-
c42ed66a
by Martijn Bastiaan at 2026-10-24T16:00:42+02:00
Add single-threaded test for #27526 + #27123
Issue #27526 is a duplicate of #27123, which has already been fixed in
HEAD. The proposed patch in the former carries a "nicer" regression test
in that it doesn't rely on multi-threading to trigger.
Closes #27526
-
7f73f515
by Simon Peyton Jones at 2026-10-24T17:29:19-04:00
Refactor QuickLook a bit
This MR simply refactors QuickLook a bit. In particular, it
simplifies `tcApp`, and moves shared code into `finishApp`.
It also adds `Note [QuickLook: arguments before result]`
responding to #26599.
There should be no user-visible changes, except perhaps in error messages,
which improve marginally.
For some reason T24984 compiles 8% faster. I'll take the win!
Metric Decrease:
T24984
-
a4a3a964
by Alan Zimmerman at 2026-10-24T17:30:03-04:00
EPA: Use AnnList for XClosedTypeFamily
We now have TTG annotations for FamilyInfo.
Make use of it to store the AnnList annotations for a closed type
family.
-
953e4c7f
by sheaf at 2026-10-26T18:19:10-04:00
Rework LogQueue to be a proper queue
Now 'LogQueue' uses a 'TQueue' with a separate 'TVar' to indicate
whether the log queue is finished logging, instead of the previous weird
data representation using a reverse-order '[Maybe Msg]' with 'Nothing'
denoting the end of the queue.
-
ec29c5fa
by Rodrigo Mesquita at 2026-10-26T18:19:10-04:00
Refactor GHC.Driver.MakeAction
Pull out of 'runParPipelines' the logic for creating a 'MakeEnv' ready
to be used by multiple threads, as that will be useful for downsweep as
well (which doesn't fit the 'runPipelines' flow), rather than being just
for upsweep.
The code is moved and re-structured to match the export list, simplify
the sequentiality checks previously both in 'runPipelines' and
'runAllPipelines', which were weirdly similar and confusing; into the
two part step where we need these checks: (1) to construct the MakeEnv,
(2) to run the MakeActions in parallel. These two steps are separate and
used to be too mixed up.
Some additional little simplifications or clean ups here and there.
-
3fb22073
by Rodrigo Mesquita at 2026-10-26T18:19:11-04:00
Refactor GHC.Driver.Downsweep in preparation for parallel downsweep
Pure refactor to improve the code to facilitate implementing parallel
downsweep in the next commit.
This commit puts a MakeEnv into the DownsweepEnv, gives the fields
proper names and uses RecordWildcards to simplify, rather than passing
around all diagnostic wrappers, driver-message-things and using 10s of
positional fields.
No behavior changes here!
-
52f385a7
by sheaf at 2026-10-26T18:19:11-04:00
Driver: enableCodeGenForTH in load', not downsweep
enableCodeGenForTH modifies the module graph for planning, creating
fresh temporary paths. So it should only be run when we are about to
execute a build plan (e.g. in load'), so that consumers that want to
know facts about the module graph don't go looking for files that don't
exist yet (in particular 'haddock --no-compilation').
-
82402d14
by sheaf at 2026-10-26T18:19:11-04:00
2-phase Cache/Search Finder monad
This commit restructures the finder abstraction by introducing the
'FinderM' monad, which splits module lookup operations into two phases:
- a cache-only phase, performing no filesystem access,
- from the first cache miss onwards, a search action which may access
the filesystem.
This allows consumers to distinguish between quick cached results versus
more expensive filesystem search operations.
-
5c302b40
by sheaf at 2026-10-26T18:19:11-04:00
Separate Home/External finder caches
The caches for home modules and modules from external units have
different lifetimes, needing to be invalidated at different points.
This commit moves the cache for modules from external units into the
'UnitState' type, which keeps the cache correct whenever package flags
or package databases change (setSessionDynFlags, :set -package ...,
Backpack's addUnit).
