Duncan Coutts pushed to branch wip/dcoutts/issue-26717 at Glasgow Haskell Compiler / GHC

Commits:

• c56567ec
  by Simon Peyton Jones at 2026-01-15T23:19:04+00:00

  Add evals for strict data-con args in worker-functions
  
  This fixes #26722, by adding an eval in a worker for
  arguments of strict data constructors, even if the
  function body uses them strictly.
  
  See (WIS1) in Note [Which Ids should be strictified]
  
  I took the opportunity to make substantial improvements in the
  documentation for call-by-value functions.  See especially
     Note [CBV Function Ids: overview] in GHC.Types.Id.Info
     Note [Which Ids should be CBV candidates?] ditto
     Note [EPT enforcement] in GHC.Stg.EnforceEpt
  among others.
  

• 9719ce5d
  by Simon Peyton Jones at 2026-01-15T23:19:04+00:00

  Improve `interestingArg`
  
  This function analyses a function's argument to see if it is
  interesting enough to deserve an inlining discount. Improvements
  for
    * LitRubbish arguments
    * exprIsExpandable arguments
  
  See Note [Interesting arguments] which is substantially rewritten.
  

• 7b616b9f
  by Cheng Shao at 2026-01-16T06:45:00-05:00

  compiler: fix regression when compiling foreign stubs in the rts unit
  
  This patch fixes a regression when compiling foreign stubs in the rts
  unit introduced in 05e25647f72bc102061af3f20478aa72bff6ff6e. A simple
  revert would fix it, but it's better to implement a proper fix with
  comment for better understanding of the underlying problem, see the
  added comment for explanation.
  
  Co-authored-by: Codex <codex@openai.com>
  

• c343ef64
  by Sylvain Henry at 2026-01-16T06:45:51-05:00

  base: remove GHC.JS.Prim.Internal.Build (#23432)
  
  See accepted CLC proposal https://github.com/haskell/core-libraries-committee/issues/329
  

• 29c0aceb
  by Simon Peyton Jones at 2026-01-16T17:18:11-05:00

  Improve newtype unwrapping
  
  Ticket #26746 describes several relatively-minor shortcomings of newtype
  unwrapping.  This MR addresses them, while also (arguably) simplifying
  the code a bit.
  
  See new Note [Solving newtype equalities: overview]
  and     Note [Decomposing newtype equalities]
  and     Note [Eager newtype decomposition]
  and     Note [Even more eager newtype decomposition]
  
  For some reason, on Windows only, runtime allocations decrease for test
  T5205 (from 52k to 48k).  I have not idea why. No change at all on Linux.
  I'm just going to accept the change.  (I saw this same effect in another
  MR so I think it's a fault in the baseline.)
  
  Metric Decrease:
      T5205
  

• 8b59e62c
  by Andreas Klebinger at 2026-01-16T17:18:52-05:00

  testsuite: Widen acceptance window for T5205.
  
  Fixes #26782
  

• 9e5e0234
  by mangoiv at 2026-01-17T06:03:03-05:00

  add a new issue template for getting verified
  
  To reduce spam created by new users, we will in future not grant
  any rights but reporting issues to new users. That is why we will
  have to be able to verify them. The added issue template serves that
  purpose.
  

• b18b2c42
  by Cheng Shao at 2026-01-17T06:03:44-05:00

  llvm: fix split sections for llvm backend
  
  This patch fixes split sections for llvm backend:
  
  - Pass missing `--data-sections`/`--function-sections` flags to
    llc/opt.
  - Use `@llvm.compiler.used` instead of `@llvm.used` to avoid sections
    being unnecessarily retained at link-time.
  
  Fixes #26770.
  
  -------------------------
  Metric Decrease:
      libdir
      size_hello_artifact
      size_hello_unicode
  -------------------------
  
  Co-authored-by: Codex <codex@openai.com>
  

• ebf66f67
  by Cheng Shao at 2026-01-17T13:16:50-05:00

  Update autoconf scripts
  
  Scripts taken from autoconf a2287c3041a3f2a204eb942e09c015eab00dc7dd
  

• 598624b9
  by Andreas Klebinger at 2026-01-17T13:17:32-05:00

  CString.hs: Update incorrect comment.
  
  Fixes #26322
  

• eea2036b
  by Cheng Shao at 2026-01-18T10:00:49-05:00

  libraries: bump haskeline submodule to 0.8.4.1
  
  This patch bumps the haskeline submodule to 0.8.4.1 which includes an
  important fix for an ANSI handling bug on Windows
  (https://github.com/haskell/haskeline/pull/126).
  

