GitLab

Brandon Chinn pushed to branch wip/T26961 at Glasgow Haskell Compiler / GHC

Commits:

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@gmail.com>
Co-authored-by: Fendor <fendor@posteo.de>

38b76b2f

by Cheng Shao at 2026-05-13T17:48:48-04:00

testsuite: mark T22159 as fragile

This patch marks T22159 as fragile on Windows for issue described in #27248.
Before we get to the bottom of those failures, this unblocks newer
Windows runners.

50188615

by Ian Duncan at 2026-05-14T13:45:07+02:00

AArch64: use ASR not LSR for MO_U_Shr at W8/W16

The unsigned right shift (MO_U_Shr) for sub-word widths (W8, W16)
with a variable shift amount was emitting ASR (arithmetic/signed shift
right) after zero-extending with UXTB/UXTH. This should be LSR
(logical/unsigned shift right). After zero-extension the upper bits
happen to be 0 so ASR produces the same result, but it is semantically
wrong and would break if the zero-extension were ever optimized away.
Includes assembly output test (grep for lsr) and runtime test
verifying unsigned right shift of Word8 and Word16 values.

28666fbf

by Vladislav Zavialov at 2026-05-19T12:44:05-04:00

Add type families: Tuple, Constraints, Tuple#, Sum# (#27179)

These type families map tuples of types to the corresponding Tuple<N>,
Tuple<N>#, CTuple<N>, and Sum<N># types. Some examples at N=2:

	Tuple (Int, Bool)          = Tuple2 Int Bool
	Constraints (Show a, Eq a) = CTuple2 (Show a) (Eq a)
	Tuple# (Int#, Float#)      = Tuple2# Int# Float#
	Sum# (Int#, Float#)        = Sum2# Int# Float#

See GHC Proposal #145 "Non-punning list and tuple syntax".

To make the Sum# instance at N=64 possible, this patch also introduces
the Sum64# constructor declaration and bumps mAX_SUM_SIZE from 63 to 64.

Metric Increase:
    ghc_experimental_dir

41c2448b

by Wen Kokke at 2026-05-19T12:44:53-04:00

rts: Add IPE event class for -l

This commit adds a new IPE event class to the -l RTS flag.
Previously, IPE events were enabled unconditionally.
However, the IPE events can easily grow to hundreds or thousands of megabytes.
With the new event class you can pass, e.g., -l-I to disable IPE events.

62536551
by Wen Kokke at 2026-05-19T12:44:53-04:00
```
ghc-internal: Add TraceFlags.traceIPE
```
e45312d1
by Wen Kokke at 2026-05-19T12:44:53-04:00
```
testsuite: Add test for TraceFlags.traceIpe
```
4768d9aa
by Wen Kokke at 2026-05-19T12:44:53-04:00
```
ghc-internal: Add DebugFlags.ipe
```
bc1b5c69
by Wen Kokke at 2026-05-19T12:44:53-04:00
```
testsuite: Add test for DebugFlags.ipe
```

0da1543f

by Duncan Coutts at 2026-05-19T12:45:37-04:00

Document removal of the signal-based interval timer

Update mentions within the RTS section of the users guide.

Add a changelog entry.

b2911514
by Duncan Coutts at 2026-05-19T12:45:37-04:00
```
Fix section for an recent changelog entry
```

d6d76a7a

by David Eichmann at 2026-05-19T12:46:19-04:00

ghc-toolchain: implement llvm program versioning logic

2dd36fa3

by Wolfgang Jeltsch at 2026-05-20T04:49:52-04:00

Turn `Trustworthy` into `Safe` in `base` where possible

f4399dd1
by Wolfgang Jeltsch at 2026-05-20T04:50:37-04:00
```
Make the current `base` buildable with GHC 10.0
```

1a7de232

by Duncan Coutts at 2026-05-20T12:26:25-04:00

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.

286f1adf

by fendor at 2026-05-20T12:27:09-04:00

Fix regression T27202: `:load` and `:add` work in GHCi

To fix the regression there are conceptually two major things that we
fix:

* We don't remove the `importDirs` from `interactive-session`
* When `:add`ing a module, we don't try to find them via PackageImports
    * The PackageImport is wrong as we can't know the package-name at
      this stage in ghc/UI.hs

What does it mean to not remove the `importDirs` from
`interactive-session`?
It means that, given some initial `DynFlags`, we will use those
`importDirs` in `interactive-session`.

The initial `DynFlags`, however, depend on how you initialise the GHC
session.
For a simple session, initialised by

    ghc -isrc -this-unit-id main

It is simple, just use the `DynFlags` given on the cli.
Thus, `main` and `interactive-session` will have the same `DynFlags`,
except for the `homeUnitId` and `interactive-session` depends on `main`
by construction of the GHCi session.

What about a multiple home unit session, though?

    ghc -unit @unit1 -unit @unit2

What are the `DynFlags` in this cli invocation? It shouldn't be either
`@unti1` nor `@unit2`, as the order shouldn't matter or any other
implicit condition.

For consistency, we decide that the initial `DynFlags` are the top
`DynFlags` on the cli, ignoring `-unit` flags.
Thus, in this example, there are no `importsDirs` regardless of what we
might find in `@unit1` and `@unit2`.

But in this invocation:

    ghc -isrc -unit @unit1 -unit @unit2

The `interactive-session` will have the `importsDirs` `src`.
Note, `-isrc` will be inherited in `@unit1` and `@unit2`, so you need to
explicitly use `-i` to clear the `importsDirs`, in order to avoid
accidentally adding `src` as an import directory to all other home
units.

This fix has been made possible by the improvements introduced in
!15888, which avoids ambiguity when a home unit shares the `importsDirs`
with the `interactive-session`, on top of being much faster for multiple
home units.

Adds regression tests for T27202 for `:load`ing and `:add`ing modules
that are located in import directories.

728662de

by fendor at 2026-05-20T12:27:09-04:00

Use home unit package db stacks in GHCi prompt and session unit

In order to import modules from home unit dependencies (e.g., `Data.Map`),
the ghci prompt unit needs to populate its `UnitState`.
This is tricky to handle correctly, which `PackageDBFlag`s should we use
to populate the `UnitState`?
We decide, the most intuitive solution for users is to depend on all
`PackageDBFlag`s, so that any dependency can be imported in GHCi.
This assumes consistency in the `PackageDBFlag`s, so no two home units
specify `PackageDBFlag`s that are inconsistent with each other.

We could simply concat all the `PackageDBFlag`s of the existing home
units, but later `PackageDBFlag`s shadow earlier ones, leading to the
last processed home units' `PackageDBFlag`s to shadow the earlier ones.
This is hard to fix, we need to give users the capability to provide ghc
options for the ghci prompt home unit.
However, as this is considerably more work, we decided on an
approximation that should work out most of the time.

Package Db stacks in cabal and stack follow a certain structure:

    -no-user-package-db > -package-db $cabal-store > -package-db $local-db

The first two arguments are always the same, namely the
`-no-user-package-db` and `-package-db`.
We compute the longest common prefix over all home units, and use that
as the start of the package db stack. Then, over the rest of the
`PackageDBFlag`s, we simply take the union and append them to our
initial stack.
We assume, that the rest of package dbs only defines very few, "local"
units that are usually not shadowing each other.

This allows us to get a relatively consistent package database stack for
the ghci prompt home unit.

Similar reasoning applies to the session unit in order to add modules to
the session and have dependencies available in the module.

We do something similar for `-package` flags, to make sure only the
correct units are actually visible in the ghci session.
This time, we simply take the union of all `PackageFlag`s, allowing us
to import modules from the home unit dependencies.

In the future, it would be beneficial to allow the user to provide the
exact ghc options to control the visibilities. For now, this will have
to do.

740d89a0

by Simon Peyton Jones at 2026-05-20T17:20:44-04:00

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.

a50fdb06

by Simon Peyton Jones at 2026-05-20T17:20:45-04:00

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%

However, strangely there seems to be a 5.0% increase in CoOpt_Read in
the x86_64-linux-fedora43-validate+debug_info+ubsan job, although
there generally a /decrease/ in this test in other builds.  The baseline
value looks strange.  Anyway I'll just accept it.

Metric Decrease:
    CoOpt_Singletons
    T12227
    T12545
    T12707
    T15703
    T18223
    T18730
    T21839c
    T5030
    T9630

Metric Increase:
    CoOpt_Read

834623d4

by Mrjtjmn at 2026-05-20T17:21:41-04:00

users-guide: Fix weird notation in "Summary of stolen syntax"

6f9d7c71

by Markus Läll at 2026-05-21T15:25:34-04:00

Use "grimily" instead of "grimly"

Fixes https://gitlab.haskell.org/ghc/ghc/-/issues/27221

50e999ca

by fendor at 2026-05-21T15:26:18-04:00

Speed up 'closure' computation in `ghc-pkg`

Cache the set of already seen `UnitId`s and use `Set` operations to
speed up 'closure' computation.

Further simplify the implementation of 'closure' to account for the
actual usage.
As a consequence, we rename 'closure' to 'brokenPackages' to reflect its
purpose better after the simplification.

7ecc6184

by sheaf at 2026-05-21T15:27:10-04:00

TcMPluginHandling: be more lenient when no plugins

This change ensures that, if a function such as 'typecheckModule' was
invoked with 'NoTcMPlugins', GHC doesn't spuriously complain about TcM
plugins having already been stopped, as there were none to start with.

72c8de5c

by Simon Jakobi at 2026-05-23T18:41:42-04:00

Implement List.elem via foldr

...in order to allow specialization to Eq instances.

The implementation of notElem is updated for consistency.`

Corresponding CLC proposal:
https://github.com/haskell/core-libraries-committee/issues/412

Addresses #27096.

3268c610

by Alan Zimmerman at 2026-05-23T18:42:30-04:00

EPA: Fix span for qualified multiline string

Fix the span for a qualified multiline string like

  Text."""
    I'm a multiline
    Text value
    !
  """

to extend to the end of the entire string, not just the first line.

Closes #27274

1f096790

by Alan Zimmerman at 2026-05-23T18:43:20-04:00

EPA: Fix exact printing namespace-specified wildcards

Ensures correct printing of imports of the form

   import Data.Bool (data True(data ..))
   import Data.Bool (data True(type ..))

Closes #27291

56ada7c0

by Mrjtjmn at 2026-05-23T18:44:19-04:00

Fix ambiguous syntax of BangPatterns in users guide

Update documentation for the BangPatterns extension to specify
how surrounding whitespace affects interpretation of `!`.

* Only when there is whitespace before `!` and no whitespace after,
  it is recognized as a BangPattern.
* Other cases `⟨varid⟩!⟨varid⟩`, `⟨varid⟩ ! ⟨varid⟩`, `⟨varid⟩! ⟨varid⟩`
  are treated as infix operators.

579aa0b7

by Simon Jakobi at 2026-05-25T16:31:26-04:00

Ensure that SetOps.{minusList,unionListsOrd} can be specialized

...by marking them INLINABLE. Haddock allocates 0.1–0.3% less as a
result.

This also removes some redundant constraints on unionListsOrd.

cccf45da

by Cheng Shao at 2026-05-25T16:32:13-04:00

wasm: ensure post-linker output is synchronous ESM

This patch fixes wasm backend's post-linker output script to ensure
it's synchronous ESM and doesn't use top-level await, which doesn't
work in ServiceWorkers. Fixes #27257.

8db331a3

by Zubin Duggal at 2026-05-26T04:54:03-04:00

Update to semaphore-compat 2.0.0 using v2 of the protocol

On Linux and other POSIX platforms, GHC's -jsem jobserver client now
speaks v2 of the semaphore-compat protocol, which uses Unix domain
sockets in place of POSIX named semaphores. This avoids the libc-ABI
issues that affected the old implementation. Windows is unaffected
and continues to use the v1 protocol (Win32 named semaphores); its
reported protocol version remains v1.

When GHC receives a -jsem name whose protocol version it does not
support, it emits a -Wsemaphore-version-mismatch warning and falls
back to -j<N> rather than crashing. ghc --info exposes the supported
version in a new "Semaphore version" entry so cabal-install can detect
a mismatch before invoking GHC.

Users on a cabal-install that predates the v2 update will continue to
build successfully on Linux/POSIX, but will lose the cross-process
-jsem coordination and fall back to -j<N> per GHC invocation. Users
must upgrade to a cabal-install that supports protocol v2 to recover
full parallelism.

Also fix a leak in cleanupSem (#27253): cleanupSem used to snapshot
heldTokens and release them before killing the loop, while the loop's
in-flight acquire/release children could still be mutating it.
Cleanup now runs inside the loop's own exit handler, after draining
the active child via a new activeChild TVar, so the snapshot has no
concurrent mutator.

See also:
- GHC proposal amendment: https://github.com/ghc-proposals/ghc-proposals/pull/673
- cabal-install patch: https://github.com/haskell/cabal/pull/11628
- semaphore-compat MR: https://gitlab.haskell.org/ghc/semaphore-compat/-/merge_requests/8

Bump semaphore-compat submodule to 2.0.0

Fixes #25087 and #27253

17be4f1f

by Alan Zimmerman at 2026-05-26T04:54:52-04:00

EPA: Record semicolons in HsModifier

Ensure the semi colons are captured in the ParsedSource for code like

  %True;; %False;
  instance C D

It makes HsModifier (and hence HsModifierOf) LocatedA, so the semi
colons can be recorded as [TrailingAnn]

Also rename pprHsModifiers to pprLHsModifiers to match.

Closes #27294

8f991755

by fendor at 2026-05-26T11:02:52-04:00

Revert prog003 acceptance

We thought the commit 286f1adff3e78d775ff325caff71d0cee25d710b fixed the
test, but due to changes to ghci, modules loaded during the GHCi
session, the test was actually no longer testing what it set out to do,
"fixing" the broken test.

