GitLab

Zubin pushed to branch wip/semaphore-v2 at Glasgow Haskell Compiler / GHC

Commits:

86bd9bfc

by fendor at 2026-03-17T23:46:09-04:00

Introduce `-fimport-loaded-targets` GHCi flag

This new flag automatically adds all loaded targets to the GHCi session
by adding an `InteractiveImport` for the loaded targets.

By default, this flag is disabled, as it potentially increases memory-usage.

This interacts with the flag `-fno-load-initial-targets` as follows:

* If no module is loaded, no module is added as an interactive import.
* If a reload loads up to a module, all loaded modules are added as
  interactive imports.
* Unloading modules removes them from the interactive context.

Fixes #26866 by rendering the use of a `-ghci-script` to achieve the
same thing redundant.

e3d4c1bb

by mniip at 2026-03-17T23:47:03-04:00

ghc-internal: Remove GHC.Internal.Data.Eq

It served no purpose other than being a re-export.

6f4f6cf0

by mniip at 2026-03-17T23:47:03-04:00

ghc-internal: Refine GHC.Internal.Base imports

Removed re-exports from GHC.Internal.Base. This reveals some modules
that don't actually use anything *defined* in GHC.Internal.Base, and
that can be pushed down a little in the import graph.

Replaced most imports of GHC.Internal.Base with non-wildcard imports
from modules where the identifiers are actually defined.

Part of #26834

Metric Decrease:
    T5321FD

7fb51f54

by mangoiv at 2026-03-17T23:48:00-04:00

ci: clone, don't copy when creating the cabal cache

Also removed WINDOWS_HOST variable detected via uname - we now just
check whether the CI job has windows in its name. This works because we
only ever care about it if the respective job is not a cross job. We
also statically detect darwin cross jobs in the same way. We only ever have
darwin -> darwin cross jobs so this is enough to detect the host
reliably.

f8817879

by mangoiv at 2026-03-17T23:48:44-04:00

ci: mark size_hello_artifact fragile on darwin x86

The size of the x86_64 hello artifact is not stable which results in flaky testruns.

Resolves #26814

e34cb6da

by Adam Gundry at 2026-03-20T12:20:00-04:00

ghci: Mention active language edition in startup banner

Per GHC proposal 632, this makes the GHCi startup banner include
the active language edition, plus an indication of whether this
was the default (as opposed to being explicitly selected via an
option such as `-XGHC2024`). For example:

```
$ ghci
GHCi, version 9.14.1: https://www.haskell.org/ghc/  :? for help
Using default language edition: GHC2024
ghci>
```

Fixes #26037.

52c3e6ba

by sheaf at 2026-03-20T12:21:09-04:00

Improve incomplete record selector warnings

This commit stops GHC from emitting spurious incomplete record selector
warnings for bare selectors/projections such as .fld

There are two places we currently emit incomplete record selector
warnings:

  1. In the desugarer, when we see a record selector or an occurrence
     of 'getField'. Here, we can use pattern matching information to
     ensure we don't give false positives.
  2. In the typechecker, which might sometimes give false positives but
     can emit warnings in cases that the pattern match checker would
     otherwise miss.

This is explained in Note [Detecting incomplete record selectors]
in GHC.HsToCore.Pmc.

Now, we obviously don't want to emit the same error twice, and generally
we prefer (1), as those messages contain fewer false positives. So we
suppress (2) when we are sure we are going to emit (1); the logic for
doing so is in GHC.Tc.Instance.Class.warnIncompleteRecSel,
and works by looking at the CtOrigin.

Now, the issue was that this logic handled explicit record selectors as
well as overloaded record field selectors such as "x.r" (which turns
into a simple GetFieldOrigin CtOrigin), but it didn't properly handle
record projectors like ".fld" or ".fld1.fld2" (which result in other
CtOrigins such as 'RecordFieldProjectionOrigin').

To solve this problem, we re-use the 'isHasFieldOrigin' introduced in
fbdc623a (slightly adjusted).

On the way, we also had to update the desugarer with special handling
for the 'ExpandedThingTc' case in 'ds_app', to make sure that
'ds_app_var' sees all the type arguments to 'getField' in order for it
to indeed emit warnings like in (1).

Fixes #26686

309d7e87

by Cheng Shao at 2026-03-20T12:21:53-04:00

rts: opportunistically grow the MutableByteArray# in-place in resizeMutableByteArray#

Following !15234, this patch improves `resizeMutableByteArray#` memory
efficiency by growing the `MutableByteArray#` in-place if possible,
addressing an old todo comment here. Also adds a new test case
`resizeMutableByteArrayInPlace` that stresses this behavior.

7d4ef162

by Matthew Craven at 2026-03-20T12:22:47-04:00

Change representation of floating point literals

This commit changes the representation of floating point literals
throughough the compiler, in particular in Core and Cmm.
The Rational type is deficient for this purpose, dealing poorly
with NaN, +/-Infinity, and negative zero. Instead, the new module
GHC.Types.Literal.Floating uses the host Float/Double type to represent
NaNs, infinities and negative zero. It also contains a Rational
constructor, for the benefit of -fexcess-precision.

Other changes:

  - Remove Note [negative zero] and related code
    This also removes the restrictions on constant-folding of division
    by zero, and should make any problems with NaN/Infinity more obvious.

  - Use -0.0 as the additive identity for Core constant folding rules
    for floating-point addition, fixing #21227.

  - Manual worker-wrapper for GHC.Float.rationalToDouble. This is
    intended to prevent the compiler's WW on this function from
    interfering with constant-folding. This change means that we now
    avoid allocating a box for the result of a 'realToFrac' call in
    T10359.

  - Combine floatDecodeOp and doubleDecodeOp.
    This change also fixes a bug in doubleDecodeOp wherein it
    would incorrectly produce an Int# instead of an Int64#
    literal for the mantissa component with 64-bit targets.

  - Use Float/Double for assembly immediates, and update the X86 and
    PowerPC backends to properly handle special values such as NaN and
    infinity.

  - Allow 'rational_to' to handle zero denominators, fixing a
    TODO in GHC.Core.Opt.ConstantFold.

Fixes #8364 #9811 #18897 #21227
Progress towards #26919

Metric Decrease:
    T10359

Co-authored-by: sheaf <sam.derbyshire@gmail.com>

-------------------------
Metric Decrease:
    T1969
    T5321FD
-------------------------

80e2dd4f

by Zubin Duggal at 2026-03-20T12:23:33-04:00

compiler/ffi: Collapse void pointer chains in capi wrappers

New gcc/clang treat -Wincompatible-pointer-types as an error by
default. Since C only allows implicit conversion from void*, not void**,
capi wrappers for functions taking e.g. abstract** would fail to compile
when the Haskell type Ptr (Ptr Abstract) was naively translated to void**.

Collapse nested void pointers to a single void* when the pointee type
has no known C representation.

Fixes #26852

1c50bd7b

by Luite Stegeman at 2026-03-20T12:24:37-04:00

Move some functions related to pointer tagging to a separate module

bfd7aafd

by Luite Stegeman at 2026-03-20T12:24:37-04:00

Branchless unpacking for enumeration types

Change unpacking for enumeration types to go to Word8#/Word16#/Word#
directly instead of going through an intermediate unboxed sum. This
allows us to do a branchless conversion using DataToTag and TagToEnum.