This also makes it easier to clear the cache of home modules, as they
are now stored separately (obviating the 'isUnitEnvInstalledModule'
check we used to perform).
-
605fbb96
by sheaf at 2026-10-26T18:19:11-04:00
Add known home modules to the finder cache
The finder looks in the file system for the on-disk source that
corresponds to a Haskell module name. There are two kinds of modules
where we need to bypass this search:
- a file passed directly in the command line, which may not be in any
search path and whose module name may differ from the file name;
- Backpack signatures and modules, which do not exist as files at all.
This commit handles these two situations by adding an immutable
'KnownHomeModules' in the finder cache, which is always consulted first
before doing any search.
This removes the ad-hoc imperative logic which relied on mutating the
finder cache at careful points.
'setModuleGraph' now also takes the known home modules, so that the
module graph and the known home modules are always set consistently.
See Note [Known home modules] in GHC.Unit.Finder.Types.
-
82718f44
by sheaf at 2026-10-26T18:19:11-04:00
Make 'UnresolvedImport' into a suitable cache key
The goal of this commit is to make 'UnresolvedImport' suitable for use
as a cache key. Specifically, during downsweep we want to be able to
cache module resolution queries. We want to do this using some kind of
map, e.g. (roughly speaking):
Map UnresolvedImport ResolvedImport
For this to work, 'UnresolvedImport' must contain **precisely** the
input data to each resolution computation. In other words:
1. If something changes that materially affects resolution, it must
be stored in the cache key.
2. If changing some input does not materially affect the outcome,
then it must not be stored in the cache key.
To satisfy (1), we change 'UnitNode' to also keep track of the home
unit in whose unit state the unit's dependencies were looked up.
For (2), 'ImportResolution' now stores a 'ModuleLookupScope' instead of an
'UnresolvedImportOrigin'. Plugin imports are expressed with a new
'LookupPlugin' scope. The source location of an import, which is
immaterial to the resolution, is stored out of band outside
'UnresolvedImport', in 'ModSummary'.
-
d4635c7c
by sheaf at 2026-10-26T18:19:11-04:00
Add GHC.Data.Dependent
This commit adds a minimal implementation of dependent sums
('Some', 'DSum') and dependent maps ('DMap').
The implementation is not entirely performance optimal, as there are a
few extraneous allocations compared to the full-blown implementation in
the 'dependent-map' package. For our use case (caching downsweep
computations), this does not matter much.
See GHC.Data.Dependent.
-
6759533e
by sheaf at 2026-10-26T18:19:11-04:00
Driver: structured concurrent worker abstraction
This commit introduces a structured concurrency framework in the style
of the 'ki' library: a collection of threads within a scope.
We implement two kinds of concurrent workers on top of this framework:
- Independent workers cannot wait for one another at all. The only
scheduling operation is to wait for quiescence.
- Coordinating workers declare an STM readiness condition (waiting on
other workers to complete) which gates their start.
See Note [Deterministic concurrent workers] in GHC.Driver.Concurrency.
This commit ports upsweep to this new framework, with downsweep being
left as subsequent work.
Further changes along the way:
- Refactoring of how concurrency is acquired to avoid the footgun of
trying to use a no-op 'AbstractSem' as a lock in the serial case.
- The "re-run with -j1" logic for semaphore opening errors no longer
triggers on late semaphore failures (part-way through a lengthy
computation).
- Logger threads are properly cleaned up on exception, with each
concurrent worker's log queue and local TmpFs properly bracketed.
- The 'GhcMessage -> AnyGhcDiagnostic' and 'Maybe Messager'
arguments of 'depanalE', 'depanalPartial' and 'downsweep', which
were all dead in practice, have been dropped.
- Concurrent logging has been completely overhauled. Each worker has
its own log queue. Workers whose logs are printed as we go are
spawned in the order in which their logs must be printed, now using
a TQueue instead of the old complicated LogQueueQueue mechanism.
'logThread' is replaced by 'withLogPrinter', which runs the thread
that prints the log queues within a concurrent worker scope.
