c by mangoiv at 2026-04-17T22:31:22-04:00 testsuite: inline elemCoreTest Some weird (probably python scoping) rule caused elemCoreTest, a regex being out of scope on ubuntu, presumably because of a newer python version. This patch just inlines the regex, which fixes the issue. Fixes #27193 - - - - - 72d6dc74 by aparker at 2026-04-20T20:15:44-04:00 NCG: Implement constant folding for vector simd ops (Issue #25030) - - - - - b9cab907 by sheaf at 2026-04-20T20:15:44-04:00 Mark some SIMD tests as broken on i386 optllvm As seen in #25498, several SIMD tests are broken on i386 in the optllvm way. This commit marks them as "expect_broken". - - - - - 76528cc3 by Wolfgang Jeltsch at 2026-04-20T20:16:25-04:00 Move most of the `System.IO` implementation into `base` This involves a rewrite of the `combine` helper function to avoid the use of `last`, which would now be flagged as an error. Metric Decrease: LinkableUsage01 T3294 Metric Increase: T12227 T12707 T5642 - - - - - 04d143c0 by Luite Stegeman at 2026-04-21T14:05:33-04:00 rts: add a few missing i386 relocations in the rts linker - - - - - 014087e7 by Luite Stegeman at 2026-04-21T14:05:34-04:00 CodeOutput: Fix finalizers on multiple platforms - ELF platforms: emit .fini_array section - wasm32/Darwin: emit initializer with __cxa_atexit call - Windows: use -Wl,--whole-archive to prevent dropping finalizer symbols - rts linker: fix crash/assertion failure unloading objects with finalizers fixes #27072 - - - - - 915bba6f by Simon Jakobi at 2026-04-21T14:06:16-04:00 Add regression test for #10531 Closes #10531. - - - - - 86a646a6 by Andreas Klebinger at 2026-04-22T13:00:05-04:00 Revert use of generic instances for compiler time perf reasons. Revert "Derive Semigroup/Monoid for instances believed could be derived in #25871" This reverts commit 11a04cbb221cc404fe00d65d7c951558ede4caa9. Revert "add Ghc.Data.Pair deriving" This reverts commit 15d9ce449e1be8c01b89fd39bdf1e700ea7d1dce. - - - - - bc9ee1cf by Wen Kokke at 2026-04-22T13:00:51-04:00 hadrian: Fix docs to remove static flavour In 638f6548, the static flavour was turned into into the fully_static flavour transformer. However, this commit did not update flavours.md. - - - - - cc9cc6d5 by Cheng Shao at 2026-04-23T09:40:46+00:00 configure: bump LlvmMaxVersion to 23 This patch bumps `LlvmMaxVersion` to 23 to support LLVM 22.x releases. - - - - - 2ea7ef8e by Cheng Shao at 2026-04-23T09:46:26+00:00 changelog: add llvm 22.x support - - - - - 5574ee10 by Cheng Shao at 2026-04-24T08:24:30-04:00 compiler: avoid unused temporary `appendFS` operands This patch fixes unused temporary `appendFS` operands in the codebase that are retained in the `FastString` table after concatenation. Rewrite rules are added so that if an operand is `fsLit`/`mkFastString`, the `appendFS` application is rewritten to append the `ShortByteString` operands first. The patch also fixes `sconcat` behavior to align with `mconcat` for the same reason. Fixes #27205. - - - - - 4ed78760 by mangoiv at 2026-04-24T08:25:13-04:00 contributing: adjust MR template to be less verbose - MR template only shows text that is relevant for submissiong - MR template was rewritten so it's readable from a user's and reviewer's perspective Resolves #27165 Co-Authored-By: @sheaf - - - - - 87db83e2 by Cheng Shao at 2026-04-24T14:37:21-04:00 ci: bump freebsd boot ghc to 9.10.3 This commit bumps freebsd boot ghc to 9.10.3 to align with other platforms and prevent outdated boot libs in boot ghc to block the freebsd job. - - - - - 17e3a0b7 by Cheng Shao at 2026-04-24T14:37:21-04:00 compiler: improve Binary instance of Array This patch improves the `Binary` instance of `Array`: - We no longer allocate intermediate lists. When serializing an `Array`, we iterate over the elements directly; when deserializing it, we allocate the result `Array` and fill it in a loop. - Now we only serialize the array bounds tuple; the length field is not needed. Closes #27109. - - - - - 2d30f7d3 by sheaf at 2026-04-24T14:38:23-04:00 Vendor mini-QuickCheck for testsuite This commit extracts the vendored QuickCheck implementation from the foundation testsuite to make it more broadly available in the GHC testsuite, and makes use of it in the simd006 test (which also used a vendored QuickCheck implementation). On the way, we update the linear congruential generator to avoid the shortcoming of only generating 31 bit large numbers. Fixes #25990 and #25969. - - - - - 1350271b by sheaf at 2026-04-27T09:32:53-04:00 Ensure TcM plugins are only initialised once This commit ensures we keep TcM plugins (typechecker plugins, defaulting plugins and hole fit plugins) running all the way through desugaring, instead of stopping them at the end of typechecking. To do this, the "stop" actions of TcPlugin and DefaultingPlugin are split into two: one for the "post-typecheck" action, and one for the final shutdown action (after desugaring). This allows the plugins to be invoked by the pattern match checker (during desugaring) without having to be repeatedly re-initialised and stopped, fixing #26839. In the process, this commit modifies 'initTc' and 'initTcInteractive', adding an extra argument that describes whether to start/stop the 'TcM' plugins. See Note [Stop TcM plugins after desugaring] for an overview. - - - - - 42549222 by sheaf at 2026-04-27T09:33:50-04:00 Hadrian: add --keep-response-files This commit adds a Hadrian flag that allows response files to be retained. This is useful for debugging a failing Hadrian command line. - - - - - 40564e8d by sheaf at 2026-04-27T09:34:46-04:00 hadrian/build-cabal.bat: fix build on Windows Commit 8cb99552f6 introduced a warning for a missing package index. However, the logic was faulty on Windows: the piping was broken, and "remote-repo-cache:" was being interpreted as a (malformed) drive letter, leading to the error: The filename, directory name, or volume label syntax is incorrect. This commit fixes that by using a temporary file instead of piping. - - - - - 14bc71e4 by Sven Tennie at 2026-04-28T13:22:47-04:00 ghc: Distinguish between having an interpreter and having an internal one Actually, these are related but different things: - ghc can run an interpreter (either internal or external) - ghc is compiled with an internal interpreter Splitting the logic solves compiler warnings and expresses the intent better. - - - - - df691563 by Vladislav Zavialov at 2026-04-28T13:23:29-04:00 Refactor HsWildCardTy to use HoleKind (#27111) The payload of this patch is that the extension fields of HsWildCardTy and HsHole now match: type instance XWildCardTy Ghc{Ps,Rn} = HoleKind type instance XHole Ghc{Ps,Rn} = HoleKind This is progress towards unification of HsExpr and HsType. Test case: T25121_status In addition to that, exact-printing of infix holes is fixed. Test case: PprInfixHole - - - - - f3485446 by fendor at 2026-04-28T13:24:12-04:00 Expose startupHpc as an rts symbol - - - - - 28f07d70 by fendor at 2026-04-28T13:24:12-04:00 Make HPC work with bytecode interpreter Add support to generate .tix files from bytecode objects and the bytecode interpreter. Conceptually, we insert HPC ticks into the bytecode similar to how we insert breakpoints. HPC and breakpoints do not share the same tick array but we use a separate tick-array for hpc/breakpoint ticks during bytecode generation. We teach the bytecode interpreter to handle hpc ticks. The implementation is quite trivial, simply increment the counter in the global hpc_ticks array for the respective module. This hpc_ticks array is generated as part of the `CStub`, so we can rely on it existing. A tricky bit is "registering" a bytecode object for HPC instrumentation. In the compiled case, this is achieved via CStub and initializer/finalizers `.init` sections which are called when the executable is run. After the initializers have been invoked, which is before `hs_init_ghc`, we then call `startup_hpc` in `hs_init_ghc` iff any modules were "registered" for hpc instrumentation via `hs_hpc_module`. Since bytecode objects are loaded after starting up GHCi, this workflow doesn't work for supporting `hpc` and the `hpc` run-time is never started, even if a module is added for instrumentation. We fix this issue by employing the same technique as is for `SptEntry`s: * We introduce a new field to `CompiledByteCode`, called `ByteCodeHpcInfo` which contains enough information to call `hs_hpc_module`, allowing us to register the module for `hpc` instrumentation`. * After registering the module, we unconditionally call `startupHpc`, to make sure the .tix file is written. Calling `startupHpc` multiple times is safe. Calling `hs_hpc_module` multiple times for the same module is also safe. If we didn't register the hpc module in this way, evaluating a bytecode object instrumented with `-fhpc` without registering it in the `hpc` run-time will simply not generate any `.tix` files for this bytecode object. However, this shouldn't happen if everything is set up correctly. Closes #27036 - - - - - 950879f0 by Vladislav Zavialov at 2026-04-28T13:24:55-04:00 Move NamespaceSpecifier from x-fields into the AST proper (#26678) This refactoring moves NamespaceSpecifier out of extension fields and into the AST proper, as it is part of the user-written source, and is not pass-specific. Summary of changes: * Move NamespaceSpecifier from GHC/Hs/Basic.hs to Language/Haskell/Syntax/ImpExp.hs and parameterise it by the compiler pass, creating the necessary extension points * Move NamespaceSpecifier out of XFixitySig into FixitySig * Move NamespaceSpecifier out of XIEThingAll (IEThingAllExt) into IEThingAll * Move NamespaceSpecifier out of XIEWholeNamespace (IEWholeNamespaceExt) into IEWholeNamespace This is a pure refactoring with no change in behaviour. - - - - - 9797052b by Simon Peyton Jones at 2026-04-28T13:25:37-04:00 Fix assertion check in checkResultTy As #27210 shows, the assertion was a little bit too eager. I refactored a bit by moving some code from GHC.Tc.Gen.App to GHC.Tc.Utils.Unify; see the new function tcSubTypeApp, which replaces tcSubTypeDS - - - - - 9f85f034 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Make cmm 'import "package" name;' syntax use consistent label types There is a little-used syntactic form in cmm imports: import "package" foo; Which means to import foo from the given package (unit id, specified as a string). This syntax is somewhat reminiscent of GHC's package import extension. This syntax form is not used in the rts cmm code, nor any of the boot libraries. It may not be used at all. Unclear. Change the kind of CLabel this syntax generates to be consistent with the others. The other cmm imports use ForeignLabel with ForeignLabelInExternalPackage. For some reason this form was using CmmLabel. Change that to also be ForeignLabel but with ForeignLabelInPackage. This specifies a specific package, rather than an unnamed external package. - - - - - a811f68f by Duncan Coutts at 2026-04-30T04:52:42-04:00 Change default cmm import statements to be internal Previously a cmm statement like: import foo; meant to expect the symbol from a different shared library than the current one. Now it means to expect the symbol from the same shared library as the current one. We'll add explicit syntax to indicate that it's a foreign import. Most existing uses are in fact intenal (rts to rts), so few imports will need to be annotated foreign. Examples would include cmm code in libraries (other than the rts) that need to access RTS APIs. In practice, this makes no difference whatsoever at the moment on any platform other than windows (where building Haskell libs as shared libs does not fully work yet), since the 'labelDynamic' treats all such labels as foreign, irrespective of the foreign label source. - - - - - 17fe5d1d by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm import syntax 'import DATA foo;' as better name for CLOSURE The existing syntax is: import CLOSURE foo; The new syntax is import DATA foo; This means to interpret the symbol foo as refering to data (i.e. a global constant or variable) rather than to code (a function). The historical syntax for this uses CLOSURE, which is rather misleading. Presumably this was done to avoid introducing new reserved words. Be less squemish about new reserved words and add DATA and use that. Keep the existing CLOSURE syntax as an alias for compatibility. - - - - - 3a530d68 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm 'import extern name;' syntax Since the default for cmm imports is now for symbols within the same shared object, we need a way to indicate we want a symbol from an external shared object: import extern foo; -- for a function import extern DATA foo; -- for data This adds a new reserved word 'extern'. We don't expect to have to use this much. Most cmm imports are intra-DSO. This makes no difference currently on ELF and MachO platforms, but does make a difference to the linking conventions on PE (Windows). In future it's plausible we could take make distinctions on ELF or MachO, so it's worth trying to get it right. Windows can be the guinea pig. - - - - - 2b8e44c7 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm syntax 'import "package" DATA foo;' for completeness We already have: import DATA foo; -- for data imports import "package" foo; -- for imports from a given unitid There's no reason not to have both at once: import "package" DATA foo; So add that. - - - - - ee05e5cc by Duncan Coutts at 2026-04-30T04:52:42-04:00 Improve the commentary for the cmm import grammar. AFAIK, this is the only place where GHC-style Cmm syntax is documented. - - - - - b35946ad by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add a changelog.d entry for the .cmm import syntax changes - - - - - d59b7c71 by Wolfgang Jeltsch at 2026-04-30T04:53:25-04:00 Move code that uses `GHC.Internal.Text.Read` into `base` This contribution serves to remove all dependencies on `GHC.Internal.Text.Read` from within `ghc-internal`, so that the implementation of `Text.Read` and ultimately more reading-related code can be moved to `base` as well. The following things are moved from `ghc-internal` to `base`: * I/O-related `Read` instances * Most of the `Numeric` implementation * The instance `Read ByteOrder` * The `parseVersion` operation * The `readConstr` operation Metric Increase: LinkableUsage01 T9198 T12425 T13035 T13820 T18140 - - - - - 5bd6a964 by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 New rts Message to {set,unset} TSO flags This commit introduces stg_MSG_SET_TSO_FLAG_info and stg_MSG_UNSET_TSO_FLAG_info, which allows setting flags of a TSO other than yourself. This is especially useful/necessary to set breakpoints and toggle breakpoints of different threads, which is needed to safely implement features like pausing, toggling step-out, toggling step-in per thread, etc. Fixes #27131 ------------------------- Metric Decrease: T3294 ------------------------- - - - - - ce97fd3e by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 test: Add test setting another TSO's flags Introduces a test that runs on two capabilities. The main thread running on Capability 0 sets the flags on a TSO running on Capability 1. The TSO from Capability 1 itself checks whether its flags were set and reports that back. This validates that the RTS messages for setting TSO flags work, even if it doesn't test a harsher scenario with race conditions to exercise why the message passing is necessary for safely setting another TSO's flags. Part of #27131 - - - - - a4ff6315 by David Eichmann at 2026-04-30T04:54:51-04:00 Hadrian: withResponseFile outputs response file when verbodity is Verbose At the Verbose verbosity, shake will display full commandlines. With the use of response files, the full command is hidden. That makes it hard to run the command manually. This commit outputs the contents of the response file so that that full command can be recreated and also hints at the use of the --keep-response-files hadrian flag. - - - - - cd732ee3 by Duncan Coutts at 2026-04-30T04:54:51-04:00 Use response files for hadrian linking with ghc (support long command lines) In future support for windows dynamic linking, we expect long command lines for linking dll files with ghc. Experiments with dynamic linking the ghc-internal library yielded a link command well over 32kb. We did not encounter this before for static libs, since we already use ar's @file feature (if available, which it is for the llvm toolchain). Co-authored-by: David Eichmann <davide(a)well-typed.com> - - - - - 3d41368f by Andreas Klebinger at 2026-04-30T04:55:32-04:00 Split GHC.Driver.Main.hs up into multiple components. This commit splits GHC.Driver.Main into four components: * GHC.Driver.Main.Compile * GHC.Driver.Main.Hsc * GHC.Driver.Main.Interactive * GHC.Driver.Main.Passes We might improve that separation further in the future but this should hopefully make it easier to reason about and work with this part of the code. - - - - - 2128ba85 by Cheng Shao at 2026-04-30T04:56:14-04:00 compiler: avoid unique OccNames for internal Names in bytecode objects This patch improves bytecode object serialization logic by avoiding the construction of unique `OccName`s when serializing/deserializing internal `Name`s. Closes #27213. ------------------------- Metric Decrease: LinkableUsage01 ------------------------- - - - - - e16854c3 by Vladislav Zavialov at 2026-04-30T04:56:57-04:00 Replace GHC 9.16 references with GHC 10.0 - - - - - 39141343 by Alice Rixte at 2026-05-01T14:09:32+02:00 Add Bounded instances for Double, Float, CDouble and CFloat - - - - - 5c4c3bf4 by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: fix flaky foundation Divisible / mulIntMayOflo# tests (#27222) Since the LCG was widened to 64 bits and the seed randomised per CI run (commit 2d30f7d3400 "Vendor mini-QuickCheck for testsuite"), two latent bugs in the foundation test surface stochastically: * The Divisible property `(x `div` y) * y + (x `mod` y) == x` raises ArithException(Overflow) when (a, b) = (minBound, -1) for fixed-width signed Integral types. Split testNumber/testDivisible into Bounded and unbounded variants and skip just that one pair, gated by `(minBound :: a) < 0` so unsigned types lose no coverage. * The `mulIntMayOflo#` test compared raw Int# bit-for-bit, but the primop is only specified to return 0/non-zero -- the exact non-zero indicator legitimately differs between backends and inlining choices. Add a dedicated `testPrimopMayOflo` helper that only compares zero / non-zero. Also fix the long-standing typo "Dividible" -> "Divisible" in identifiers. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply(a)anthropic.com> - - - - - e242ce4f by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: catch and display exceptions in MiniQuickCheck Exceptions raised while evaluating a property are now caught and reported as a normal failure (with arguments and seed), instead of aborting the test. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply(a)anthropic.com> - - - - - 3b75cccd by fendor at 2026-05-02T03:40:14-04:00 Fix name of Note [Structure of dep_boot_mods] - - - - - 9a9ae4df by Duncan Coutts at 2026-05-05T14:44:37-04:00 Use __attribute__((dllimport)) for external RTS symbol declarations This is needed to be hygenic about DLL symbol imports and exports. The attribute is ignored on platforms other than Windows. Use of the attribute however means that external data symbols do not have a compile-time constant address (they are loaded using an indirection). This means we have to adjust the rtsSyms initial linker table so that it is a local constant in a function, rather than a global constant. We now define it within a function that pre-populates the symbol table with the RTS symbols. - - - - - 2ad3e01e by Duncan Coutts at 2026-05-05T14:44:37-04:00 Fix the rts linker declarations for a few data symbols and ensure that the (windows only) rts_IOManagerIsWin32Native data symbol is marked as externally visible. - - - - - 8ff4fdb5 by David Eichmann at 2026-05-05T14:44:37-04:00 Hadrian: Disable runtime pseudo relocations for RTS on windows hosts - - - - - 96974723 by Teo Camarasu at 2026-05-05T14:45:20-04:00 ghci/TH: refactor to use IORef QState This is a pure refactor and shouldn't modify semantics at all - - - - - eff6bfaf by Teo Camarasu at 2026-05-05T14:45:20-04:00 iserv: recover/getQ/putQ should behave same as internal interpreter The internal and external interpreter should behave the same when handling `recover`, the exeception recovery method of Q. In practice, they diverge. In case of failure, the internal interpreter only restores error message state to before the computation, wheras the external interperter restores error message state *and* the state of putQ/getQ. As far as I can tell this is a simple mistake in the implementation. Note [TH recover with -fexternal-interpreter] describes the correct behaviour but the implementation doesn't mirror this. This change restores the correct behaviour by keeping the effects of putQ in the erroring computation. This is a breaking change since it modifies the behaviour of programs that rely on recover ignoring putQ from failling computations when used with the external interpreter. Although I highly doubt anyone relies on this behaviour. This divergence was first introduced in d00c308633fe7d216d31a1087e00e63532d87d6d. As far as I can tell this was unintentional and tha commit was trying to solve a different bug. Resolves #27022 - - - - - 1cb1d672 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add dynamic trace flags API This commit adds an API to the RTS (exposed via Rts.h) that allows users to dynamically change the trace flags. Prior to this commit, users were able to stop and start the profiling and heap profiling timers (via startProfTimer/stopProfTimer and startHeapProfTimer/stopHeapProfTimer). This extends that functionality to also cover the core event types. The getTraceFlag/setTraceFlag functions read and write the values of the trace flag cache, which is allocated by Trace.c, rather than modifying the members of RtsFlags.TraceFlags. This is done under the assumption that the members of RtsFlags should not be modified after RTS initialisation. Consequently, if the user modifies the trace flags using setTraceFlag, the object returned by getTraceFlags (from base) will not reflect these changes. The trace flags are not protected by locks of any sort. Hence, these functions are not thread-safe. However, the trace flags are not modified by the RTS after initialisation, only read, so the race conditions introduced by one user modifying them are most likely benign. This PR also puts the trace flag cache in a single global struct, as opposed to a collection of global variables, and changes the types of the individual flags from uint8_t to bool, as these have the same size on both Clang and GCC and are a better semantic match. Prior to the change to uint8_t, they had type int, see 42c47cd6. Even with its deprecation in C23, I don't think there should be any issue depending on stdbool.h. The TRACE_X macros are redefined to access the global struct, with values cast to const bool to ensure they are read-only. - - - - - 9d54dc94 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Ensure TRACE_X values are used in place of RtsFlags.TraceFlags.X - - - - - 418d737b by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Fix nonmoving-GC tracing The current nonmoving-GC tracing functions were written in a different style from the other tracing functions. They were directly implemented as, e.g., a traceConcMarkEnd function that called postConcMarkEnd. The other tracing functions are implemented as, e.g., traceThreadLabel_, a function that posts the thread label event, and traceThreadLabel, a macro that checks whether TRACE_scheduler is set. This commit fixes that implementation, and ensures that the nonmoving-GC tracing functions only emit events if nonmoving-GC tracing is enabled. - - - - - 99f4afa4 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for get/setTraceFlag - - - - - 7e9eb8b9 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for start/endEventLogging - - - - - 3a3045fb by Wen Kokke at 2026-05-06T09:53:41-04:00 rts: Add changelog entry - - - - - a3b339a4 by Teo Camarasu at 2026-05-06T09:54:25-04:00 interface-stability/base: don't distinguish ws-32 The interface of base is identical when the Word size is 32bits. Therefore, there is no need to have another file for this case. So, we delete it. Step towards: #26752 - - - - - eb922183 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add a rts posix FdWakup utility module This will be used to implement wakeupIOManager for in-RTS I/O managers. It provides a notification/wakeup mechanism using FDs, suitable for situations when a thread is blocked on a set of fds anyway. It uses the classic self-pipe trick, or equivalently eventfd on supported platforms. This will initially be used to implement prompt interrupt or shutdown of the posix ticker thread. - - - - - 01b0e233 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add prompt shutdown to the pthread ticker implementation. The Linux timerfd ticker monitors a pipe which is used by exitTicker to ensure a prompt wakeup and shutdown. The pthread ticker lacked this and so would only exit at the next ticker wakeup (10ms by default). This patch adds the same mechanism to the pthread ticker. This changes the pthread ticker from waiting by using nanosleep() to waiting using either ppoll() or select(), so that it can wait on both a time and a file descriptor. On Linux at least, a test program to compare the timing jitter of these APIs shows that using nanpsleep, ppoll or select makes no statistical difference to the maximum or average jitter. This is a step towards unifying the posix ticker implementations, so that we can have just one portable one (albeit with some limited cpp). It is also a step towards using the ticker as part of a more general implementation of wakeUpRts, since this will require a method to wake the rts from a signal handler context (ctl-c handler). - - - - - bc41d646 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Update ticker header commentary It was antique and didn't apply even to the previous implementation, and certainly not to the updated one. - - - - - 4ed9a386 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Remove the timerfd-based ticker implementation There does not appear to be any remaining advantage on Linux to using the timerfd ticker implementation over the portable one (using ppoll on Linux for precise timing). The eventfd implementation was originally added at a time when Linux was still using a signal based implementation. So it made sense at the time. See (closed) issue #10840. - - - - - 97504fa6 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Consolidate to a single posix ticker implementation Previously we had four implementations, two using signals and two using threads. Having just one should make behaviour more consistent between platforms, and should make maintenance easier. - - - - - 1e60023b by Facundo Domínguez at 2026-05-07T18:01:16-04:00 Generalize so_inline to specify which bindings should be preserved This commit generalizes the so_inline option of the simple optimizer so we can indicate with a predicate the specific bindings that should be kept. This feature is important for the LiquidHaskell plugin, which relies on the simple optimizer to make core programs easier to read, but needs to preserve bindings that are relevant for verification. See https://gitlab.haskell.org/ghc/ghc/-/issues/24386 for the full discussion. - - - - - 44cf9cd7 by Wolfgang Jeltsch at 2026-05-12T09:48:18-04:00 Move the `Text.Read` implementation into `base` - - - - - 4ac3f7d6 by Vladislav Zavialov at 2026-05-12T09:49:03-04:00 EPA: Use AnnParen for tuples and sums Summary of changes * Do not use AnnParen in XListTy, replace it with EpToken "[" and "]" * Specialise AnnParen to tuple/sums by dropping the AnnParensSquare and keeping only AnnParens and AnnParensHash * Use AnnParen in XExplicitTuple * Use AnnParen in XExplicitTupleTy * Use AnnParen in XTuplePat * Use AnnParen in XExplicitSum (via AnnExplicitSum) * Use AnnParen in XSumPat (via EpAnnSumPat) This is a refactoring with no user-facing changes. - - - - - 1bdcddec by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support to ghc-toolchain The dlltool is a tool that can create dll import libraries from .def files. These .def files list the exported symbols of dlls. Its somewhat like gnu linker scripts, but more limited. We will need dlltool to build the rts and ghc-internal libraries as DLLs on Windows. The rts and ghc-internal libraries have a recursive dependency on each other. Import libraries can be used to resolve recursive dependencies between dlls. We will use an import library for the rts when linking the ghc-internal library. - - - - - f7fc3770 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support into ./configure Find dlltool, and hopefully support finding it within the bundled llvm toolchain on windows. - - - - - e4e22bfb by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update the default host and target files for dlltool support - - - - - 5666c8f9 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add dlltool as a hadrian builder Optional except on windows. - - - - - 5e14fe3f by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update and generate libHSghc-internal.def from .def.in file The only symbol that the rts imports from the ghc-internal package now is init_ghc_hs_iface. So the rts only needs an import lib that defines that one symbol. Also, remove the libHSghc-prim.def because it is redundant. The rts no longer imports anything from ghc-prim. Keep libHSffi.def for now. We may yet need it once it is clear how libffi is going to be built/used for ghc. - - - - - 3d91e4a6 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add rule to build libHSghc-internal.dll.a and link into the rts On windows only, with dynamic linking. This is needed because on windows, all symbols in dlls must be resolved. No dangling symbols allowed. References to external symbols must be explicit. We resolve this with an import library. We create an import library for ghc-internal, a .dll.a file. This is a static archive containing .o files that define the symbols we need, and crucially have ".idata" sections that specifies the symbols the dll imports and from where. Note that we do not install this libHSghc-internal.dll.a, and it does not need to list all the symbols exported by that package. We create a special purpose import lib and only use it when linking the rts dll, so it only has to list the symbols that the rts uses from ghc-internal (which is exactly one symbol: init_ghc_hs_iface). - - - - - c8dae539 by Alice Rixte at 2026-05-12T09:50:52-04:00 Script for downloading and copying `base-exports` file - - - - - 4df3fe3c by Duncan Coutts at 2026-05-13T11:33:42+01:00 Hadrian: remove legacy rts .so symlinks For compatibility with the old makefile based build system, hadrian had rules to generate symlinks from unversioned to versioned names for the rts .so/.dynlib file, like libHSrts-ghcx.y.so -> libHSrts-1.0.3-ghcx.y.so We no longer need these symlinks since the makefile build system has been retired some time ago. The need for these symlinks is awkward on windows where we cannot (in practice) create symlinks. So rather than make them conditional (non-windows), just remove them entirely. - - - - - 725 changed files: - .gitlab-ci.yml - .gitlab/ci.sh - .gitlab/generate-ci/gen_ci.hs - .gitlab/issue_templates/release_tracking.md - .gitlab/jobs.yaml - .gitlab/merge_request_templates/Default.md - + changelog.d/T15973 - + changelog.d/T19174.md - + changelog.d/T25636 - + changelog.d/T27022 - + changelog.d/T27121.md - + changelog.d/T27124.md - + changelog.d/T27131 - + changelog.d/binary-array-no-list - + changelog.d/bytecode-interpreter-hpc-support - + changelog.d/changelog-entries - + changelog.d/cmm-import-syntax-changes - + changelog.d/config - + changelog.d/dynamic-trace-flags - + changelog.d/fix-duplicate-pmc-warnings - + changelog.d/fix-finalizers-27072 - + changelog.d/fix-ghci-duplicate-warnings-26233 - + changelog.d/ghc-api-epa-parens - + changelog.d/ghc-api-holes-ast-27111 - + changelog.d/ghc-api-namespace-specifier-26678 - + changelog.d/ghc-pkg-long-path-support - + changelog.d/hadrian-response-files.md - + changelog.d/hadrian-warn-missing-package-index-16484 - + changelog.d/llvm-22 - + changelog.d/simd_constant_folding - + changelog.d/skip-test - + changelog.d/so_inline_is_a_predicate - + changelog.d/tcplugin_init.md - + changelog.d/tcplugins-pmc.md - + changelog.d/typecheckModule-API.md - + changelog.d/withTcPlugins.md - compiler/GHC.hs - compiler/GHC/Builtin/primops.txt.pp - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/ByteCode/Binary.hs - compiler/GHC/ByteCode/Breakpoints.hs - compiler/GHC/ByteCode/InfoTable.hs - compiler/GHC/ByteCode/Instr.hs - compiler/GHC/ByteCode/Linker.hs - compiler/GHC/ByteCode/Types.hs - compiler/GHC/Cmm/CommonBlockElim.hs - compiler/GHC/Cmm/Dataflow/Graph.hs - compiler/GHC/Cmm/Dataflow/Label.hs - compiler/GHC/Cmm/LayoutStack.hs - compiler/GHC/Cmm/Lexer.x - compiler/GHC/Cmm/Liveness.hs - compiler/GHC/Cmm/Opt.hs - compiler/GHC/Cmm/Parser.y - compiler/GHC/Cmm/Utils.hs - compiler/GHC/CmmToAsm/CFG.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToLlvm/CodeGen.hs - compiler/GHC/Core/Lint.hs - + compiler/GHC/Core/Lint/SubstTypeLets.hs - compiler/GHC/Core/Multiplicity.hs - compiler/GHC/Core/Opt/DmdAnal.hs - compiler/GHC/Core/Opt/FloatOut.hs - compiler/GHC/Core/Opt/OccurAnal.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/RoughMap.hs - compiler/GHC/Core/SimpleOpt.hs - compiler/GHC/Core/Subst.hs - compiler/GHC/Core/TyCo/Ppr.hs - compiler/GHC/Core/TyCon/Env.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Data/FastString.hs - compiler/GHC/Data/FastString/Env.hs - compiler/GHC/Data/Pair.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Lazy.hs - compiler/GHC/Data/Word64Map/Strict.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Driver/Backend.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/CodeOutput.hs - compiler/GHC/Driver/Config.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/Driver/Env/Types.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Main.hs - + compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Main.hs-boot → compiler/GHC/Driver/Main/Compile.hs-boot - + compiler/GHC/Driver/Main/Hsc.hs - + compiler/GHC/Driver/Main/Interactive.hs - + compiler/GHC/Driver/Main/Passes.hs - + compiler/GHC/Driver/Main/Passes.hs-boot - compiler/GHC/Driver/Pipeline.hs - compiler/GHC/Driver/Pipeline/Execute.hs - compiler/GHC/Driver/Pipeline/Monad.hs - compiler/GHC/Driver/Pipeline/Phases.hs - compiler/GHC/Driver/Plugins.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Basic.hs - compiler/GHC/Hs/Binds.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Expr.hs-boot - compiler/GHC/Hs/ImpExp.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Syn/Type.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Breakpoints.hs - 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compiler/GHC/Rename/Env.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/HsType.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Pat.hs - compiler/GHC/Runtime/Eval.hs - compiler/GHC/Runtime/Heap/Inspect.hs - compiler/GHC/Runtime/Interpreter.hs - compiler/GHC/Runtime/Interpreter/Types/SymbolCache.hs - compiler/GHC/Runtime/Loader.hs - compiler/GHC/Stg/Debug.hs - compiler/GHC/StgToByteCode.hs - compiler/GHC/StgToCmm.hs - compiler/GHC/StgToCmm/Bind.hs - compiler/GHC/StgToCmm/Closure.hs - compiler/GHC/StgToCmm/DataCon.hs - compiler/GHC/StgToCmm/Env.hs - compiler/GHC/StgToCmm/Expr.hs - compiler/GHC/StgToCmm/Foreign.hs - compiler/GHC/StgToCmm/Heap.hs - compiler/GHC/StgToCmm/InfoTableProv.hs - compiler/GHC/StgToCmm/Layout.hs - compiler/GHC/StgToCmm/Prim.hs - compiler/GHC/StgToCmm/Prof.hs - compiler/GHC/StgToCmm/Ticky.hs - compiler/GHC/StgToCmm/Utils.hs - compiler/GHC/StgToJS/Prim.hs - compiler/GHC/Tc/Deriv/Generate.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Errors/Hole.hs - 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testsuite/tests/typecheck/should_compile/holes3.stderr - testsuite/tests/typecheck/should_compile/subsumption_sort_hole_fits.stderr - testsuite/tests/typecheck/should_compile/valid_hole_fits.stderr - testsuite/tests/typecheck/should_fail/T21130.stderr - + testsuite/tests/typecheck/should_fail/T27210.hs - + testsuite/tests/typecheck/should_fail/T27210.stderr - testsuite/tests/typecheck/should_fail/T9497d.stderr - testsuite/tests/typecheck/should_fail/all.T - testsuite/tests/typecheck/should_run/T9497a-run.stderr - testsuite/tests/typecheck/should_run/T9497b-run.stderr - testsuite/tests/typecheck/should_run/T9497c-run.stderr - testsuite/tests/wasm/should_run/control-flow/LoadCmmGroup.hs - + utils/changelog-d/ChangelogD.hs - + utils/changelog-d/LICENSE - + utils/changelog-d/README.md - + utils/changelog-d/changelog-d.cabal - utils/check-exact/ExactPrint.hs - utils/check-exact/Main.hs - utils/check-exact/Transform.hs - utils/deriveConstants/Main.hs - utils/ghc-pkg/Main.hs - utils/ghc-pkg/ghc-pkg.cabal.in - utils/ghc-toolchain/exe/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Target.hs - utils/haddock/haddock-api/haddock-api.cabal - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Backends/LaTeX.hs - utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/AttachInstances.hs - utils/haddock/haddock-api/src/Haddock/Interface/Create.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Interface/RenameType.hs - utils/haddock/haddock-api/src/Haddock/InterfaceFile.hs - utils/haddock/haddock-api/src/Haddock/Types.hs - utils/haddock/haddock-library/haddock-library.cabal - utils/haddock/haddock-test/haddock-test.cabal - utils/haddock/haddock.cabal - utils/haddock/html-test/ref/Bug1004.html - utils/haddock/html-test/ref/Bug973.html - utils/haddock/html-test/ref/ConstructorPatternExport.html - utils/haddock/html-test/ref/DefaultSignatures.html - utils/haddock/html-test/ref/Hash.html - utils/haddock/html-test/ref/PatternSyns.html - utils/haddock/html-test/ref/PatternSyns2.html - utils/haddock/html-test/ref/QuasiExpr.html - utils/haddock/html-test/ref/Test.html - utils/haddock/html-test/src/LinearTypes.hs - utils/haddock/latex-test/src/LinearTypes/LinearTypes.hs - utils/hsc2hs - utils/jsffi/dyld.mjs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/3ebe2202bd74665aa20debbf916f96… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/3ebe2202bd74665aa20debbf916f96… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/davide/ghc-toolchain-llvm-versions] ghc-toolchain: implement llvm program versioning logic