Fixes #26970

72b20fc0

by Luite Stegeman at 2026-03-20T12:25:30-04:00

bytecode: Carefully SLIDE off the end of a stack chunk

The SLIDE bytecode instruction was not checking for stack chunk
boundaries and could corrupt the stack underflow frame, leading
to crashes.

We add a check to use safe writes if we cross the chunk boundary
and also handle stack underflow if Sp is advanced past the underflow
frame.

fix #27001

2e22b43c

by Cheng Shao at 2026-03-20T12:26:14-04:00

ghci: serialize BCOByteArray buffer directly when possible

This patch changes the `Binary` instances of `BCOByteArray` to
directly serialize the underlying buffer when possible, while also
taking into account the issue of host-dependent `Word` width. See
added comments and amended `Note [BCOByteArray serialization]` for
detailed explanation. Closes #27020.

89d9ba37

by Sylvain Henry at 2026-03-20T12:27:34-04:00

JS: replace BigInt with Number arithmetic for 32/64-bit quot/rem (#23597)

Replace BigInt-based implementations of quotWord32, remWord32,
quotRemWord32, quotRem2Word32, quotWord64, remWord64, quotInt64, and
remInt64 with pure Number (double/integer) arithmetic to avoid the
overhead of BigInt promotion.

ae4ddd60

by Sylvain Henry at 2026-03-20T12:28:28-04:00

Core: add constant-folding rules for Addr# eq/ne (#18032)

3e767f98

by Matthew Pickering at 2026-03-20T12:29:11-04:00

Use OsPath rather than FilePath in Downsweep cache

This gets us one step closure to uniformly using `OsPath` in the
compiler.

2c57de29

by Cheng Shao at 2026-03-20T12:29:55-04:00

hadrian: fix ghc-in-ghci flavour stage0 shared libraries

This patch fixes missing stage0 shared libraries in hadrian
ghc-in-ghci flavour, which was accidentally dropped in
669d09f950a6e88b903d9fd8a7571531774d4d5d and resulted in a regression
in HLS support on linux/macos. Fixes #27057.

5b1be555

by Sylvain Henry at 2026-03-20T12:30:48-04:00

JS: install rts/Types.h header file (#27033)

It was an omission, making HsFFI.h not usable with GHC using the JS
backend.

b883f08f

by Cheng Shao at 2026-03-20T12:31:33-04:00

hadrian: don't compile RTS with -Winline

This patch removes `-Winline` from cflags when compiling the RTS,
given that:

1. It generates a huge pile of spam and hurts developer experience
2. Whether inlining happens is highly dependent on toolchains,
   flavours, etc, and it's not really an issue to fix if inlining
   doesn't happen; it's a hint to the C compiler anyway.

Fixes #27060.

333387d6

by Cheng Shao at 2026-03-20T12:31:33-04:00

hadrian: compile libffi-clib with -Wno-deprecated-declarations

This patch adds `-Wno-deprecated-declarations` to cflags of
`libffi-clib`, given that it produces noise at compile-time that
aren't really our issue to fix anyway, it's from vendored libffi
source code.

67c47771

by Rodrigo Mesquita at 2026-03-20T12:32:17-04:00

Expose decodeStackWithIpe from ghc-experimental

This decoding is useful to the debugger and it wasn't originally
exported as an oversight.

18513365

by Matthew Pickering at 2026-03-21T04:43:26-04:00

Add support for custom external interpreter commands

It can be useful for GHC API clients to implement their own external
interpreter commands.

For example, the debugger may want an efficient way to inspect the
stacks of the running threads in the external interpreter.

4636d906

by mangoiv at 2026-03-21T04:44:10-04:00

ci: remove obsolete fallback for old debian and ubuntu versions

2e3a2805

by mangoiv at 2026-03-21T04:44:10-04:00

ci: drop ubuntu 18 and 20

Ubuntu 18 EOL: May 2023
Ubuntu 20 EOL: May 2025

We should probably not make another major release supporting these platforms.

Also updates the generator script.

Resolves #25876

de54e264

by Cheng Shao at 2026-03-21T17:52:08+01:00

rts: fix -Wcompare-distinct-pointer-types errors

This commit fixes `-Wcompare-distinct-pointer-types` errors in the RTS
which should have been caught by the `validate` flavour but was
warnings in CI due to the recent `+werror` regression.

b9bd73de

by Cheng Shao at 2026-03-21T17:52:08+01:00

ghc-internal: fix unused imports

This commit fixes unused imports in `ghc-internal` which should have
been caught by the `validate` flavour but was warnings in CI due to
the recent `+werror` regression. Fixes #26987 #27059.

da946a16

by Cheng Shao at 2026-03-21T17:03:51+00:00

ghci: fix unused imports

This commit fixes unused imports in `ghci` which should have been
caught by the `validate` flavour but was warnings in CI due to the
recent `+werror` regression. Fixes #26987 #27059.

955b1cf8

by Cheng Shao at 2026-03-21T17:03:51+00:00

compiler: fix unused imports in GHC.Tc.Types.Origin

This commit fixes unused imports in `GHC.Tc.Types.Origin` which should
have been caught by the `validate` flavour but was warnings in CI due
to the recent `+werror` regression. Fixes #27059.

3b1aeb50

by Cheng Shao at 2026-03-21T17:03:51+00:00

hadrian: fix missing +werror in validate flavour

This patch fixes missing `+werror` in validate flavour, which was an
oversight in bb3a2ba1eefadf0b2ef4f39b31337a23eec67f29. Fixes #27066.

44f118f0

by Cheng Shao at 2026-03-22T04:54:01-04:00

ci: bump CACHE_REV and add the missing reminder

This patch bumps `CACHE_REV` to address recent `[Cabal-7159]` CI
errors due to stale cabal cache on some runners, and also adds a
reminder to remind future maintainers. Fixes #27075.

2a218737

by ARATA Mizuki at 2026-03-23T11:11:39-04:00

Add 128-bit SIMD support to AArch64 NCG

Changes:

- Add `Format` field to vector-capable instructions.
  These instructions will emit `vN.4s` (for example) as a operand.
- Additional constructors for `Operand`:
  `OpVecLane` represents a vector lane and will be emitted as `vN.<width>[<index>]` (`vN.s[3]` for example).
  `OpScalarAsVec` represents a scalar, but printed as a vector lane like `vN.<width>[0]` (`vN.s[0]` for example).
- Integer quot/rem are implemented in C, like x86.

Closes #26536

Metric Increase:
    T3294

5d6e2be9

by ARATA Mizuki at 2026-03-23T11:11:39-04:00

AArch64 NCG: Improve code generation for floating-point and vector constants

Some floating-point constants can be directly encoded using the FMOV instruction.
Similarly, a class of vectors with same values can be encoded using FMOV, MOVI, or MVNI.

c6d262aa
by Simon Jakobi at 2026-03-23T11:12:22-04:00
```
Add regression test for #13729

Closes #13729.
```

aa5dfe67

by Sylvain Henry at 2026-03-26T03:48:56-04:00

Check that shift values are valid

In GHC's codebase in non-DEBUG builds we silently substitute shiftL/R
with unsafeShiftL/R for performance reasons. However we were not
checking that the shift value was valid for unsafeShiftL/R, leading to
wrong computations, but only in non-DEBUG builds.