These changes allow us to fix issues with the exception handling:
we now always flush remaining log queues before exiting (even when
the action throws an exception), and exceptions that arise while
printing are properly rethrown. This fixes #28009.
-
38a99006
by sheaf at 2026-10-26T18:19:11-04:00
Rule-based deterministic concurrent downsweep
This commit rewrites downsweep as a single query-answering rule
(see 'DownsweepRule') that can be executed by concurrent worker threads.
The design allows every expensive operation (preprocessing files with CPP,
parsing headers, reading interfaces) to be performed concurrently
according to the -j<N>/-jsem flags.
See Note [Rules-based downsweep] in GHC.Driver.Downsweep.
The rules are run by "GHC.Driver.Concurrency.runRules" in a demand-driven
way: each worker can demand other workers to run, but never wait on
another worker. Every piece of work is done at most once.
Fixes #27514
Memory usage can increase due to doing more work concurrently:
-------------------------
Metric Increase:
MultiComponentModulesRecomp
MultiComponentModulesRecomp100
mhu-perf
-------------------------
-
9fa7b7be
by sheaf at 2026-10-26T18:19:11-04:00
Acquire/release semaphore tokens more readily
This commit reworks GHC.Driver.MakeSem to use the scoped worker
abstraction of GHC.Utils.Concurrent.Scope. This allows us to get rid of
a lot of the tricky logic in GHC.Driver.MakeSem involving manual
exception handling, thread spawning and lifetime management, etc.
The main user-visible change is that token acquisition is no longer
rate limited (due to a bug, there previously was a 1s rate limit on
acquisition of semaphore tokens), with the release debounce period
shortened from 1s to 10ms.
Other changes:
- With -jsem, the number of capabilities is now capped at the number
of processors, bringing it in line with the -jN behaviour.
- Pending jobs whose wait for a token is interrupted by an exception
are now withdrawn from the jobserver, instead of acquiring a token
that it hung onto without doing useful work.
Fixes #27763
-
c83c6733
by Alan Zimmerman at 2026-10-26T18:19:55-04:00
EPA: Update AnnClsInstDecl to contain AnnList
It was already separately tracking the '{', '}' and leading ';' values.
This aligns it with layout-introducing parser productions ('vocurly'),
so the layout processing can be handled uniformly
-
ac870ad5
by Simon Jakobi at 2026-10-28T04:40:42-04:00
X86 NCG: use 32-bit POPCNT for sub-word popcounts
A 32-bit write zero-extends the result to the full register, so we
don't need to emit additional code for this.
We also skip emitting zero-extension instructions for the argument
when it is already visibly zero-extended.
For the byte-wise popcount loop from #24813, this shrinks the popcount
sequence from 5 instructions to 3.
Assisted-by: Claude Fable 5.1
-
53087373
by Facundo Domínguez at 2026-10-28T04:41:32-04:00
Use a ShortByteString in Serialized instead of [Word8]
This makes the in-memory representation 40x more compact for all values
stored in annotations.
A test is added to measure the representation size of annotations
specified in the compiler input.
The GHC API is modified. All functions that previously handled annotations
in [Word8] form now use ShortByteString. The following definitions have
modified types:
* GHC.findGlobalAnns
* GHC.Tc.Gen.Splice.getAnnotationsByTypeRep
* GHC.Core.Opt.Monad.getAnnotations
* GHC.Core.Opt.Monad.getFirstAnnotations
* GHC.Types.Annotations.deserializeAnns
* GHC.Types.Annotations.findAnns
* GHC.Types.Annotations.findAnnsByTypeRep
* GHC.Serialized.Serialized
* GHC.Serialized.toSerialized
* GHC.Serialized.fromSerialized
* GHC.Serialized.serializeWithData
* GHC.Serialized.deserializeWithData
* GHCi.Message.ReifyAnnotations
Fixes #28002.