• 87d8f6c2
  by Cheng Shao at 2026-01-18T10:01:30-05:00

  hadrian: replace default -H32m/-H64m with -O64M to improve mutator productivity
  
  Most hadrian build flavours pass `-H32m`/`-H64m` to GHC as
  conventional wisdom to improve mutator productivity and reduce GC
  overhead. They were inherited from the legacy Make build system, and
  there used to be make flags to instrument a build process with
  `-Rghc-timing` option to collect GC stats of each GHC run from stderr.
  
  It's time to revisit whether there are better defaults for
  `-H32m`/`-H64m`, and this patch changes it to `-O64M` which indeed
  improves mutator productivity based on real statistics. `-O64M` is
  more aggressive than `-H64m`; it allows the old generation to grow to
  at least 64M before triggering major GC and reduces major GC runs.
  
  The stats of a clean build with `validate` flavour and `-H64m`:
  
  ```
  h64m.log
    matched RTS stat lines: 5499
    sum MUT cpu     : 2400.808 s
    sum GC cpu      : 1378.292 s
    sum MUT elapsed : 2788.253 s
    sum GC elapsed  : 1389.233 s
    GC/MUT cpu ratio     : 0.574 (GC is 57.4% of MUT)
    GC/MUT elapsed ratio : 0.498 (GC is 49.8% of MUT)
    GC fraction of (MUT+GC) cpu     : 36.5%
    GC fraction of (MUT+GC) elapsed : 33.3%
    per-line GC/MUT cpu ratio: median 0.691, p90 1.777
    per-line GC/MUT elapsed ratio: median 0.519, p90 1.081
  ```
  
  The stats of a clean build with `validate` flavour and `-O64M`:
  
  ```
  o64m.log
    matched RTS stat lines: 5499
    sum MUT cpu     : 2377.383 s
    sum GC cpu      : 1127.146 s
    sum MUT elapsed : 2758.857 s
    sum GC elapsed  : 1135.587 s
    GC/MUT cpu ratio     : 0.474 (GC is 47.4% of MUT)
    GC/MUT elapsed ratio : 0.412 (GC is 41.2% of MUT)
    GC fraction of (MUT+GC) cpu     : 32.2%
    GC fraction of (MUT+GC) elapsed : 29.2%
    per-line GC/MUT cpu ratio: median 0.489, p90 1.099
    per-line GC/MUT elapsed ratio: median 0.367, p90 0.806
  ```
  
  Mutator time is roughly in the same ballpark, but GC CPU time has
  reduced by 18.22%, and mutator productivity has increased from 63.5%
  to 67.8%.
  

• 8372e13d
  by Cheng Shao at 2026-01-18T10:02:12-05:00

  rts: remove unused .def files from rts/win32
  
  This patch removes unused .def files from `rts/win32`, given we don't
  build .dll files for rts/ghc-internal/ghc-prim at all. Even when we
  resurrect win32 dll support at some point in the future, these .def
  files still contain incorrect symbols anyway and won't be of any use.
  

• f6af485d
  by Cheng Shao at 2026-01-18T10:03:19-05:00

  .gitmodules: use gitlab mirror for the libffi-clib submodule
  
  This patch fixes .gitmodules to use the gitlab mirror for the
  libffi-clib submodule, to make it coherent with other submodules that
  allow ghc developers to experiment with wip branches in submodules for
  ghc patches. Fixes #26783.
  

• 41432d25
  by Cheng Shao at 2026-01-18T10:05:13-05:00

  hadrian: remove the horrible i386 speedHack
  
  When hadrian builds certain rts objects for i386, there's a horrible
  speedHack that forces -fno-PIC even for dynamic ways of those objects.
  This is not compatible with newer versions of gcc/binutils as well as
  clang/lld, and this patch removes it. Fixes #26792.
  

• 323eb8f0
  by Cheng Shao at 2026-01-18T21:48:19-05:00

  hadrian: enable split sections for cross stage0
  
  This patch fixes a minor issue with `splitSectionsArgs` in hadrian:
  previously, it's unconditionally disabled for stage0 libraries because
  it's not going to be shipped in the final bindists. But it's only true
  when not cross compiling. So for now we also need to enable it for
  cross stage0 as well.
  