This patch adds the necessary checks and reports an error when a wrong
shift value is passed.

c8a7b588

by Sylvain Henry at 2026-03-26T03:48:56-04:00

Implement basic value range analysis (#25718)

Perform basic value range analysis to try to determine at compile time
the result of the application of some comparison primops (ltWord#, etc.).

This subsumes the built-in rewrite rules used previously to check if one
of the comparison argument was a bound (e.g. (x :: Word8) <= 255 is
always True). Our analysis is more powerful and handles type
conversions: e.g. word8ToWord x <= 255 is now detected as always True too.

We also use value range analysis to filter unreachable alternatives in
case-expressions. To support this, we had to allow case-expressions for
primitive types to not have a DEFAULT alternative (as was assumed before
and checked in Core lint).

a5ec467e

by ARATA Mizuki at 2026-03-26T03:49:49-04:00

rts: Align stack to 64-byte boundary in StgRun on x86

When LLVM spills AVX/AVX-512 vector registers to the stack, it requires
32-byte (__m256) or 64-byte (__m512) alignment. If the stack is not
sufficiently aligned, LLVM inserts a realignment prologue that reserves
%rbp as a frame pointer, conflicting with GHC's use of %rbp as an STG
callee-saved register and breaking the tail-call-based calling convention.

Previously, GHC worked around this by lying to LLVM about the stack
alignment and rewriting aligned vector loads/stores (VMOVDQA, VMOVAPS)
to unaligned ones (VMOVDQU, VMOVUPS) in the LLVM Mangler. This had two
problems:

- It did not extend to AVX-512, which requires 64-byte alignment. (#26595)
- When Haskell calls a C function that takes __m256/__m512 arguments on
  the stack, the callee requires genuine alignment, which could cause a
  segfault. (#26822)

This patch genuinely aligns the stack to 64 bytes in StgRun by saving
the original stack pointer before alignment and restoring it in
StgReturn. We now unconditionally advertise 64-byte stack alignment to
LLVM for all x86 targets, making rewriteAVX in the LLVM Mangler
unnecessary. STG_RUN_STACK_FRAME_SIZE is increased from 48 to 56 bytes
on non-Windows x86-64 to store the saved stack pointer.

Closes #26595 and #26822

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

661da815

by Teo Camarasu at 2026-03-26T03:50:33-04:00

ghc-internal: Float Generics to near top of module graph

We remove GHC.Internal.Generics from the critical path of the
`ghc-internal` module graph. GHC.Internal.Generics used to be in the
middle of the module graph, but now it is nearer the top (built later).
This change thins out the module graph and allows us to get rid of the
ByteOrder hs-boot file.

We implement this by moving Generics instances from the module where the
datatype is defined to the GHC.Internal.Generics module. This trades off
increasing the compiled size of GHC.Internal.Generics with reducing the
dependency footprint of datatype modules.

Not all instances are moved to GHC.Internal.Generics. For instance,
`GHC.Internal.Control.Monad.Fix` keeps its instance as it is one of the
very last modules compiled in `ghc-internal` and so inverting the
relationship here would risk adding GHC.Internal.Generics back onto the
critical path.
We also don't change modules that are re-exported from the `template-haskell` or `ghc-heap`.
This is done to make it easy to eventually move `Generics` to `base`
once something like #26657 is implemented.

Resolves #26930

Metric Decrease:
    T21839c

45428f88

by sheaf at 2026-03-26T03:51:31-04:00

Avoid infinite loop in deep subsumption

This commit ensures we only unify after we recur in the deep subsumption
code in the FunTy vs non-FunTy case of GHC.Tc.Utils.Unify.tc_sub_type_deep,
to avoid falling into an infinite loop.

See the new Wrinkle [Avoiding a loop in tc_sub_type_deep] in
Note [FunTy vs non-FunTy case in tc_sub_type_deep] in GHC.Tc.Utils.Unify.

Fixes #26823

Co-authored-by: simonpj <simon.peytonjones@gmail.com>

2823b039

by Ian Duncan at 2026-03-26T03:52:21-04:00

AArch64: fix MOVK regUsageOfInstr to mark dst as both read and written

MOVK (move with keep) modifies only a 16-bit slice of the destination
register, so the destination is both read and written. The register
allocator must know this to avoid clobbering live values. Update
regUsageOfInstr to list the destination in both src and dst sets.

No regression test: triggering the misallocation requires specific
register pressure around a MOVK sequence, which is difficult to
reliably provoke from Haskell source.

57b7878d
by Simon Jakobi at 2026-03-26T03:53:07-04:00
```
Add regression test for #12002

Closes #12002.
```

c8f9df2d

by Simon Jakobi at 2026-03-26T03:53:07-04:00

Add regression test for #12046

Closes #12046.

Co-authored-by: Andreas Klebinger <klebinger.andreas@gmx.at>

615d72ac
by Simon Jakobi at 2026-03-26T03:53:07-04:00
```
Add regression test for #13180

Closes #13180.
```
423eebcf
by Simon Jakobi at 2026-03-26T03:53:07-04:00
```
Add regression test for #11141

Closes #11141.
```
286849a4
by Simon Jakobi at 2026-03-26T03:53:07-04:00
```
Add regression test for #11505

Closes #11505.
```

7db149d9

by Simon Jakobi at 2026-03-26T03:53:07-04:00

Add regression perf test for #13820

Closes #13820.

e73c4adb
by Simon Jakobi at 2026-03-26T03:53:07-04:00
```
Add regression test for #10381

Closes #10381.
```

5ebcfb57

by Benjamin Maurer at 2026-03-26T03:54:02-04:00

Generate assembly on x86 for word2float (#22252)

We used to emit C function call for MO_UF_Conv primitive.
Now emits direct assembly instead.

Co-Authored-By: Sylvain Henry <sylvain@haskus.fr>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

5b550754

by Matthew Pickering at 2026-03-26T03:54:51-04:00

rts: forward clone-stack messages after TSO migration

MSG_CLONE_STACK assumed that the target TSO was still owned by the
capability that received the message. This is not always true: the TSO
can migrate before the inbox entry is handled.

When that happened, handleCloneStackMessage could clone a live stack from
the wrong capability and use the wrong capability for allocation and
performTryPutMVar, leading to stack sanity failures such as
checkStackFrame: weird activation record found on stack.

Fix this by passing the current capability into
handleCloneStackMessage, rechecking msg->tso->cap at handling time, and
forwarding the message if the TSO has migrated. Once ownership matches,
use the executing capability consistently for cloneStack, rts_apply, and
performTryPutMVar.

Fixes #27008

ef0a1bd2

by mangoiv at 2026-03-26T03:55:34-04:00

release tracking: adopt release tracking ticket from #16816

a7f40fd9

by mangoiv at 2026-03-26T03:55:34-04:00

release tracking: add a release tracking ticket

Brings the information in the release tracking ticket up to date with
https://gitlab.haskell.org/ghc/ghc-hq/-/blob/main/release-management.mkd

Resolves #26691

161d3285

by Teo Camarasu at 2026-03-26T03:56:18-04:00

Revert "Set default eventlog-flush-interval to 5s"

Flushing the eventlog forces a synchronisation of all the capabilities
and there was a worry that this might lead to a performance cost for
some highly parallel workloads.

This reverts commit 66b96e2a591d8e3d60e74af3671344dfe4061cf2.