-
cc533b66
by Sasha Bogicevic at 2026-10-31T09:18:15-04:00
Don't report -XStrict-generated bangs under -Wredundant-bang-patterns
The -XStrict flag causes the desugarer to insert bang patterns.
These are not user-written, so -Wredundant-bang-patterns must not
report them.
To achieve this, the desugarer now tracks whether it is desugaring
compiler-generated code (similar to the typechecker's 'tcl_in_gen_code').
Bangs inserted by -XStrict are given generated spans, which suppresses
the "redundant bang" warnings without otherwise affecting pattern-match
warnings.
Fixes #27323
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13d38047
by Luite Stegeman at 2026-10-31T09:19:11-04:00
rts: tombstone Weak# copies that lose an evacuation race (#23160)
Mark the losing copy of a Weak# during an evacuation race in parallel
GC with stg_DEAD_WEAK_info. This ensures that the nonmoving GC
doesn't follow dangling pointers, leading to crashes.
Fixes #23160
-
63347328
by Zubin Duggal at 2026-10-31T09:19:52-04:00
ghci: Drop GHCi's exception context when rethrowing in ghc -e
Fixes #27847.
-
a85fef3f
by Zubin Duggal at 2026-10-31T09:19:52-04:00
base: Preserve exception context in modifyIOError
Fixes #27851.
CLC proposal: https://github.com/haskell/core-libraries-committee/issues/446
-
1d60b591
by Zubin Duggal at 2026-10-31T09:19:52-04:00
base: Preserve exception context in mapException
Fixes #27851.
CLC proposal: https://github.com/haskell/core-libraries-committee/issues/446
-
3c029a1b
by Zubin Duggal at 2026-10-31T09:19:52-04:00
base: Preserve exception context when rethrowing exceptions in Handle reads
Fixes #27875.
CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447
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ab2b317a
by Zubin Duggal at 2026-10-31T09:19:52-04:00
base: Preserve exception context when rethrowing exceptions in hClose
Fixes #27875.
CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447
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f5abf277
by Zubin Duggal at 2026-10-31T09:19:52-04:00
base: Preserve exception context when rethrowing exceptions in Windows openFile
Fixes #27875.
CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447
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d842c672
by Zubin Duggal at 2026-10-31T09:19:52-04:00
base: Preserve exception context when rethrowing exceptions in executablePath
Fixes #27875.
CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447
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c5a8bb9f
by Simon Peyton Jones at 2026-10-31T09:20:34-04:00
Simplify a tc-trace which could crash the compiler
The trace formatted an error message, which prematurely
read the ExpType in a FunResCtxt.
Solution: don't put call the error message formatting
when tc-tracing.
-
ab49b1d2
by Simon Peyton Jones at 2026-10-31T09:20:34-04:00
Tiny comment change to uniqAway
-
6efe4ba3
by Simon Peyton Jones at 2026-10-31T09:20:34-04:00
Make niFixSubst idempotent
I discovered (when fixing #27994) that `niFixSubst` didn't actually
generate an idempotent subsitution despite its claims. It could
return a substitution that mentions domain variables on in its range,
when those variables are hidden inside the kind of a type variable
occurrence. As a result it can generate ill-kinded types. Boo!
The fix is simple, and uses deep substitution.
See Note [Finding the substitution fixpoint]
I don't think it actually /caused/ any bugs, so there is no
regression test.
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3b60ae7e
by Simon Peyton Jones at 2026-10-31T09:20:34-04:00
Fix a nasty bug in fundeps
This MR fixes #27994, which turned out to be very tricky.
See Note [Exploiting closed type famililes], especially (CF7). I was
ending up with TyVars (not TcTyVars) in the solver, because the
substitution computed in `getRelevantBranches` mixed the two.
The code was just too clever. I ended up simplifying it quite a bit.
For /closed/ families we no longer call `trimQtvs` (was `trim_qtvs`).
Open families still do use `trimQtvs`. See Note [trimQTvs]
This patch also fixes one other buglet in the same code.
* Over-saturated type families were being mis-handled.
See the new use of `saturatedFamApp_maybe`.