by David Eichmann (＠DavidEichmann) 13 May '26

13 May '26

David Eichmann pushed to branch wip/davide/ghc-toolchain-llvm-versions at Glasgow Haskell Compiler / GHC Commits: 6278067c by David Eichmann at 2026-05-13T11:23:03+01:00 ghc-toolchain: implement llvm program versioning logic - - - - - 3 changed files: - m4/ghc_toolchain.m4 - utils/ghc-toolchain/exe/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Program.hs Changes: ===================================== m4/ghc_toolchain.m4 ===================================== @@ -55,6 +55,8 @@ AC_DEFUN([FIND_GHC_TOOLCHAIN], rm -f acargs echo "--triple=$HostPlatform" >> acargs echo "--output=$1/default.host.target.ghc-toolchain" >> acargs + echo "--llvm-min-version=$LlvmMinVersion" >> acargs + echo "--llvm-max-version-excl=$LlvmMaxVersion" >> acargs echo "--cc=$CC_STAGE0" >> acargs echo "--cc-link=$CC_STAGE0" >> acargs echo "--ar=$AR_STAGE0" >> acargs @@ -82,6 +84,8 @@ AC_DEFUN([FIND_GHC_TOOLCHAIN], echo "--triple=$target" >> acargs echo "--output=$1/default.target.ghc-toolchain" >> acargs echo "--llvm-triple=$LlvmTarget" >> acargs + echo "--llvm-min-version=$LlvmMinVersion" >> acargs + echo "--llvm-max-version-excl=$LlvmMaxVersion" >> acargs echo "--cc=$CC" >> acargs echo "--cxx=$CXX" >> acargs echo "--cpp=$CPPCmd" >> acargs ===================================== utils/ghc-toolchain/exe/Main.hs ===================================== @@ -39,6 +39,8 @@ data Opts = Opts , optTargetPrefix :: Maybe String , optLocallyExecutable :: Maybe Bool , optLlvmTriple :: Maybe String + , optLlvmMinVersion :: Maybe Int -- ^ Minimum supported LLVM version (inclusive) + , optLlvmMaxVersion :: Maybe Int -- ^ Maximum supported LLVM version (inclusive) , optOutput :: Maybe String , optCc :: ProgOpt , optCxx :: ProgOpt @@ -98,6 +100,8 @@ emptyOpts = Opts , optTargetPrefix = Nothing , optLocallyExecutable = Nothing , optLlvmTriple = Nothing + , optLlvmMinVersion = Nothing + , optLlvmMaxVersion = Nothing , optOutput = Nothing , optCc = po0 , optCxx = po0 @@ -163,6 +167,10 @@ _optTriple = Lens optTriple (\x o -> o {optTriple=x}) _optLlvmTriple :: Lens Opts (Maybe String) _optLlvmTriple = Lens optLlvmTriple (\x o -> o {optLlvmTriple=x}) +_optLlvmMinVersion, _optLlvmMaxVersion :: Lens Opts (Maybe Int) +_optLlvmMinVersion = Lens optLlvmMinVersion (\x o -> o {optLlvmMinVersion=x}) +_optLlvmMaxVersion = Lens optLlvmMaxVersion (\x o -> o {optLlvmMaxVersion=x}) + _optOutput :: Lens Opts (Maybe String) _optOutput = Lens optOutput (\x o -> o {optOutput=x}) @@ -192,6 +200,8 @@ options = [ tripleOpt , targetPrefixOpt , llvmTripleOpt + , llvmMinVersionOpt + , llvmMaxVersionOpt , verbosityOpt , keepTempOpt , outputOpt @@ -259,6 +269,9 @@ options = tripleOpt = Option ['t'] ["triple"] (ReqArg (set _optTriple . Just) "TRIPLE") "Target triple" llvmTripleOpt = Option [] ["llvm-triple"] (ReqArg (set _optLlvmTriple . Just) "LLVM-TRIPLE") "LLVM Target triple" + llvmMinVersionOpt = Option [] ["llvm-min-version"] (ReqArg (set _optLlvmMinVersion . Just . read) "LLVM-MIN-VERSION") "LLVM min version (inclusive)" + llvmMaxVersionOpt = Option [] ["llvm-max-version-excl"] (ReqArg (set _optLlvmMaxVersion . Just . subtract 1 . read) "LLVM-MAX-VERSION") "LLVM max version (exclusive)" + targetPrefixOpt = Option ['T'] ["target-prefix"] (ReqArg (set _optTargetPrefix . Just) "PREFIX") "A target prefix which will be added to all tool names when searching for toolchain components" @@ -289,13 +302,11 @@ formatOpts = [ validateOpts :: Opts -> [String] validateOpts opts = mconcat - [ assertJust _optTriple "missing --triple flag" - , assertJust _optOutput "missing --output flag" + [ ["missing --triple flag" | isNothing (optTriple opts)] + , ["missing --output flag" | isNothing (optOutput opts)] + , ["missing --llvm-min-version flag" | isNothing (optLlvmMinVersion opts) ] + , ["missing --llvm-max-version-excl flag" | isNothing (optLlvmMinVersion opts) ] ] - where - assertJust :: Lens Opts (Maybe a) -> String -> [String] - assertJust lens msg = - [ msg | Nothing <- pure $ view lens opts ] main :: IO () main = do @@ -448,6 +459,8 @@ mkTarget opts = do normalised_triple <- normaliseTriple (fromMaybe (error "missing --triple") (optTriple opts)) -- Use Llvm target if specified, otherwise use triple as llvm target let tgtLlvmTarget = fromMaybe normalised_triple (optLlvmTriple opts) + let llvmMinVersion = fromMaybe (error "missing --llvm-min-version") (optLlvmMinVersion opts) + let llvmMaxVersion = fromMaybe (error "missing --llvm-max-version-excl") (optLlvmMaxVersion opts) (archOs, tgtVendor) <- do cc0 <- findBasicCc (optCc opts) @@ -480,13 +493,14 @@ mkTarget opts = do throwE "Neither a object-merging tool (e.g. ld -r) nor an ar that supports -L is available" -- LLVM toolchain - llc <- optional $ findProgram "llc" (optLlc opts) ["llc"] - opt <- optional $ findProgram "opt" (optOpt opts) ["opt"] - llvmAs <- optional $ findProgram "llvm assembler" (optLlvmAs opts) ["clang"] + let findLlvmProgram' = findLlvmProgram llvmMinVersion llvmMaxVersion + llc <- optional $ findLlvmProgram' "llc" (optLlc opts) "llc" True + opt <- optional $ findLlvmProgram' "opt" (optOpt opts) "opt" True + llvmAs <- optional $ findLlvmProgram' "llvm assembler" (optLlvmAs opts) "clang" True -- for windows, also used for cross compiling windres <- optional $ findProgram "windres" (optWindres opts) ["windres"] - dlltool <- optional $ findProgram "dlltool" (optDlltool opts) ["llvm-dlltool"] + dlltool <- optional $ findLlvmProgram' "dlltool" (optDlltool opts) "llvm-dlltool" False -- Darwin-specific utilities (otool, installNameTool) <- ===================================== utils/ghc-toolchain/src/GHC/Toolchain/Program.hs ===================================== @@ -16,6 +16,7 @@ module GHC.Toolchain.Program , _poPath , _poFlags , findProgram + , findLlvmProgram -- * Compiler programs , compile , supportsTarget @@ -23,7 +24,8 @@ module GHC.Toolchain.Program import Control.Monad import Control.Monad.IO.Class -import Data.List (intercalate, isPrefixOf) +import Data.Char (isDigit) +import Data.List (find, intercalate, isPrefixOf, tails) import Data.Maybe import System.FilePath import System.Directory @@ -131,17 +133,13 @@ programFromOpt userSpec path flags = Program { prgPath = fromMaybe path (poPath -- in the given list of candidates. -- -- If the 'ProgOpt' program flags are unspecified the program will have an empty list of flags. -findProgram :: String +findProgram :: String -- ^ The program description -> ProgOpt -- ^ path provided by user -> [FilePath] -- ^ candidate names -> M Program findProgram description userSpec candidates - | Just path <- poPath userSpec = do - let err = - [ "Failed to find " ++ description ++ "." - , "Looked for user-specified program '" ++ path ++ "' in the system search path." - ] - toProgram <$> find_it path <|> throwEs err + | Just findProgramFromProgOpts <- maybeFindProgramFromProgOpts description userSpec + = findProgramFromProgOpts | otherwise = do env <- getEnv @@ -154,17 +152,78 @@ findProgram description userSpec candidates [ "Failed to find " ++ description ++ "." , "Looked for one of " ++ show candidates' ++ " in the system search path." ] - toProgram <$> oneOf' err (map find_it candidates') <|> throwEs err + mkProgram userSpec <$> oneOf' err (map findExecutableErr candidates') <|> throwEs err + +-- | Tries to find an llvm program with the highest supported llvm versions. +-- This searches for an explicitly versioned executable (postfixed with the llvm version). +-- If an explicitly versioned executable is not found, then this searches for a non-explicitly +-- versioned executable. If supported, the llvm version is checked by passing @--version@ to +-- the executable. +-- +-- If the 'ProgOpt' program flags are unspecified the program will have an empty list of flags. +findLlvmProgram :: Int -- ^ Min llvm version (inclusive) + -> Int -- ^ Max llvm version (inclusive) + -> String -- ^ The llvm program description + -> ProgOpt -- ^ path provided by user + -> FilePath -- ^ Candidate name + -> Bool -- ^ True if the program supports the @--version@ flag and the output + -- contains the llvm version number in the form @version <LLVM_VERSION>@ + -> M Program +findLlvmProgram minLlvmVersion maxLlvmVersion description userSpec candidate checkVersion + | Just findProgramFromProgOpts <- maybeFindProgramFromProgOpts description userSpec + = findProgramFromProgOpts + + | otherwise = do + program <- findProgram description userSpec (versionedCandidates ++ [candidate]) + when checkVersion $ do + -- Extract the version from the `--version` output + versionOutput <- readProgramStdout program ["--version"] + let versionStrPrefix = "version " + + versionMay :: Maybe Int + versionMay = fmap (read . takeWhile isDigit . drop (length versionStrPrefix)) + . find (versionStrPrefix `isPrefixOf`) + $ tails versionOutput + + errSupportedVersions = prgPath program <> ": We only support llvm " <> show minLlvmVersion <> " upto " <> show maxLlvmVersion <> " (non-inclusive)" + case versionMay of + Nothing -> throwE (errSupportedVersions <> " (no version found).") + Just version -> when + (version < minLlvmVersion || version > maxLlvmVersion) + (throwE $ errSupportedVersions <> " (found " <> show version <> ").") + return program where - toProgram path = Program { prgPath = path, prgFlags = fromMaybe [] (poFlags userSpec) } - - find_it name = do - r <- liftIO $ findExecutable name - case r of - Nothing -> throwE $ name ++ " not found in search path" - -- Use the given `prgPath` or candidate name rather than the - -- absolute path returned by `findExecutable`. - Just _x -> return name + versionedCandidates = + [ candidate <> postfix + | llvmVersion <- show <$> [minLlvmVersion, minLlvmVersion-1 .. maxLlvmVersion] + , postfix <- + [ "-" <> llvmVersion + , "-" <> llvmVersion <> ".0" + , llvmVersion + ] + ] + +maybeFindProgramFromProgOpts :: String -> ProgOpt -> Maybe (M Program) +maybeFindProgramFromProgOpts description userSpec = case poPath userSpec of + Nothing -> Nothing + Just path -> do + let err = + [ "Failed to find " ++ description ++ "." + , "Looked for user-specified program '" ++ path ++ "' in the system search path." + ] + Just (mkProgram userSpec <$> findExecutableErr path <|> throwEs err) + +mkProgram :: ProgOpt -> FilePath -> Program +mkProgram userSpec path = Program { prgPath = path, prgFlags = fromMaybe [] (poFlags userSpec) } + +findExecutableErr :: String -> M FilePath +findExecutableErr name = do + r <- liftIO $ findExecutable name + case r of + Nothing -> throwE $ name ++ " not found in search path" + -- Use the given `prgPath` or candidate name rather than the + -- absolute path returned by `findExecutable`. + Just _x -> return name -------------------- Compiling utilities -------------------- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/6278067c48bac1668f26bb8cc6b5f81… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/6278067c48bac1668f26bb8cc6b5f81… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 12 commits: Move the `Text.Read` implementation into `base`
by Marge Bot (＠marge-bot) 13 May '26

13 May '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 44cf9cd7 by Wolfgang Jeltsch at 2026-05-12T09:48:18-04:00 Move the `Text.Read` implementation into `base` - - - - - 4ac3f7d6 by Vladislav Zavialov at 2026-05-12T09:49:03-04:00 EPA: Use AnnParen for tuples and sums Summary of changes * Do not use AnnParen in XListTy, replace it with EpToken "[" and "]" * Specialise AnnParen to tuple/sums by dropping the AnnParensSquare and keeping only AnnParens and AnnParensHash * Use AnnParen in XExplicitTuple * Use AnnParen in XExplicitTupleTy * Use AnnParen in XTuplePat * Use AnnParen in XExplicitSum (via AnnExplicitSum) * Use AnnParen in XSumPat (via EpAnnSumPat) This is a refactoring with no user-facing changes. - - - - - 1bdcddec by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support to ghc-toolchain The dlltool is a tool that can create dll import libraries from .def files. These .def files list the exported symbols of dlls. Its somewhat like gnu linker scripts, but more limited. We will need dlltool to build the rts and ghc-internal libraries as DLLs on Windows. The rts and ghc-internal libraries have a recursive dependency on each other. Import libraries can be used to resolve recursive dependencies between dlls. We will use an import library for the rts when linking the ghc-internal library. - - - - - f7fc3770 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support into ./configure Find dlltool, and hopefully support finding it within the bundled llvm toolchain on windows. - - - - - e4e22bfb by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update the default host and target files for dlltool support - - - - - 5666c8f9 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add dlltool as a hadrian builder Optional except on windows. - - - - - 5e14fe3f by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update and generate libHSghc-internal.def from .def.in file The only symbol that the rts imports from the ghc-internal package now is init_ghc_hs_iface. So the rts only needs an import lib that defines that one symbol. Also, remove the libHSghc-prim.def because it is redundant. The rts no longer imports anything from ghc-prim. Keep libHSffi.def for now. We may yet need it once it is clear how libffi is going to be built/used for ghc. - - - - - 3d91e4a6 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add rule to build libHSghc-internal.dll.a and link into the rts On windows only, with dynamic linking. This is needed because on windows, all symbols in dlls must be resolved. No dangling symbols allowed. References to external symbols must be explicit. We resolve this with an import library. We create an import library for ghc-internal, a .dll.a file. This is a static archive containing .o files that define the symbols we need, and crucially have ".idata" sections that specifies the symbols the dll imports and from where. Note that we do not install this libHSghc-internal.dll.a, and it does not need to list all the symbols exported by that package. We create a special purpose import lib and only use it when linking the rts dll, so it only has to list the symbols that the rts uses from ghc-internal (which is exactly one symbol: init_ghc_hs_iface). - - - - - c8dae539 by Alice Rixte at 2026-05-12T09:50:52-04:00 Script for downloading and copying `base-exports` file - - - - - a2864f45 by Simon Peyton Jones at 2026-05-13T05:03:40-04:00 Do not use mkCast during typechecking This commit fixes #27219. The problem was that the typechecker was using `mkCast`, whose assertion checks legitimately fail when applied to types that contain unification variables. - - - - - c8da36a9 by Simon Peyton Jones at 2026-05-13T05:03:40-04:00 Major refactor of the Simplifier The main payload of this patch is to refactor the Simplifer to avoid repeated simplification when using Plan (AFTER) for rule rewrites. The need for this was shown up by #26989. See Note [Avoid repeated simplification] in GHC.Core.Opt.Simplify.Iteration. Related refactoring: * Refactor the two fields `sc_dup` and `sc_env` in `ApplyToVal` into one, `sc_env`. Reason: the envt is irrelevant in the "simplified" case, so the data type describes the possiblitiies much more accurately now. * Some refactoring in `knownCon` to split off `wrapDataConFloats`. * Refactor `lookupRule` and its auxiliary functions to return `RuleMatch`, a new data type. See Note [data RuleMatch] in GHC.Core. Ditto for BuiltinRule. This RuleMatch returns fragments of the target in rm_args and rm_floats, leaving `rm_rhs` to be the stuff from the RULE itself. Doing this has routine consequences in GHC.Core.Opt.ConstantFold. Many changes there but all routine. * When doing occurrence analysis on RULEs, make the occ-info on the rule binders relate just to the RHS, not the LHS. See (OUR1) in Note Note [OccInfo in unfoldings and rules] This means that Lint must not complain about the fact that the patterns in the RULE mentions binders that are marked dead. See Note [Dead occurrences] in GHC.Core.Lint. I changed the Core pretty-printer so that it didn't suppress dead binders, else I can't see those binders in RULEs. That led to quite a lot of testsuite wibbles. * Refactor FloatBinds, so that it is used both by `exprIsConApp_mabye` and by `lookupRule` * Move the definition of FloatBinds out of GHc.Core.Make, into GHC.Core. * Add FloatTick as an extra constructor. * Refactor `lookupRule` to use `FloatBinds` instead of `BindWrapper`. This refactor just shares more code. (Rename GHC.Core.Opt.FloatOut.FloatBinds to FloatLets, to avoid gratuitious name clash with GHC.Core.FloatBinds.) Corecion optimisation * In simpleOpt, when composing coercions, call new function `optTransCo`. This is much lighter weight than full blown coercion optimisation. * Make `GHC.Core.Opt.Arity.pushCoValArg` and `pushCoTyArg` return the coercionLKind of the coercion. This saves recomputing that coercionLKind at the key call sites in