As modules are added to the `interactive-session` home unit, the object code needs
to be compiled with `-this-unit-id interactive-session`, otherwise the
object code won't be used.
Once this has been fixed in the test, the test fails as expected again.

277a3687

by mangoiv at 2026-05-26T11:03:40-04:00

libraries/process: bump submodule to v1.6.29.0

This submodule bump resolves a segfault on macos 15.
Fixes #27144

6779bb0c

by mangoiv at 2026-05-26T11:03:40-04:00

libraries/unix: in submodule, don't pick branch 2.7

The 2.7 branch is outdated and the module has been advanced far beyond
it anyway, so remove that line.

4a645683

by Simon Peyton Jones at 2026-05-27T21:41:59-04:00

Trim the continuation in mkDupableContWithDmds

When there are no remaining argument demands, it means the application
is bottoming. In this case, we can trim the continuation to avoid the
panic that was observed in #27261.

See Note [Trimming the continuation for bottoming functions] in
GHC.Core.Opt.Simplify.Iteration.

8ab506ff

by Cheng Shao at 2026-05-27T21:42:47-04:00

ghci: fix module name string lifetime in hs_hpc_module invocation

This patch makes hpcAddModule pass a properly malloced module name
string to hs_hpc_module, instead of using useAsCString which causes
use-after-free of module name string. Fixes #27297.

Co-authored-by: Codex <codex@openai.com>

b0233814

by sheaf at 2026-05-27T21:43:31-04:00

Relax acceptance threshold for T10421

As seen in #27289, the 1% acceptance threshold for this text was
overly narrow, resulting in spurious test failures. This commit widens
the acceptance threshold to 2%. Fixes #27289.

63ce5770

by Luite Stegeman at 2026-05-28T12:23:35-04:00

Fixes for black holes

 - suspend duplicate work for eager black holes
 - detect eager black holes in checkBlockingQueues
 - don't overwrite existing black holes even if they're not
     in an eager blackhole frame
 - don't deadlock on self when thunk is already blackholed

Fixes #26936

037a80dc

by Tom McLaughlin at 2026-05-28T12:24:36-04:00

Event/Windows.hsc: rethrow exceptions in overlapped IO

This prevents the WinIO manager from swallowing exceptions in overlapped IO. It
was added to make WinIO support possible in the `network` library. See
https://gitlab.haskell.org/ghc/ghc/-/issues/27283.

We also bump __IO_MANAGER_WINIO__ to 2 so libraries can gate on this using CPP.

2d53bcdb

by Wolfgang Jeltsch at 2026-05-28T12:25:21-04:00

Allow `downsweep` to use nodes of an existing module graph

To this end, `downsweep` has not been able to use the nodes of a module
graph obtained from a previous downsweeping round. In some GHC API
applications, downsweeping is performed somewhat incrementally and
therefore could profit from reusing such existing results. This
contribution makes this possible.

Resolves #27054.

Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com>

f4fbb583
by Simon Jakobi at 2026-05-28T12:26:04-04:00
```
Add regression test for T11226

Closes #11226.
```

ed29a5e6

by Sven Tennie at 2026-05-28T17:30:36-04:00

Add optional config setting for LibDir (#19174)

Previously, the `libDir` was derived from `topDir`. This won't work for
inplace stage2 cross-compilers where binaries and libraries are in
different stage dirs (`_build/stage1/` for executables and
`_build/stage2` for libraries).

`LibDir` is set in the inplace `settings` files. For bindists, we
generate a new `settings` file with no `LibDir` entry. GHC then defaults
to use `topDir` as `libDir` again. This keeps the bindist relocatable.

If `LibDir` is a relative path, it is interpreted relatively to
`topDir`.

The global package db is part of the `lib/` folder. If we want to point
for inplace cross-compilers to the succeeding stage's folder, this is
done by setting `LibDir`. Thus, the global package db must be found
relative to `libDir`` (which may default to `topDir` or be set by
`LibDir`).

The complexity of settings becomes scary. So, add a test to ensure
`LibDir` works as expected.

8339cf8f

by Sven Tennie at 2026-05-28T17:30:36-04:00

Add Haddock to FileSettings

Helping to understand the fields' meanings without deeper analyses.

4ce251e4

by Sylvain Henry at 2026-05-28T17:31:39-04:00

foundation test: skip signed minBound `quot` (-1) (#27222)

`minBound `quot` (-1)` for fixed-width signed integers is platform
dependent: the mathematical result -minBound is not representable in
the type. On x86, IDIV traps; LLVM's sdiv is undefined behaviour in
this case; on AArch64/RISC-V, SDIV wraps to minBound.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

b8ba7e61

by Simon Jakobi at 2026-05-28T17:32:23-04:00

Prevent dictionary-passing in checkTyEqRhs

...by pre-specializing it to TcM.

Previously, wherever checkTyEqRhs was used in other modules, the
Core showed dictionary passing ($fMonadIOEnv). The added SPECIALIZE
pragma prevents this.

d603477f

by David Eichmann at 2026-05-29T13:17:12-04:00

Hadrian: create a ghc-internal .def file per ghc-internal dll

The .def file generated from rts/win32/libHSghc-internal.def.in contains
the name of the ghc-internal dll. The correct dll name differs based
on if the dll is inplace/final and if using the Dynamic way. Previously,
this was not accounted for and inconsistent dlls names where used. That
led to failure when loading dlls at runtime in experiments with windows
dynamic linking.

1fc21753

by Sylvain Henry at 2026-05-29T13:18:14-04:00

ghc-bignum: copy backend interface haddocks to Native backend (#27305)

The haddock comments documenting the BigNat backend interface (function
contracts, expected MutableWordArray# sizes, return-value semantics, etc.)
were attached to the FFI backend module. Copy them to the Native backend
so they remain in tree once the FFI backend is removed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

717059df

by Sylvain Henry at 2026-05-29T13:18:14-04:00

ghc-bignum: remove FFI backend (#27305)

The FFI backend of ghc-bignum (now part of ghc-internal) had no known
users and is easy to recreate by relinking ghc-internal with a custom
backend. Remove the backend module, the bignum-ffi cabal flag, and the
ffi option from Hadrian's --bignum selector. The backend interface
documentation now lives in the Native backend module.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

4bb3b1d8

by Sylvain Henry at 2026-05-29T13:18:14-04:00

ghc-bignum: remove Check backend (#27305)

The Check backend of ghc-bignum (now part of ghc-internal) compared the
selected backend's output against the Native backend for validation.
It had no known users. Remove the backend module, the bignum-check
cabal flag, the bignumCheck Hadrian flavour field, and the check-
prefix in Hadrian's --bignum selector.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

6b3044a0
by David Eichmann at 2026-05-30T11:58:48-04:00
```
Add code comments to allocator code
```

f4e04210

by Matthew Pickering at 2026-05-30T11:59:34-04:00

hadrian: Refactor system-cxx-std-lib rules

I noticed a few things wrong with the hadrian rules for
`system-cxx-std-lib` rules.

* For `text` there is an ad-hoc check to depend on `system-cxx-std-lib`
outside of `configurePackage`.
* The `system-cxx-std-lib` dependency is not read from cabal files.
* Recache is not called on the packge database after the `.conf` file is
generated, a more natural place for this rule is `registerRules`.

Treating this uniformly like other packages is complicated by it not
having any source code or a cabal file. However we can do a bit better
by reporting the dependency firstly in `PackageData` and then needing
the `.conf` file in the same place as every other package in
`configurePackage`.

This commit increases the `shakeVersion`, to provide backwards
compatibility to previous builds with different PackageData.

Fixes #25303

Co-authored-by: Sven Tennie <sven.tennie@gmail.com>

576987d0

by Simon Jakobi at 2026-06-02T04:53:36-04:00

compiler: use nubOrd from containers

Address #27103 by replacing GHC.Utils.Misc.ordNub[On] with
Data.Containers.ListUtils.nubOrd[On].

Note that nubOrd suffers from a small inefficiency, a fix for which
will be included in the next containers release:

  https://github.com/haskell/containers/issues/1202

deea53c3

by David Eichmann at 2026-06-02T04:54:22-04:00

Hadrian: disable response files for GHC/Haddock builders on non-Windows

This makes debugging build errors easier on non-windows hosts.
See issue #27230

f2f5c6ba
by Nikita Efremov at 2026-06-02T16:04:54+00:00
```
fix typo : compete with performance, not complete
```

5524ea0e

by Wolfgang Jeltsch at 2026-06-03T08:01:26-04:00

Make the current `base` buildable with GHC 9.14

This comprises the following changes:

  * Disable some imports into `GHC.Base` for GHC 9.14
  * Disable some imports into `Prelude` for GHC 9.14
  * Disable separate `ArrowLoop` import for GHC 9.14
  * Disable `GHC.Internal.STM` import for GHC 9.14
  * Disable `GHC.Internal.Unicode.Version` import for GHC 9.14
  * Disable `GHC.Internal.TH.Monad` import for GHC 9.14
  * Add alternative `fixIO` import for GHC 9.14
  * Add alternative `unsafeCodeCoerce` import for GHC 9.14
  * Disable hiding of imported SIMD operations for GHC 9.14
  * Disable use of GHC 9.14’s `printToHandleFinalizerExceptionHandler`
  * Enable use of `getFileHash` from `ghc-internal` for GHC 9.14
  * Make `thenA` available for GHC 9.14
  * Make `thenM` available for GHC 9.14
  * Disable translation of `IoManagerFlagPoll` for GHC 9.14
  * Add `hGetNewlineMode` for GHC 9.14

d3438055
by Enrico Maria De Angelis at 2026-06-03T08:02:17-04:00
```
Fix #27067 - Clarify haddocks on `minusNaturalMaybe`
```

f9bcfac2

by sheaf at 2026-06-03T14:47:19-04:00

Avoid mkTick in Core Prep breaking ANF

As discovered in #27182, mkTick can break ANF. This patch introduces a
variant of mkTick that skips the single optimisation that could break
ANF. This is preferrable over switching to the raw Tick constructor,
as the latter may introduce spurious cost centres in profiling reports.

This is a temporary measure until we more thoroughly refactor how
mkTick works (see #27141).

See Note [mkTick breaks ANF] in GHC.CoreToStg.Prep.

Fixes #27182

cf1fd661

by Artem Pelenitsyn at 2026-06-03T14:48:09-04:00

clarify comment for getSizeofMutableByteArray#: we get the size in bytes, not "elements"

a3b431f3

by David Eichmann at 2026-06-04T10:10:19+00:00

Hadrian: convert env variable ACLOCAL_PATH to unix paths.

Convert ACLOCAL_PATH to a unix style path when invoking autoreconf.
Autoreconf doesn't handle windows paths.
See Note [Autoreconf unix paths from ACLOCAL_PATH].

Fixes #27311

18f6138a

by Simon Jakobi at 2026-06-04T20:20:31-04:00

testsuite: Deduplicate --only test names

config.only is assumed to be a set, but supplying --only overwrote it
with the (list) argparse result, which can contain duplicates. When a
test ran, config.only.remove(name) dropped only the first occurrence,
so a duplicated name lingered and was later misreported as a
"test not found" framework failure. Store it as a set instead.

Fixes #27322

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

2f3cc9ff

by Simon Jakobi at 2026-06-08T07:55:49-04:00

testsuite: detect fast bignum via ghc-internal, not removed ghc-bignum

The ghc-bignum package was merged into ghc-internal, so the BIGNUM_GMP
probe in test.mk ran `ghc-pkg field ghc-bignum exposed-modules`, which
fails with "cannot find package ghc-bignum". That error went to stderr
and leaked into the captured stderr of every makefile_test, causing
spurious [bad stderr] failures across the suite. The probe also silently
returned empty, so config.have_fast_bignum was wrongly False even on GMP
builds.

Probe ghc-internal's extra-libraries for the gmp library instead: the
GMP backend module is an other-module (not exposed), but GMP_LIBS adds
gmp to extra-libraries only on a GMP build, so this distinguishes the
backends. Redirect stderr to keep any future missing-package error off
the harness's stderr.

This also removes a stale comment as per suggestion from hsyl20.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

eb3bf6e7

by Alan Zimmerman at 2026-06-08T07:56:32-04:00

EPA: Rename Transform.anchorEof to addModuleCommentOrigDeltas

This now matches what it actually does.

498bb21a

by David Eichmann at 2026-06-09T18:02:39-04:00

Hadrian: avoid response files when command line is short enough

This replaces the logic of always using response files on Windows.
With the new condition based on command line lenght, reponse files
can be avoided in many more cases (on windows).

Now that response files are only used in a small number of cases,
response files are always kept and the -r / --keep-response-files
command line options have been removed

The response file paths are nolonger randomized. They are placed in the
`_build/rsp` directory. This ensures they are ignored by git and we
that Hadrian reuses response file paths when rebuilding rather than
leaving stale response files around.

Update user guide putting response files in its own section

87f510a5
by Simon Hengel at 2026-06-09T18:03:25-04:00
```
Don't use non-breaking spaces
```

41a19379

by David Eichmann at 2026-06-09T18:04:11-04:00

Hadrian: remove unused wrapper scripts from windows bindist

These wrapper scripts are only installed on non-relocatable builds
which are not generally supported on windows.

ce01ccb6

by sheaf at 2026-06-10T05:08:48-04:00

Don't drop ticks around variables of type `IO ()`

GHC.Core.Utils.mkTick is responsible for placing a tick on a Core
expression. It contains logic for dropping SCCs (non-counting profiling
ticks) around non-function variables, as such variables cannot
meaningfully contribute to profiles. However, the logic for what counts
as a function was incorrect: it used `isFunTy` which returns 'False' for
types such as 'IO ()' where the function arrow is hidden under a
newtype.

We now use 'mightBeFunTy' instead of 'isFunTy'. This ensures we don't
drop ticks in cases we aren't sure.

On the way, we improve the documentation of 'isFunTy', 'isPiTy' and
'mightBeFunTy', and update the latter's implementation to consistently
handle unary classes.