-
e4610f2d
by Facundo Domínguez at 2026-10-31T09:21:24-04:00
Have haddock --incremental look for the module in -this-unit-id
-
bc6c0db6
by sheaf at 2026-10-31T09:22:20-04:00
mightBeFunTy: hotfix for #27979
ce01ccb6 refactored 'GHC.Types.RepType.mightBeFunTy' to look through
unary classes. That change introduced the helper function 'unwrap_type'
which was supposed to always return an unwrapped type, but its fallback
equation mistakenly returned the original type. This caused the
subsequent 'tyConAppTyCon_maybe' to fail in cases where it should
succeed (e.g. looking through foralls).
In this commit, we move all the unary class unwrapping logic into
'unwrapType' where it belonged from the start, and update the
documentation of 'unwrapType' to better explain what it should be used
for (#26695).
Fixes #27979 #26695
-------------------------
Metric Increase:
T5642
-------------------------
-
233cce46
by Alan Zimmerman at 2026-10-31T09:23:01-04:00
EPA: Tidy up ExactPrint.markAnnListA'
It takes an action which can modify the AnnList, but this
is never used. So remove it.
-
3594a908
by Sylvain Henry at 2026-10-31T09:23:51-04:00
gitmodules: ignore dirty libffi-clib submodule (#26785)
`./boot` runs autoreconf in libraries/libffi-clib, which leaves
`configure~` behind and rewrites the tracked `aclocal.m4` whenever the
local automake version differs from the one that generated it. Every
checkout then looks dirty. Ignore working-tree changes in the submodule
(`ignore = dirty`); a changed submodule commit is still reported.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
-
341223c0
by Rodrigo Mesquita at 2026-10-31T09:24:33-04:00
refactor: Keep the interactive Ids directly rather than Name
Removes things like
names <- map idName ids
map (\i -> let id = find (\x -> i==idName x) names) idso
and is more straightforward because there's less state going around (no
more updating HscEnv as an output)
It also kills `printTypeOfNames` completely, since now we just have the
Ids. No longer `lookupName` names to get back the ids...
```
printTypeOfName :: GHC.GhcMonad m => Name -> m ()
printTypeOfName n
= do maybe_tything <- GHC.lookupName n
case maybe_tything of
Nothing -> return ()
Just thing -> printTyThing thing
```
now is just `printTyThing . AnId`
Also:
```diff
- tythings <- catMaybes `liftM` mapM GHC.lookupName namesSorted
- docs <- mapM pprTypeAndContents [i | AnId i <- tythings]
+ docs <- mapM pprTypeAndContents idsSorted
```
(and yes, in ExecBreaks there are only Ids, no TyThings, bc they are
only constructed by the interpreter execution which can only bind ids.
for TyThings use runDecls which doesn't return execBreaks.)
There's some care to be had to make sure we use the "most refined" Ids,
whereas when using `Name`s we'd always fetch the most refined Id from
scratch.
Fixes #28052
-
df3558b6
by Apoorv Ingle at 2026-11-02T11:54:55-06:00
Work on #27156
- Add `RebindableSyntaxTable` to store function/operator names while renaming in the XBlah fields
- Expand the following expressions right before typechecking instead of in the renamer
* OverloadedLabel
* RecordDotSyntax: HsGetField and HsProjection
* ExplicitList
* RecordUpd
* HsIf
* HsDo (Vanilla cases)
-
4604dfea
by Apoorv Ingle at 2026-11-02T11:54:55-06:00
make a new ReSynBinds to store the module name
-
0ff6e353
by Apoorv Ingle at 2026-11-02T11:54:55-06:00
add ReSynBindsE, ReSynBindsRn and ReSynBindsTc
-
d1a01e4c
by Apoorv Ingle at 2026-11-02T11:54:55-06:00
add reSynBindsE in GHC.Essentials. Remove ReSynBindsTc as we should not need it. Add a tcExpand stub for ReSynBindsRn that should expand to the appropriate expression