GHC.Core.Opt.Simplify.Iteration.pushCast. * Rename `addCoerce` in GHC.Core.Simplify.Iteration to become `pushCast`. * In the `ApplyToVal` case of `pushCast` we had a very unsavoury call to `simplArg`. I eliminated it by adding a field `sc_cast` to `ApplyToVal` that records any pending casts. Much nicer now. See Note [The sc_cast field of ApplyToVal]. * Don't optimise coercions if the type-substitution is empty. See Note [Optimising coercions] in GHC.Core.Opt.Simplify.Iteration. The fix for #26838 is dramatic. For the test in perf/compiler/T26839 we have Compiler allocs: Before: 7,363M After: 688M Compile time goes down generally. Here are compiler-alloc changes over 0.5%: CoOpt_Read(normal) 729,184,920 -0.7% CoOpt_Singletons(normal) 666,916,960 -4.6% GOOD LargeRecord(normal) 1,227,056,876 +1.1% T12227(normal) 256,827,604 -4.6% GOOD T12425(optasm) 76,879,410 -0.8% T12545(normal) 787,826,918 -10.8% GOOD T12707(normal) 775,186,464 -0.9% T13253(normal) 318,599,596 -0.8% T14766(normal) 685,857,320 -1.0% T15304(normal) 1,123,333,422 -2.2% T15630(normal) 123,142,330 -2.6% T15630a(normal) 123,092,100 -2.6% T15703(normal) 299,751,682 -2.9% GOOD T17516(normal) 964,072,280 +1.0% T18223(normal) 367,016,820 -6.2% GOOD T18730(optasm) 130,643,770 -3.3% GOOD T20261(normal) 535,608,584 -0.7% T21839c(normal) 340,340,436 -0.9% T24984(normal) 85,568,392 -1.9% T3064(normal) 174,631,992 -1.2% T3294(normal) 1,215,886,432 -0.7% T5030(normal) 141,449,704 -17.2% GOOD T5321Fun(normal) 258,484,744 -1.9% T8095(normal) 770,532,232 -2.7% T9630(normal) 858,423,408 -14.5% GOOD T9872c(normal) 1,591,709,448 +0.7% info_table_map_perf(normal) 19,700,614,458 -1.3% geo. mean -0.7% minimum -17.2% maximum +1.1% Metric Decrease: CoOpt_Singletons T12227 T12545 T15703 T18223 T18730 T21839c T5030 T9630 - - - - - 2ceed450 by Wolfgang Jeltsch at 2026-05-13T05:03:40-04:00 Introduce a cache of home module name providers This contribution introduces to the module graph a cache that maps home module names to sets of units providing them and changes the finder to use that cache. This is a performance optimization, especially for multi-home-unit builds. The particular changes are as follows: * In `GHC.Unit.Module.Graph`, `ModuleGraph` is extended with a new field `mg_home_module_name_providers_map`, exposed as `mgHomeModuleNameProvidersMap`. This is a cache that assigns to each home module name the set of IDs of home units that define it. Operations that construct module graphs are updated such that this cache stays synchronized. * In `GHC.Unit.Finder`, `findImportedModule` is changed to pull `mgHomeModuleNameProvidersMap` from `hsc_mod_graph` and pass it to `findImportedModuleNoHsc`, which now does not search home units in arbitrary order but prioritizes those units that the cache mentions as potential providers of the requested module. In addition, this contribution adds variants of the two multi-component compiler performance tests that use 100 units instead of 20, because with just 20 units the benefits from caching of home module name providers are still negligible. The following table shows the total time needed for running both multi-component tests before and after this contribution and with different numbers of units: | # of units | Before | After | |-----------:|-------:|------:| | 20 | 0:12 | 0:12 | | 100 | 0:47 | 0:42 | | 200 | 3:05 | 2:08 | Note that there seems to be a general overhead of 12 seconds that is not attributable to the actual tests, so that the real running times should be 12 seconds smaller than shown above. Resolves #27055. Metric Decrease: MultiComponentModules MultiComponentModulesRecomp Co-authored-by: Matthew Pickering <matthewtpickering(a)gmail.com> Co-authored-by: Fendor <fendor(a)posteo.de> - - - - - 103 changed files: - + changelog.d/ghc-api-epa-parens - + changelog.d/more-efficient-home-unit-imports-finding - compiler/GHC/Core.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion/Opt.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Make.hs - compiler/GHC/Core/Opt/Arity.hs - compiler/GHC/Core/Opt/ConstantFold.hs - compiler/GHC/Core/Opt/FloatIn.hs - compiler/GHC/Core/Opt/FloatOut.hs - compiler/GHC/Core/Opt/OccurAnal.hs - compiler/GHC/Core/Opt/Simplify/Env.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - compiler/GHC/Core/Opt/SpecConstr.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Ppr.hs - compiler/GHC/Core/Rules.hs - compiler/GHC/Core/SimpleOpt.hs - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Data/List/SetOps.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Tc/Types/Evidence.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Unit/Finder.hs - compiler/GHC/Unit/Module/Graph.hs - configure.ac - distrib/configure.ac.in - hadrian/cfg/default.host.target.in - hadrian/cfg/default.target.in - hadrian/src/Builder.hs - hadrian/src/Rules/Generate.hs - hadrian/src/Rules/Library.hs - hadrian/src/Rules/Rts.hs - libraries/base/src/Data/Functor/Classes.hs - libraries/base/src/Data/Functor/Compose.hs - libraries/base/src/Prelude.hs - libraries/base/src/Text/Read.hs - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/src/GHC/Internal/IO/Encoding.hs - − libraries/ghc-internal/src/GHC/Internal/Text/Read.hs - m4/find_llvm_prog.m4 - m4/fp_setup_windows_toolchain.m4 - m4/ghc_toolchain.m4 - m4/prep_target_file.m4 - rts/.gitignore - + rts/win32/libHSghc-internal.def.in - testsuite/tests/codeGen/should_compile/T25177.stderr - testsuite/tests/deSugar/should_compile/T13208.stdout - testsuite/tests/ghc-api/T25121_status.stdout - + testsuite/tests/interface-stability/.gitignore - testsuite/tests/interface-stability/README.mkd - + testsuite/tests/interface-stability/download-base-exports.sh - testsuite/tests/linters/notes.stdout - testsuite/tests/numeric/should_compile/T15547.stderr - testsuite/tests/numeric/should_compile/T20347.stderr - testsuite/tests/numeric/should_compile/T20374.stderr - testsuite/tests/numeric/should_compile/T20376.stderr - testsuite/tests/parser/should_compile/DumpParsedAst.stderr - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/parser/should_compile/KindSigs.stderr - testsuite/tests/parser/should_compile/T20452.stderr - testsuite/tests/perf/compiler/Makefile - + testsuite/tests/perf/compiler/T26989.hs - + testsuite/tests/perf/compiler/T26989a.hs - testsuite/tests/perf/compiler/all.T - testsuite/tests/perf/compiler/genMultiComp.py - testsuite/tests/printer/T18052a.stderr - testsuite/tests/simplCore/should_compile/DsSpecPragmas.stderr - testsuite/tests/simplCore/should_compile/RewriteHigherOrderPatterns.stderr - testsuite/tests/simplCore/should_compile/T15205.stderr - testsuite/tests/simplCore/should_compile/T18668.stderr - testsuite/tests/simplCore/should_compile/T19246.stderr - testsuite/tests/simplCore/should_compile/T19599.stderr - testsuite/tests/simplCore/should_compile/T19599a.stderr - testsuite/tests/simplCore/should_compile/T21917.stderr - testsuite/tests/simplCore/should_compile/T23074.stderr - testsuite/tests/simplCore/should_compile/T24359a.stderr - testsuite/tests/simplCore/should_compile/T25160.stderr - testsuite/tests/simplCore/should_compile/T25718c.stderr-ws-64 - testsuite/tests/simplCore/should_compile/T26051.stderr - testsuite/tests/simplCore/should_compile/T26116.stderr - testsuite/tests/simplCore/should_compile/T8331.stderr - testsuite/tests/simplCore/should_compile/T8848a.stderr - testsuite/tests/simplCore/should_compile/spec004.stderr - testsuite/tests/th/T24111.stdout - testsuite/tests/typecheck/should_compile/T13032.stderr - testsuite/tests/typecheck/should_compile/subsumption_sort_hole_fits.stderr - testsuite/tests/typecheck/should_fail/T21130.stderr - utils/check-exact/ExactPrint.hs - utils/ghc-toolchain/exe/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Target.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2282fa36362d7d20c06ab622769564… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2282fa36362d7d20c06ab622769564… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/dcoutts/issue-27105-stopTicker] 4 commits: Fix for RTS stopTicker not being synchronous
by Duncan Coutts (＠dcoutts) 12 May '26

12 May '26

Duncan Coutts pushed to branch wip/dcoutts/issue-27105-stopTicker at Glasgow Haskell Compiler / GHC Commits: cdcac142 by Duncan Coutts at 2026-05-12T22:41:16+01:00 Fix for RTS stopTicker not being synchronous Fixes issue #27105. The stopTicker() action was asynchronous (on both posix and win32) but it was being used in several places as if it were synchronous. It turns out there are two uses for stopTicker: 1. for concurrency safety: to avoid the tick handler running concurrently with some other critical section. 2. for efficiency: to reduce CPU wakeups when the RTS goes idle. The first case is where it relies on the stopTicker() being synchronous (which it wasn't), while the second case can be asynchronous for performance. In fact it _must_ be asynchronous because it is called within the tick handler itself, and it cannot wait on itself. So in this patch we deprecate stopTicker/startTicker and replace it with two pairs: block/unblockTicker for case 1, and pause/unpauseTicker for case 2. We update all calls of stop/startTicker with the appropriate replacement. In the posix implementation, we take care to keep the tick action cheap. Since block/unblock are used very infrequently, we make them more expensive and complicated to allow the normal hot path in the tick action to be cheap. We avoid locks and atomic memory ops in the hot path. We use message passing via an eventfd or pipe. In the win32 implementation, we continue to use the TimerQueue API, and we make use of its ability to delete timers synchronously or asynchronously. Add a changelog entry. - - - - - 9f2084b7 by Duncan Coutts at 2026-05-12T22:41:16+01:00 Make win32 ticker wait interval for initial tick too There is no need to tick immediately. This is consistent with the posix implementation. - - - - - b29c4462 by Duncan Coutts at 2026-05-12T22:41:16+01:00 Remove now-unnecessary layer of RTS ticker block/unblocking There was an atomic variable used to block *part* of the actions of the tick handler. This still did not make stopTimer synchronous, even for the part of the the handle_tick actions it covered. It also added a more expensive (sequentuially consistent) atomic operation in the hot path for the handle_tick action, whereas our new design requires no atomic ops at all. Now that we have a proper synchronous solution, we don't need this not-quite-working-anyway atomic protocol. - - - - - 5d283c9b by Duncan Coutts at 2026-05-12T22:41:16+01:00 Add TODOs about issue #27250: too much being done from handle_tick The handle_tick should not perform I/O, block, perform long-running operations or call arbitrary user code. Unfortunately, everything to do with the eventlog (at the moment) falls into all those categories. - - - - - 11 changed files: - + changelog.d/T27105 - rts/Capability.c - rts/RtsStartup.c - rts/Schedule.c - rts/Ticker.h - rts/Timer.c - rts/Timer.h - rts/include/rts/Timer.h - rts/include/stg/SMP.h - rts/posix/Ticker.c - rts/win32/Ticker.c Changes: ===================================== changelog.d/T27105 ===================================== @@ -0,0 +1,13 @@ +section: rts +issues: #27105 +mrs: !16023 +synopsis: RTS stopTicker is asynchronous, but is used relying on it being synchronous. +description: { + As a result of the fix, the exported RTS APIs `stopTimer` and `startTimer` + are now no-ops and are deprecated. They were called at least by the process + and unix libraries. No replacement is needed. + + They were used by libraries to temporarily block the RTS's use of the timer + signal. These functions no longer have a purpose since the RTS interval + timer no longer uses signals. +} ===================================== rts/Capability.c ===================================== @@ -31,6 +31,7 @@ #include "sm/OSMem.h" #include "sm/BlockAlloc.h" // for countBlocks() #include "IOManager.h" +#include "Timer.h" #include <string.h> @@ -448,7 +449,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS) // as we free it. The alternative would be to protect the capabilities // array with a lock but this seems more expensive than necessary. // See #17289. - stopTimer(); + blockTimer(); if (to == 1) { // THREADED_RTS must work on builds that don't have a mutable @@ -471,7 +472,7 @@ moreCapabilities (uint32_t from USED_IF_THREADS, uint32_t to USED_IF_THREADS) debugTrace(DEBUG_sched, "allocated %d more capabilities", to - from); - startTimer(); + unblockTimer(); #endif } ===================================== rts/RtsStartup.c ===================================== @@ -415,8 +415,8 @@ hs_init_ghc(int *argc, char **argv[], RtsConfig rts_config) traceInitEvent(dumpIPEToEventLog); initHeapProfiling(); - /* start the virtual timer 'subsystem'. */ - startTimer(); + /* start the timer (after initTimer above) */ + unblockTimer(); #if defined(RTS_USER_SIGNALS) if (RtsFlags.MiscFlags.install_signal_handlers) { @@ -512,14 +512,12 @@ hs_exit_(bool wait_foreign) } #endif - /* stop the ticker */ - stopTimer(); - /* - * it is quite important that we wait here as some timer implementations - * (e.g. pthread) may fire even after we exit, which may segfault as we've - * already freed the capabilities. + /* We rely on the guarantee that exitTimer stops the timer synchronously, + * which ensures the timer handler does not get run again after this point. + * We are about to start freeing resources used by the timer handler (like + * the capabilities, eventlog and profiling data structures). */ - exitTimer(true); + exitTimer(); /* * Dump the ticky counter definitions ===================================== rts/Schedule.c ===================================== @@ -454,7 +454,7 @@ run_thread: prev = setRecentActivity(ACTIVITY_YES); if (prev == ACTIVITY_DONE_GC) { #if !defined(PROFILING) - startTimer(); + unpauseTimer(); #endif } break; @@ -1935,7 +1935,7 @@ delete_threads_and_gc: // it will get re-enabled if we run any threads after the GC. setRecentActivity(ACTIVITY_DONE_GC); #if !defined(PROFILING) - stopTimer(); + pauseTimer(); #endif break; } @@ -2100,7 +2100,7 @@ forkProcess(HsStablePtr *entry ACQUIRE_LOCK(&all_tasks_mutex); #endif - stopTimer(); // See #4074 + blockTimer(); // See #4074 #if defined(TRACING) flushAllCapsEventsBufs(); // so that child won't inherit dirty file buffers @@ -2110,7 +2110,7 @@ forkProcess(HsStablePtr *entry if (pid) { // parent - startTimer(); // #4074 + unblockTimer(); // #4074 RELEASE_LOCK(&sched_mutex); RELEASE_LOCK(&sm_mutex); @@ -2224,8 +2224,9 @@ forkProcess(HsStablePtr *entry generations[g].threads = END_TSO_QUEUE; } - // On Unix, all timers are reset in the child, so we need to start - // the timer again. + // The timer thread is not present in the child process, so we need + // to initialise the timer again. Note that the timer is in a blocked + // state when we re-init, and this is permitted. initTimer(); // TODO: need to trace various other things in the child @@ -2236,7 +2237,7 @@ forkProcess(HsStablePtr *entry // start timer after the IOManager is initialized // (the idle GC may wake up the IOManager) - startTimer(); + unblockTimer(); // Install toplevel exception handlers, so interruption // signal will be sent to the main thread. @@ -2307,7 +2308,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS) // N.B. We must stop the interval timer while we are changing the // capabilities array lest handle_tick may try to context switch // an old capability. See #17289. - stopTimer(); + blockTimer(); stopAllCapabilities(&cap, task); @@ -2394,7 +2395,7 @@ setNumCapabilities (uint32_t new_n_capabilities USED_IF_THREADS) // Notify IO manager that the number of capabilities has changed. notifyIOManagerCapabilitiesChanged(&cap); - startTimer(); + unblockTimer(); rts_unlock(cap); ===================================== rts/Ticker.h ===================================== @@ -12,9 +12,59 @@ typedef void (*TickProc)(int); -void initTicker (Time interval, TickProc handle_tick); -void startTicker (void); -void stopTicker (void); -void exitTicker (bool wait); +/* The ticker is initialised in a blocked state. Use unblockTicker to start. */ +void initTicker(Time interval, TickProc handle_tick); + +/* Stop and terminate the ticker. It does not need to be stopped first. */ +void exitTicker(void); + +/* Block and unblock the ticker handle_tick action. + * + * The blockTicker action is *synchronous*. When it returns the caller is + * guaranteed that the tick action is blocked. The unblockTicker may be + * asynchronous. + * + * These should be used for the purpose of *concurrency safety*: to prevent + * the tick action from running concurrently with some other critical section. + * + * The blockTicker action is moderately expensive (because it is synchronous) + * and the implementation is optimised on the assumption that this action is + * infrequent (e.g. compared to tick frequency). + * + * It is *not* safe to call these functions from within the tick handler itself. + * + * It is safe to use these functions concurrently from multiple threads. They + * are *not* idempotent however: each thread must pair up each blockTicker call + * with exactly one corresponding unblockTicker. Additionally, initTicker acts + * like blockTicker and also must be matched by a corresponding unblockTicker. + */ +void blockTicker(void); +void unblockTicker(void); + +/* Pause and unpause (resume) the ticker. + * + * The pauseTicker and unpauseTicker actions are *asynchronous*. After calling + * pauseTicker, the ticker will pause eventually, but there may be another tick + * action before it does pause (and theoretically there could be several but + * in practice this is unlikely). Similarly, after calling unpauseTicker the + * ticker will start up again eventually, but there is an unspecified delay + * between the unpause and the next tick action (but in practice it is short). + * + * This should be used for the purpose of *efficiency*: to avoid unnecessary + * OS thread wakeups caused by the ticker. + * + * The pairing of unpauseTicker and the handle_tick action form a + * synchonises-with relation: values written before unpauseTicker can be + * read from the resulting handle_tick action. + * + * It *is* safe to call these functions from within the tick handler itself. + * + * It is safe to use these functions concurrently from multiple threads, but + * note that they *are* idempotent. This means it is not appropriate to use + * paired pause/unpause calls concurrently. They can be used by threads based + * on consistent use of some shared state or observation. + */ +void pauseTicker(void); +void unpauseTicker(void); #include "EndPrivate.h" ===================================== rts/Timer.c ===================================== @@ -33,15 +33,6 @@ #define HAVE_PREEMPTION #endif -// This global counter is used to allow multiple threads to stop the -// timer temporarily with a stopTimer()/startTimer() pair. If -// timer_enabled == 0 timer is enabled -// timer_disabled == N, N > 0 timer is disabled by N threads -// When timer_enabled makes a transition to 0, we enable the timer, -// and when it makes a transition to non-0 we disable it. - -static StgWord timer_disabled; - /* ticks left before next pre-emptive context switch */ static int ticks_to_ctxt_switch = 0; @@ -112,9 +103,9 @@ static void handle_tick(int unused STG_UNUSED) { - handleProfTick(); - if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0 - && SEQ_CST_LOAD_ALWAYS(&timer_disabled) == 0) + handleProfTick(); // Bad or worse: see issue #27250. + + if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) { ticks_to_ctxt_switch--; if (ticks_to_ctxt_switch <= 0) { @@ -128,7 +119,7 @@ handle_tick(int unused STG_UNUSED) ticks_to_eventlog_flush--; if (ticks_to_eventlog_flush <= 0) { ticks_to_eventlog_flush = RtsFlags.TraceFlags.eventlogFlushTicks; - flushEventLog(NULL); + flushEventLog(NULL); // Bad or worse: see issue #27250. } } #endif @@ -153,7 +144,7 @@ handle_tick(int unused STG_UNUSED) RtsFlags.MiscFlags.tickInterval; #if defined(THREADED_RTS) wakeUpRts(); - // The scheduler will call stopTimer() when it has done + // The scheduler will call pauseTimer() when it has done // the GC. #endif } else { @@ -165,10 +156,10 @@ handle_tick(int unused STG_UNUSED) #if defined(PROFILING) if (!