Fixes #27225

-------------------------
Metric Decrease:
    T5642
-------------------------

d311c4f1

by Simon Jakobi at 2026-06-10T05:09:32-04:00

testsuite: Add regression test for #4081

Check that a strict constructor field is unboxed once outside an
enclosing loop, not re-inspected each iteration (the float-out
case-floating from 9cb20b488). Uses simonpj's `data T a = T !a` example
from the ticket; T4081.stderr captures the expected Core.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

333df444

by sheaf at 2026-06-10T05:10:25-04:00

Check for cabal-install >= 3.12 upfront

Starting with commit 8cb99552f607f6bc4000e45ab32532d50c8bb996, Hadrian
requires cabal-install >= 3.12 in order to use the 'cabal path' command
that was introduced in version 3.12, as per
  https://github.com/haskell/cabal/blob/a51c4ee1556d816ad86e90db7e6330dd51b0b6e7/release-notes/cabal-install-3.12.1.0.md?plain=1#L45

This was not reflected in the Hadrian build script, causing a delayed
build failure instead of enforcing the version requirement upfront,
which this patch does.

Fixes #27317

98c20394

by sheaf at 2026-06-10T05:11:09-04:00

Fix crash in Data.Data instance for HsCtxt

The Data.Data instance for HsCtxt contained an error for the 'toConstr'
method, which could trigger for example when looking at -ddump-tc-ast
traces. Replace it with the 'abstractConstr' pattern used in the rest of
the codebase.

5ac9ce7d

by Zubin Duggal at 2026-06-10T21:26:32+05:30

hadrian: Remove old package.conf files when generating new ones

Old package.conf files might exists with different hashes, causing issues like #26661

Fixes #26661

c9015f09

by sheaf at 2026-06-11T12:40:28-04:00

Fix AArch64 clobbering bug for MUL2

On AArch64, the code generator could clobber one of the input operands
when computing the lower bits of a MUL2 operation. This rendered invalid
the subsequent computation of the high bits.
This commit fixes that by using a temporary register. The register
allocator can remove the redundant move in the common case when the
registers do not conflict.

Fixes #27046

7ab90288

by Rodrigo Mesquita at 2026-06-11T12:41:11-04:00

fix: make T27131 less flaky

It seems that T27131 fails flakily in a race where we check the flag
before the capability had the chance to process the mailbox which sets
the flag. This seemingly should only happen if the capability ends up
being the same for setting and checking the flag.

8965cb76
by Marc Scholten at 2026-06-12T04:53:22-04:00
```
haddock: render modules concurrently
```

8cc0b64a

by Duncan Coutts at 2026-06-12T04:54:06-04:00

Promote HAVE_PREEMPTION from Timer.c to OSThreads.h

We will want to know about HAVE_PREEMPTION in more places.

HAVE_PREEMPTION tells us that we do have OS threads available,
irrespective of whether THREADED is defined. In particular,
HAVE_PREEMPTION is defined on all proper OSs, but not on WASM (and
hyopthetically may not be true on some other platforms like
micro-controllers, RTOSs, VM hypervisors etc).

cce574ed

by Duncan Coutts at 2026-06-12T04:54:06-04:00

Define ACQUIRE_LOCK_ALWAYS and friends

Fix issue #27335

Like the atomic _ALWAYS variants, these lock actions are always defined,
rather than being dependent on whether we are in the THREADED case. All
the "normal" LOCK macros are defined to be no-ops when !THREADED.

The use case for the _ALWAYS variants is where we are using OS threads
even in the non-threaded RTS. This includes everything to do with the
timer/ticker thread, which is used in the non-threaded RTS too.

In particular, we will want to use this for eventlog things, because the
timer thread performs eventlogging concurrently with the main
capability, even in the non-threaded RTS.

1f28d1f6

by Duncan Coutts at 2026-06-12T04:54:06-04:00

Use ACQUIRE/RELEASE_LOCK_ALWAYS with eventBufMutex

Even in the non-threaded RTS the eventBufMutex is needed by both the
main capability and the timer/ticker thread, so always use the mutex.

This should fix #25165 which is about the main capability and the timer
thread posting events to the eventlog buffer concurrently and thereby
corrupting the buffer data.

0ff29782

by Duncan Coutts at 2026-06-12T04:54:06-04:00

Expose eventBufMutex in the EventLog interface/header

We will need it in forkProcess to ensure we don't write to the global
eventlog buffer concurrently with trying to flush eventlog buffers and
do the fork().

7a688395

by Duncan Coutts at 2026-06-12T04:54:07-04:00

Split flushAllCapsEventsBufs into safe and unlocked version

Following the convention that unlocked versions have a trailing _
underscore in their name. This one requires the caller to hold the
eventlog global buffer mutex. We will need this in forkProcess.

341ed474

by Duncan Coutts at 2026-06-12T04:54:07-04:00

Remove redundant use of stopTimer in setNumCapabilities

Historically, the comment here was:

  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.

and

  We must disable the timer while we do this since the tick handler may
  call contextSwitchAllCapabilities, which may see the capabilities array
  as we free it.

What this refers to is that historically, when changing the number of
capabilities, the array of capabilities was reallocated to a new size,
allocating new ones and freeing the old ones, thus invalidating all
existing capbility pointers.

Strangely, for good measure the code used to call stopTimer twice (hence
the two similar comments above).

However, since commit a3eccf06292dd666b24606251a52da2b466a9612, the
capabilities array is no longer reallocated. Instead the array is
allcoated once on RTS startup to the maximum size it could ever be
allowed to be, and then capabilities get enabled/disabled at runtime. So
the capability pointers never become invalid anymore. At worst, they may
point to capabilities that are disabled.

Thus we no longer need to stop the timer (twice) while we change the
number of enabled capabilities. This also partially solves issue #27105,
which notes that stopTimer is being used as if it were synchronous, when
it is not. At least for this case, the solution is that stopTimer is not
needed at all!

674858e3

by Duncan Coutts at 2026-06-12T04:54:07-04:00

Remove redundant use of stopTimer in forkProcess

but replace it with taking the eventlog buffer lock during the fork.

Fixes issue #27105

The original reason to block the timer during a fork was that
historically the timer was implemented using a periodic timer signal,
and the signal itself would interrupt the fork system call (returning
EINTR). For large processes (where fork() takes a while) this could
permanently livelock: the timer always would go off before the fork
could complete, which got retried in a loop forever.

The timer is no longer implemented as a unix signal, but uses threads.
Thus the original problem no longer exists. The only remaining reason to
block the timer tick is to prevent actions taken by the tick from
interfering with the delicate process involved in fork (taking a load of
locks and pausing everything).

The only thing we need to do is to prevent the eventlog from being
written to or flushed while the fork is taking place. To achieve this
all we need to do is hold the mutex for the global eventlog buffer.

This removes the last use of stopTimer that expects stopTimer to work
synchronously (which it was not) and thus solves issue #27105. To be
clear, we solve issue #27105 not by making stopTimer synchronous, but by
eliminating the use sites that expected it to be synchronous.

40764930

by sheaf at 2026-06-12T14:54:43-04:00

Add type family performance test for #26426

Some GHC versions produced large numbers of coercions after typechecking
and desugaring when compiling the program in #26426:

Version | Typechecker time | Typechecker allocations | Coercions
-------:|-----------------:|------------------------:|---------:
9.6     |   47 ms          |  48 MB                  |    110k
9.8     | 1000 ms          | 486 MB                  | 10,437k
9.10    |  922 ms          | 489 MB                  | 10,436k
9.12    |  906 ms          | 482 MB                  | 10,437k
9.14    |   63 ms          |  55 MB                  |    333k
10.0    |   47 ms          |  64 MB                  |     35k

The improvement 9.12 -> 9.14 was due to commit 22d11fa818fae2c95c494fc0fac1f8cb4c6e7cb6,
while the improvement 9.14 -> 10.0 was due to commit 0b7df6db9e46df40e86fbff1a66dc10440b99db5.

As the behaviour of GHC seems better than it's ever been on this program,
we declare victory, adding this performance test to ensure we don't
regress on this program.

On the way, we update Note [Combining equalities] in GHC.Tc.SolveR.Equality
with the explanation of the 9.12 -> 9.14 improvement (getting rid of an
exponential blowup in coercion sizes), and we update
Note [Exploiting closed type families] in GHC.Tc.Solver.FunDeps with
the explanation of the 9.14 -> 10.0 improvement (bringing down coercion
size growth from cubic to quadratic).

0f3d0a71

by Zubin Duggal at 2026-06-12T14:55:30-04:00

compiler: mark tool messages as errors/warnings depending on the exit code

Fixes #27370

d9ea2d76

by mangoiv at 2026-06-13T04:41:51-04:00

libraries/process: bump submodule to v1.6.30.0

- bump the submodule to the appropriate tag
- suppress benign warning resulting from the change

6ebaaba3

by David Eichmann at 2026-06-13T04:42:37-04:00

ghc-toolchain: don't throw when candidate executables are not found

Fixes #27369

6c65e1e1

by David Eichmann at 2026-06-13T04:43:23-04:00

CI: lint-changelog checks for no-changelog label in script instead of rules

bab37cc6

by konsumlamm at 2026-06-13T19:10:21+02:00

Implement CLC proposal #378

Add `Data.Double` and `Data.Float` modules
Document that GHC uses IEEE 754

fb5246ad

by fendor at 2026-06-15T18:07:23-04:00

Drop `preloadClosure` from `UnitState`

It is always hard-coded to the same value.

Backpack Unit instantiation isn't using it any more.
Allows us to simplify the API and get rid of `improveUnit`.

291ce3aa

by ARATA Mizuki at 2026-06-15T18:08:26-04:00

RISC-V NCG: Zero-extend the result of castFloatToWord32

According to the ISA manual, FMV.X.W sign-extends the result.
We need to truncate the result to avoid creating an exotic Word32 value.

Fixes #27300

011be91f

by ARATA Mizuki at 2026-06-15T18:08:26-04:00

RISC-V NCG: Treat d28-d31 (ft8-ft11) as caller-saved

According to the calling convention, the registers d28-d31 (ft8-ft11) are caller-saved.

Fixes #27306

e8a54713

by ARATA Mizuki at 2026-06-15T18:08:26-04:00

RISC-V NCG: Set rounding mode when emitting `truncate`

If we omit the rounding mode for `fcvt`, `dyn` will be used.
We do not want that for `truncate`, so we set `rtz`.
In other places, we set `rne` because we do not use the dynamic rounding mode.

Fixes #27303

9438bec7

by Zubin Duggal at 2026-06-15T18:09:11-04:00

rts: fix validate build with gcc 16. `__attribute__((regparm(1)))` is ignored on x86_64 and now
gcc warns that it is ignored:

rts/sm/Evac.h:35:1: error:
     error: ‘regparm’ attribute ignored [-Werror=attributes]

See https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=ccead81bbc39668376eb5cf47066acb446cc43f3

Fixes #27366

893e6133

by Andrew Lelechenko at 2026-06-15T23:55:36+01:00

base: more NonEmpty zips

CLC proposal: https://github.com/haskell/core-libraries-committee/issues/409

1314f2fd
by David Eichmann at 2026-06-16T05:46:52-04:00
```
Hadrian: fix ghc-internal .def file name
```

7f72bcb3

by mangoiv at 2026-06-16T05:47:39-04:00

compiler: ignore camelCase and Eta reduce hlint hints

These do not cohere with the style used in GHC. After disabling them,
hlint lints are much less noisy again.

842bef9f
by Alan Zimmerman at 2026-06-16T05:48:25-04:00
```
EPA: Use standard type family declaration for Anno
```

f6d30767

by Wolfgang Jeltsch at 2026-06-16T15:32:34-04:00

Fix two issues in the documentation of pipeline interruption

One issue is a typo (“interreuptible”), the other one the lack of an end
of a sentence, which has been reconstructed from the message of
633bbc1fd4762a2bb73ba1c5b9e0c279f1dd3c40, the commit that introduced
said documentation.

a3fa10e0

by Christian Georgii at 2026-06-16T15:33:26-04:00

Find plugins in sibling home units in multiple-home-unit sessions

In a multiple-home-unit session (e.g. `cabal repl --enable-multi-repl` or HLS), enabling a plugin with -fplugin that is defined in (or reexported by) another home unit failed with a "hidden package" error. The plugin module finder only searched the current home unit and the registered external packages, never the sibling home units.

findPluginModuleNoHsc now searches the home units that the current home unit depends on, following module reexports and respecting hidden modules, exactly as ordinary import resolution does in findImportedModuleNoHsc. To avoid two divergent copies of this logic, the shared home-unit search (the current home unit first, then its dependencies in priority order, with the accompanying ordering invariant) is extracted into findHomeModuleAmongDeps, which both findImportedModuleNoHsc and findPluginModuleNoHsc now call.

Add testsuite/tests/driver/multipleHomeUnits/plugin01, which loads a plugin as byte-code from a sibling home unit, and plugin02, in which the consumer enables a plugin reexported by a sibling home unit without depending on the plugin's own home unit directly.

Fixes #27349

d216412b

by Ian-Woo Kim at 2026-06-16T20:25:57-04:00

Make the order of usages deterministic

It has been observed that the ordering of usages can be non-determinstic
in parallel builds. Therefore, this contribution introduces sorting of
usages based on a platform- and race-independent sorting criterion.

Resolves #26877.

Co-authored-by: Wolfgang Jeltsch <wolfgang@well-typed.com>

8e1cc105

by Wolfgang Jeltsch at 2026-06-16T20:25:57-04:00

Change the descriptions of two existing changelog entries

The descriptions now describe the changes in a user-friendly manner, as
opposed to describing the contributions that led to these changes in a
developer-friendly manner.