36eed985

by Cheng Shao at 2026-03-26T03:57:03-04:00

ghc-boot: move GHC.Data.SmallArray to ghc-boot

This commit moves `GHC.Data.SmallArray` from the `ghc` library to
`ghc-boot`, so that it can be used by `ghci` as well:

- The `Binary` (from `ghc`) instance of `SmallArray` is moved to
  `GHC.Utils.Binary`
- Util functions `replicateSmallArrayIO`, `mapSmallArrayIO`,
  `mapSmallArrayM_`, `imapSmallArrayM_` , `smallArrayFromList` and
  `smallArrayToList` are added
- The `Show` instance is added
- The `Binary` (from `binary`) instance is added

fdf828ae

by Cheng Shao at 2026-03-26T03:57:03-04:00

compiler: use `Binary` instance of `BCOByteArray` for bytecode objects

This commit defines `Binary` (from `compiler`) instance of
`BCOByteArray` which serializes the underlying buffer directly, and
uses it directly in bytecode object serialization. Previously we reuse
the `Binary` (from `binary`) instance, and this change allows us to
avoid double-copying via an intermediate `ByteString` when using
`put`/`get` in `binnary`. Also see added comment for explanation.

3bf62d0a

by Cheng Shao at 2026-03-26T03:57:03-04:00

ghci: use SmallArray directly in ResolvedBCO

This patch makes ghci use `SmallArray` directly in `ResolvedBCO` when
applicable, making the memory representation more compact and reducing
marshaling overhead. Closes #27058.

3d6492ce

by Wen Kokke at 2026-03-26T03:57:53-04:00

Fix race condition between flushEventLog and start/endEventLogging.

This commit changes `flushEventLog` to acquire/release the `state_change` mutex to prevent interleaving with `startEventLogging` and `endEventLogging`. In the current RTS, `flushEventLog` _does not_ acquire this mutex, which may lead to eventlog corruption on the following interleaving:

- `startEventLogging` writes the new `EventLogWriter` to `event_log_writer`.
- `flushEventLog` flushes some events to `event_log_writer`.
- `startEventLogging` writes the eventlog header to `event_log_writer`.

This causes the eventlog to be written out in an unreadable state, with one or more events preceding the eventlog header.

This commit renames the old function to `flushEventLog_` and defines `flushEventLog` simply as:

```c
void flushEventLog(Capability **cap USED_IF_THREADS)
{
  ACQUIRE_LOCK(&state_change_mutex);
  flushEventLog_(cap);
  RELEASE_LOCK(&state_change_mutex);
}
```

The old function is still needed internally within the compilation unit, where it is used in `endEventLogging` in a context where the `state_change` mutex has already been acquired. I've chosen to mark `flushEventLog_` as static and let other uses of `flushEventLog` within the RTS refer to the new version. There is one use in `hs_init_ghc` via `flushTrace`, where the new locking behaviour should be harmless, and one use in `handle_tick`, which I believe was likely vulnerable to the same race condition, so the new locking behaviour is desirable.

I have not added a test. The behaviour is highly non-deterministic and requires a program that concurrently calls `flushEventLog` and `startEventLogging`/`endEventLogging`. I encountered the issue while developing `eventlog-socket` and within that context have verified that my patch likely addresses the issue: a test that used to fail within the first dozen or so runs now has been running on repeat for several hours.

7b9a75f0

by Phil Hazelden at 2026-03-26T03:58:37-04:00

Fix build with werror on glibc 2.43.

We've been defining `_XOPEN_SOURCE` and `_POSIX_C_SOURCE` to the same
values as defined in glibc prior to 2.43. But in 2.43, glibc changes
them to new values, which means we get a warning when redefining them.
By `#undef`ing them first, we no longer get a warning.

Closes #27076.

fe6e76c5

by Tobias Haslop at 2026-03-26T03:59:30-04:00

Fix broken Haddock link to Bifunctor class in description of Functor class

404b71c1

by Luite Stegeman at 2026-03-27T04:40:49-04:00

Fix assert in Interpreter.c

If we skip exactly the number of words on the stack we end up on
the first word in the next chunk.

a85bd503

by Luite Stegeman at 2026-03-27T04:40:49-04:00

Support arbitrary size unboxed tuples in bytecode

This stores the size (number of words on the stack) of the next
expected tuple in the TSO, ctoi_spill_size field, eliminating
the need of stg_ctoi_tN frames for each size.

Note: On 32 bit platform there is still a bytecode tuple size
limit of 255 words on the stack.

Fixes #26946

e2209031

by Luite Stegeman at 2026-03-27T04:40:49-04:00

Add specialized frames for small tuples

Small tuples are now returned more efficiently to the interpreter.
They use one less word of stack space and don't need manipulation
of the TSO anymore.

b26bb2ea

by VeryMilkyJoe at 2026-03-27T04:41:38-04:00

Remove backwards compatibility pattern synonym `ModLocation`

Fixes #24932

66e5e324

by Vladislav Zavialov at 2026-03-27T04:42:25-04:00

Extend HsExpr with the StarIsType syntax (#26587, #26967)

This patch allows kinds of the form `k -> *` and `* -> k` to occur in
expression syntax, i.e. to be used as required type arguments.

For example:

	{-# LANGUAGE RequiredTypeArguments, StarIsType #-}
	x1 = f (* -> * -> *)
	x2 = f (forall k. k -> *)
	x3 = f ((* -> *) -> Constraint)

Summary of the changes:

* Introduce the HsStar constructor of HsExpr and its extension field XStar.
  It is analogous to HsStarTy in HsType.

* Refactor HsStarTy to store the unicode flag as TokStar, defined as
    type TokStar = EpUniToken "*" "★"  -- similar to TokForall, TokRArrow, etc.
  The token is stored in the extension field and replaces the Bool field.

* Extend the `infixexp2` nonterminal to parse `*` as a direct argument of `->`.
  This is more limited than the full StarIsType syntax, but has the nice
  property of not conflicting with the multiplication operator `a * b`.

Test case: T26967 T26967_tyop

f8de456f

by Sylvain Henry at 2026-03-27T04:43:22-04:00

STM: don't create a transaction in the rhs of catchRetry# (#26028)

We don't need to create a transaction for the rhs of (catchRetry#)
because contrary to the lhs we don't need to abort it on retry. Moreover
it is particularly harmful if we have code such as (#26028):

  let cN = readTVar vN >> retry
      tree = c1 `orElse` (c2 `orElse` (c3 `orElse` ...))
  atomically tree

Because it will stack transactions for the rhss and the read-sets of all
the transactions will be iteratively merged in O(n^2) after the
execution of the most nested retry.

This is the second attempt at implementing this. The first attempt
triggered segfaults (#26291) and has been reverted.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fcf092dd

by Luite Stegeman at 2026-03-27T04:44:17-04:00

Windows: remove StgAsyncIOResult and fix crash/leaks

In stg_block_async{_void}, a stack slot was reserved for
an StgAsyncIOResult. This slot would be filled by the IO
manager upon completion of the async call.

However, if the blocked thread was interrupted by an async
exception, we would end up in an invalid state:

 - If the blocked computation was never re-entered, the
   StgAsyncIOResult would never be freed.
 - If the blocked computation was re-entered, the thread would
   find an unitialized stack slot for the StgAsyncIOResult,
   leading to a crash reading its fields, or freeing the pointer.