(RtsFlags.ProfFlags.doHeapProfile || RtsFlags.CcFlags.doCostCentres)) { - stopTimer(); + pauseTimer(); } #else - stopTimer(); + pauseTimer(); #endif } } else { @@ -181,48 +172,71 @@ handle_tick(int unused STG_UNUSED) } } -void -initTimer(void) +void initTimer(void) { #if defined(HAVE_PREEMPTION) initProfTimer(); if (RtsFlags.MiscFlags.tickInterval != 0) { initTicker(RtsFlags.MiscFlags.tickInterval, handle_tick); } - SEQ_CST_STORE_ALWAYS(&timer_disabled, 1); #endif } -void -startTimer(void) +/* Deprecated exported functions. Now no-ops. + * Historically they were used by the process and unix libraries to disable + * the signal-based interval timer, since otherwise the timer signal would + * keep going off in the child process and confusing everything. The interval + * timer no longer uses signals, so there is no need any more for libraries to + * disable the timer. Also, the timer internal API has changed. + */ +void stopTimer(void) { /* no-op */ } +void startTimer(void) { /* no-op */ } + +/* We allow multiple threads to block the timer temporarily with a + * blockTimer()/unblockTimer() pair. The counting for this is done by + * the ticker implementation when using blockTicker()/unblockTicker(). + */ +void unblockTimer(void) { #if defined(HAVE_PREEMPTION) - if (SEQ_CST_SUB_ALWAYS(&timer_disabled, 1) == 0) { - if (RtsFlags.MiscFlags.tickInterval != 0) { - startTicker(); - } + if (RtsFlags.MiscFlags.tickInterval != 0) { + unblockTicker(); } #endif } -void -stopTimer(void) +void blockTimer(void) { #if defined(HAVE_PREEMPTION) - if (SEQ_CST_ADD_ALWAYS(&timer_disabled, 1) == 1) { - if (RtsFlags.MiscFlags.tickInterval != 0) { - stopTicker(); - } + if (RtsFlags.MiscFlags.tickInterval != 0) { + blockTicker(); } #endif } -void -exitTimer (bool wait) +void pauseTimer(void) +{ +#if defined(HAVE_PREEMPTION) + if (RtsFlags.MiscFlags.tickInterval != 0) { + pauseTicker(); + } +#endif +} + +void unpauseTimer(void) +{ +#if defined(HAVE_PREEMPTION) + if (RtsFlags.MiscFlags.tickInterval != 0) { + unpauseTicker(); + } +#endif +} + +void exitTimer (void) { #if defined(HAVE_PREEMPTION) if (RtsFlags.MiscFlags.tickInterval != 0) { - exitTicker(wait); + exitTicker(); } #endif } ===================================== rts/Timer.h ===================================== @@ -8,5 +8,15 @@ #pragma once -RTS_PRIVATE void initTimer (void); -RTS_PRIVATE void exitTimer (bool wait); +#include "BeginPrivate.h" + +void initTimer(void); +void exitTimer(void); + +void blockTimer(void); +void unblockTimer(void); + +void pauseTimer(void); +void unpauseTimer(void); + +#include "EndPrivate.h" ===================================== rts/include/rts/Timer.h ===================================== @@ -13,6 +13,6 @@ #pragma once -void startTimer (void); -void stopTimer (void); +void startTimer (void); // Deprecated: see issue #27086 +void stopTimer (void); // Deprecated: see issue #27086 int rtsTimerSignal (void); // Deprecated: see issue #27073 ===================================== rts/include/stg/SMP.h ===================================== @@ -29,6 +29,8 @@ void arm_atomic_spin_unlock(void); // Acquire/release atomic operations #define ACQUIRE_LOAD_ALWAYS(ptr) __atomic_load_n(ptr, __ATOMIC_ACQUIRE) #define RELEASE_STORE_ALWAYS(ptr,val) __atomic_store_n(ptr, val, __ATOMIC_RELEASE) +#define RELEASE_ADD_ALWAYS(ptr,val) __atomic_add_fetch(ptr, val, __ATOMIC_RELEASE) +#define RELEASE_SUB_ALWAYS(ptr,val) __atomic_sub_fetch(ptr, val, __ATOMIC_RELEASE) // Sequentially consistent atomic operations #define SEQ_CST_LOAD_ALWAYS(ptr) __atomic_load_n(ptr, __ATOMIC_SEQ_CST) ===================================== rts/posix/Ticker.c ===================================== @@ -103,120 +103,212 @@ #include <unistd.h> #include <fcntl.h> -static Time itimer_interval = DEFAULT_TICK_INTERVAL; - -// Should we be firing ticks? -// Writers to this must hold the mutex below. -static bool stopped = false; - -// should the ticker thread exit? -// This can be set without holding the mutex. -static bool exited = true; +static Time ticker_interval = DEFAULT_TICK_INTERVAL; + +// Atomic variable used by client threads to communicate their request to the +// ticker thread to block the ticks. +static int block_request_count; + +// Condition, mutex and cond var to communicate confirmation that the ticker is +// indeed blocked. +static bool block_confirmed; // must hold the mutex to get/set +static Mutex block_confirmed_mutex; +static Condition block_confirmed_cond; + +// Atomic variable used by client threads to communicate that they want the +// ticker thread to pause. This communication is one-way, with no +// acknowledgement. +static bool pause_request; + +// Atomic variable used by other threads to communicate that they want the +// ticker thread to exit. +static bool exit_request; +// Used to wait for the ticker thread to terminate after asking it to exit. +static OSThreadId ticker_thread_id; + +// Fds used with sendFdWakeup to notify the ticker thread that any of the +// *_request variables above have been set. +static int notifyfd_r = -1, notifyfd_w = -1; + + +// Synchronous, request and confirm. Not idempotent. +// Request the ticker to stop ticking, and wait until it confirms +// this. This guarantees no more ticks after this returns. +void blockTicker(void) +{ + // Request + // atomic increment with release memory order + RELEASE_ADD_ALWAYS(&block_request_count, 1); + + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + if (!block_confirmed) { + // Avoid notifying if it's not necessary. This always happens during + // rts startup, since initTicker starts in the blocked state and then + // moreCapabilities() uses block/unblockTicker. + sendFdWakeup(notifyfd_w); + } + // Wait for confirmation + while (!block_confirmed) { + waitCondition(&block_confirmed_cond, &block_confirmed_mutex); + } + OS_RELEASE_LOCK(&block_confirmed_mutex); +} -// Signaled when we want to (re)start the timer -static Condition start_cond; -static Mutex mutex; -static OSThreadId thread; +// Asynchronous request. Not idempotent. +void unblockTicker(void) +{ + // Request + RELEASE_SUB_ALWAYS(&block_request_count, 1); + sendFdWakeup(notifyfd_w); +} -// fds for interrupting the ticker -static int interruptfd_r = -1, interruptfd_w = -1; +// Asynchronous request. Idempotent. +void pauseTicker(void) +{ + RELEASE_STORE_ALWAYS(&pause_request, true); + sendFdWakeup(notifyfd_w); +} -static void *itimer_thread_func(void *_handle_tick) +// Asynchronous request. Idempotent. +void unpauseTicker(void) { - TickProc handle_tick = _handle_tick; + RELEASE_STORE_ALWAYS(&pause_request, false); + sendFdWakeup(notifyfd_w); +} -#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 - struct pollfd pollfds[1]; +// Synchronous. Not idempotent. +// The ticker is guaranteed stopped after this. +void exitTicker(void) +{ + ASSERT(!RELAXED_LOAD_ALWAYS(&exit_request)); + RELEASE_STORE_ALWAYS(&exit_request, true); + sendFdWakeup(notifyfd_w); - pollfds[0].fd = interruptfd_r; - pollfds[0].events = POLLIN; + // wait for ticker thread to terminate + if (pthread_join(ticker_thread_id, NULL)) { + sysErrorBelch("Ticker: Failed to join: %s", strerror(errno)); + } + closeFdWakeup(notifyfd_r, notifyfd_w); + closeMutex(&block_confirmed_mutex); + closeCondition(&block_confirmed_cond); +} - struct timespec ts = { .tv_sec = TimeToSeconds(itimer_interval) - , .tv_nsec = TimeToNS(itimer_interval) % 1000000000 - }; +#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 +typedef struct timespec timeout; // for ppoll() +typedef struct { struct pollfd pollfds[1]; } fdset; #else - fd_set selectfds; - FD_ZERO(&selectfds); - FD_SET(interruptfd_r, &selectfds); - - struct timeval tv = { .tv_sec = TimeToSeconds(itimer_interval) - /* convert remainder time in nanoseconds - to microseconds, rounding up: */ - , .tv_usec = ((TimeToNS(itimer_interval) % 1000000000) - + 999) / 1000 - }; +typedef struct timeval timeout; // for select() +typedef struct { int fd; fd_set selectfds; } fdset; // need to stash fd #endif - // Relaxed is sufficient: If we don't see that exited was set in one iteration we will - // see it next time. - while (!RELAXED_LOAD_ALWAYS(&exited)) { +// local helpers, to hide the difference between ppoll() and select() +static void poll_init_timeout(timeout *tv, Time t); +static void poll_init_fdset(fdset *fds, int fd); // single fd only +// These two return: >0 if fd ready, ==0 if timeout, <0 if error +static int poll_no_timeout(fdset *fdset); +static int poll_with_timeout(fdset *fdset, timeout *t); -#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 - int nfds = 1; - int nready = ppoll(pollfds, nfds, &ts, NULL); -#else - struct timeval tv_tmp = tv; // copy since select may change this value. - int nfds = interruptfd_r+1; - int nready = select(nfds, &selectfds, NULL, NULL, &tv_tmp); -#endif - // In either case (ppoll or select), the result nready is the number - // of fds that are ready. - if (RTS_LIKELY(nready == 0)) { - // Timer expired, not interrupted, continue. - } else if (nready > 0) { - // We only monitor one fd (the interruptfd_r), so we know - // it is that fd that is ready without any further checks. - collectFdWakeup(interruptfd_r); - // No further action needed, continue on to handling the final tick - // and then stop. - - // Note that we rely on sendFdWakeup and select/poll to provide the - // happens-before relation. So if 'exited' was set before calling - // sendFdWakeup, then we should be able to reliably read it after. - // And thus reading 'exited' in the while loop guard is ok. +static void *ticker_thread_func(void *_handle_tick) +{ + TickProc handle_tick = _handle_tick; + + // Thread-local view of our state. We compare these with the corresponding + // atomic shared variables used to request state changes. + bool blocked = true; // compare to atomic shared var block_request_count + bool paused = false; // updated from atomic shared var pause_request + bool exit = false; // updated from atomic shared var exit_request + + timeout timeout; + fdset fdset; + poll_init_timeout(&timeout, ticker_interval); + poll_init_fdset(&fdset, notifyfd_r); + + while (!exit) { + + int notify; + if (blocked || paused) { + notify = poll_no_timeout(&fdset); } else { - // While the RTS attempts to mask signals, some foreign libraries - // that rely on signal delivery may unmask them. Consequently we - // may see EINTR. See #24610. - if (errno != EINTR) { - sysErrorBelch("Ticker: poll failed: %s", strerror(errno)); - } + notify = poll_with_timeout(&fdset, &timeout); } - // first try a cheap test - if (RELAXED_LOAD_ALWAYS(&stopped)) { - OS_ACQUIRE_LOCK(&mutex); - // should we really stop? - if (stopped) { - waitCondition(&start_cond, &mutex); - } - OS_RELEASE_LOCK(&mutex); - } else { + if (RTS_LIKELY(notify == 0)) { + // The time expired, no state change notification. handle_tick(0); + + } else if (notify > 0) { + // State change notification, check the request variables. + + // We rely on sendFdWakeup and select/poll to provide the + // happens-before relation. So if the request variables are set + // before calling sendFdWakeup, then we should be able to reliably + // read them here afterwards. + collectFdWakeup(notifyfd_r); + + paused = ACQUIRE_LOAD_ALWAYS(&pause_request); + exit = RELAXED_LOAD_ALWAYS(&exit_request); + int block_request_count_snapshot = + ACQUIRE_LOAD_ALWAYS(&block_request_count); + + if (block_request_count_snapshot > 0 && !blocked) { + // State change: !blocked -> blocked + blocked = true; // local state + + // confirm to requesting thread(s) + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + block_confirmed = true; + // Must use broadcastCondition not signalCondition since there + // could be concurrent requesting threads. + broadcastCondition(&block_confirmed_cond); + OS_RELEASE_LOCK(&block_confirmed_mutex); + + } else if (block_request_count_snapshot == 0 && blocked) { + // State change: blocked -> !blocked + blocked = false; // local state + + OS_ACQUIRE_LOCK(&block_confirmed_mutex); + block_confirmed = false; + OS_RELEASE_LOCK(&block_confirmed_mutex); + } + + } else if (errno != EINTR) { + // While the RTS attempts to mask signals, some foreign libraries + // that rely on signal delivery may unmask them. Consequently we + // may see EINTR. See #24610. + sysErrorBelch("Ticker: poll failed: %s", strerror(errno)); } } return NULL; } +/* Initialise the ticker on startup or re-initialise the ticker after a fork(). + * In the fork case, the thread will not be present, but fds are inherited. + * + * The ticker is started in the blocked state. A single unblockTicker should + * be used to unblock. + */ void initTicker (Time interval, TickProc handle_tick) { - itimer_interval = interval; - stopped = true; - exited = false; + ticker_interval = interval; + block_request_count = 1; + pause_request = false; + exit_request = false; + #if defined(HAVE_SIGNAL_H) sigset_t mask, omask; int sigret; #endif int ret; - initCondition(&start_cond); - initMutex(&mutex); + block_confirmed = true; + initMutex(&block_confirmed_mutex); + initCondition(&block_confirmed_cond); /* Open the interrupt fd synchronously. * - * We used to do it in itimer_thread_func (i.e. in the timer thread) but it + * We used to do it in ticker_thread_func (i.e. in the timer thread) but it * meant that some user code could run before it and get confused by the * allocation of the timerfd. * @@ -226,11 +318,11 @@ initTicker (Time interval, TickProc handle_tick) * descriptor closed by the first call! (see #20618) */ - if (interruptfd_r != -1) { + if (notifyfd_r != -1) { // don't leak the old file descriptors after a fork (#25280) - closeFdWakeup(interruptfd_r, interruptfd_w); + closeFdWakeup(notifyfd_r, notifyfd_w); } - newFdWakeup(&interruptfd_r, &interruptfd_w); + newFdWakeup(&notifyfd_r, &notifyfd_w); /* * Create the thread with all blockable signals blocked, leaving signal @@ -242,7 +334,7 @@ initTicker (Time interval, TickProc handle_tick) sigfillset(&mask); sigret = pthread_sigmask(SIG_SETMASK, &mask, &omask); #endif - ret = createAttachedOSThread(&thread, "ghc_ticker", itimer_thread_func, (void*)handle_tick); + ret = createAttachedOSThread(&ticker_thread_id, "ghc_ticker", ticker_thread_func, (void*)handle_tick); #if defined(HAVE_SIGNAL_H) if (sigret == 0) pthread_sigmask(SIG_SETMASK, &omask, NULL); @@ -253,47 +345,65 @@ initTicker (Time interval, TickProc handle_tick) } } -void -startTicker(void) +/* Implementation of the local helpers, to hide the difference between ppoll() + * and select(). + */ +#if defined(HAVE_DECL_PPOLL) && HAVE_DECL_PPOLL == 1 +static void poll_init_timeout(timeout *tv, Time t) { - OS_ACQUIRE_LOCK(&mutex); - RELAXED_STORE(&stopped, false); - signalCondition(&start_cond); - OS_RELEASE_LOCK(&mutex); + tv->tv_sec = TimeToSeconds(t); + tv->tv_nsec = TimeToNS(t) % 1000000000; } -/* There may be at most one additional tick fired after a call to this */ -void -stopTicker(void) +static void poll_init_fdset(fdset *fds, int fd) { - OS_ACQUIRE_LOCK(&mutex); - RELAXED_STORE(&stopped, true); - OS_RELEASE_LOCK(&mutex); + fds->pollfds[0].fd = fd; + fds->pollfds[0].events = POLLIN; } -/* There may be at most one additional tick fired after a call to this */ -void -exitTicker (bool wait) +static int poll_no_timeout(fdset *fds) { - ASSERT(!SEQ_CST_LOAD(&exited)); - SEQ_CST_STORE(&exited, true); - // ensure that ticker wakes up if stopped - startTicker(); - sendFdWakeup(interruptfd_w); - - // wait for ticker to terminate if necessary - if (wait) { - if (pthread_join(thread, NULL)) { - sysErrorBelch("Ticker: Failed to join: %s", strerror(errno)); - } - closeFdWakeup(interruptfd_r, interruptfd_w); - closeMutex(&mutex); - closeCondition(&start_cond); - } else { - pthread_detach(thread); - } + int nfds = 1; + return ppoll(fds->pollfds, nfds, NULL, NULL); +} + +static int poll_with_timeout(fdset *fds, timeout *ts) +{ + int nfds = 1; + return ppoll(fds->pollfds, nfds, ts, NULL); +} + +#else // select() + +static void poll_init_timeout(timeout *tv, Time t) +{ + tv->tv_sec = TimeToSeconds(t); + /* convert remainder time in nanoseconds to microseconds, rounding up: */ + tv->tv_usec = ((TimeToNS(t) % 1000000000) + 999) / 1000; +} + +static void poll_init_fdset(fdset *fds, int fd) +{ + FD_ZERO(&fds->selectfds); + FD_SET(fd, &fds->selectfds); + fds->fd = fd; +} + +static int poll_no_timeout(fdset *fds) +{ + int nfds = fds->fd+1; + return select(nfds, &fds->selectfds, NULL, NULL, NULL); } +static int poll_with_timeout(fdset *fds, timeout *tv) +{ + struct timeval tv_tmp = *tv; // copy since select may change this value. + int nfds = fds->fd+1; + return select(nfds, &fds->selectfds, NULL, NULL, &tv_tmp); +} +#endif + +/* This is obsolete, but is used in the unix package for now */ int rtsTimerSignal(void) { ===================================== rts/win32/Ticker.c ===================================== @@ -9,10 +9,14 @@ #include <stdio.h> #include <process.h> +static Time tick_interval = 0; static TickProc tick_proc = NULL; + +static Mutex mutex; // To