636c1c7a

by Ian Duncan at 2026-06-16T20:26:50-04:00

AArch64: use SXTH, not SXTW, for W32 signExtendReg

signExtendReg was using SXTH (sign-extend halfword, 16-bit) for
W32-to-W64 sign extension. This should be SXTW (sign-extend word,
32-bit). SXTH only sign-extends the lower 16 bits, producing wrong
results for 32-bit values whose bit 15 differs from bit 31.

Other fixes:

  - At sub-W64, code gen for MO_S_Mul2 should use W32 registers for
    SMULL source operands as per the ARM spec (SMULL Xd, Wn, Wm),
    and not W64.

  - Ensure signExtendReg uses the source width for the source operand
    in SXTW/SXTH/SXTB instructions. GNU as requires sxtw Xd,Wn (not
    sxtw Xd,Xn), while LLVM's integrated assembler on macOS is lenient.

  - Fix overflow flag computation for `MO_S_Mul2`. The overflow bit
    was exactly inverted for sub-W64 operands.

Fixes #26978 and #27047

b734c75d

by Igor Ranieri at 2026-06-16T20:27:32-04:00

haddock: Update CONTRIBUTING with missing step, add missing test
dependency

7fe4f2ec

by Luite Stegeman at 2026-06-17T05:35:09-04:00

tag inference: don't confuse functions with their return values

inferTagRhs was mixing up taggedness for closures and return values
for function closures. We really shouldn't assign TagTuple to a
properly tagged function returning a tuple.

We fix this by keeping track of functions (TagFun) separately from
values (TagVal) and keeping track of their return value. TagFun is
also used for join points.

fixes #27005

4671c126

by Sebastian Graf at 2026-06-17T05:35:55-04:00

Seed the simplifier's in-scope set for open expressions

simplifyExpr simplifies expressions typed at the GHCi prompt and the
results of Template Haskell splices. Such an expression may be open: at a
GHCi debugger breakpoint its free variables include RuntimeUnk skolems
standing for as-yet-unknown types.

The simplifier began with an in-scope set holding only the wildcard
binder, so when it instantiated the unsafeCoerce# wrapper that GHCi
builds around a result, it formed a substitution whose range mentioned a
free skolem that was not in scope. That breaks the substitution invariant
and, in a compiler built with assertions, trips substTy's sanity check.

Seed the initial in-scope set with the free variables of the expression.
For a closed expression this adds nothing.

See Note [Seed the in-scope set for open expressions].

Fixes #17833 and its duplicate #21118.

67d41299

by Sebastian Graf at 2026-06-18T05:18:24-04:00

Desugar a `case` scrutinee only once (#27383, #20251)

In `dsExpr` for `HsCase` we desugared the scrutinee /twice/: once to
build the Core `case` itself, and again inside `matchWrapper`, which
re-desugared the source scrutinee (via `addHsScrutTmCs`) purely to
record long-distance information for the pattern-match checker.

For a single `case` that is merely wasteful.  But for nested cases it
is catastrophic.  Consider

    case (case (case e of ... ) of ... ) of ...

Desugaring the outer scrutinee desugars the middle `case` twice, each
of which desugars the inner `case` twice, and so on.  The work doubles
at every level, so desugaring takes O(2^n) time in the nesting depth.
That is the blowup reported in #27383; it is also what makes the
machine-generated program in #20251 take an age to compile.

The fix is simple.  `matchWrapper` is handed the scrutinee anyway, so
we give it the Core expression we have /already/ desugared, and record
the long-distance term constraint with `addCoreScrutTmCs` instead of
re-desugaring from source.  This is just what `matchSinglePatVar`
already does for single-pattern matches.

So:

* `matchWrapper` now takes `Maybe [CoreExpr]` rather than
  `Maybe [LHsExpr GhcTc]`.

* The `HsCase` equation of `dsExpr` passes the already-desugared
  `core_discrim`; the arrow desugarer passes its match variables.

* `addHsScrutTmCs` had no other use, so it is gone.

Desugaring is now linear in the nesting depth.  (The coverage checker
still runs `simpleOptExpr` over each scrutinee, which leaves the total
at O(n^2); that is ample.)  The long-distance information itself is
unchanged: the checker sees precisely the Core that backs the
generated code.

Test: deSugar/should_compile/T27383

fa5defde

by Rodrigo Mesquita at 2026-06-18T05:19:11-04:00

fix: Save FastStrings in the PMC

There is no point in adding the unique to the occurrence FastString we
create, since it is part of the Id anyway.

Adding it to the FastString, meant each FastString was unique
unnecessarily!

In a separate branch, running the compiler on test `InstanceMatching`
observed 30000 `FastString`s created by this code path.

Plus, `fsLit "pm"` follows the existing pattern in `mkPmId`.

4efb4a66

by Alan Zimmerman at 2026-06-18T14:41:14-04:00

TTG: Add extension points to HsConDetails

Extend HsConDetails as

    data HsConDetails p arg rec
      = PrefixCon !(XPrefixCon p) [arg]    -- C @t1 @t2 p1 p2 p3
      | RecCon    !(XRecCon p)    rec      -- C { x = p1, y = p2 }
      | InfixCon  !(XInfixCon p)  arg arg  -- p1 `C` p2
      | XHsConDetails !(XXHsConDetails p)

    type family XPrefixCon      p
    type family XRecCon         p
    type family XInfixCon       p
    type family XXHsConDetails  p

c8d27dd4

by Simon Jakobi at 2026-06-18T14:41:59-04:00

CI: quiet submodule clean output in after_script and setup

The clean and cleanup_submodules functions ran 'git submodule foreach
git clean -xdf', flooding the job log with 'Entering ...' and
'Removing ...' lines. Pass --quiet to 'git submodule' and -q to 'git
clean' to drop the success output; errors are still reported.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

09326ca6

by Matthew Pickering at 2026-06-20T23:41:12+02:00

Add missing req_interp modifier to T18441fail3 and T18441fail19

These tests require the interpreter but they were failing in a different
way with the javascript backend because the interpreter was disabled and
stderr is ignored by the test.

521e55bf

by Matthew Pickering at 2026-06-20T23:41:13+02:00

hadrian: Fill in more of the default.host toolchain file

When you are building a cross compiler this file will be used to build
stage1 and it's libraries, so we need enough information here to work
accurately. There is still more work to be done (see for example, word
size is still fixed).

23c9b6c3

by Matthew Pickering at 2026-06-20T23:42:52+02:00

hadrian: Build stage 2 cross compilers

* Most of hadrian is abstracted over the stage in order to remove the
  assumption that the target of all stages is the same platform. This
  allows the RTS to be built for two different targets for example.
* Abstracts the bindist creation logic to allow building either normal
  or cross bindists. Normal bindists use stage 1 libraries and a stage 2
  compiler. Cross bindists use stage 2 libararies and a stage 2
  compiler.
* hadrian: Make binary-dist-dir the default build target. This allows us
  to have the logic in one place about which libraries/stages to build
  with cross compilers. Fixes #24192

New hadrian target:

* `binary-dist-dir-cross`: Build a cross compiler bindist (compiler =
  stage 1, libraries = stage 2)

This commit also contains various changes to make stage2 compilers
feasible.

-------------------------
Metric Decrease:
    LinkableUsage02
    ManyAlternatives
    ManyConstructors
    MultiComponentModulesRecomp
    MultiLayerModulesRecomp
    RecordUpdPerf
    T10421
    T12150
    T12227
    T12425
    T12707
    T13035
    T13379
    T13820
    T15703
    T16577
    T18140
    T18282
    T18698a
    T18698b
    T18923
    T1969
    T20049
    T21839c
    T3294
    T4801
    T5030
    T5321FD
    T5321Fun
    T5631
    T5642
    T6048
    T783
    T9020
    T9198
    T9233
    T9630
    T9872d
    T9961
    parsing001
    T3064

Metric Increase:
    T26989
    hard_hole_fits
-------------------------

Co-authored-by: Sven Tennie <sven.tennie@gmail.com>

26fed8ab

by Matthew Pickering at 2026-06-20T23:42:52+02:00

ci: Test cross bindists

We remove the special logic for testing in-tree cross
compilers and instead test cross compiler bindists, like we do for all
other platforms.

80c8910e

by Matthew Pickering at 2026-06-20T23:42:52+02:00

ci: Introduce CROSS_STAGE variable

In preparation for building and testing stage3 bindists we introduce the
CROSS_STAGE variable which is used by a CI job to determine what kind of
bindist the CI job should produce.

At the moment we are only using CROSS_STAGE=2 but in the future we will
have some jobs which set CROSS_STAGE=3 to produce native bindists for a
target, but produced by a cross compiler, which can be tested on by
another CI job on the native platform.

CROSS_STAGE=2: Build a normal cross compiler bindist
CROSS_STAGE=3: Build a stage 3 bindist, one which is a native compiler and library for the target

8215573d

by Sven Tennie at 2026-06-20T23:42:52+02:00

ci: Increase timeout for emulators

Test runs with emulators naturally take longer than on native machines.

Generate jobs.yml

5acb7dbc

by Matthew Pickering at 2026-06-20T23:42:52+02:00

ci: Javascript don't set CROSS_EMULATOR

There is no CROSS_EMULATOR needed to run javascript binaries, so we
don't set the CROSS_EMULATOR to some dummy value.

48345343

by Sven Tennie at 2026-06-20T23:42:52+02:00

Javascript skip T23697

See #22355 about how HSC2HS and the Javascript target don't play well
together.

5e44fd05

by Sven Tennie at 2026-06-20T23:42:52+02:00

Mark T24602 as fragile

It was skipped before (due to CROSS_EMULATOR being set, which changed
for JS), so we don't make things worse by marking it as fragile.

ab349ec2

by Sven Tennie at 2026-06-20T23:42:52+02:00

Fix T22744 for GHCJS

In fact, this test needs Template Haskell, not necessarily an
interpreter.

c73352d8

by Sven Tennie at 2026-06-20T23:42:52+02:00

haddock-test: fix GHCJS haddock test failures

Add --ghc-pkg-path flag support so haddock test runner can find
cross-prefixed ghc-pkg (e.g. javascript-unknown-ghcjs-ghc-pkg) which
is not on $PATH in cross install directories.

Skip haddockHtmlTest on GHCJS: Threaded.hs uses forkOS in a TH splice,
which GHCJS RTS doesn't support. Mark with js_skip in all.T.

5e814e76

by Andreas Klebinger at 2026-06-22T23:00:24-04:00

compiler: Deduplicate hscTidy

This function was accidentally duplicated during a refactor.

Fixes #27351

473b97eb

by sheaf at 2026-06-22T23:01:22-04:00

Avoid mkTick in Core Prep breaking ANF (part II)

Hotfix for 2f9579765f55b3920ceb2e04995ff41a9d0e2d4e fixing a small
oversight in the call to tickTickedExpr from mkTick, in which we
improperly recursively called mkTick without passing on the preserve_anf
flag.

Fixes #27386

9284a1f7

by Simon Hengel at 2026-06-23T05:55:33-04:00

Don't use global variables to address concurrency bugs! (fixes #27234)

This was originally introduce with
88f38b03025386f0f1e8f5861eed67d80495168a to address #17922.

In this specific case a better fix would have been to synchronize on
stderr:

    withHandle_ "stderrSupportsAnsiColors" stderr $ \ _ -> do
      ...

But apparently the dependency on `terminfo` was removed in
32ab07bf3d6ce45e8ea5b55e8095174a6b42a7f0, preventing #17922 in the first
place.

44309cd3

by Alan Zimmerman at 2026-06-23T05:56:20-04:00

EPA: remove LocatedL / SrcSpanAnnL and  LocatedLI / SrcSpanAnnLI

This is part of a refactor towards only having LocatedA / SrcSpanAnnA

It removes the stated items, but has to add back one for BooleanFormula,
LocatedBF / SrcSpanAnnBF

This commit also use the HsConDetails RecCon extension point to
capture the braces in a record constructor

2f6a5534

by Simon Jakobi at 2026-06-23T15:46:20+02:00

Add -dstable-core-dump-order for stable Core dump ordering (#27296)

The order of top-level bindings in Core dumps (-ddump-simpl etc.) is the
compiler's Unique-sensitive internal processing order, so an unrelated
upstream change can reorder them and defeat a textual diff of two dumps.

This adds an opt-in flag -dstable-core-dump-order that reorders the
top-level bindings of dumps routed through dumpPassResult into a stable,
Unique-independent order, so two dumps line up across rebuilds. See
Note [Stable Core dump order] in GHC.Core.Ppr for the sort key and its
rationale.

Adds tests T27296 (binders GHC emits in non-source order by default,
asserted to come out stably ordered under the flag) and T27296b (an
untidied -ddump-float-out dump pinning the ordering of the anonymous lvl
floats by literal value).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

141986e3

by mangoiv at 2026-06-24T15:51:14-04:00

compiler: refactor error reporting code for ExplicitLevelImports

Refactors error reporting code for ExplicitLevelImports to pass in a
RdrName and a GlobalReaderElt to be able to report errors that are
faithful to the source and to more precisely distinguish between names
that are in scope from different qualifications.

Fixes #27385 and #26616

aa7df6b6

by Simon Hengel at 2026-06-24T15:52:18-04:00

Set GHC_VERSION when calling custom pre-processors (see #25952)

(so that pre-processors can emit backwards compatible code)

a9e494f2

by Simon Hengel at 2026-06-24T15:54:08-04:00

Add a flag to control GHCi specific error hints (close #27409)

a805b2a2

by Simon Hengel at 2026-06-24T15:55:20-04:00

Reference correct package in error messages for reexported modules

(fixes #27417)

f235d183

by Simon Jakobi at 2026-06-25T05:51:18-04:00

Add explicit setBit/clearBit/complementBit for instance Bits Integer (#21176)

The default setBit, clearBit, and complementBit methods allocate
intermediate Integers per call. Define them explicitly via the new
integerSetBit[#], integerClearBit[#] and integerComplementBit[#], built
on the BigNat# primitives, which avoid those allocations. Allocation is not
eliminated entirely -- the negative (IN) cases would need in-place mutation,
which is left as future work.