We fix this by removing the StgAsyncIOResult altogether and writing
the result directly to the stack.

Fixes #26341

05094993

by Luite Stegeman at 2026-03-27T04:45:12-04:00

Don't refine DEFAULT alt for unary typeclasses

A non-DEFAULT data alt for a unary typeclass dictionary would
interfere with Unary Class Magic, leading to segfaults.

fixes #27071

4ee260cf

by sheaf at 2026-03-27T04:46:06-04:00

Fix several oversights in hsExprType

This commit fixes several oversights in GHC.Hs.Syn.Type.hsExprType:

  - The 'RecordCon' case was returning the type of the constructor,
    instead of the constructor application. This is fixed by using
    'splitFunTys'.
  - The 'ExplicitTuple' case failed to take into account tuple sections,
    and was also incorrectly handling 1-tuples (e.g. 'Solo') which can
    be constructed using Template Haskell.
  - The 'NegApp' case was returning the type of the negation operator,
    again failing to apply it to the argument. Fixed by using
    'funResultTy'.
  - The 'HsProc' case was computing the result type of the arrow proc
    block, without taking into account the argument type. Fix that by
    adding a new field to 'CmdTopTc' that stores the arrow type, so that
    we can construct the correct result type `arr a b` for
    `proc (pat :: a) -> (cmd :: b)`.
  - The 'ArithSeq' and 'NegApp' cases were failing to take into account
    the result 'HsWrapper', which could e.g. silently drop casts.
    This is fixed by introducing 'syntaxExpr_wrappedFunResTy' which, on
    top of taking the result type, applies the result 'HsWrapper'.

These fixes are validated by the new GHC API test T26910.

Fixes #26910

e97232ce

by Hai at 2026-03-27T04:47:04-04:00

Parser.y: avoid looking at token with QualifiedDo

This changes the behavior of 'hintQualifiedDo' so that the supplied
token is not inspected when the QualifiedDo language extension bit is
set.

9831385b

by Vladislav Zavialov at 2026-03-27T17:22:30-04:00

Infix holes in types (#11107)

This patch introduces several improvements that follow naturally from
refactoring HsOpTy to represent the operator as an HsType, aligning it
with the approach taken by OpApp and HsExpr.

User-facing changes:

1. Infix holes (t1 `_` t2) are now permitted in types, following the
   precedent set by term-level expressions.

   Test case: T11107

2. Error messages for illegal promotion ticks are now reported at more
   precise source locations.

   Test case: T17865

Internal changes:

* The definition of HsOpTy now mirrors that of OpApp:

    | HsOpTy (XOpTy p)  (LHsType p) (LHsType p) (LHsType p)
    | OpApp  (XOpApp p) (LHsExpr p) (LHsExpr p) (LHsExpr p)

  This moves us one step closer to unifying HsType and HsExpr.

* Ignoring locations,
    the old pattern match (HsOpTy x prom lhs op rhs)
    is now written as     (HsOpTy x lhs (HsTyVar x' prom op) rhs)
    but we also handle    (HsOpTy x lhs (HsWildCardTy x')    rhs)

  Constructors other than HsTyVar and HsWildCardTy never appear
  in the operator position.

* The various definitions across the compiler have been updated to work
  with the new representation, drawing inspiration from the term-level
  pipeline where appropriate.  For example,

     ppr_infix_ty       <=> ppr_infix_expr
     get_tyop           <=> get_op
     lookupTypeFixityRn <=> lookupExprFixityRn
           (the latter is factored out from rnExpr)

Test cases: T11107 T17865

5b6757d7

by mangoiv at 2026-03-27T17:23:19-04:00

ci: build i386 non-validate for deb12

This is a small fix that will unlock ghcup metadata to run, i386 debian
12 was missing as a job.

cf942119

by Cheng Shao at 2026-03-30T15:24:37-04:00

ghc-boot: remove unused SizedSeq instances and functions

This commit removes unused `SizedSeq` instances and functions, only
keeping the bits we need for hpc tick sequence for now.

22c5b7cc

by Cheng Shao at 2026-03-30T15:24:38-04:00

ghci: remove unused GHCi.BinaryArray

This patch removes the unused `GHCi.BinaryArray` module from `ghci`.
Closes #27108.

77abb4ab

by Cheng Shao at 2026-03-30T15:25:21-04:00

testsuite: mark T17912 as fragile on Windows

T17912 is still fragile on Windows, it sometimes unexpectedly pass in
CI. This especially strains our already scarce Windows CI runner
resources. Mark it as fragile on Windows for the time being.

d741a6cc

by Andreas Klebinger at 2026-03-31T04:39:33-04:00

Bump minimum shake version for hadrian.

We also add the shake version we want to stack.yaml

Fixes #26884

5e556f9e

by Vladislav Zavialov at 2026-03-31T04:40:16-04:00

Status check for the HsType~HsExpr refactoring (#25121)

Add a test case to track the status of a refactoring project within GHC
whose goal is to arrive at the following declaration:

	type HsType = HsExpr

The rationale for this is to increase code reuse between the term- and
type-level code in the compiler front-end (AST, parser, renamer, type checker).

The status report is saved to testsuite/tests/ghc-api/T25121_status.stdout
and provides useful insights into what needs to happen to make progress on
the ticket.

acffb1b1

by fendor at 2026-03-31T04:41:02-04:00

Extract Binary instances to `GHC.ByteCode.Binary`

e2ea8e25

by fendor at 2026-03-31T04:41:02-04:00

Add `seqNonEmpty` for evaluating `NonEmpty a`

048b00b7

by fendor at 2026-03-31T04:41:02-04:00

Record `LinkableUsage` instead of `Linkable` in `LoaderState`

Retaining a ByteCode `Linkable` after it has been loaded retains its
`UnlinkedBCO`, keeping it alive for the remainder of the program.
This starts accumulating a lot of `UnlinkedBCO` and memory over time.
However, the `Linkable` is merely used to later record its usage in
`mkObjectUsage`, which  is used for recompilation checking.

However, this is incorrect, as the interface file and bytecode objects
could be in different states, e.g. the interface changes, but the
bytecode library hasn't changed so we don't need to recompile and vice
versa.

By computing a `Fingerprint` for the `ModuleByteCode`, and recording it
in the `LinkableUsage`, we know precisely whether the `ByteCode` object
on disk is outdated.

Thus, parts of this commit just makes sure that we efficiently compute a
`Fingerprint` for `ModuleByteCode` and store it in the on-disk
representation of `ModuleByteCode`.

We change the `LoaderState` to retain `LinkableUsage`, which is smaller
representation of a `Linkable`. This allows us to free the unneeded
fields of `Linkable` after linking them.

We declare the following memory invariants that this commit implements:

* No `LinkablePart` should be retained from `LoaderState`.
* `Linkable`s should be unloaded after they have been loaded.

These invariants are unfortunately tricky to automatically uphold, so we
are simply documenting our assumptions for now.

We introduce the `linkable-space` test which makes sure that after
loading, no `DotGBC` or `UnlinkedBCO` is retained.

-------------------------
Metric Increase:
    MultiLayerModulesTH_OneShot
-------------------------

We allocate a bit more, but the peak number of bytes doesn't change.
While a bit unfortunate, accepting the metric increase.

We add multiple new performance measurements where we were able to
observe the desired memory invariants. Further, we add regression tests
to validate that the recompilation checker behaves more correct than
before.