protect the timer and state vars below static HANDLE timer_queue = NULL; static HANDLE timer = NULL; -static Time tick_interval = 0; +static int blocked_count; +static Bool paused; static VOID CALLBACK tick_callback( PVOID lpParameter STG_UNUSED, @@ -39,9 +43,13 @@ static VOID CALLBACK tick_callback( void initTicker (Time interval, TickProc handle_tick) { + ASSERT(timer_queue == NULL); tick_interval = interval; tick_proc = handle_tick; + OS_INIT_LOCK(mutex); + blocked_count = 1; // starts blocked + paused = false; timer_queue = CreateTimerQueue(); if (timer_queue == NULL) { sysErrorBelch("CreateTimerQueue"); @@ -49,39 +57,94 @@ initTicker (Time interval, TickProc handle_tick) } } -void -startTicker(void) -{ - BOOL r; - - r = CreateTimerQueueTimer(&timer, - timer_queue, - tick_callback, - 0, - 0, - TimeToMS(tick_interval), // ms - WT_EXECUTEINTIMERTHREAD); +static void startTicker(void) { + ASSERT(timer_queue != NULL && timer == NULL); + DWORD interval = TimeToMS(tick_interval); // ms + BOOL r = CreateTimerQueueTimer(&timer, + timer_queue, + tick_callback, + NULL, // callback param + interval, // inital interval + interval, // recurrant interval + WT_EXECUTEINTIMERTHREAD); + //TODO: using WT_EXECUTEINTIMERTHREAD is fine for context switching, and + // plausibly also ok for profile sampling but is way out for eventlog + // flushing. The eventlog flush does a global synchronisation of all + // capabilities and I/O! And with eventlog providers, it calls arbitrary + // user code. This is not ok! See issue #27250. if (r == 0) { sysErrorBelch("CreateTimerQueueTimer"); stg_exit(EXIT_FAILURE); } + ASSERT(timer != NULL); } -void -stopTicker(void) +static void stopTicker(bool synchronous) { + ASSERT(timer_queue != NULL && timer != NULL); + // From the docs for DeleteTimerQueueTimer + // If this parameter is INVALID_HANDLE_VALUE, the function waits for any + // running timer callback functions to complete before returning. + HANDLE completion = synchronous ? INVALID_HANDLE_VALUE : NULL; + DeleteTimerQueueTimer(timer_queue, timer, completion); + timer = NULL; +} + +// Synchronous. Not idempotent. +void blockTicker() { - if (timer_queue != NULL && timer != NULL) { - DeleteTimerQueueTimer(timer_queue, timer, NULL); - timer = NULL; + OS_ACQUIRE_LOCK(mutex); + if (blocked_count == 0 && !paused) { + stopTicker(true /* synchronous */); } + blocked_count++; + OS_RELEASE_LOCK(mutex); } -void -exitTicker (bool wait) +// Asynchronous. Not idempotent. +void unblockTicker() { - stopTicker(); - if (timer_queue != NULL) { - DeleteTimerQueueEx(timer_queue, wait ? INVALID_HANDLE_VALUE : NULL); - timer_queue = NULL; + OS_ACQUIRE_LOCK(mutex); + if (blocked_count == 1 && !paused) { + startTicker(); } + blocked_count--; + OS_RELEASE_LOCK(mutex); +} + +// Asynchronous. Idempotent. +void pauseTicker() +{ + OS_ACQUIRE_LOCK(mutex); + if (!paused && blocked_count == 0) { + /* pauseTicker is called from within the handle_tick, so stopping + * the ticker here /must/ be asynchronous or we will deadlock! */ + stopTicker(false /* asynchronous */); + } + paused = true; + OS_RELEASE_LOCK(mutex); +} + +// Asynchronous. Idempotent. +void unpauseTicker() +{ + OS_ACQUIRE_LOCK(mutex); + if (paused && blocked_count == 0) { + startTicker(); + } + paused = false; + OS_RELEASE_LOCK(mutex); +} + +void exitTicker() +{ + ASSERT(timer_queue != NULL); + blockTicker(); + // From the docs for DeleteTimerQueueEx: + // If this parameter is INVALID_HANDLE_VALUE, the function waits + // for all callback functions to complete before returning. + // This is a belt-and-braces approach to ensuring exitTicker is synchronous, + // since blockTicker() is already synchronous and there's only one timer. + HANDLE completion = INVALID_HANDLE_VALUE; + DeleteTimerQueueEx(timer_queue, completion); + timer_queue = NULL; } View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/84ff228b498bbc1b25d77fecfe0fc3… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/84ff228b498bbc1b25d77fecfe0fc3… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Deleted branch wip/jeltsch/text-read-implementation-into-base
by Wolfgang Jeltsch (＠jeltsch) 12 May '26

12 May '26

Wolfgang Jeltsch deleted branch wip/jeltsch/text-read-implementation-into-base at Glasgow Haskell Compiler / GHC -- You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/jeltsch/more-efficient-home-unit-imports-finding] 47 commits: Make cmm 'import "package" name;' syntax use consistent label types
by Wolfgang Jeltsch (＠jeltsch) 12 May '26

12 May '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/more-efficient-home-unit-imports-finding at Glasgow Haskell Compiler / GHC Commits: 9f85f034 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Make cmm 'import "package" name;' syntax use consistent label types There is a little-used syntactic form in cmm imports: import "package" foo; Which means to import foo from the given package (unit id, specified as a string). This syntax is somewhat reminiscent of GHC's package import extension. This syntax form is not used in the rts cmm code, nor any of the boot libraries. It may not be used at all. Unclear. Change the kind of CLabel this syntax generates to be consistent with the others. The other cmm imports use ForeignLabel with ForeignLabelInExternalPackage. For some reason this form was using CmmLabel. Change that to also be ForeignLabel but with ForeignLabelInPackage. This specifies a specific package, rather than an unnamed external package. - - - - - a811f68f by Duncan Coutts at 2026-04-30T04:52:42-04:00 Change default cmm import statements to be internal Previously a cmm statement like: import foo; meant to expect the symbol from a different shared library than the current one. Now it means to expect the symbol from the same shared library as the current one. We'll add explicit syntax to indicate that it's a foreign import. Most existing uses are in fact intenal (rts to rts), so few imports will need to be annotated foreign. Examples would include cmm code in libraries (other than the rts) that need to access RTS APIs. In practice, this makes no difference whatsoever at the moment on any platform other than windows (where building Haskell libs as shared libs does not fully work yet), since the 'labelDynamic' treats all such labels as foreign, irrespective of the foreign label source. - - - - - 17fe5d1d by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm import syntax 'import DATA foo;' as better name for CLOSURE The existing syntax is: import CLOSURE foo; The new syntax is import DATA foo; This means to interpret the symbol foo as refering to data (i.e. a global constant or variable) rather than to code (a function). The historical syntax for this uses CLOSURE, which is rather misleading. Presumably this was done to avoid introducing new reserved words. Be less squemish about new reserved words and add DATA and use that. Keep the existing CLOSURE syntax as an alias for compatibility. - - - - - 3a530d68 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm 'import extern name;' syntax Since the default for cmm imports is now for symbols within the same shared object, we need a way to indicate we want a symbol from an external shared object: import extern foo; -- for a function import extern DATA foo; -- for data This adds a new reserved word 'extern'. We don't expect to have to use this much. Most cmm imports are intra-DSO. This makes no difference currently on ELF and MachO platforms, but does make a difference to the linking conventions on PE (Windows). In future it's plausible we could take make distinctions on ELF or MachO, so it's worth trying to get it right. Windows can be the guinea pig. - - - - - 2b8e44c7 by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add cmm syntax 'import "package" DATA foo;' for completeness We already have: import DATA foo; -- for data imports import "package" foo; -- for imports from a given unitid There's no reason not to have both at once: import "package" DATA foo; So add that. - - - - - ee05e5cc by Duncan Coutts at 2026-04-30T04:52:42-04:00 Improve the commentary for the cmm import grammar. AFAIK, this is the only place where GHC-style Cmm syntax is documented. - - - - - b35946ad by Duncan Coutts at 2026-04-30T04:52:42-04:00 Add a changelog.d entry for the .cmm import syntax changes - - - - - d59b7c71 by Wolfgang Jeltsch at 2026-04-30T04:53:25-04:00 Move code that uses `GHC.Internal.Text.Read` into `base` This contribution serves to remove all dependencies on `GHC.Internal.Text.Read` from within `ghc-internal`, so that the implementation of `Text.Read` and ultimately more reading-related code can be moved to `base` as well. The following things are moved from `ghc-internal` to `base`: * I/O-related `Read` instances * Most of the `Numeric` implementation * The instance `Read ByteOrder` * The `parseVersion` operation * The `readConstr` operation Metric Increase: LinkableUsage01 T9198 T12425 T13035 T13820 T18140 - - - - - 5bd6a964 by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 New rts Message to {set,unset} TSO flags This commit introduces stg_MSG_SET_TSO_FLAG_info and stg_MSG_UNSET_TSO_FLAG_info, which allows setting flags of a TSO other than yourself. This is especially useful/necessary to set breakpoints and toggle breakpoints of different threads, which is needed to safely implement features like pausing, toggling step-out, toggling step-in per thread, etc. Fixes #27131 ------------------------- Metric Decrease: T3294 ------------------------- - - - - - ce97fd3e by Rodrigo Mesquita at 2026-04-30T04:54:08-04:00 test: Add test setting another TSO's flags Introduces a test that runs on two capabilities. The main thread running on Capability 0 sets the flags on a TSO running on Capability 1. The TSO from Capability 1 itself checks whether its flags were set and reports that back. This validates that the RTS messages for setting TSO flags work, even if it doesn't test a harsher scenario with race conditions to exercise why the message passing is necessary for safely setting another TSO's flags. Part of #27131 - - - - - a4ff6315 by David Eichmann at 2026-04-30T04:54:51-04:00 Hadrian: withResponseFile outputs response file when verbodity is Verbose At the Verbose verbosity, shake will display full commandlines. With the use of response files, the full command is hidden. That makes it hard to run the command manually. This commit outputs the contents of the response file so that that full command can be recreated and also hints at the use of the --keep-response-files hadrian flag. - - - - - cd732ee3 by Duncan Coutts at 2026-04-30T04:54:51-04:00 Use response files for hadrian linking with ghc (support long command lines) In future support for windows dynamic linking, we expect long command lines for linking dll files with ghc. Experiments with dynamic linking the ghc-internal library yielded a link command well over 32kb. We did not encounter this before for static libs, since we already use ar's @file feature (if available, which it is for the llvm toolchain). Co-authored-by: David Eichmann <davide(a)well-typed.com> - - - - - 3d41368f by Andreas Klebinger at 2026-04-30T04:55:32-04:00 Split GHC.Driver.Main.hs up into multiple components. This commit splits GHC.Driver.Main into four components: * GHC.Driver.Main.Compile * GHC.Driver.Main.Hsc * GHC.Driver.Main.Interactive * GHC.Driver.Main.Passes We might improve that separation further in the future but this should hopefully make it easier to reason about and work with this part of the code. - - - - - 2128ba85 by Cheng Shao at 2026-04-30T04:56:14-04:00 compiler: avoid unique OccNames for internal Names in bytecode objects This patch improves bytecode object serialization logic by avoiding the construction of unique `OccName`s when serializing/deserializing internal `Name`s. Closes #27213. ------------------------- Metric Decrease: LinkableUsage01 ------------------------- - - - - - e16854c3 by Vladislav Zavialov at 2026-04-30T04:56:57-04:00 Replace GHC 9.16 references with GHC 10.0 - - - - - 39141343 by Alice Rixte at 2026-05-01T14:09:32+02:00 Add Bounded instances for Double, Float, CDouble and CFloat - - - - - 5c4c3bf4 by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: fix flaky foundation Divisible / mulIntMayOflo# tests (#27222) Since the LCG was widened to 64 bits and the seed randomised per CI run (commit 2d30f7d3400 "Vendor mini-QuickCheck for testsuite"), two latent bugs in the foundation test surface stochastically: * The Divisible property `(x `div` y) * y + (x `mod` y) == x` raises ArithException(Overflow) when (a, b) = (minBound, -1) for fixed-width signed Integral types. Split testNumber/testDivisible into Bounded and unbounded variants and skip just that one pair, gated by `(minBound :: a) < 0` so unsigned types lose no coverage. * The `mulIntMayOflo#` test compared raw Int# bit-for-bit, but the primop is only specified to return 0/non-zero -- the exact non-zero indicator legitimately differs between backends and inlining choices. Add a dedicated `testPrimopMayOflo` helper that only compares zero / non-zero. Also fix the long-standing typo "Dividible" -> "Divisible" in identifiers. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply(a)anthropic.com> - - - - - e242ce4f by Sylvain Henry at 2026-05-02T03:39:28-04:00 testsuite: catch and display exceptions in MiniQuickCheck Exceptions raised while evaluating a property are now caught and reported as a normal failure (with arguments and seed), instead of aborting the test. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply(a)anthropic.com> - - - - - 3b75cccd by fendor at 2026-05-02T03:40:14-04:00 Fix name of Note [Structure of dep_boot_mods] - - - - - 9a9ae4df by Duncan Coutts at 2026-05-05T14:44:37-04:00 Use __attribute__((dllimport)) for external RTS symbol declarations This is needed to be hygenic about DLL symbol imports and exports. The attribute is ignored on platforms other than Windows. Use of the attribute however means that external data symbols do not have a compile-time constant address (they are loaded using an indirection). This means we have to adjust the rtsSyms initial linker table so that it is a local constant in a function, rather than a global constant. We now define it within a function that pre-populates the symbol table with the RTS symbols. - - - - - 2ad3e01e by Duncan Coutts at 2026-05-05T14:44:37-04:00 Fix the rts linker declarations for a few data symbols and ensure that the (windows only) rts_IOManagerIsWin32Native data symbol is marked as externally visible. - - - - - 8ff4fdb5 by David Eichmann at 2026-05-05T14:44:37-04:00 Hadrian: Disable runtime pseudo relocations for RTS on windows hosts - - - - - 96974723 by Teo Camarasu at 2026-05-05T14:45:20-04:00 ghci/TH: refactor to use IORef QState This is a pure refactor and shouldn't modify semantics at all - - - - - eff6bfaf by Teo Camarasu at 2026-05-05T14:45:20-04:00 iserv: recover/getQ/putQ should behave same as internal interpreter The internal and external interpreter should behave the same when handling `recover`, the exeception recovery method of Q. In practice, they diverge. In case of failure, the internal interpreter only restores error message state to before the computation, wheras the external interperter restores error message state *and* the state of putQ/getQ. As far as I can tell this is a simple mistake in the implementation. Note [TH recover with -fexternal-interpreter] describes the correct behaviour but the implementation doesn't mirror this. This change restores the correct behaviour by keeping the effects of putQ in the erroring computation. This is a breaking change since it modifies the behaviour of programs that rely on recover ignoring putQ from failling computations when used with the external interpreter. Although I highly doubt anyone relies on this behaviour. This divergence was first introduced in d00c308633fe7d216d31a1087e00e63532d87d6d. As far as I can tell this was unintentional and tha commit was trying to solve a different bug. Resolves #27022 - - - - - 1cb1d672 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add dynamic trace flags API This commit adds an API to the RTS (exposed via Rts.h) that allows users to dynamically change the trace flags. Prior to this commit, users were able to stop and start the profiling and heap profiling timers (via startProfTimer/stopProfTimer and startHeapProfTimer/stopHeapProfTimer). This extends that functionality to also cover the core event types. The getTraceFlag/setTraceFlag functions read and write the values of the trace flag cache, which is allocated by Trace.c, rather than modifying the members of RtsFlags.TraceFlags. This is done under the assumption that the members of RtsFlags should not be modified after RTS initialisation. Consequently, if the user modifies the trace flags using setTraceFlag, the object returned by getTraceFlags (from base) will not reflect these changes. The trace flags are not protected by locks of any sort. Hence, these functions are not thread-safe. However, the trace flags are not modified by the RTS after initialisation, only read, so the race conditions introduced by one user modifying them are most likely benign. This PR also puts the trace flag cache in a single global struct, as opposed to a collection of global variables, and changes the types of the individual flags from uint8_t to bool, as these have the same size on both Clang and GCC and are a better semantic match. Prior to the change to uint8_t, they had type int, see 42c47cd6. Even with its deprecation in C23, I don't think there should be any issue depending on stdbool.h. The TRACE_X macros are redefined to access the global struct, with values cast to const bool to ensure they are read-only. - - - - - 9d54dc94 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Ensure TRACE_X values are used in place of RtsFlags.TraceFlags.X - - - - - 418d737b by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Fix nonmoving-GC tracing The current nonmoving-GC tracing functions were written in a different style from the other tracing functions. They were directly implemented as, e.g., a traceConcMarkEnd function that called postConcMarkEnd. The other tracing functions are implemented as, e.g., traceThreadLabel_, a function that posts the thread label event, and traceThreadLabel, a macro that checks whether TRACE_scheduler is set. This commit fixes that implementation, and ensures that the nonmoving-GC tracing functions only emit events if nonmoving-GC tracing is enabled. - - - - - 99f4afa4 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for