The default methods constant-folded on literal arguments via the
integerOr/integerAnd/integerXor rules, which fold literal Integers of any
size. The explicit functions have no such rule, so they (their Word-argument
wrappers, and the Bits Integer methods) are marked INLINE to expose the
underlying primops to the simplifier; see Note [INLINE for constant folding
of bit operations]. This restores folding only on the small-int (IS) path --
large literal Integers (IP/IN) are no longer constant-folded, a minor
regression for that case. T8832 covers the IS-path folding.

The new golden-output test T21176 checks all three operations against the
default implementations across the sign/size boundaries, recording each
result plus its integerCheck validity. The base and ghc-bignum interface-
stability export goldens gain the new functions.

The main changelog entry lives in changelog.d under a new ghc-internal
section (renamed from ghc-prim).

CLC proposal: https://github.com/haskell/core-libraries-committee/issues/423

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

202ed264

by Marc Scholten at 2026-06-25T05:52:21-04:00

haddock: use Text in documentation pipeline

This patch moves Haddock's documentation pipeline from String to Text
where the data is already textual. It avoids repeated conversions while
keeping the existing decoding behavior for invalid UTF-8 docstring
chunks.

The main changes are:

* Render and carry docstrings as Text in Haddock-facing paths.
* Use the Binary Text instance from GHC.Utils.Binary for Haddock
  interface files, and bump the Haddock binary interface version.
* Add a FastString HTML instance so XHTML rendering avoids
  intermediate String allocation.
* Keep HsDocStringChunk decoding lenient, matching the previous
  unpackHDSC behavior on invalid UTF-8 input.
* Update the xhtml submodule to 3000.4.1.0, which contains the
  apostrophe escaping fix used by the Haddock test output.

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Assisted-by: Codex <codex@openai.com>

a72ff58f

by mangoiv at 2026-06-25T05:53:07-04:00

compiler: rename ZonkAny to UnusedType and add pretty printing logic

ZonkAny is a hard to understand name for users who do not know how the
compiler works internally. Additionally, it is confusing that ZonkAny,
while being a concrete type *represents* a meta variable, espeically in
the compiler output.
This patch changes the name of ZonkAny to UnusedType which is closer to
its intended semantics and adds special pretty printing logic to display
this type in the same fashion the compiler displays meta variables in
other places, whenever they leak from the implementation to the user.
It also exports the type from ghc-internal:GHC.Internal.Types in order
to expose documentation.

Fixes #27390

Co-Authored-By: Sam Derbyshire <sam.derbyshire@gmail.com>

6813f002

by Simon Jakobi at 2026-06-26T04:51:47-04:00

Reg.Linear: drop Platform argument from most FR (FreeRegs) methods

The FR class has one instance per CPU architecture, so any
architecture-constant information its methods derived from the Platform
argument can instead be baked into the instance. This removes the now
needless Platform argument from frAllocateReg, frGetFreeRegs and
frReleaseReg.

frInitFreeRegs keeps its Platform argument: the initial allocatable set is
genuinely platform-dependent, see Note [Aarch64 Register x18 at Darwin and
Windows].

Fixes #26665

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

3b2a9409

by Zubin Duggal at 2026-06-26T04:52:39-04:00

testsuite: Report fragile failures as skipped in JUnit output

27463426

by Rodrigo Mesquita at 2026-06-26T20:54:58-04:00

perf: Share Module in Iface Symbol Table

This commit modifies the structure of the serialized `SymbolTable Name`
to then re-use and share the `Module` (both on disk and in memory) across
all `Name`s from the same module.

The new structure looks like:

  <total name count>
  $modules.size
  for (mod, names) in $modules:
    $mod
    $names.size
    for table_ix, occ in $names
      $table_ix
      $occ

i.e. we put the module just once, followed by all names in that module.
When deserializing, we deserialize the module just once, and all the
following `Name`s are constructed with a pointer to that same decoded
`Module`.

In `hoogle-test`, we must use `DNameEnv` rather than `Map Name`,
otherwise the output fixities order was susceptible to changes in the
uniques assigned to each Names, which is not stable.

Fixes #27401

-------------------------
Metric Decrease:
    InstanceMatching
    LinkableUsage01
    LinkableUsage02
    hard_hole_fits
-------------------------

412f1675

by Simon Hengel at 2026-06-26T20:55:41-04:00

Rename `MCDiagnostic` to `InternalMCDiagnostic`

`MCDiagnostic` is meant to be used for compiler diagnostics.

Any code that creates `MCDiagnostic` directly, without going through
`GHC.Driver.Errors.printMessage`, sidesteps `-fdiagnostics-as-json` (see
e.g. !14616, !14475, !14492 !14548).

To avoid this in the future, this change more narrowly controls who
creates `MCDiagnostic` (see #24113).

6f212121
by Facundo Domínguez at 2026-06-26T20:56:27-04:00
```
Encapsulate options of occurAnalysePgm in a record
```

adfbb179

by Facundo Domínguez at 2026-06-26T20:56:27-04:00

Allow to configure the occurrence analyser to retain some dead bindings

This is needed by plugins that are the only consumers of a binding which
is otherwise unused in the program.

See Note [Controlling elimination of dead bindings in occurrence analysis]
added in this commit, or
https://gitlab.haskell.org/ghc/ghc/-/issues/27240 for more discussion.

c745b11f
by Copilot at 2026-06-26T20:56:27-04:00
```
Address documentation feedback
```

2c2a4a2a

by Copilot at 2026-06-26T20:56:27-04:00

Keep the imp_rules parameter of occurPgmAnalysePgm and add occ_opts to OccEnv

e2262b0e

by Copilot at 2026-06-26T20:56:27-04:00

Strengthen T27240.hs with a binding that should be removed

5f9d9268

by Copilot at 2026-06-26T20:56:27-04:00

Move the reference #27240 to a related paragraph

d86d2644

by Simon Hengel at 2026-06-26T20:57:10-04:00

Remove deprecated flag `-ddump-json` (see #24113)

This was first deprecated in 9.10.1.

3b15ff03

by Simon Jakobi at 2026-06-27T18:48:34+02:00

Tweak mk_mod_usage_info

* Use O(log n) `elemModuleEnv` instead of O(n) `elem` to filter the
  direct imports.
* Use `nonDetModuleEnvKeys` to avoid sorting the ent_map keys twice.
* Prepend the presumably shorter list when creating all_mods with
  `(++)`. Actually this eliminates the `(++)` entirely, as it seems to
  fuse with the `filter` expression.

As a result there is a tiny speed-up when generating the .hi-files for
modules with many imports.

None of the changes affect compilation determinism as the module list
is explicitly sorted to ensure a canonical order.

2d0fd154

by Alan Zimmerman at 2026-06-29T11:44:00-04:00

EPA: Remove LocatedC / SrcSpanAnnC

This is part of a cleanup of the zoo of
SrcSpanAnnXXX types for exact print annotations.

This one removes SrcSpanAnnC used for storing exact print annotations
for contexts. It replaces it with an explicit `HsContext` data type
that carries the annotations and the context.

So, replace

  type HsContext pass = [LHsType pass]

with

  type HsContext pass = HsContextDetails pass (LHsType pass)

  data HsContextDetails pass arg
    = HsContext
      { hsc_ext  :: !(XHsContext pass)
      , hsc_ctxt :: [arg]
      }
    | XHsContextDetails !(XXHsContextDetails pass)

We need the parameterised HsContextDetails because it is used both for
HsQual carrying 'LHsExpr p' and "normal" contexts carrying 'LHsType p'.

cca0d589

by Luite Stegeman at 2026-06-30T13:33:40-04:00

rts: handle large AP closures in compacting GC

The function update_fwd_large in the compacting GC could run into
an unexpected object with the following error:

  internal error: update_fwd_large: unknown/strange object  24

Closure type 24 is the AP closure, which was not handled in
upd_fwd_large. This patch adds handling them.

fixes #27434

42935858

by Luite Stegeman at 2026-06-30T13:33:40-04:00

testsuite: use compacting_gc way instead of hardcoding +RTS -c

bf7b5ce6

by Alan Zimmerman at 2026-06-30T13:34:23-04:00

EPA: Remove LocatedLW from LStmtLR

HsDo already had its XDo extension point for an
AnnList, which also appeared in LocatedLW.
So we remove the redundant one and use the one inside HsDo
as originally intended.

Also delete LocatedLC/LocatedLS as they were unused

d7cfea49

by Recursion Ninja at 2026-06-30T21:37:12-04:00

Decoupling 'L.H.S' from 'GHC.Types.SourceText'

  * Migrated 'IntegralLit'   to 'L.H.S.Lit'.
  * Migrated 'FractionalLit' to 'L.H.S.Lit'.
  * Migrated 'StringLiteral' to 'L.H.S.Lit'.
  * Added TTG extension points to the types above.
  * Added nice export list to 'GHC.Hs.Lit'.
  * Added 'rnOverLitVal' and 'tcOverLitVal' functions to 'GHC.Hs.Lit'.
  * Added instance 'Anno (StringLiteral (GhcPass p)) = SrcSpanAnnN'
  * Moved [Notes] about 'SourceText' from 'L.H.S.*' to 'GHC.*'.
  * Removed all references to 'SourceText' from 'L.H.S'.
  * Removed the trailing comma record field from  'StringLiteral'
  * Renamed exported functions for nomenclature consistency.
  * Deprecated the renamed functions

Fixes #26953

a1f2558b

by Recursion Ninja at 2026-06-30T21:37:12-04:00

Monomorphising GHC pass parameters where appropriate

7bf9e3c5

by Teo Camarasu at 2026-06-30T21:38:03-04:00

Make Q abstract

This patch aims to clearly demarcate the internal and external interfaces
of Q.
In the past the `Quasi` typeclass was both part of the external,
public-facing interface, and was used to give the implementation of `Q`.

Now we separate out these two distinct roles. `Quasi` continues to exist
in the public interface, but we introduce a new `MetaHandlers` type,
which is equivalent to `Dict Quasi`.

`Q a` is now defined to be `MetaHandlers -> IO a`, and, crucially,
the constructor and the new `MetaHandlers` type are not exposed from the
public interface.

This gives us the ability to vary the interface on the GHC side without
forcing a breaking change on the `template-haskell` side.
Similarly `template-haskell` has more freedom to change the `Quasi`
typeclass without needing any changes in `lib:ghc`.

Implements https://github.com/ghc-proposals/ghc-proposals/pull/700

Resolves #27341

4262af36

by L0neGamer at 2026-06-30T21:38:56-04:00

generically defines mconcat in terms of internal type's Semigroup instance

add changelog entry

use simpler definition for mconcat

`nonEmpty` isn't available yet; inline branches in case

add test case

fixup generically defines mconcat in terms of internal type's Semigroup instance

add comment on Generically and deriving mishaps

swap mconcat to foldr version

add some strictness testing for mconcat

add to `base` changelog entry

e22ad997

by Cheng Shao at 2026-06-30T21:39:43-04:00

hadrian/rts: fix unregisterised build for gcc 15+

This patch fixes unregisterised build for gcc 15+:

- Pass -optc-Wno-error in hadrian when +werror enables -optc-Werror,
  see added comment for details.
- For RTS functions that the codegen would emit calls, ensure their
  real prototype is hidden when the header is included in .hc fies
  (IN_STG_CODE), and the dummy prototype is provided to match the EFF_
  convention.

In the future we should get rid of EFF_ (#14647) and remove these
hacks, but for now this patch makes unregisterised work again on newer
toolchains. Fixes #27404.

Co-authored-by: Codex <codex@openai.com>

3f00f234

by Cheng Shao at 2026-06-30T21:40:32-04:00

compiler: fix missing handling of CmmUnsafeForeignCall node in LayoutStack

This patch fixes missing handling of `CmmUnsafeForeignCall` middle
node in the `LayoutStack` pass.

Before proc-points splitting, this pass computes liveliness of local
registers, and spills those alive across a Cmm native call onto the
stack. It need to traverse all middle nodes in each block and check
whether a local register is an assignee, if so then the previous
mapping in `sm_regs` is invalidated and needs to be dropped. However,
it didn't handle `CmmUnsafeForeignCall` node which may also assign to
a local register. When proc-points splitting is enabled, this can
produce an invalid basic block that doesn't properly backup the
updated local register to the stack before doing a Cmm call, resulting
in completely invalid runtime behavior.

The patch also adds a `T27447` regression test. With no-TNTC or with
LLVM backend, without the fix the test case would output a stale
0x1111111111111111 value, instead of the expected 0x2222222222222222
output.

Fixes #27447.

Co-authored-by: Codex <codex@openai.com>

701088db

by Ben Gamari at 2026-07-01T10:34:03-04:00

gitlab-ci: Drop vestigial references to make build system

62d54a53

by Ben Gamari at 2026-07-01T10:34:03-04:00

gitlab-ci: Add support for running specifying a job's testsuite ways

7f97ac2c

by Ben Gamari at 2026-07-01T10:34:03-04:00

gitlab-ci: Run llvm testsuite ways in llvm jobs

Addresses #25762.

7ea75116

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Add normalise_ddump_deriv setup function

Some tests check the result of -ddump-deriv, which may contain INLINE pragmas depending on optimization flags.
With normalise_ddump_deriv setup function, INLINE pragmas are stripped off.

c7a8199f

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Use -dsuppress-idinfo to make tests more robust

Previously, T18052a and T21755 were failing on 'optasm' and 'optllvm' ways because of visibility of unfoldings.

a12122e5

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Use a trick to keep large objects alive

Previously, T17574 and T19381 were failing on 'optasm' and 'optllvm' ways because of compiler optimizations.
Change them to use NOINLINE to prevent unwanted optimizations.

1a95b327

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Only run T24224 in 'normal' way

This test is a frontend-only one and breaks if optimizations are enabled.