• 3fadfefe
  by Andreas Klebinger at 2026-01-18T21:49:01-05:00

  RTS: Document -K behaviour better
  

• 30f442a9
  by Teo Camarasu at 2026-01-20T13:57:26-05:00

  base: don't expose GHC.Num.{BigNat, Integer, Natural}
  
  We no longer expose GHC.Num.{BigNat, Integer, Natural} from base instead users should get these modules from ghc-bignum.
  We make this change to insulate end users from changes to GHC's implementation of big numbers.
  Implements CLC proposal 359: https://github.com/haskell/core-libraries-committee/issues/359
  

• 75a9053d
  by Teo Camarasu at 2026-01-20T13:58:07-05:00

  base: deprecate GHC internals in GHC.Num
  
  Implements CLC proposal: https://github.com/haskell/core-libraries-committee/issues/360
  

• 9534b032
  by Andreas Klebinger at 2026-01-20T13:58:50-05:00

  ghc-experimental: Update Changelog
  
  I tried to reconstruct a high level overview of the changes and when
  they were made since we introduced it.
  
  Fixes #26506
  
  Co-authored-by: Teo Camarasu <teofilcamarasu@gmail.com>
  

• 346f2f5a
  by Cheng Shao at 2026-01-20T13:59:30-05:00

  hadrian: remove RTS options in ghc-in-ghci flavour
  
  This patch removes the RTS options passed to ghc in ghc-in-ghci
  flavour, to workaround command line argument handling issue in
  hls/hie-boot that results in `-O64M` instead of `+RTS -O64M -RTS`
  being passed to ghc. It's not a hadrian bug per se, since ghc's own
  ghc-in-ghci multi repl works fine, but we should still make sure HLS
  works. Closes #26801.
  

• 759fd15a
  by Andreas Klebinger at 2026-01-21T16:05:28-05:00

  Don't build GHC with -Wcompat
  
  Without bumping the boot compiler the warnings it produces are often not
  actionable leading to pointless noise.
  
  Fixes #26800
  

• 3172db94
  by Torsten Schmits at 2026-01-21T16:06:11-05:00

  Use the correct field of ModOrigin when formatting error message listing hidden reexports
  

• 485c12b2
  by Cheng Shao at 2026-01-21T16:06:54-05:00

  Revert "hadrian: handle findExecutable "" gracefully"
  
  This reverts commit 1e5752f64a522c4025365856d92f78073a7b3bba. The
  underlying issue has been fixed in
  https://github.com/haskell/directory/commit/75828696e7145adc09179111a0d631b9a09963a4
  and present since 1.3.9.0, and hadrian directory lower bound is
  1.3.9.0, so we can revert our own in house hack now.
  

• 5efb58dc
  by Cheng Shao at 2026-01-21T16:07:36-05:00

  rts: fix typo in TICK_ALLOC_RTS
  
  This patch fixes a typo in the `TICK_ALLOC_RTS` macro, the original
  `bytes` argument was silently dropped. The Cmm code has its own
  version of `TICK_ALLOC_RTS` not affected by this typo, it affected the
  C RTS, and went unnoticed because the variable `n` happened to also be
  available at its call site. But the number was incorrect. Also fixes
  its call site since `WDS()` is not available in C.
  

• c406ea69
  by Cheng Shao at 2026-01-21T16:07:36-05:00

  rts: remove broken & unused ALLOC_P_TICKY
  
  This patch removes the `ALLOC_P_TICKY` macro from the rts, it's
  unused, and its expanded code is already broken.
  

• 34a27e20
  by Simon Peyton Jones at 2026-01-21T16:08:17-05:00

  Make the implicit-parameter class have representational role
  
  This MR addresses #26737, by making the built-in class IP
  have a representational role for its second parameter.
  
  See Note [IP: implicit parameter class] in
    ghc-internal:GHC.Internal.Classes.IP
  
  In fact, IP is (unfortunately, currently) exposed by
  base:GHC.Base, so we ran a quick CLC proposal to
  agree the change:
    https://github.com/haskell/core-libraries-committee/issues/385
  
  Some (small) compilations get faster because they only need to
  load (small) interface file GHC.Internal.Classes.IP.hi,
  rather than (large) GHC.Internal.Classes.hi.
  
  Metric Decrease:
      T10421
      T12150
      T12425
      T24582
      T5837
      T5030
  

• ca79475f
  by Cheng Shao at 2026-01-21T16:09:00-05:00

  testsuite: avoid re.sub in favor of simple string replacements
  
  This patch refactors the testsuite driver and avoids the usage of
  re.sub in favor of simple string replacements when possible. The
  changes are not comprehensive, and there are still a lot of re.sub
  usages lingering around the tree, but this already addresses a major
  performance bottleneck in the testsuite driver that might has to do
  with quadratic or worse slowdown in cpython's regular expression
  engine when handling certain regex patterns with large strings.
  Especially on i386, and i386 jobs are the bottlenecks of all full-ci
  validate pipelines!
  