get/setTraceFlag - - - - - 7e9eb8b9 by Wen Kokke at 2026-05-06T09:53:40-04:00 rts: Add SymI_HasProto for start/endEventLogging - - - - - 3a3045fb by Wen Kokke at 2026-05-06T09:53:41-04:00 rts: Add changelog entry - - - - - a3b339a4 by Teo Camarasu at 2026-05-06T09:54:25-04:00 interface-stability/base: don't distinguish ws-32 The interface of base is identical when the Word size is 32bits. Therefore, there is no need to have another file for this case. So, we delete it. Step towards: #26752 - - - - - eb922183 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add a rts posix FdWakup utility module This will be used to implement wakeupIOManager for in-RTS I/O managers. It provides a notification/wakeup mechanism using FDs, suitable for situations when a thread is blocked on a set of fds anyway. It uses the classic self-pipe trick, or equivalently eventfd on supported platforms. This will initially be used to implement prompt interrupt or shutdown of the posix ticker thread. - - - - - 01b0e233 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Add prompt shutdown to the pthread ticker implementation. The Linux timerfd ticker monitors a pipe which is used by exitTicker to ensure a prompt wakeup and shutdown. The pthread ticker lacked this and so would only exit at the next ticker wakeup (10ms by default). This patch adds the same mechanism to the pthread ticker. This changes the pthread ticker from waiting by using nanosleep() to waiting using either ppoll() or select(), so that it can wait on both a time and a file descriptor. On Linux at least, a test program to compare the timing jitter of these APIs shows that using nanpsleep, ppoll or select makes no statistical difference to the maximum or average jitter. This is a step towards unifying the posix ticker implementations, so that we can have just one portable one (albeit with some limited cpp). It is also a step towards using the ticker as part of a more general implementation of wakeUpRts, since this will require a method to wake the rts from a signal handler context (ctl-c handler). - - - - - bc41d646 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Update ticker header commentary It was antique and didn't apply even to the previous implementation, and certainly not to the updated one. - - - - - 4ed9a386 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Remove the timerfd-based ticker implementation There does not appear to be any remaining advantage on Linux to using the timerfd ticker implementation over the portable one (using ppoll on Linux for precise timing). The eventfd implementation was originally added at a time when Linux was still using a signal based implementation. So it made sense at the time. See (closed) issue #10840. - - - - - 97504fa6 by Duncan Coutts at 2026-05-07T14:28:50+01:00 Consolidate to a single posix ticker implementation Previously we had four implementations, two using signals and two using threads. Having just one should make behaviour more consistent between platforms, and should make maintenance easier. - - - - - 1e60023b by Facundo Domínguez at 2026-05-07T18:01:16-04:00 Generalize so_inline to specify which bindings should be preserved This commit generalizes the so_inline option of the simple optimizer so we can indicate with a predicate the specific bindings that should be kept. This feature is important for the LiquidHaskell plugin, which relies on the simple optimizer to make core programs easier to read, but needs to preserve bindings that are relevant for verification. See https://gitlab.haskell.org/ghc/ghc/-/issues/24386 for the full discussion. - - - - - 44cf9cd7 by Wolfgang Jeltsch at 2026-05-12T09:48:18-04:00 Move the `Text.Read` implementation into `base` - - - - - 4ac3f7d6 by Vladislav Zavialov at 2026-05-12T09:49:03-04:00 EPA: Use AnnParen for tuples and sums Summary of changes * Do not use AnnParen in XListTy, replace it with EpToken "[" and "]" * Specialise AnnParen to tuple/sums by dropping the AnnParensSquare and keeping only AnnParens and AnnParensHash * Use AnnParen in XExplicitTuple * Use AnnParen in XExplicitTupleTy * Use AnnParen in XTuplePat * Use AnnParen in XExplicitSum (via AnnExplicitSum) * Use AnnParen in XSumPat (via EpAnnSumPat) This is a refactoring with no user-facing changes. - - - - - 1bdcddec by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support to ghc-toolchain The dlltool is a tool that can create dll import libraries from .def files. These .def files list the exported symbols of dlls. Its somewhat like gnu linker scripts, but more limited. We will need dlltool to build the rts and ghc-internal libraries as DLLs on Windows. The rts and ghc-internal libraries have a recursive dependency on each other. Import libraries can be used to resolve recursive dependencies between dlls. We will use an import library for the rts when linking the ghc-internal library. - - - - - f7fc3770 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add minimal dlltool support into ./configure Find dlltool, and hopefully support finding it within the bundled llvm toolchain on windows. - - - - - e4e22bfb by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update the default host and target files for dlltool support - - - - - 5666c8f9 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add dlltool as a hadrian builder Optional except on windows. - - - - - 5e14fe3f by Duncan Coutts at 2026-05-12T09:49:48-04:00 Update and generate libHSghc-internal.def from .def.in file The only symbol that the rts imports from the ghc-internal package now is init_ghc_hs_iface. So the rts only needs an import lib that defines that one symbol. Also, remove the libHSghc-prim.def because it is redundant. The rts no longer imports anything from ghc-prim. Keep libHSffi.def for now. We may yet need it once it is clear how libffi is going to be built/used for ghc. - - - - - 3d91e4a6 by Duncan Coutts at 2026-05-12T09:49:48-04:00 Add rule to build libHSghc-internal.dll.a and link into the rts On windows only, with dynamic linking. This is needed because on windows, all symbols in dlls must be resolved. No dangling symbols allowed. References to external symbols must be explicit. We resolve this with an import library. We create an import library for ghc-internal, a .dll.a file. This is a static archive containing .o files that define the symbols we need, and crucially have ".idata" sections that specifies the symbols the dll imports and from where. Note that we do not install this libHSghc-internal.dll.a, and it does not need to list all the symbols exported by that package. We create a special purpose import lib and only use it when linking the rts dll, so it only has to list the symbols that the rts uses from ghc-internal (which is exactly one symbol: init_ghc_hs_iface). - - - - - c8dae539 by Alice Rixte at 2026-05-12T09:50:52-04:00 Script for downloading and copying `base-exports` file - - - - - 5fab2238 by Wolfgang Jeltsch at 2026-05-12T21:24:27+03:00 Introduce a cache of home module name providers This contribution introduces to the module graph a cache that maps home module names to sets of units providing them and changes the finder to use that cache. This is a performance optimization, especially for multi-home-unit builds. The particular changes are as follows: * In `GHC.Unit.Module.Graph`, `ModuleGraph` is extended with a new field `mg_home_module_name_providers_map`, exposed as `mgHomeModuleNameProvidersMap`. This is a cache that assigns to each home module name the set of IDs of home units that define it. Operations that construct module graphs are updated such that this cache stays synchronized. * In `GHC.Unit.Finder`, `findImportedModule` is changed to pull `mgHomeModuleNameProvidersMap` from `hsc_mod_graph` and pass it to `findImportedModuleNoHsc`, which now does not search home units in arbitrary order but prioritizes those units that the cache mentions as potential providers of the requested module. In addition, this contribution adds variants of the two multi-component compiler performance tests that use 100 units instead of 20, because with just 20 units the benefits from caching of home module name providers are still negligible. The following table shows the total time needed for running both multi-component tests before and after this contribution and with different numbers of units: | # of units | Before | After | |-----------:|-------:|------:| | 20 | 0:12 | 0:12 | | 100 | 0:47 | 0:42 | | 200 | 3:05 | 2:08 | Note that there seems to be a general overhead of 12 seconds that is not attributable to the actual tests, so that the real running times should be 12 seconds smaller than shown above. Resolves #27055. Metric Decrease: MultiComponentModules MultiComponentModulesRecomp Co-authored-by: Matthew Pickering <matthewtpickering(a)gmail.com> Co-authored-by: Fendor <fendor(a)posteo.de> - - - - - 148 changed files: - + changelog.d/T27022 - + changelog.d/T27131 - + changelog.d/cmm-import-syntax-changes - + changelog.d/dynamic-trace-flags - + changelog.d/ghc-api-epa-parens - + changelog.d/more-efficient-home-unit-imports-finding - + changelog.d/so_inline_is_a_predicate - compiler/GHC/ByteCode/Binary.hs - compiler/GHC/Cmm/Lexer.x - compiler/GHC/Cmm/Parser.y - compiler/GHC/Core/SimpleOpt.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Config.hs - compiler/GHC/Driver/Env/Types.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Main.hs - + compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Main.hs-boot → compiler/GHC/Driver/Main/Compile.hs-boot - + compiler/GHC/Driver/Main/Hsc.hs - + compiler/GHC/Driver/Main/Interactive.hs - + compiler/GHC/Driver/Main/Passes.hs - + compiler/GHC/Driver/Main/Passes.hs-boot - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Types/Error.hs - compiler/GHC/Types/Error.hs-boot - compiler/GHC/Unit/Finder.hs - compiler/GHC/Unit/Module/Deps.hs - compiler/GHC/Unit/Module/Graph.hs - compiler/ghc.cabal.in - configure.ac - distrib/configure.ac.in - docs/users_guide/debug-info.rst - docs/users_guide/exts/explicit_namespaces.rst - docs/users_guide/exts/linear_types.rst - docs/users_guide/exts/modifiers.rst - docs/users_guide/exts/qualified_strings.rst - docs/users_guide/exts/required_type_arguments.rst - docs/users_guide/using-warnings.rst - docs/users_guide/using.rst - hadrian/cfg/default.host.target.in - hadrian/cfg/default.target.in - hadrian/src/Builder.hs - hadrian/src/Hadrian/Builder.hs - hadrian/src/Hadrian/Utilities.hs - hadrian/src/Rules/Generate.hs - hadrian/src/Rules/Library.hs - hadrian/src/Rules/Rts.hs - hadrian/src/Settings/Builders/Ghc.hs - hadrian/src/Settings/Packages.hs - libraries/base/changelog.md - libraries/base/src/Data/Data.hs - libraries/base/src/Data/Functor/Classes.hs - libraries/base/src/Data/Functor/Compose.hs - libraries/base/src/Data/Version.hs - libraries/base/src/GHC/ByteOrder.hs - libraries/base/src/Numeric.hs - libraries/base/src/Prelude.hs - libraries/base/src/System/IO.hs - libraries/base/src/Text/Printf.hs - libraries/base/src/Text/Read.hs - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/include/CTypes.h - libraries/ghc-internal/src/GHC/Internal/Data/Data.hs - libraries/ghc-internal/src/GHC/Internal/Data/Version.hs - libraries/ghc-internal/src/GHC/Internal/Float.hs - libraries/ghc-internal/src/GHC/Internal/IO/Device.hs - libraries/ghc-internal/src/GHC/Internal/IO/Encoding.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Types.hs - libraries/ghc-internal/src/GHC/Internal/IO/IOMode.hs - libraries/ghc-internal/src/GHC/Internal/Numeric.hs - libraries/ghc-internal/src/GHC/Internal/Read.hs - − libraries/ghc-internal/src/GHC/Internal/Text/Read.hs - libraries/ghci/GHCi/TH.hs - m4/find_llvm_prog.m4 - m4/fp_setup_windows_toolchain.m4 - m4/ghc_toolchain.m4 - m4/prep_target_file.m4 - rts/.gitignore - rts/IOManager.h - rts/Interpreter.c - rts/Linker.c - rts/LinkerInternals.h - rts/Messages.c - rts/RtsSymbols.c - rts/RtsSymbols.h - rts/StgMiscClosures.cmm - rts/Threads.c - rts/Threads.h - rts/Trace.c - rts/Trace.h - rts/include/rts/EventLogWriter.h - rts/include/rts/storage/Closures.h - rts/include/stg/MiscClosures.h - rts/linker/Elf.c - + rts/posix/FdWakeup.c - + rts/posix/FdWakeup.h - rts/posix/Ticker.c - − rts/posix/ticker/Pthread.c - − rts/posix/ticker/TimerFd.c - rts/rts.cabal - rts/sm/NonMoving.c - + rts/win32/libHSghc-internal.def.in - testsuite/tests/MiniQuickCheck.hs - + testsuite/tests/ghc-api/T24386.hs - testsuite/tests/ghc-api/T25121_status.stdout - testsuite/tests/ghc-api/all.T - + testsuite/tests/interface-stability/.gitignore - testsuite/tests/interface-stability/README.mkd - testsuite/tests/interface-stability/base-exports.stdout - testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs - testsuite/tests/interface-stability/base-exports.stdout-mingw32 - − testsuite/tests/interface-stability/base-exports.stdout-ws-32 - + testsuite/tests/interface-stability/download-base-exports.sh - testsuite/tests/linters/notes.stdout - testsuite/tests/numeric/should_run/foundation.hs - testsuite/tests/parser/should_compile/DumpParsedAst.stderr - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/parser/should_compile/KindSigs.stderr - testsuite/tests/parser/should_compile/T20452.stderr - testsuite/tests/perf/compiler/Makefile - testsuite/tests/perf/compiler/all.T - testsuite/tests/perf/compiler/genMultiComp.py - testsuite/tests/plugins/plugins09.stdout - testsuite/tests/plugins/plugins10.stdout - testsuite/tests/plugins/plugins11.stdout - testsuite/tests/plugins/static-plugins.stdout - + testsuite/tests/rts/T27131.hs - + testsuite/tests/rts/T27131.stdout - + testsuite/tests/rts/T27131_c.c - testsuite/tests/rts/all.T - testsuite/tests/th/T24111.stdout - + testsuite/tests/th/T27022.hs - + testsuite/tests/th/T27022.stdout - testsuite/tests/th/all.T - testsuite/tests/typecheck/should_compile/subsumption_sort_hole_fits.stderr - testsuite/tests/typecheck/should_fail/T21130.stderr - testsuite/tests/typecheck/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/ghc-toolchain/exe/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Target.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/70b1325e3c101c0fcaabf2d5a84538… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/70b1325e3c101c0fcaabf2d5a84538… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/jeltsch/more-efficient-home-unit-imports-finding] Introduce a cache of home module name providers
by Wolfgang Jeltsch (＠jeltsch) 12 May '26

12 May '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/more-efficient-home-unit-imports-finding at Glasgow Haskell Compiler / GHC Commits: 70b1325e by Wolfgang Jeltsch at 2026-05-12T21:22:32+03:00 Introduce a cache of home module name providers This contribution introduces to the module graph a cache that maps home module names to sets of units providing them and changes the finder to use that cache. This is a performance optimization, especially for multi-home-unit builds. The particular changes are as follows: * In `GHC.Unit.Module.Graph`, `ModuleGraph` is extended with a new field `mg_home_module_name_providers_map`, exposed as `mgHomeModuleNameProvidersMap`. This is a cache that assigns to each home module name the set of IDs of home units that define it. Operations that construct module graphs are updated such that this cache stays synchronized. * In `GHC.Unit.Finder`, `findImportedModule` is changed to pull `mgHomeModuleNameProvidersMap` from `hsc_mod_graph` and pass it to `findImportedModuleNoHsc`, which now does not search home units in arbitrary order but prioritizes those units that the cache mentions as potential providers of the requested module. In addition, this contribution adds variants of the two multi-component compiler performance tests that use 100 units instead of 20, because with just 20 units the benefits from caching of home module name providers are still negligible. The following table shows the total time needed for running both multi-component tests before and after this contribution and with different numbers of units: | # of units | Before | After | |-----------:|-------:|------:| | 20 | 0:12 | 0:12 | | 100 | 0:47 | 0:42 | | 200 | 3:05 | 2:08 | Note that there seems to be a general overhead of 12 seconds that is not attributable to the actual tests, so that the real running times should be 12 seconds smaller than shown above. Resolves #27055. Metric Decrease: MultiComponentModules MultiComponentModulesRecomp Co-authored-by: Matthew Pickering <matthewtpickering(a)gmail.com> Co-authored-by: Fendor <fendor(a)posteo.de> - - - - - 6 changed files: - + changelog.d/more-efficient-home-unit-imports-finding - compiler/GHC/Unit/Finder.hs - compiler/GHC/Unit/Module/Graph.hs - testsuite/tests/perf/compiler/Makefile - testsuite/tests/perf/compiler/all.T - testsuite/tests/perf/compiler/genMultiComp.py Changes: ===================================== changelog.d/more-efficient-home-unit-imports-finding ===================================== @@ -0,0 +1,15 @@ +section: compiler +synopsis: Introduce a cache of home module name providers +issues: #27055 +mrs: !15888 +description: { + This contribution optimizes the algorithm for finding out which home + unit provides the module that a certain import declaration refers + to. The previous approach has been to simply search all home units + in no particular order. This change introduces a cache that allows + for efficiently determining those complete home units that provide a + certain module name and changes the module-finding algorithm such + that it searches these units before the other home units. This leads + to significant performance improvements in situations where there + are lots of home units. +} ===================================== compiler/GHC/Unit/Finder.hs ===================================== @@ -44,6 +44,11 @@ import GHC.Data.OsPath import GHC.Unit.Env import GHC.Unit.Types import GHC.Unit.Module +import GHC.Unit.Module.Graph + ( + HomeModuleNameProvidersMap, + mgHomeModuleNameProvidersMap + ) import GHC.Unit.Home import GHC.Unit.Home.Graph (UnitEnvGraph) import qualified GHC.Unit.Home.Graph as HUG @@ -72,7 +77,8 @@ import GHC.Driver.Config.Finder import GHC.Types.Unique.Set import qualified Data.List as L(sort) import Data.List.NonEmpty ( NonEmpty (..) ) -import qualified Data.Set as Set (toList) +import Data.Set (Set) +import qualified Data.Set as Set (empty, intersection, difference, null, toList) import qualified System.Directory as SD import qualified System.OsPath as OsPath import qualified Data.List.NonEmpty as NE @@ -177,12 +183,13 @@ getDirHash dir = do findImportedModule :: HscEnv -> ModuleName -> PkgQual -> IO FindResult findImportedModule hsc_env