8abea737

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Ignore T18118's stderr

When optimizations are enabled, the compiler emits a warning (You cannot SPECIALISE ...).
The message is not important, so ignore it.

9453a722

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Mark T816 and tc216 broken with optimizations

These tests are about type checking, so we should not care too much if they are broken with optimizations.

See #26952

0aef9ec0

by Ben Gamari at 2026-07-01T10:34:03-04:00

testsuite: ds014 is not longer broken

It now appears to pass in the ways it was marked as broken in.

Closes #14901.

4692d1e4

by Ben Gamari at 2026-07-01T10:34:03-04:00

testsuite: Only run stack cloning tests in the normal way

These are too dependent upon code generation specifics to pass in most
other ways.

c154df26

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Update options_ghc_fbyte-code

The `-fbyte-code` option used to be overriden by `-fllvm` but it is no longer true since !14872 was merged.

I updated the test to accept the new behavior.

Closes #27049

5d8bb7b5

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Only run T22744 in 'normal' way

This test takes a long time on optimized ways.

d1e74c8e

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Disable tests that use -finfo-table-map on llvm ways

Currently, -finfo-table-map does not work with -fllvm. See #26435

3bf38c84

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Don't run T24726 on optimized ways

If optimizations are enabled, the rewrite rule just fires and -drule-check will report nothing.

e4eef116

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Use -fno-unoptimized-core-for-interpreter when running LinkableUsage01/02

Optimizations for the bytecode interpreter are considered experimental, and need a flag to be enabled.

234a9872

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Suppress unwanted optimizations on T25284

99a2af2f

by ARATA Mizuki at 2026-07-01T10:34:03-04:00

testsuite: Don't run stack_big_ret with optimizations

Stack layout may change with optimizations enabled.

04c836df

by ARATA Mizuki at 2026-07-01T10:34:04-04:00

testsuite: Mark memo001 broken on optimized ways

See #27396

1a8a24f4

by ARATA Mizuki at 2026-07-01T10:34:04-04:00

testsuite: Mark syn-perf broken on optimized ways

See #27398

40412093

by Duncan Coutts at 2026-07-01T10:34:50-04:00

Add a test for thread scheduler fairness

It also tests that the interval timer and context switching works.
We also test that fairness is lost when the context switching interval
is too coarse for the duration of the test.

We add this test before doing surgery on the interval timer, so we have
decent coverage.

3f34d557

by Duncan Coutts at 2026-07-01T10:34:50-04:00

Make exported stop/startTimer no-ops, and rename internal functions

Specifically, internally rename:
stop/startTimer to pause/unpauseTimer
stop/startTicker to pause/unpauseTicker

and keep stop/startTimer as exported functions, but now as no-ops.

In the past the stop/startTicker actions were used incorrectly as if
they were synchronous, which they are not. See issue #27105. We now
document pause/unpackTicker as being async and not to be used for the
purpose of concurrency safety.

The existing stop/startTimer (note Timer not Ticker, the Timer calls the
Ticker!) are also exported from the RTS as a public API. This was
historically because the ticker used signals and it was important to
suspend the timer signel over a process fork. So these functions were
exported to be used by the process and unix libraries.

We cannot just remove the RTS exports, but we now make them no-ops, and
they can be removed from the process and unix library later. This
was already documented in a changelog.d entry no-more-timer-signal but
due to changes during the MR process the change to make stop/startTicker
into no-ops didn't make it into the earlier MR.

02e84e5f

by Duncan Coutts at 2026-07-01T10:34:51-04:00

Make exitTicker/exitTimer unconditionally synchronous

We never use them asynchronously, and we should never need to do so.

And update some related comments.

13db6a72

by Duncan Coutts at 2026-07-01T10:34:51-04:00

posix ticker: update and improve comments on (un)pause and exit

Clarify what is async vs sync.

43d9a07d

by Duncan Coutts at 2026-07-01T10:34:51-04:00

posix ticker: split out ppoll/select helper functions

Move the #ifdefs out of the main code body by introducing local helper
functions and types, which themselves have two implementations (with a
common API) based on ppoll or select.

This helps improve clarity/readability.

a5491baa

by Duncan Coutts at 2026-07-01T10:34:51-04:00

posix ticker: improve the implementation

The existing implementation supported pausing and exiting, with the
implementation of pausing reling on a mutex and condition variable.
It needed to check the pause and stop shared variables on every
iteration. It relies on ppoll or select, to wait on the timeout and also
wait on an interrupt fd. The interrupt fd was only used for prompt
exit/shutdown, and not for pausing or other notification. The pause only
needed a lock and a memory operation, but the pause was not prompt. The
resume used a lock, and signaling a cond var.

The new implementation uses a somewhat more regular design: every
notification is done by setting a shared variable and
interrupting/notifying the ticker via the fd. The ticker thread does not
need to check any shared variables on normal timer expiry, only when it
recevies notification. This may be a micro-optimisation, but the tick
occurs 100 times a second by default so any improvements in the hot path
are amplified. When the ticker thread does receive notification it can
check the various shared variables and update its local state. The
blocking relies on using ppoll/select but without a timeout. This avoids
the condition var and also allows further notifications when paused
(also used for unpausing).

This design can be extended with further notification types if needed by
using and checking further shared vars (or making existing shared vars
an enum or counter). This may be used in future for additional
notifications to the ticker thread. This will likely be used to proxy
wakeUpRts from a single handler context for example. And this approach,
avoiding mutexes, is compatible with use from signal handlers.

So overall, it's:
 * slightly simpler / more regular;
 * easier to extend with additional notifications;
 * probably slightly more efficient (but a micro-optimisation);
 * and supports calling notification from signal handlers

5b20821e

by Duncan Coutts at 2026-07-01T10:34:51-04:00

posix ticker: further minor local renaming for code clarity

Improve the clarity with better choice of names for several local vars
and function.

1f3ec5e0
by Duncan Coutts at 2026-07-01T10:34:51-04:00
```
win32 ticker: split out local helper functions
```

596e7307

by Duncan Coutts at 2026-07-01T10:34:51-04:00

win32 ticker: provide guarantee about concurrency and idempotency

Use a lock to ensure pause/unpause can be used concurrently. Use a
paused variable, protected by the lock, to ensure that pause and unpause
are both idempotent. This is what the portable API expects.

1870edd7

by Duncan Coutts at 2026-07-01T10:34:51-04:00

win32 ticker: make the initial tick be after one wait interval

There is no need to tick immediately. This is consistent with the
posix implementation.

7c15ab5b

by Duncan Coutts at 2026-07-01T10:34:51-04:00

ticker: remove now-unnecessary layer of enable/disable

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 eliminate the need for synchronous stop/startTicker,
we don't need this not-quite-working-anyway atomic protocol. The new
pause/unpauseTicker is explicitly asynchronous and idempotent.

8585f8cb

by Duncan Coutts at 2026-07-01T10:34:51-04:00

ticker: 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.

6e381626

by Duncan Coutts at 2026-07-01T22:29:55+01:00

Adjust releaseCapability_ precondition to allow cap->running_task == NULL

There are two use cases for releaseCapability_:

1. The current Task (cap->running_task) releases the Capability.
   The Capability is marked free, and if there is any work to do,
   an appropriate Task is woken up.

2. There is no current task (cap->task == NULL), and thus the
   Capability is idle, and we want to wake up an idle Task to animate
   the Capability. This case uses always_wakeup.

Currently, the precondition for releaseCapability_ is
  cap->running_task != NULL
and so the 2nd use cases have to set cap->running_task (which is then
immediately overwritten) just to satisfy the precondition. See the
use cases in sendMessage and prodCapability.

So we can relax the precondition to be:
  cap->running_task != NULL || always_wakeup
so that in the always_wakeup case, we say it is ok for the
cap->running_task to be NULL.

This lets us simplify sendMessage and prodCapability. In particular it
will allow prodCapability to not need a Task parameter.

The ulterior motive for all this is that I want to be able to call
prodCapability from an OS thread that is not itself a Task, in persuit
of issue #27086: disentangle I/O managers from wakeUpRts. The most
straightforward way to wake the RTS is using prodCapability, but the
context in which we will need to do that are threads that are not Tasks.

89404ebc

by Duncan Coutts at 2026-07-01T22:29:55+01:00

prodCapability no longer needs to take a Task param

Now that releaseCapability_ can accept cap->running_task == NULL then it
is no longer necessary for prodCapability to require a Task.

4e60c5f6

by Duncan Coutts at 2026-07-01T22:29:56+01:00

Define prodOneCapability

There was an existing declaration for this in the header file, but no
definition.

Similarly, there is a declaration for prodAllCapabilities but no
definition, and we don't need it, so remove the declaration.

2527026f

by Duncan Coutts at 2026-07-01T22:29:56+01:00

Add a wakeUpRtsViaTicker feature to the posix ticker

It proxies a call to wakeUpRts, but crucially, this can be called from
a signal handler context. It will be used for ctl-c handling.

aa5a03a5

by Duncan Coutts at 2026-07-01T22:29:56+01:00

Change how wakeUpRts works

Previously it would call wakeupIOManager to get a capability to wake up
and run. This works but it entangles the I/O managers with unrelated
features: ctl-c handling and idle gc (the two features that use wakeUpRts).

The reason it used wakeupIOManager is that this action is safe to use
from a posix signal handler, since it just posts bytes to a pipe.
Otherwise the more direct approach (used e.g. by sendMessage when the
target capability is idle) is to use releaseCapability. But that uses
condition variables and mutexes, which are not safe to use from within a
signal handler.

So instead of entangling the (multiple) I/O managers with this, we make
wakeUpRts use the direct approach (using prodOneCapability). On win32
the ctl-c console handler can call wakeUpRts directly, since it is
called in a proper thread. On posix, to deal with the signal handler
problem, we make the signal handler ask the ticker thread to proxy the
call to wakeUpRts, since the ticker thread is also a proper thread.

This will allow the I/O managers to no longer be concerned with this.
This is good because there are many I/O managers (and they're
complicated), but there is (on posix) only one ticker implementation. So
this is an overall reduction in coupling and complexity.

Fixes issue #27086

c6d53c16

by sheaf at 2026-07-02T21:35:44-04:00

Test driver: normalise line numbers into libraries

When comparing the stdout of tests that print out callstacks, we can't
rely on the stability of exact line:column spans pointing into libraries
(e.g. ghc-internal), as any change (such as adding a comment) can change
them.

This commit addresses this by normalising away line:column in callstacks,
but only when those point into internal libraries. We don't do this in
general, as the exact span might be important to the test (e.g. for a
span within the test module itself).

Fixes #27387

81ee62e0

by Alan Zimmerman at 2026-07-02T21:36:33-04:00

EPA: Remove LocatedLW from MatchGroup

This is the last usage of LocatedLW / SrcSpanAnnLW

925959db

by Recursion Ninja at 2026-07-04T04:14:12-04:00

Decoupling 'L.H.S' from 'GHC.Hs.Doc'

  * Migrated 'GHC.Hs.Doc' and 'GHC.Hs.DocString' AST defintions from 'GHC.*' namespace,
    to new 'Language.Haskell.Syntax.Doc' module in the 'L.H.S' "namespace."
  * Updated 'HsDocString to be TTG-parameterised as 'HsDocString pass'.
  * Added 'GHC.Hs.Extension.Pass': splits 'GhcPass'/'Pass' and all 'HsDocString'
    TTG instances out of 'GHC.Hs.Extension', which re-exports it unchanged
    (this is backwards compatible and prevents the introduction of a boot file).
  * Deleted 'GHC.Hs.Doc.hs-boot'; removed all 'L.H.S.*' imports of 'GHC.Hs.Doc'.
  * Updated 'GHC.Hs.DocString' to be TTG pass-parameterised throughout; moved
    'mkHsDocStringChunk'/'unpackHDSC' here (require 'GHC.Utils.Encoding').
  * Split 'GHC.Rename.Doc.rnHsDoc' from 'rnHsDocIdentifiersOnly'.
  * Updated parser, renamer, typechecker, HIE, and exact-print for new types.
  * Added 'HsDocString' TTG instances for 'DocNameI' to 'Haddock.Types'.
  * Killed the last module loop between GHC.* and LHS.*.
        - Only edges from LHS.* to GHC.Data.FastString now!

Resolves #26971

b7e24044

by mangoiv at 2026-07-04T04:14:56-04:00

ci: retry fetching test metrics

Retry fetching test metrics to make the CI not fail if the services is
temporarily unavailable

4180af3f

by Zubin Duggal at 2026-07-04T04:15:38-04:00

Bump semaphore-compat submodule to 2.0.1

This versions includes some cruicial fixes for darwin

242d4317

by sheaf at 2026-07-04T04:16:19-04:00

Remove outdated comment in GHC.Data.ShortText

There was a long comment in GHC.Data.ShortText about a workaround that
was necessary when bootstrapping with GHC 9.2 and below. The actual
logic has since been dropped, but the comment remained. This commit
removes the vestigial comment.

9b714c4c

by Zubin Duggal at 2026-07-05T09:40:36+05:30

CorePrep: Don't speculatively evaluate bindings that we have already discovered to be absent

In #25924, we segfault because speculation forces a projection out of a RUBBISH dictionary
(which we generated because it absent).

Solution: Don't speculate on bindings we already know are absent.

Fixes 25924

4a59b3ee

by Zubin Duggal at 2026-07-05T09:40:36+05:30

Don't make absent fillers for terminating types

In #25924 we discovered that we could speculatively evaluate an absent filler
for a dictionary, and project a field (a superclass selector) out of it,
resulting in segfaults.

Solution: Never make an absent filler or rubbish literal for a terminating type
like a dictionary. mkAbsentFiller returns Nothing for isTerminatingType, so
worker/wrapper and the specialiser keep the real argument instead.

Some small metric decreases because we do a little less work in the
simplifier now.