  Here are the elapsed times of testing x86_64/i386 with -j48 before
  this patch:
  
  x86_64: `Build completed in 6m06s`
  i386: `Build completed in 1h36m`
  
  And with this patch:
  
  x86_64: `Build completed in 4m55s`
  i386: `Build completed in 4m23s`
  
  Fixes #26786.
  
  Co-authored-by: Codex <codex@openai.com>
  

• 88c93796
  by Zubin Duggal at 2026-01-21T16:09:42-05:00

  ghc-toolchain: Also configure windres on non-windows platforms.
  It may be needed for cross compilation.
  
  Fixes #24588
  

• 9788c0ec
  by Cheng Shao at 2026-01-21T16:10:24-05:00

  ghci: print external interpreter trace messages to stderr instead of stdout
  
  This patch makes ghci print external interpreter trace messages to
  stderr instead of stdout, which is a much saner choice for diagnostic
  information. Closes #26807.
  

• 0491f08a
  by Sylvain Henry at 2026-01-22T03:44:26-05:00

  GC: don't use CAS without PARALLEL_GC on
  
  If we're not using the parallel GC, there is no reason to do a costly
  CAS. This was flagged as taking time in a perf profile.
  

• 211a8f56
  by Sylvain Henry at 2026-01-22T03:44:26-05:00

  GC: suffix parallel GC with "par" instead of "thr"
  
  Avoid some potential confusion (see discussion in !15351).
  

• 77a23cbd
  by fendor at 2026-01-22T03:45:08-05:00

  Remove blanket ignore that covers libraries/
  

• 18bf7f5c
  by Léana Jiang at 2026-01-22T08:58:45-05:00

  doc: update Flavour type in hadrian user-settings
  

• 3d5a1365
  by Cheng Shao at 2026-01-22T08:59:28-05:00

  hadrian: add missing notCross predicate for stage0 -O0
  
  There are a few hard-coded hadrian args that pass -O0 when compiling
  some heavy modules in stage0, which only makes sense when not
  cross-compiling and when cross-compiling we need properly optimized
  stage0 packages. So this patch adds the missing `notCross` predicate
  in those places.
  

• ee937134
  by Matthew Pickering at 2026-01-22T09:00:10-05:00

  Fix ghc-experimental GHC.Exception.Backtrace.Experimental module
  
  This module wasn't added to the cabal file so it was never compiled or
  included in the library.
  

• 1b490f5a
  by Zubin Duggal at 2026-01-22T09:00:53-05:00

  hadrian: Add ghc-{experimental,internal}.cabal to the list of dependencies of the doc target
  We need these files to detect the version of these libraries
  
  Fixes #26738
  

• cdb74049
  by Cheng Shao at 2026-01-22T14:52:36-05:00

  rts: avoid Cmm loop to initialize Array#/SmallArray#
  
  Previously, `newArray#`/`newSmallArray#` called an RTS C function to
  allocate the `Array#`/`SmallArray#`, then used a Cmm loop to
  initialize the elements. Cmm doesn't have native for-loop so the code
  is a bit awkward, and it's less efficient than a C loop, since the C
  compiler can effectively vectorize the loop with optimizations.
  
  So this patch moves the loop that initializes the elements to the C
  side. `allocateMutArrPtrs`/`allocateSmallMutArrPtrs` now takes a new
  `init` argument and initializes the elements if `init` is non-NULL.
  

• 4c784f00
  by Cheng Shao at 2026-01-22T14:53:19-05:00

  Fix testsuite run for +ipe flavour transformer
  
  This patch makes the +ipe flavour transformer pass the entire
  testsuite:
  
  - An RTS debug option `-DI` is added, the IPE trace information is now
    only printed with `-DI`. The test cases that do require IPE trace
    are now run with `-DI`.
  - The testsuite config option `ghc_with_ipe` is added, enabled when
    running the testsuite with `+ipe`, which skips a few tests that are
    sensitive to eventlog output, allocation patterns etc that can fail
    under `+ipe`.
  
  This is the first step towards #26799.
  
  Co-authored-by: Codex <codex@openai.com>
  

• be8e5236
  by Ben Gamari at 2026-01-23T03:28:45-05:00

  hadrian: Bump QuickCheck upper bound
  
  This patch bumps QuickCheck upper bound to 2.18. selftest rule
  manually tested to work with current latest QuickCheck-2.17.1.0.
  

• 5aa328fb
  by Zubin Duggal at 2026-01-23T03:29:30-05:00

  Add genindex to index.rst. This adds a link to the index in the navigation bar.
  