2d1c1997

by Simon Jakobi at 2026-03-31T04:41:46-04:00

Eliminate dictionary-passing in ListMap operations

Mark the ListMap helpers 'INLINABLE' so importing modules can specialise
the 'TrieMap (ListMap m)' methods and avoid recursive dictionary-passing.

See Note [Making ListMap operations specialisable].

Fixes #27097

ed2c6570

by Cheng Shao at 2026-03-31T04:42:33-04:00

testsuite: fix testdir cleanup logic on Windows

testdir cleanup is unreliable on Windows (#13162) and despite existing
hacks in the driver, new failure mode has occurred. This patch makes
it print the warning and carry on when failed to clean up a testdir,
instead of reporting a spurious framework failure. See added comment
for detailed explanation.

d9388e29

by Simon Jakobi at 2026-03-31T13:14:59-04:00

Add regression test for #18177

Closes #18177.

Assisted-by: Codex

6a10045c

by mangoiv at 2026-03-31T13:15:43-04:00

ci: allow metric decrease for two tests on i386

There has been a nightly failure on i386 due to a compiler runtime
improvement on i386 debian 12. We allow that.

Metric Decrease (test_env='i386-linux-deb12'):
  T12707 T8095

7fbb4fcb

by Rodrigo Mesquita at 2026-04-01T12:16:33+00:00

Bump default language edition to GHC2024

As per the accepted ghc-proposal#632

Fixes #26039

5ae43275

by Peng Fan at 2026-04-01T19:01:06-04:00

NCG/LA64: add cmpxchg and xchg primops

And append some new instructions for LA664 uarch.

Apply fix to cmpxchg-prim by Andreas Klebinger.

Suggestions in https://gitlab.haskell.org/ghc/ghc/-/merge_requests/15515

8f95534a

by Duncan Coutts at 2026-04-01T19:01:52-04:00

Remove signal-based ticker implementations

Fixes issue #27073

All supported platforms should work with the pthreads + nanosleep based
ticker implementation. This avoids all the problems with using signals.

In practice, all supported platforms were probably using the non-signal
tickers already, which is probably why we do not get lots of reports
about deadlocks and other weirdness: we were definately using functions
that are not async signal safe in the tick handler (such as fflush to
flussh the eventlog).

Only Solaris was explicitly using the timer_create ticker impl, and even
Solaris could probably use the pthreads one (if anyone cared: Solaris is
no longer a Teir 3 supported platform).

Plausibly the only supported platform that this will change will be AIX,
which should now use the pthreads impl.

51b32b0d
by Duncan Coutts at 2026-04-01T19:01:52-04:00
```
Tidy up some timer/ticker comments elsewhere
```

7562bcd7

by Duncan Coutts at 2026-04-01T19:01:52-04:00

Remove now-unused install_vtalrm_handler

Support function used by both of the signal-based ticker
implementations.

6da127c7

by Duncan Coutts at 2026-04-01T19:01:52-04:00

No longer probe for timer_create in rts/configure

It was only used by the TimerCreate.c ticker impl.

3fd490fa
by Duncan Coutts at 2026-04-01T19:01:53-04:00
```
Note that rtsTimerSignal is deprecated.
```
63099b0f
by Simon Jakobi at 2026-04-01T19:02:39-04:00
```
Add perf test for #13960

Closes #13960.
```

58009c14

by Apoorv Ingle at 2026-04-02T09:51:24+01:00

Streamline expansions using HsExpansion (#25001)

Notes added [Error Context Stack] [Typechecking by expansion: overview]
Notes updated Note [Expanding HsDo with XXExprGhcRn] [tcApp: typechecking applications]

-------------------------
Metric Decrease:
    T9020
-------------------------

There are 2 key changes:

1. `HsExpand` datatype mediates between expansions
2. Replace `ErrCtxtM` to a simpler `HsCtxt` that does not depend on a `TidyEnv`

This has some consequences detailed below:

1. `HsExpand` datatype mediates between expansions
   * Simplifies the implementations of `tcExpr` to work on `XExpr`
   * Removes `VACtxt` (and its associated `VAExpansion` and `VACall`) datatype, it is subsumed by simply a `SrcSpan`.
   * Removes the function `addHeadCtxt` as it is now mearly setting a location
   * The function `tcValArgs` does its own argument number management
   * move `splitHsTypes` out of `tcApp`
   * Removes special case of tcBody from `tcLambdaMatches`
   * Removes special case of `dsExpr` for `ExpandedThingTc`
   * Renames `tcMonoExpr` -> `tcMonoLExpr`, `tcMonoExprNC` -> `tcMonoLExpr`
   * Renames `EValArg`, `EValArgQL` fields: `ea_ctxt` -> `ea_loc_span` and `eaql_ctx` -> `eaql_loc_span`
   * Remove `PopErrCtxt` from `XXExprGhcRn`
   * `fun_orig` in tcInstFun depends on the SrcSpan of the head of the application chain (similar to addArgCtxt)
     - it references the application chain head if it is user located, or
      uses the error context stack  as a fallback if it's a generated
      location
   * Make a new variant `GeneratedSrcSpan` in `SrcSpan` for HIEAst Nodes
    - Expressions wrapped around `GeneratedSrcSpan` are ignored and never added to the error context stack
    - In Explicit list expansion `fromListN` is wrapped with a `GeneratedSrcSpan` with `GeneratedSrcSpanDetails` field to store the original srcspan

2. Replace `ErrCtxtM` to a simpler `HsCtxt` that does not depend on a `TidyEnv`
   * Merge `HsThingRn` to `HsCtxt`
   * Landmark Error messages are now just computed on the fly
   * Make HsExpandedRn and HsExpandedTc payload a located HsExpr GhcRn
   * `HsCtxt` are tidied and zonked at the end right before printing

Co-authored-by: simonpj <simon.peytonjones@gmail.com>

bc4b4487

by Zubin Duggal at 2026-04-03T14:22:27-04:00

driver: recognise .dyn_o as a valid object file to link if passed on the command line.
This allows plugins compiled with this suffix to run.

Fixes #24486

5ebb9121
by Simon Jakobi at 2026-04-03T14:23:11-04:00
```
Add regression test for #16145

Closes #16145.
```

c1fc1c44

by Simon Peyton Jones at 2026-04-03T19:56:07-04:00

Refactor eta-expansion in Prep

The Prep pass does eta-expansion but I found cases where it was
doing bad things.  So I refactored and simplified it quite a bit.

In the new design
* There is no distinction between `rhs` and `body`; in particular,
  lambdas can now appear anywhere, rather than just as the RHS of
  a let-binding.

* This change led to a significant simplification of Prep, and
  a more straightforward explanation of eta-expansion. See the new
     Note [Eta expansion]

* The consequences is that CoreToStg needs to handle naked lambdas.
  This is very easy; but it does need a unique supply, which forces
  some simple refactoring.  Having a unique supply to hand is probably
  a good thing anyway.

21beda2c

by Simon Peyton Jones at 2026-04-03T19:56:07-04:00

Clarify Note [Interesting dictionary arguments]

Ticket #26831 ended up concluding that the code for
GHC.Core.Opt.Specialise.interestingDict was good, but the
commments were a bit inadequate.

This commit improves the comments slightly.