Metric Decrease:
    T9872a
    T9872b
    T9872c
    TcPlugin_RewritePerf

383ddcd4

by Alan Zimmerman at 2026-07-06T07:08:16-04:00

EPA: Move the 'where' annotation for PatSynBind

This allows us to move it out of the MatchGroup exact print annotation
too

66d1a5d5

by fendor at 2026-07-07T16:57:56-04:00

Add 'backendInfoTableMapValidity' backend predicate

Check whether the backend supports the `-finfo-table-map` flag and
ignore it otherwise.

Improve by-design documentation of `backendCodeOutput`.

`Backend` is **abstract by design**. Make this clearer in
`backendCodeOutput` which is incorrectly being used as a proxy for
`Backend`.

Instead, define the desired property predicates in GHC.Driver.Backend
In the process, make `backendCodeOutput` total.

74f1071d

by fendor at 2026-07-07T16:57:56-04:00

Add failing test for `-finfo-table-map` and bytecode backend

If you compile a module using the bytecode backend, with
-finfo-table-map, then the info table map doesn't get populated for the
module.

This is because the -finfo-table-map code path is implemented mostly in
the StgToCmm phase which isn't run when creating bytecode.

Ticket #27039

28d63bca

by mangoiv at 2026-07-07T16:59:16-04:00

ci: don't fail nightly if there have been no changes that night

Fixes #27127

4ebfc478

by Rodrigo Mesquita at 2026-07-08T04:47:53-04:00

ttg: Using ShortText over FastString in the AST

To make the AST independent of GHC, this commit replaces usages of
`FastString` with `HText` in the AST, killing the last edge from
Language.Haskell.* to GHC.* modules.

Even though we /do/ want to use FastStrings in general -- critically in
Names or Ids -- there is no particular reason for the FastStrings that
occur in the AST proper to be FastStrings. Strings in the AST are
typically unique and don't benefit particularly from being interned
FastStrings with Uniques for fast comparison.

`HText` is a type synonym for `ShortText` which uses GHC's Modified
UTF-8 encoding exclusively.

Modified UTF-8 must be used to represent the Haskell AST because the
Haskell Report allows surrogate code points. `Data.Text.Text` functions
use Standard UTF-8 which replace surrogates with a placeholder value,
thus `Data.Text.Text` is unsuitable for AST strings. See the
`Language.Haskell.Syntax.Text` module header for more details.

Final progress towards #21592

Closes #21628

d910b353

by Simon Peyton Jones at 2026-07-08T04:48:36-04:00

Update equality-type documenation in GHC.Builtin.Types.Prim

Fix #27466

b2530542

by Simon Peyton Jones at 2026-07-08T04:48:36-04:00

Honour -dsuppress-coercions in GHC.Core.TyCo.pprCo

Fixes #27467

9a73179a

by Facundo Domínguez at 2026-07-08T04:49:26-04:00

Add item to MR checklist asking to squash fixup commits after approval

The checklist has an item that reads

    All commits are either individually buildable or squashed.

This item could be checked immediately after sending the merge request
though. If reviewers ask for amends later on, and the author amends
the merge request, there was no item that would remind the contributors
to squash the fixup commits before landing.

This commit adds a new item

    After all approvals and before landing: all fixup commits are squashed with their originating commits.

which should be harder to mark as done before approvals have been given.

ed09895d

by Andreas Klebinger at 2026-07-08T16:53:27-04:00

Fix a profiling race condition resulting in segfaults.

StgToCmm: Don't assume tagged FUN closures in closureCodeBody.
When entering a closure the self/node pointer might not be tagged in
some situations when a thunk is evaluated by multiple threads.
So we most AND away the tag bits rather than subtracting an expected tag.

Apply.cmm: Fix a race condition occuring when a thunk is mutated during GC.

In stg_ap_0_fast when might need to run GC before entering a thunk. If this happens
another thread or the GC itself might mutate the closure making entering it no longer
valid. We now check for this.

Add test and changelog for #27123 fixes.

67c03eb2

by Cheng Shao at 2026-07-08T16:54:09-04:00

ghc-heap: fix invalid srtlen returned by peekItbl when no-TNTC

This patch fixes the no-TNTC code path of `peekItbl` so that it looks
at the right memory address when reading the `srt` field from the
`StgInfoTable_` struct. Also adds a `T27465` regression test that
reproduces the bug on no-TNTC builds before the fix. Fixes #27465.

Co-authored-by: Codex <codex@openai.com>

2ecabb4f

by Zubin Duggal at 2026-07-09T09:23:25-04:00

hadrian: binary-dist-dir should not be the default target

Revert behaviour to pre 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2

In 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2, we applied the following behaviour change:

```
hadrian: Build stage 2 cross compilers
...
* hadrian: Make binary-dist-dir the default build target. This allows us
  to have the logic in one place about which libraries/stages to build
  with cross compilers. Fixes #24192
```

This is a major regression to development experience, a plain hadrian/build
--freeze1 now takes ages because we rebuild all docs (which need to go in the
binary dist dir).

`binary-dist-dir` is the wrong default target for regular GHC development work

Fixes #27445

e16388e3

by Zubin Duggal at 2026-07-09T09:23:25-04:00

.gitignore: Add the hadrian system.config introduced by commit 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2

Since

commit 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2
Author: Matthew Pickering <matthewtpickering@gmail.com>
Date:   Thu Dec 21 16:17:41 2023 +0000

    hadrian: Build stage 2 cross compilers

./configure produces /hadrian/cfg/system.config.{host,target}

Add these to .gitignore

7e8abf41

by Alan Zimmerman at 2026-07-09T09:24:12-04:00

EPA: Replace AnnListItem with simply [TrailingAnn]

Remove the unnecessary wrapper around a single field.

29032f17

by Zubin Duggal at 2026-07-09T09:24:58-04:00

testsuite: Keep real reason for fragile test failures

c34e03a7

by Zubin Duggal at 2026-07-09T09:24:58-04:00

testsuite: Fall back to the failure reason for empty JUnit bodies

409d40f0

by Zubin Duggal at 2026-07-09T09:24:58-04:00

testsuite: Show output diffs in JUnit output

Also refactor compare_outputs to return essentially a `Maybe Diff`
(`CompareOutput`) instead of a bool, but more pythonic. This
allows us to pass the diff through nice.

06fee1ab

by Zubin Duggal at 2026-07-09T09:24:58-04:00

perf notes: include stat deviation and acceptance window in notes so they show up in gitlab

57c0f32c

by mangoiv at 2026-07-10T11:08:38-04:00

driver: enable -finter-module-far-jumps by default

this fixes a compatibility bug with certain binutils/gcc versions where
we were seeing jump offset overflow errors.
This commit can probably reverted if we stop supporting the problematic
binutils/gcc verions (2.44 and 14.2, respectively)

Reolves #26994

4396a6f2
by Andrea Vezzosi at 2026-07-10T11:09:25-04:00
```
[Fix #27287] preserve ModBreaks in ModIface
```

ed261a7e

by Cheng Shao at 2026-07-14T17:59:38-04:00

hadrian: fix HLS support

This patch fixes hadrian's HLS support so one can rely on HLS when
working on the hadrian codebase. Fixes #27480.

Not building/linking shared libraries for hadrian is a severely
premature optimization; this top-level setting in `cabal.project` only
affects home packages while the dependencies in the cabal store are
built with vanilla/dynamic anyway, and even adding dynamic builds to
home packages would not be costly due to cabal's usage of
`-dynamic-too`.

eee8ec5b

by Cheng Shao at 2026-07-14T18:00:20-04:00

compiler: fix miscompiled %load_relaxed, add missing %store_relaxed

This patch fixes the %load_relaxed cmm primop compilation logic to
correctly use relaxed memory ordering, and adds the missing
%store_relaxed primop. Parsing logic of %load/%store with explicit
ordering is covered in the AtomicFetch test case. Fixes #27483.

Co-authored-by: Codex <codex@openai.com>

1718230f

by Alan Zimmerman at 2026-07-14T18:01:06-04:00

EPA: Keep binds and sigs together in HsValBindsLR

We combine them into a single list for GhcPs, wrapped in the
ValBind data type, which is the bind equivalent of ValD, having
constructors for binds and sigs.

This simplifies exact print processing, especially when using it to
update the contents of local binds, as we no longer need AnnSortKey
BindTag

6bd1ad2a

by Andreas Klebinger at 2026-07-14T18:01:49-04:00

Bump nofib submodule to account for MonoLocalBinds.

New versions of GHC enable MonoLocalBinds by default.
This breaks some of the benchmarks. I've fixed this and
this bump pulls in that fix.

7eb0f1c9

by Cheng Shao at 2026-07-14T18:02:31-04:00

testsuite: fix bytecodeIPE test under +ipe flavours

This patch fixes the bytecodeIPE test under +ipe flavours. It used to
fail under +ipe because the RTS is built with IPE info, then
stg_AP_info in RTS carries IPE info, so whereFrom wouldn't return
Nothing. Now the test checks IPE info of a datacon in the ghci-loaded
module which is not affected by whether the RTS is built with IPE info
or not. Fixes #27498.

Co-authored-by: Codex <codex@openai.com>

ef038aae

by cydparser at 2026-07-15T04:35:41-04:00

Reduce bytes allocated for `capabilities` in RTS (fixes #27487)

In rts/Capability.c, `capabilities` is an array of pointers, but it was allocated as if it were an
array of Capability's.

d377e83e

by Cheng Shao at 2026-07-15T04:36:27-04:00

rts: fix missing UNTAG in stg_readTVarIOzh

This patch fixes missing UNTAG on the current value closure read from
StgTVar. UNTAG is a no-op when it's stg_TREC_HEADER_info which is word
aligned; it may be a tagged closure, and reading info table from the
tagged address is an unaligned load which may cause issues on
platforms with strict alignment requirements.

Co-authored-by: Codex <codex@openai.com>

8ed03842

by Cheng Shao at 2026-07-15T04:36:27-04:00

rts: fix missing UNTAG in stg_control0zh_ll

This patch fixes missing UNTAG on the cont closure returned by
captureContinuationAndAbort. In case it's not NULL,
captureContinuationAndAbort returns a tagged StgContinuation closure,
in which case it must be untagged before accessing the
apply_mask_frame field.

In the past it worked out of luck: when apply_mask_frame was NULL then
mask_frame_offset is also 0 so the control flow didn't diverge to a
wrong path. Still, this is horribly wrong and will crash once
StgContinuation struct is refactored and fields are shuffled around.

Co-authored-by: Codex <codex@openai.com>

5aa7000a

by Cheng Shao at 2026-07-15T04:37:08-04:00

compiler: fix redundant AP thunk codegen when not using -ticky-ap-thunk

This patch fixes a double negation confusion in !7525 that results in
some redundant AP thunk code generation when not using
-ticky-ap-thunk. Now, we use `stgToCmmUseStdApThunk` to indicate
whether precomputed AP thunks in the RTS should be used, which
defaults to `True`, unless `-ticky-ap-thunk` is passed.
`-finfo-table-map` now also implies `-ticky-ap-thunk`, since when
doing IPE profiling we want the generated AP thunks to be unique.
Fixes #27502.

-------------------------
Metric Decrease:
    T3064
-------------------------

Co-authored-by: Codex <codex@openai.com>

d43a7b7a

by Brian McKenna at 2026-07-15T20:10:04+02:00

Strip ticks when desugaring bool guards

The special `considerAccessible` pattern was broken when compiling
with debug info. Compiling with debug info wraps expressions with
`SourceNote` ticks, which broke the internals of the
`desugarBoolGuard` function. Ticks are now ignored within this
function.

Fixes #27360

ede4b17b

by Ben Gamari at 2026-07-15T22:59:53-04:00

base: Display ExceptionContext in WhileHandling's textual description

As originally-implemented the implementation for
`WhileHandling(displayExceptionAnnotation)` would display the
`ExceptionContext` of the exception which it carries (as this was the
behavior of `displayException`, in terms of which
`displayExceptionAnnotation` was implemented).

However, in 284ffab3 the definition of `SomeException(displayException)`
was changed to exclude the `ExceptionContext`. This means that
`WhileHandling(displayExceptionAnnotation)` fails to describe the
provenance of the exception which it captures, greatly limiting its
utility.

Return the implementation to its originally-specified behavior by
implementing `WhileHandling(displayExceptionAnnotation)` in terms of
`displayExceptionWithInfo`.

Fixes #27456.

0f64f348

by Cheng Shao at 2026-07-16T15:41:08+00:00

ci: add missing docker permission workaround in abi-test job

660cb239

by Cheng Shao at 2026-07-16T19:37:48+00:00

bindist: Fix make install -j race condition on macos/freebsd

This patch fixes make install -j race condition on macos/freebsd. BSD
install fails with EEXIST when multiple install processes concurrently
create the same prefix directory. So we add an `install_dirs`
prerequisite job that sequentially creates the directories for
subsequent jobs to work with. Fixes #27499.

Co-authored-by: Codex <codex@openai.com>

08130257

by Cheng Shao at 2026-07-16T19:37:48+00:00

ci: run bindist make install with -j

This patch makes the ci scripts run `make install` with `-j` to reduce
wall clock time when installing the bindist, see related issue for
benchmark numbers. This only affects ghc ci logic, the user-facing
default is up to distributors and is still `-j1`. Closes #27029.

d5ae6906

by Adam Gundry at 2026-07-17T04:57:43-04:00

Mark various language extension flags as deprecated (see #27329)

The following language extensions are now deprecated:

 - AlternativeLayoutRule
 - AlternativeLayoutRuleTransitional
 - ParallelArrays
 - PolymorphicComponents
 - Rank2Types

In addition, the warning `-Walternative-layout-rule-transitional`
has been marked as deprecated, as it is emitted only under the
deprecated extension `XAlternativeLayoutRuleTransitional`.

fe3b059c

by Andrew Lelechenko at 2026-07-17T04:58:26-04:00

base: re-export GHC.Environment.getFullArgs from System.Environment

CLC proposal https://github.com/haskell/core-libraries-committee/issues/431

722236dd

by sheaf at 2026-07-18T08:48:31-04:00

Coercion optimisation: avoid double-Sym for InstCo

Ticket #27374 pointed out an issue with GHC.Core.Coercion.Opt.optCoercion's
handling of InstCo: it contravened (LC2) in Note [The LiftingContext in optCoercion]
because it applied the ambient 'sym' to a coercion that was then added
to the lifting context substitution.