mod pkg_qual = - let fc = hsc_FC hsc_env - mhome_unit = hsc_home_unit_maybe hsc_env - dflags = hsc_dflags hsc_env - fopts = initFinderOpts dflags + let fc = hsc_FC hsc_env + mb_home_unit = hsc_home_unit_maybe hsc_env + dflags = hsc_dflags hsc_env + fopts = initFinderOpts dflags in do - findImportedModuleNoHsc fc fopts (hsc_unit_env hsc_env) mhome_unit mod pkg_qual + let home_module_name_providers_map = mgHomeModuleNameProvidersMap (hsc_mod_graph hsc_env) + findImportedModuleNoHsc fc fopts (hsc_unit_env hsc_env) home_module_name_providers_map mb_home_unit mod pkg_qual findImportedModuleWithIsBoot :: HscEnv -> ModuleName -> IsBootInterface -> PkgQual -> IO FindResult findImportedModuleWithIsBoot hsc_env mod is_boot pkg_qual = do @@ -195,55 +202,126 @@ findImportedModuleNoHsc :: FinderCache -> FinderOpts -> UnitEnv + -> HomeModuleNameProvidersMap -> Maybe HomeUnit -> ModuleName -> PkgQual -> IO FindResult -findImportedModuleNoHsc fc fopts ue mhome_unit mod_name mb_pkg = +findImportedModuleNoHsc fc fopts ue home_module_name_providers_map mb_home_unit mod_name mb_pkg = case mb_pkg of NoPkgQual -> unqual_import - ThisPkg uid | (homeUnitId <$> mhome_unit) == Just uid -> home_import + ThisPkg uid | (homeUnitId <$> mb_home_unit) == Just uid -> home_import | Just os <- lookup uid other_fopts -> home_pkg_import (uid, os) - | otherwise -> pprPanic "findImportModule" (ppr mod_name $$ ppr mb_pkg $$ ppr (homeUnitId <$> mhome_unit) $$ ppr uid $$ ppr (map fst all_opts)) + | otherwise -> pprPanic "findImportModule" (ppr mod_name $$ ppr mb_pkg $$ ppr (homeUnitId <$> mb_home_unit) $$ ppr uid $$ ppr (map fst all_opts)) OtherPkg _ -> pkg_import where - all_opts = case mhome_unit of - Nothing -> other_fopts - Just home_unit -> (homeUnitId home_unit, fopts) : other_fopts + mb_home_unit_id :: Maybe UnitId + mb_home_unit_id = homeUnitId <$> mb_home_unit - home_import = case mhome_unit of - Just home_unit -> findHomeModule fc fopts home_unit mod_name - Nothing -> pure $ NoPackage (panic "findImportedModule: no home-unit") + all_opts :: [(UnitId, FinderOpts)] + all_opts = case mb_home_unit_id of + Nothing -> other_fopts + Just home_unit_id -> (home_unit_id, fopts) : other_fopts + home_import :: IO FindResult + home_import = case mb_home_unit of + Just home_unit -> findHomeModule fc fopts home_unit mod_name + Nothing -> pure $ + NoPackage (panic "findImportedModule: no home-unit") + home_pkg_import :: (UnitId, FinderOpts) -> IO FindResult home_pkg_import (uid, opts) - -- If the module is reexported, then look for it as if it was from the perspective - -- of that package which reexports it. - | Just real_mod_name <- lookupUniqMap (finder_reexportedModules opts) mod_name = - findImportedModuleNoHsc fc opts ue (Just $ DefiniteHomeUnit uid Nothing) real_mod_name NoPkgQual - | elementOfUniqSet mod_name (finder_hiddenModules opts) = - return (mkHomeHidden uid) - | otherwise = - findHomePackageModule fc opts uid mod_name - - -- Do not be smart and change this to `foldr orIfNotFound home_import hs` as - -- that is not the same!! home_import is first because we need to look within ourselves - -- first before looking at the packages in order. - any_home_import = foldr1 orIfNotFound (home_import:| map home_pkg_import other_fopts) - - pkg_import = findExposedPackageModule fc fopts units mod_name mb_pkg - - unqual_import = any_home_import - `orIfNotFound` - findExposedPackageModule fc fopts units mod_name NoPkgQual - - units = case mhome_unit of - Nothing -> ue_homeUnitState ue - Just home_unit -> HUG.homeUnitEnv_units $ ue_findHomeUnitEnv (homeUnitId home_unit) ue - hpt_deps :: [UnitId] - hpt_deps = Set.toList (homeUnitDepends units) - other_fopts = map (\uid -> (uid, initFinderOpts (homeUnitEnv_dflags (ue_findHomeUnitEnv uid ue)))) hpt_deps + -- If the module is reexported, then look for it as if it was from the + -- perspective of that package which reexports it. + | Just real_mod_name + <- lookupUniqMap (finder_reexportedModules opts) mod_name + = findImportedModuleNoHsc fc opts ue home_module_name_providers_map + (Just $ DefiniteHomeUnit uid Nothing) + real_mod_name + NoPkgQual + | elementOfUniqSet mod_name (finder_hiddenModules opts) + = return (mkHomeHidden uid) + | otherwise + = findHomePackageModule fc opts uid mod_name + + any_home_import :: IO FindResult + any_home_import = foldr1 orIfNotFound $ + home_import :| map home_pkg_import other_fopts + -- Do not try to be smart and change this to `foldr orIfNotFound home_import + -- (map home_pkg_import other_fopts)`, as that would not be the same. + -- `home_import` is first because we need to first look within the current + -- unit before looking at the other units in order. + + pkg_import :: IO FindResult + pkg_import = findExposedPackageModule fc fopts unit_state mod_name mb_pkg + + unqual_import :: IO FindResult + unqual_import + = any_home_import + `orIfNotFound` + findExposedPackageModule fc fopts unit_state mod_name NoPkgQual + + unit_state :: UnitState + unit_state = case mb_home_unit_id of + Nothing -> ue_homeUnitState ue + Just home_unit_id -> HUG.homeUnitEnv_units $ + ue_findHomeUnitEnv home_unit_id ue + + home_unit_deps :: Set UnitId + home_unit_deps = homeUnitDepends unit_state + + ranked_home_unit_deps :: [UnitId] + ranked_home_unit_deps = rankedHomeUnitDeps home_module_name_providers_map + mod_name + home_unit_deps + + other_fopts :: [(UnitId, FinderOpts)] + other_fopts + = [ + (uid, opts) | + uid <- ranked_home_unit_deps, + let opts = initFinderOpts $ + homeUnitEnv_dflags (ue_findHomeUnitEnv uid ue) + ] + +-- | Yields the unit IDs from the given set as a list with those that refer to +-- providers of the given home module name coming first. This is to prioritize +-- such providers during module finding. +rankedHomeUnitDeps :: HomeModuleNameProvidersMap + -> ModuleName + -> Set UnitId + -> [UnitId] +rankedHomeUnitDeps _ _ home_unit_deps | Set.null home_unit_deps + = [] +-- The special handling of the situation where the dependency set is empty does +-- not change the result, but it avoids triggering evaluation of the module +-- graph. This is particularly important in one-shot mode, where the module +-- graph is not needed. Computing it nevertheless would result in a, possibly +-- dramatic, increase of memory usage. Worse, GHC would erroneously look for the +-- sources of modules, which would, for example, cause test `boot1` to fail with +-- the following error message: +-- +-- B.hs:3:1: error: [GHC-87110] +-- Could not find module ‘A’. +-- Use -v to see a list of the files searched for. +-- | +-- 3 | import {-# source #-} A +-- | ^^^^^^^^^^^^^^^^^^^^^^^ +rankedHomeUnitDeps home_module_name_providers_map mod_name home_unit_deps + = Set.toList cached_deps ++ Set.toList uncached_deps + where + + cached_providers :: Set UnitId + cached_providers = lookupWithDefaultUniqMap home_module_name_providers_map + Set.empty + mod_name + + cached_deps :: Set UnitId + cached_deps = Set.intersection home_unit_deps cached_providers + + uncached_deps :: Set UnitId + uncached_deps = Set.difference home_unit_deps cached_providers -- | Locate a plugin module requested by the user, for a compiler -- plugin. This consults the same set of exposed packages as @@ -261,15 +339,15 @@ findPluginModule :: HscEnv -> ModuleName -> IO FindResult findPluginModule hsc_env mod_name = do let fc = hsc_FC hsc_env let units = hsc_units hsc_env - let mhome_unit = hsc_home_unit_maybe hsc_env - findPluginModuleNoHsc fc (initFinderOpts (hsc_dflags hsc_env)) units mhome_unit mod_name + let mb_home_unit = hsc_home_unit_maybe hsc_env + findPluginModuleNoHsc fc (initFinderOpts (hsc_dflags hsc_env)) units mb_home_unit mod_name -- | A version of findExactModule which takes the exact parts of the HscEnv it needs -- directly. findExactModuleNoHsc :: FinderCache -> FinderOpts -> UnitEnvGraph FinderOpts -> UnitState -> Maybe HomeUnit -> InstalledModule -> IsBootInterface -> IO InstalledFindResult -findExactModuleNoHsc fc fopts other_fopts unit_state mhome_unit mod is_boot = do - res <- case mhome_unit of +findExactModuleNoHsc fc fopts other_fopts unit_state mb_home_unit mod is_boot = do + res <- case mb_home_unit of Just home_unit | isHomeInstalledModule home_unit mod -> findInstalledHomeModule fc fopts (homeUnitId home_unit) (moduleName mod) ===================================== compiler/GHC/Unit/Module/Graph.hs ===================================== @@ -67,6 +67,8 @@ module GHC.Unit.Module.Graph , mgLookupModule , mgLookupModuleName , mgHasHoles + , HomeModuleNameProvidersMap + , mgHomeModuleNameProvidersMap , showModMsg -- ** Reachability queries @@ -156,10 +158,12 @@ import GHC.Unit.Module.ModIface import GHC.Utils.Misc ( partitionWith ) import System.FilePath +import Data.Set (Set) +import qualified Data.Set as Set +import Data.Map (Map) import qualified Data.Map as Map import GHC.Types.Unique.DSet -import qualified Data.Set as Set -import Data.Set (Set) +import GHC.Types.Unique.Map (UniqMap, emptyUniqMap, listToUniqMap_C) import GHC.Unit.Module import GHC.Unit.Module.ModNodeKey import GHC.Unit.Module.Stage @@ -202,14 +206,32 @@ data ModuleGraph = ModuleGraph -- Cached computation, whether any of the ModuleGraphNode are isHoleModule, -- This is only used for a hack in GHC.Iface.Load to do with backpack, please -- remove this at the earliest opportunity. + , mg_home_module_name_providers_map :: HomeModuleNameProvidersMap + -- ^ For each module name, which home units provide it. } +type HomeModuleNameProvidersMap = UniqMap ModuleName (Set UnitId) + +mkHomeModuleNameProvidersMap :: [ModuleGraphNode] -> HomeModuleNameProvidersMap +mkHomeModuleNameProvidersMap nodes + = listToUniqMap_C Set.union $ + [ + (moduleName, Set.singleton unitID) | + ModuleNode _ moduleNodeInfo <- nodes, + let moduleName = moduleNodeInfoModuleName moduleNodeInfo, + let unitID = moduleNodeInfoUnitId moduleNodeInfo + ] + +mgHomeModuleNameProvidersMap :: ModuleGraph -> HomeModuleNameProvidersMap +mgHomeModuleNameProvidersMap = mg_home_module_name_providers_map + -- | Why do we ever need to construct empty graphs? Is it because of one shot mode? emptyMG :: ModuleGraph emptyMG = ModuleGraph [] (graphReachability emptyGraph, const Nothing) (graphReachability emptyGraph, const Nothing) (graphReachability emptyGraph, const Nothing) False + emptyUniqMap -- | Construct a module graph. This function should be the only entry point for -- building a 'ModuleGraph', since it is supposed to be built once and never modified. @@ -308,7 +330,7 @@ checkModuleGraph ModuleGraph{..} = where duplicate_errs = rights (Map.elems node_types) - node_types :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) + node_types :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) node_types = Map.fromListWithKey go [ (mkNodeKey n, Left (moduleNodeType n)) | n <- mg_mss ] where -- Multiple nodes with the same key are not allowed. @@ -319,7 +341,7 @@ checkModuleGraph ModuleGraph{..} = -- | Check that all dependencies in the graph are present in the node_types map. -- This is a helper function used by checkModuleGraph. -checkAllDependenciesInGraph :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) +checkAllDependenciesInGraph :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) -> ModuleGraphNode -> Maybe ModuleGraphInvariantError checkAllDependenciesInGraph node_types node = @@ -334,7 +356,7 @@ checkAllDependenciesInGraph node_types node = -- | Check if for the fixed module node invariant: -- -- Fixed nodes can only depend on other fixed nodes. -checkFixedModuleInvariant :: Map.Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) +checkFixedModuleInvariant :: Map NodeKey (Either ModuleNodeType ModuleGraphInvariantError) -> ModuleGraphNode -> Maybe ModuleGraphInvariantError checkFixedModuleInvariant node_types node = case node of @@ -484,13 +506,17 @@ isEmptyMG = null . mg_mss -- To preserve invariants, 'f' can't change the isBoot status. mapMG :: (ModSummary -> ModSummary) -> ModuleGraph -> ModuleGraph mapMG f mg@ModuleGraph{..} = mg - { mg_mss = flip fmap mg_mss $ \case - InstantiationNode uid iuid -> InstantiationNode uid iuid - LinkNode uid nks -> LinkNode uid nks - ModuleNode deps (ModuleNodeFixed key loc) -> ModuleNode deps (ModuleNodeFixed key loc) - ModuleNode deps (ModuleNodeCompile ms) -> ModuleNode deps (ModuleNodeCompile (f ms)) - UnitNode deps uid -> UnitNode deps uid + { mg_mss = new_mss + , mg_home_module_name_providers_map = mkHomeModuleNameProvidersMap new_mss } + where + new_mss = + flip fmap mg_mss $ \case + InstantiationNode uid iuid -> InstantiationNode uid iuid + LinkNode uid nks -> LinkNode uid nks + ModuleNode deps (ModuleNodeFixed key loc) -> ModuleNode deps (ModuleNodeFixed key loc) + ModuleNode deps (ModuleNodeCompile ms) -> ModuleNode deps (ModuleNodeCompile (f ms)) + UnitNode deps uid -> UnitNode deps uid -- | Map a function 'f' over all the 'ModSummaries', in 'IO'. -- To preserve invariants, 'f' can't change the isBoot status. @@ -856,7 +882,7 @@ moduleNodeInfoBootString mn@(ModuleNodeFixed {}) = -- described in the export list haddocks. -------------------------------------------------------------------------------- -newtype NodeMap a = NodeMap { unNodeMap :: Map.Map NodeKey a } +newtype NodeMap a = NodeMap { unNodeMap :: Map NodeKey a } deriving (Functor, Traversable, Foldable) -- | Transitive dependencies, including SOURCE edges @@ -932,7 +958,7 @@ moduleGraphNodesZero summaries = lookup_key :: ZeroScopeKey -> Maybe Int lookup_key = fmap zeroSummaryNodeKey . lookup_node - node_map :: Map.Map ZeroScopeKey ZeroSummaryNode + node_map :: Map ZeroScopeKey ZeroSummaryNode node_map = Map.fromList [ (s, node) | node <- nodes @@ -1031,7 +1057,7 @@ moduleGraphNodesStages summaries = lookup_key :: (NodeKey, ModuleStage) -> Maybe Int lookup_key = fmap stageSummaryNodeKey . lookup_node - node_map :: Map.Map (NodeKey, ModuleStage) StageSummaryNode + node_map :: Map (NodeKey, ModuleStage) StageSummaryNode node_map = Map.fromList [ (s, node) | node <- nodes @@ -1049,10 +1075,13 @@ moduleGraphNodesStages summaries = extendMG :: ModuleGraph -> ModuleGraphNode -> ModuleGraph extendMG ModuleGraph{..} node = ModuleGraph - { mg_mss = node : mg_mss - , mg_graph = mkTransDeps (node : mg_mss) - , mg_loop_graph = mkTransLoopDeps (node : mg_mss) - , mg_zero_graph = mkTransZeroDeps (node : mg_mss) + { mg_mss = new_mss + , mg_graph = mkTransDeps new_mss + , mg_loop_graph = mkTransLoopDeps new_mss + , mg_zero_graph = mkTransZeroDeps new_mss , mg_has_holes = mg_has_holes || maybe False isHsigFile (moduleNodeInfoHscSource =<< mgNodeIsModule node) + , mg_home_module_name_providers_map = mkHomeModuleNameProvidersMap new_mss } + where + new_mss = node : mg_mss ===================================== testsuite/tests/perf/compiler/Makefile ===================================== @@ -31,7 +31,11 @@ MultiModulesDefsWithCore: ./genMultiLayerModulesCore MultiComponentModulesRecomp: - '$(PYTHON)' genMultiComp.py + '$(PYTHON)' genMultiComp.py 20 20 + TEST_HC='$(TEST_HC)' TEST_HC_OPTS='$(TEST_HC_OPTS)' ./run + +MultiComponentModulesRecomp100: + '$(PYTHON)' genMultiComp.py 100 20 TEST_HC='$(TEST_HC)' TEST_HC_OPTS='$(TEST_HC_OPTS)' ./run MultiLayerModulesTH_Make_Prep: ===================================== testsuite/tests/perf/compiler/all.T ===================================== @@ -507,13 +507,31 @@ test('MultiComponentModulesRecomp', test('MultiComponentModules', [ collect_compiler_runtime(2), - pre_cmd('$PYTHON ./genMultiComp.py'), + pre_cmd('$PYTHON ./genMultiComp.py 20 20'), extra_files(['genMultiComp.py']), compile_timeout_multiplier(5) ], multiunit_compile, [['unitp%d' % n for n in range(20)], '-fno-code -fwrite-interface -v0']) +test('MultiComponentModulesRecomp100', + [ collect_compiler_runtime(2), + pre_cmd('$MAKE -s --no-print-directory MultiComponentModulesRecomp100'), + extra_files(['genMultiComp.py']), + compile_timeout_multiplier(5) + ], + multiunit_compile, + [['unitp%d' % n for n in range(100)], '-fno-code -fwrite-interface -v0']) + +test('MultiComponentModules100', + [ collect_compiler_runtime(2), + pre_cmd('$PYTHON ./genMultiComp.py 100 20'), + extra_files(['genMultiComp.py']), + compile_timeout_multiplier(5) + ], + multiunit_compile, + [['unitp%d' % n for n in range(100)], '-fno-code -fwrite-interface -v0']) + test('ManyConstructors', [ collect_compiler_stats('bytes allocated',2), pre_cmd('./genManyConstructors'), ===================================== testsuite/tests/perf/compiler/genMultiComp.py ===================================== @@ -7,11 +7,12 @@ # * A number of modules names Mod_<pid>_<mid>, each module imports all the top # modules beneath it, and all the modules in the current unit beneath it. +import sys import os import stat -modules_per = 20 -packages = 20 +packages = int(sys.argv[1]) +modules_per = int(sys.argv[2]) total = modules_per * packages def unit_dir(p): View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/70b1325e3c101c0fcaabf2d5a84538e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/70b1325e3c101c0fcaabf2d5a84538e… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/jeltsch/more-efficient-home-unit-imports-finding] Add changelog entry
by Wolfgang Jeltsch (＠jeltsch) 12 May '26

12 May '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/more-efficient-home-unit-imports-finding at Glasgow Haskell Compiler / GHC Commits: 482135cc by Wolfgang Jeltsch at 2026-05-12T21:16:35+03:00 Add changelog entry - - - - - 1 changed file: - + changelog.d/more-efficient-home-unit-imports-finding Changes: ===================================== changelog.d/more-efficient-home-unit-imports-finding ===================================== @@ -0,0 +1,15 @@ +section: compiler +synopsis: Introduce a cache of home module name providers +issues: #27055 +mrs: !15888 +description: { + This contribution optimizes the algorithm for finding out which home + unit provides the module that a certain import declaration refers + to. The previous approach has been to simply search all home units + in no particular order. This change introduces a cache that allows + for efficiently determining those complete home units that provide a + certain module name and changes the module-finding algorithm such + that it searches these units before the other home units. This leads + to significant performance improvements in situations where there + are lots of home units. +} View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/482135cc1cc94e9639984a2b0f3d7f6… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/482135cc1cc94e9639984a2b0f3d7f6… You're receiving this email because of your account on gitlab.haskell.org.

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