3eaac1f2

by Simon Peyton Jones at 2026-04-03T19:56:07-04:00

Make inlining a bit more eager for overloaded functions

If we have
   f d = ... (class-op d x y) ...
we should be eager to inline `f`, because that may change the
higher order call (class-op d x y) into a call to a statically
known function.

See the discussion on #26831.

Even though this does a bit /more/ inlining, compile times
decrease by an average of 0.4%.

Compile time changes:

 DsIncompleteRecSel3(normal)     431,786,104  -2.2%
    ManyAlternatives(normal)     670,883,768  -1.6%
    ManyConstructors(normal)   3,758,493,832  -2.6% GOOD
MultilineStringsPerf(normal)      29,900,576  -2.8%
            T14052Type(ghci)   1,047,600,848  -1.2%
              T17836(normal)     392,852,328  -5.2%
              T18478(normal)     442,785,768  -1.4%
             T21839c(normal)     341,536,992 -14.1% GOOD
               T3064(normal)     174,086,152  +5.3%  BAD
               T5631(normal)     506,867,800  +1.0%
      hard_hole_fits(normal)     209,530,736  -1.3%
 info_table_map_perf(normal)  19,523,093,184  -1.2%
          parsing001(normal)     377,810,528  -1.1%
          pmcOrPats(normal)       60,075,264  -0.5%

                                 geo. mean    -0.4%
                                 minimum     -14.1%
                                 maximum      +5.3%

Runtime changes
    haddock.Cabal(normal)   27,351,988,792  -0.7%
     haddock.base(normal)   26,997,212,560  -0.6%
 haddock.compiler(normal)  219,531,332,960  -1.0%

Metric Decrease:
    LinkableUsage01
    ManyConstructors
    T17949
    T21839c
    T13035
    TcPlugin_RewritePerf
    hard_hole_fits

Metric Increase:
    T3064

5cbc2c82

by Matthew Pickering at 2026-04-03T19:57:02-04:00

bytecode: Add magic header/version to bytecode files

In order to avoid confusing errors when using stale interface files (ie
from an older compiler version), we add a simple header/version check
like the one for interface files.

Fixes #27068

d95a1936

by fendor at 2026-04-03T19:57:02-04:00

Add constants for bytecode in-memory buffer size

Introduce a common constant for the default size of the .gbc and
.bytecodelib binary buffer.

The buffer is by default set to 1 MB.

b822c30a

by mangoiv at 2026-04-03T19:57:49-04:00

testsuite: filter stderr for static001 on darwin

This reactivates the test on x86_64 darwin as this should have been done
long ago and ignores warnings emitted by ranlib on newer version of the
darwin toolchain since they are benign. (no symbols for stub libraries)

Fixes #27116

28ce1f8a

by Andreas Klebinger at 2026-04-03T19:58:44-04:00

Give the Data instance for ModuleName a non-bottom toConstr implementation.

I've also taken the liberty to add Note [Data.Data instances for GHC AST Types]
describing some of the uses of Data.Data I could find.

Fixes #27129

8ca41ffe
by mangoiv at 2026-04-03T19:59:30-04:00
```
issue template: fix add bug label
```

3981db0c

by Sylvain Henry at 2026-04-03T20:00:33-04:00

Add more canned GC functions for common register patterns (#27142)

Based on analysis of heap-check sites across the GHC compiler and Cabal,
the following patterns were not covered by existing canned GC functions
but occurred frequently enough to warrant specialisation:

  stg_gc_ppppp  -- 5 GC pointers
  stg_gc_ip     -- unboxed word + GC pointer
  stg_gc_pi     -- GC pointer + unboxed word
  stg_gc_ii     -- two unboxed words
  stg_gc_bpp    -- byte (I8) + two GC pointers

Adding these reduces the fraction of heap-check sites falling back to
the generic GC path from ~1.4% to ~0.4% when compiling GHC itself.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

d17d1435

by Matthew Pickering at 2026-04-03T20:01:19-04:00

Make home unit dependencies stored as sets

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

92a97015

by Simon Peyton Jones at 2026-04-05T00:58:57+01:00

Add Invariant (NoTypeShadowing) to Core

This commit addresses #26868, by adding
a new invariant (NoTypeShadowing) to Core.

See Note [No type-shadowing in Core] in GHC.Core

8b5a5020

by Simon Peyton Jones at 2026-04-05T00:58:57+01:00

Major refactor of free-variable functions

For some time we have had two free-variable mechanims for types:

* The "FV" mechanism, embodied in GHC.Utils.FV, which worked OK, but
  was fragile where eta-expansion was concerned.

* The TyCoFolder mechanism, using a one-shot EndoOS accumulator

I finally got tired of this and refactored the whole thing, thereby
addressing #27080.   Now we have

* `GHC.Types.Var.FV`, which has a composable free-variable result type,
  very much in the spirit of the old `FV`, but much more robust.
  (It uses the "one shot trick".)

* GHC.Core.TyCo.FVs now has just one technology for free variables.

All this led to a lot of renaming.

There are couple of error-message changes.  The change in T18451
makes an already-poor error message even more mysterious.  But
it really needs a separate look.

We also now traverse the AST in a different order leading to a different
but still deterministic order for FVs and test output has been adjusted
accordingly.

4bf040c6

by sheaf at 2026-04-05T14:56:29-04:00

Add utility pprTrace_ function

This function is useful for quick debugging, as it can be added to a
where clause to pretty-print debugging information:

  fooBar x y
    | cond      = body1
    | otherwise = body2
    where
      !_ = pprTrace_ "fooBar" $
           vcat [ text "x:" <+> ppr x
                , text "y:" <+> ppr y
                , text "cond:" <+> ppr cond
                ]

502e6ffe

by Andrew Lelechenko at 2026-04-07T04:47:21-04:00

base: improve error message for Data.Char.chr

As per https://github.com/haskell/core-libraries-committee/issues/384

b21bd52e
by Simon Peyton Jones at 2026-04-07T04:48:07-04:00
```
Refactor FunResCtxt a bit

Fixes #27154
```

7fe84ea5

by Zubin Duggal at 2026-04-07T19:11:52+05:30

compiler: Warn when -finfo-table-map is used with -fllvm

These are currently not supported together.

Fixes #26435

4a45a7da

by Matthew Pickering at 2026-04-08T04:37:29-04:00

packaging: correctly propagate build/host/target to bindist configure script

At the moment the host and target which we will produce a compiler for
is fixed at the initial configure time. Therefore we need to persist
the choice made at this time into the installation bindist as well so we
look for the right tools, with the right prefixes at install time.

In the future, we want to provide a bit more control about what kind of
bindist we produce so the logic about what the host/target will have to
be written by hadrian rather than persisted by the configure script. In
particular with cross compilers we want to either build a normal stage 2
cross bindist or a stage 3 bindist, which creates a bindist which has a
native compiler for the target platform.

Fixes #21970

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

b0950df6

by Sven Tennie at 2026-04-08T04:37:29-04:00

Cross --host and --target no longer required for cross (#21970)

We set sane defaults in the configure script. Thus, these paramenters
aren't required any longer.

fef35216

by Sven Tennie at 2026-04-08T04:37:30-04:00

ci: Define USER_CONF_CC_OPTS_STAGE2 for aarch64/mingw

ghc-toolchain doesn't see $CONF_CC_OPTS_STAGE2 when the bindist gets
configured. So, the hack to override the compiler gets lost.