Fixes #27374

Co-authored-by: Simon Jakobi <simon.jakobi@gmail.com>

ff70fc75

by sheaf at 2026-07-18T08:48:31-04:00

Coercion optimisation: avoid exponential behaviour

The change to coercion optimisation of 'InstCo' in the previous commit
introduces exponential behaviour to the coercion optimiser. To avoid
this, this commit provides a way to push in 'Sym' of an already-optimised
coercion: GHC.Core.Coercion.Opt.mkDeepSymCo.

See Note [Pushing Sym without re-optimising] in GHC.Core.Coercion.Opt.

dfef27f0

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Move THREADED_RTS-conditional struct members to end of Capability

Accessing members of the Capability struct from CMM code rely on
accessor macros. (The macros are generated by deriveConstants).

These macros have a single definition. This means that the offsets of
all struct members must *not* vary based on THREADED_RTS vs
!THREADED_RTS. This requires that any struct members that are
conditional on THREADED_RTS must occur after the unconditional struct
members. Hence we move all the ones that are conditional on
THREADED_RTS to the end.

Add a deriveConstants entry for the iomgr member of the Capability
struct, which was the motivation for this change.

Add warning messages to help our future selves. Debugging this took me
a couple hours in gdb!

c254e022

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Make the IOManager API use CapIOManager rather than Capability

This makes the API somewhat more self-contained and more consistent.
Now the IOManager API and each of the backends takes just the I/O
manager structure. Previously we had a bit of a mixture, depending on
whether the function needed access to the Capability or just the
CapIOManager.

We still need access to the cap, so we introduce a back reference to
reach the capability, via iomgr->cap.

Convert all uses in select and poll backends, but not win32 ones.
Convert callers in the scheduler and elsewhere.

Also convert the three CMM primops that call IOManager APIs. They just
need to use Capability_iomgr(MyCapability()).

4f3d8f31

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Split posix/MIO.c out of posix/Signals.c

The MIO I/O manager was secretly living inside the Signals file.

Now it gets its own file, like any other self-respecting I/O manager.

52ce04a9

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Rationalise some scheduler run queue utilities

Move them all to the same place in the file.

Make some static that were used only internally.

Also remove a redundant assignment after calling truncateRunQueue that
is already done within truncateRunQueue.

75bbdebc

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Rename initIOManager{AfterFork} to {re}startIOManager

These are more accurate names, since these actions happen after
initialisation and are really about starting (or restarting) background
threads.

724c0517

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Free per-cap I/O managers during shutdown and forkProcess

Historically this was not strictly necessary. The select and win32
legacy I/O managers did not maintain any dynamically allocated
resources. The new poll one does (an auxillary table), and so this
should be freed.

After forkProcess, all threads get deleted. This includes threads
waiting on I/O or timers. So as of this patch, resetting the I/O
manager is just about tidying things up. For example, for the poll
I/O manager this will reset the size of the AIOP table (which
otherwise grows but never shrinks).

In future however the re-initialising will become neeecessary for
functionality, since some I/O managers will need to re-initialise
wakeup fds that are set CLOEXEC.

c007d122

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Add a TODO to the MIO I/O manager

The direction of travel is to make I/O managers per-capability and have
all their state live in the struct CapIOManager. The MIO I/O manager
however still has a number of global variables.

It's not obvious how handle these globals however.

b65ab7b3
by Duncan Coutts at 2026-07-18T08:49:12-04:00
```
Add a FIXME note in the Poll I/O manager
```

daf2bd6f

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Add missing updateRemembSetPushClosure in poll I/O manager

For the non-moving GC.

e33ca830

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Minor doc improvement to struct StgAsyncIOOp member outcome

Mention the enumeration names, as well as their numeric values. The rest
of the code uses the enum names.

4edd2579

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Minor doc improvements for StgTSOBlockInfo

Clarify that certain union members are used only by certain legacy
I/O managers. Hopefully we will be able to remove these at some point.

536bedbb

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Avoid exporting various win32-specific rts symbols

The BeginPrivate.h / EndPrivate.h scheme works perfectly well on
Windows, but all of the rts/win32/*.h files were not using it.

8139b5ac

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Remove wakeupIOManager, ioManagerWakeup and setIOManagerWakeupFd

We no longer need wakeupIOManager for the threaded RTS case, so we can
remove it and the bits only needed to support it. This includes the
pipe/eventfd fd shared between the RTS and the in-library I/O manager
used for waking up the I/O manager thread. The pipe/eventfd still
exists, but it no longer has to be communicated to the RTS, since the
RTS no longer needs to use it.

So we remove the RTS API export setIOManagerWakeupFd, and remove uses of
it within the I/O managers in ghc-internal.

74fe7c66

by Duncan Coutts at 2026-07-18T08:49:12-04:00

Add a new interruptIOManager API for the I/O managers

It will be used to interrupt awaitCompletedTimeoutsOrIO. Also update the
return type and docs for awaitCompletedTimeoutsOrIO to have it return
false when it gets interrupted, and have no useful post condition in
that case.

38792843

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Add interruptIOManager support for select I/O manager

Uses the FdWakup mechanism.

2f3b00aa

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Add interruptIOManager support for poll I/O manager

Uses the FdWakup mechanism.

A quirk we have to cope with is that we now need to poll one more fd --
the wakeup_fd_r -- but this fd has no corresponding entry in the
aiop_table. This is awkward since we have set up our aiop_poll_table to
be an auxilliary table with matching indicies.

The solution this patch uses (and described in the comments) is to have
two tables: struct pollfd *aiop_poll_table, *full_poll_table;
and to have the aiop_poll_table alias the tail of the full_poll_table.
The head entry in the full_poll_table is the extra fd. So we poll the
full_poll_table, while the aiop_poll_table still has matching indicies
with the aiop_table.

Hurrah for C aliasing rules.

cee50131

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Add interruptIOManager support for win32 legacy I/O manager

And remove unused related helper resetAbandonRequestWait. It is not
called because the event is created in auto-reset mode, so never needs
to be reset manually.

cf453143

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Note lack of interruptIOManager support for WinIO I/O manager

Though there's a plausible design, we can't sanely test it at the moment
due to related WinIO bugs. Filed as issue #27403.

1b74a0ad

by Duncan Coutts at 2026-07-18T08:49:13-04:00

Be more explicit about enum IOReadOrWrite values, and type within cmm

Belt and braces.

b388d093

by Brian McKenna at 2026-07-18T17:51:50-04:00

Ignore ticks in the pattern-match term oracle

The term-oracle in the pattern-match checker is keyed by a canonical
form of the scrutinee, computed by `makeDictsCoherent`. That canonical
form was tick-sensitive: two occurrences of an otherwise identical
expression that happened to carry different ticks were treated as
distinct values, breaking long-distance information.

This shows up in practice under `-finfo-table-map`, because the
desugarer wraps every record-selector use site in a `SourceNote`
carrying that site's span. For example:

     data Box = Box { unBox :: Maybe Int }
     f b = case unBox b of
       Nothing -> 0
       Just _  -> let Just x = unBox b in x

The two `unBox b` expressionss carry different SourceNote spans, the
pattern-match checker sees them as different, the long-distance
information from the outer `Just _` branch never reaches the
let-pattern, and `Just x = unBox b` is wrongly reported as
non-exhaustive.

We now strip all ticks in `makeDictsCoherent`.  This is documented as
Wrinkle (UD1) of Note [Unique dictionaries in the TmOracle CoreMap].

Fixes #27314

c23e1acb

by Mrjtjmn at 2026-07-18T17:52:45-04:00

Add explanations for unsolved Typeable constraints

This commit adds explanations for unsolved 'Typeable' constraints.

GHC will now provide additional explanations for an unsolved constraint
of the form 'Typeable ty', explain why GHC did not solve Typeable constraint.
e.g.:
 - 'ty' is a polymorphic type (e.g. forall a. a -> a)
 - 'ty' is a qualified type (e.g. Eq Int => Int)
 - 'ty' is an unboxed sum type
 - 'ty' is an unreduced type family application
 - 'ty' whose kind is not typeable

Fixes #26532

cbef021e
by Artem Pelenitsyn at 2026-07-19T07:49:55-04:00
```
ghc-internal: Lock.hs: fix typo and indentation
```

42918646

by Duncan Coutts at 2026-07-19T07:50:36-04:00

Fix failing test GcStaticPointers for non-moving GC

Minor mistake in asserting something before checking for that same
thing.

Specifically, Bdescr asserts HEAP_ALLOCED_GC, but Bdescr was being used
prior to a guard that checks HEAP_ALLOCED_GC. The solution is just to
move the use of Bdescr after the guard.

Thanks to Simon Jakobi for identifying the problem.

c2f6dcd4

by Sasha Bogicevic at 2026-07-20T10:31:56+02:00

Improve error messages for invalid record wildcards

Record wildcard hints are now shown in more contexts and include
constructor arity; matching with `..` on a fieldless constructor
now produces a dedicated error message.

Fixes #21101

4c02e76b

by Duncan Coutts at 2026-07-21T10:37:21-04:00

Mark test T27105 as fragile, citing issue #27522

Scheduler fairness is fine, except when it isn't. And it isn't on CI
machines surprisingly often! See the issue for details.

43dd2b15

by Recursion Ninja at 2026-07-21T17:09:53-04:00

Resolving many TTG related orphan type-class instances

This is part a technical debt removal effort made possible now
that separating out the AST via TTG has come to a close.

As the AST in 'L.H.S' has been incrementally separated from the GHC internals,
there are many accumulated orphan instance of 'Binary', 'NFData', 'Outputable',
and 'Uniquable'. The orphan instance of data-types from within 'L.H.S' have had
their orphan instances moved to either:
  1. The module which defines the data-type
  2. The module which defines the type-class;
     i.e. moving an orphan 'Binary' instance to 'GHC.Utils.Binary'

Orphan instances resolved (37):

  | Data-type            | Resolved instance(s)       | Former orphan module(s)   |
  | -------------------- | -------------------------- | ------------------------- |
  | Role                 | Binary, NFData, Outputable | GHC.Core.Coercion.Axiom   |
  | SrcStrictness        | Binary, NFData, Outputable | GHC.Core.DataCon          |
  | SrcUnpackedness      | Binary, NFData, Outputable | GHC.Core.DataCon          |
  | Fixity               | Binary, Outputable         | GHC.Hs.Basic              |
  | FixityDirection      | Binary, Outputable         | GHC.Hs.Basic              |
  | LexicalFixity        | Outputable                 | GHC.Hs.Basic              |
  | CCallTarget          | NFData                     | GHC.Hs.Decls.Foreign      |
  | CType                | NFData                     | GHC.Hs.Decls.Foreign      |
  | Header               | NFData                     | GHC.Hs.Decls.Foreign      |
  | OverlapMode          | Binary, NFData             | GHC.Hs.Decls.Overlap      |
  | WithHsDocIdentifiers | NFData, Outputable         | GHC.Hs.Doc                |
  | HsDocString          | NFData                     | GHC.Hs.DocString          |
  | HsDocStringChunk     | Binary, Outputable         | GHC.Hs.DocString          |
  | HsDocStringDecorator | Binary, Outputable         | GHC.Hs.DocString          |
  | NamespaceSpecifier   | Outputable                 | GHC.Hs.ImpExp             |
  | ForAllTyFlag         | Binary, NFData, Outputable | GHC.Hs.Specificity        |
  | Specificity          | Binary, NFData             | GHC.Hs.Specificity        |
  | PromotionFlag        | Binary, Outputable         | GHC.Types.Basic           |
  | FieldLabelString     | Outputable, Uniquable      | GHC.Types.FieldLabel      |
  | InlinePragma         | Binary                     | GHC.Types.InlinePragma    |

-------------------------
Metric Decrease:
    hard_hole_fits
-------------------------

Closes #21262, #27469

ab9ab895

by Cheng Shao at 2026-07-21T17:10:53-04:00

rts: always use StgInt to represent cost center id

Currently cost center id is modeled as `Int` and it should be `StgInt`
uniformly in the RTS, hence this patch. Fixes #27524.

94d8f83b

by Cheng Shao at 2026-07-22T11:30:40-04:00

hadrian: clean up stale cabal package flags in the tree

This patch cleans up stale cabal package flags in the tree and related
hadrian/autoconf logic. Closes #27474.

Co-authored-by: Codex <codex@openai.com>

0bf1d8c9

by Sasha Bogicevic at 2026-07-22T11:31:21-04:00

parser: don't suggest ImportQualifiedPost when it is already enabled

-Wprepositive-qualified-module unconditionally attached a hint to
enable ImportQualifiedPost, even when the extension was already on
(as it is by default under GHC2021). Record the extension's state in
the PsWarnImportPreQualified diagnostic and drop the hint when it is
already enabled.

Fixes #27380

700a1dd1

by Simon Jakobi at 2026-07-23T11:21:20-04:00

ci: Reduce lint job setup costs

Avoid fetching unnecessary history and submodules for lightweight lint
jobs. Run changelog validation without Hadrian.

Because the lint-author job is now based on the .lint template directly,
we enhance it to allow Git to read from the runner-owned checkouts,
In the previously used .lint-params template, this permissions issue was
addressed via `chown`.

Closes #27521.

Assisted-by: gpt-5.6-sol via Codex CLI

26a44fb0

by ARATA Mizuki at 2026-07-23T11:22:10-04:00

testsuite: Fix memory issues of doublex2_* and simd010

doublex2_* had reads from uninitialized memory.

simd010 had out-of-bounds array access.

Fixes #27544

4d798b17