8dd6f453

by Cheng Shao at 2026-04-08T04:38:11-04:00

ghci: use ShortByteString for LookupSymbol/LookupSymbolInDLL/LookupClosure messages

This patch refactors ghci to use `ShortByteString` for
`LookupSymbol`/`LookupSymbolInDLL`/`LookupClosure` messages as the
first part of #27147.

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

371ef200

by Cheng Shao at 2026-04-08T04:38:11-04:00

ghci: use ShortByteString for MkCostCentres message

This patch refactors ghci to use `ShortByteString` for `MkCostCentres`
messages as a first part of #27147. This also considerably lowers the
memory overhead of breakpoints when cost center profiling is enabled.

-------------------------
Metric Decrease:
    interpreter_steplocal
-------------------------

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

4a122bb6

by Phil Hazelden at 2026-04-08T20:49:42-04:00

Implement modifiers syntax.

The `%m` syntax of linear types is now accepted in more places, to allow
use by future extensions, though so far linear types is still the only
consumer.

This may break existing code where it

* Uses -XLinearTypes.
* Has code of the form `a %m -> b`, where `m` can't be inferred to be
  kind Multiplicity.

The code can be fixed either by adding a kind annotation, or by setting
`-XLinearTypes -XNoModifiers`.

Proposal:
https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0370-modifiers.rst

07267f79

by Zubin Duggal at 2026-04-08T20:50:25-04:00

hadrian: Don't include the package hash in the haddock directory

Since GHC 9.8 and hash_unit_ids, haddock urls have looked like`ghc-9.10.3/doc/html/libraries/base-4.20.2.0-39f9/**/*.html`

The inclusion of the hash makes it hard for downstream non-boot packages to properly link to these files, as the hash is not
part of a standard cabal substitution.

Since we only build one version of each package, we don't need the hash to disambiguate anything, we can just remove it.

Fixes #26635

0a83b95b

by ARATA Mizuki at 2026-04-08T20:51:18-04:00

testsuite: Allow multiple ways to be run by setting multiple command-line options

This patch allows multiple `--test-way`s to take effect, like:

$ hadrian/build test --test-way=normal --test-way=llvm

Previously, only one way was run if the test speed was 'normal' or 'fast'.

Closes #26926

Co-authored-by: sheaf <sam.derbyshire@gmail.com>

e841931c

by Teo Camarasu at 2026-04-08T20:52:00-04:00

doc: improve eventlog-flush-interval flag documentation

We mention the performance cost and how this flag can be turned off.

Resolves #27056

e332db25
by Teo Camarasu at 2026-04-08T20:52:01-04:00
```
docs/user_guide: fix typo
```

5b82080a

by Simon Jakobi at 2026-04-08T20:52:44-04:00

Fix -dsuppress-uniques for free variables in demand signatures

Before:          Str=b{sXyZ->S}
With this patch: Str=b{S}

T13143.stderr is updated accordingly.

Fixes #27106.

b7a084cc

by Simon Jakobi at 2026-04-08T20:53:27-04:00

Documentation fixes for demand signature notation

Fixes #27115.

59391132

by Simon Jakobi at 2026-04-08T20:54:08-04:00

Use upsert for non-deleting map updates

Some compiler functions were using `alter`, despite never removing
any entries: they only update an existing entry or insert a new one.

These functions are converted to using `upsert`:

    alter  :: (Maybe a -> Maybe a) -> Key -> Map a -> Map a
    upsert :: (Maybe a ->       a) -> Key -> Map a -> Map a

`upsert` variants are also added to APIs of the various Word64Map
wrapper types.

The precedent for this `upsert` operation is in the containers library:
see https://github.com/haskell/containers/pull/1145

    Metrics: compile_time/bytes allocated
    -------------------------------------

        geo. mean:    -0.1%
        minimum:      -0.5%
        maximum:      +0.0%

Resolves #27140.

da7e82f4

by Cheng Shao at 2026-04-08T20:54:49-04:00

testsuite: fix testsuite run for +ipe again

This patch makes the +ipe flavour transformer pass the entire
testsuite again by dropping stdout/stderr checks of certain tests that
are sensitive to stack layout changes with `+ipe`. Related: #26799.

b135a87d

by Zubin Duggal at 2026-04-09T19:36:50+05:30

Bump directory submodule to 1.3.11.0 (unreleased)

3a291d07
by Zubin Duggal at 2026-04-09T19:36:50+05:30
```
Bump file-io submodule to 0.2.0
```
e0ab606d
by Zubin Duggal at 2026-04-10T18:40:20+05:30
```
Release notes for GHC 10.0
```
e08b9b34
by Zubin Duggal at 2026-04-10T18:40:20+05:30
```
Bump ghc-prim version to 0.14.0
```

a92aac6e

by Zubin Duggal at 2026-04-10T18:40:20+05:30

Bump template-haskell to 2.25.0.0; update submodule exceptions for TH 2.25

f254d9e8
by Zubin Duggal at 2026-04-10T18:40:20+05:30
```
Bump GHC version to 10.0
```

6ce0368a

by Zubin Duggal at 2026-04-10T18:40:28+05:30

Bump base to 4.23.0.0; update submodules for base 4.24 upper bound

702fb8a5

by Zubin Duggal at 2026-04-10T18:40:28+05:30

Bump GHC version to 10.1; update submodules template-haskell-lift and template-haskell-quasiquoter for ghc-internal 10.200

75df1ca4

by Zubin Duggal at 2026-04-10T18:40:28+05:30

Use changelog.d for release notes (#26002)

GHC now uses a fragment-based changelog workflow using a custom script adapted from https://codeberg.org/fgaz/changelog-d.

Contributors add a file in changelog.d/ for each user-facing change.
At release time, these are assembled into release notes for sphinx (in RST) format, using
the tool.

New hadrian `changelog` target to generate changelogs

CI job to validate changelog entries for MRs unless skipped with ~"no-changelog" label

Teach sphinx about ghc-mr: extlink to link to MRs

Remove `ghc-package-list` from sphinx, and implement it in changelog-d instead (Fixes #26476).

(cherry picked from commit 989c07249978f418dfde1353abfad453f024d61a)

585d7450

by Luite Stegeman at 2026-04-11T02:17:13-04:00

tc: discard warnings in tcUserStmt Plan C

We typecheck let_stmt twice, but we don't want the warnings twice!

see #26233

2df604e9

by Sylvain Henry at 2026-04-11T02:19:30-04:00

Introduce TargetInt to represent target's Int (#15973)

GHC was using host 'Int' in several places to represent values that
live in the target machine's 'Int' type.  This is silently wrong when
cross-compiling from a 32-bit host to a 64-bit target: the host Int
is 32 bits while the target Int is 64 bits.

See Note [TargetInt] in GHC.Platform.

Also used the opportunity to make DynTag = Word8.

Fixes #15973

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

d419e972

by Luite Stegeman at 2026-04-13T15:16:04-04:00

Suppress desugaring warnings in the pattern match checker

Avoid duplicating warnings from the actual desugaring pass.

fixes #25996

c5b80dd0
by Phil de Joux at 2026-04-13T15:16:51-04:00
```
Typo ~/ghc/arch-os-version/environments
```
71462fff
by Luite Stegeman at 2026-04-13T15:17:38-04:00
```
add changelog entry for #26233
```

d1ddfd4b