  Fixes #26437
  

• 917ab8ff
  by Oleg Grenrus at 2026-01-23T10:52:55-05:00

  Export labelThread from Control.Concurrent
  

• 3f5e8d80
  by Cheng Shao at 2026-01-23T10:53:37-05:00

  ci: only push perf notes on master/release branches
  
  This patch fixes push_perf_notes logic in ci.sh to only push perf
  notes on master/release branches. We used to unconditionally push perf
  notes even in MRs, but the perf numbers in the wip branches wouldn't
  be used as baseline anyway, plus this is causing a space leak in the
  ghc-performance-notes repo. See #25317 for the perf notes repo size
  problem.
  
  Co-authored-by: Codex <codex@openai.com>
  

• 414b9593
  by Cheng Shao at 2026-01-24T07:11:51-05:00

  ci: remove duplicate keys in .gitlab-ci.yml
  
  This patch removes accidentally duplicate keys in `.gitlab-ci.yml`.
  The YAML spec doesn't allow duplicate keys in the first place, and
  according to GitLab docs
  (https://docs.gitlab.com/ci/yaml/yaml_optimization/#anchors), the
  latest key overrides the earlier entries.
  

• e5cb5491
  by Cheng Shao at 2026-01-24T07:12:34-05:00

  hadrian: drop obsolete configure/make builder logic for libffi
  
  This patch drops obsolete hadrian logic around `Configure
  libffiPath`/`Make libffiPath` builders, they are no longer needed
  after libffi-clib has landed. Closes #26815.
  

• 2d160222
  by Simon Hengel at 2026-01-24T07:13:17-05:00

  Fix typo in roles.rst

• 56db94f7
  by Peter Trommler at 2026-01-26T11:26:18+01:00

  PPC NCG: Generate clear right insn at arch width
  
  The clear right immediate (clrrxi) is only available in word and
  doubleword width. Generate clrrxi instructions at architecture
  width for all MachOp widths.
  
  Fixes #24145
  

• 5957a8ad
  by Wolfgang Jeltsch at 2026-01-27T06:11:40-05:00

  Add operations for obtaining operating-system handles
  
  This contribution implements CLC proposal #369. It adds operations for
  obtaining POSIX file descriptors and Windows handles that underlie
  Haskell handles. Those operating system handles can also be obtained
  without such additional operations, but this is more involved and, more
  importantly, requires using internals.
  

• 86a0510c
  by Greg Steuck at 2026-01-27T06:12:34-05:00

  Move flags to precede patterns for grep and read files directly
  
  This makes the tests pass with non-GNU (i.e. POSIX-complicant) tools.
  There's no reason to use cat and pipe where direct file argument works.
  

• 50761451
  by Cheng Shao at 2026-01-27T21:51:23-05:00

  ci: update darwin boot ghc to 9.10.3
  
  This patch updates darwin boot ghc to 9.10.3, along with other related
  updates, and pays off some technical debt here:
  
  - Update `nixpkgs` and use the `nixpkgs-25.05-darwin` channel.
  - Update the `niv` template.
  - Update LLVM to 21 and update `llvm-targets` to reflect LLVM 21
    layout changes for arm64/x86_64 darwin targets.
  - Use `stdenvNoCC` to prevent nix packaged apple sdk from being used
    by boot ghc, and manually set `DEVELOPER_DIR`/`SDKROOT` to enforce
    the usage of system-wide command line sdk for macos.
  - When building nix derivation for boot ghc, run `configure` via the
    `arch` command so that `configure` and its subprocesses pick up the
    manually specified architecture.
  - Remove the previous horrible hack that obliterates `configure` to
    make autoconf test result in true. `configure` now properly does its
    job.
  - Remove the now obsolete configure args and post install settings
    file patching logic.
  - Use `scheme-small` for texlive to avoid build failures in certain
    unused texlive packages, especially on x86_64-darwin.
  

• 94dcd15e
  by Matthew Pickering at 2026-01-27T21:52:05-05:00

  Evaluate backtraces for "error" exceptions at the moment they are thrown
  
  See Note [Capturing the backtrace in throw] and
  Note [Hiding precise exception signature in throw] which explain the
  implementation.
  
  This commit makes `error` and `throw` behave the same with regard to
  backtraces. Previously, exceptions raised by `error` would not contain
  useful IPE backtraces.
  
  I did try and implement `error` in terms of `throw` but it started to
  involve putting diverging functions into hs-boot files, which seemed to
  risky if the compiler wouldn't be able to see if applying a function
  would diverge.
  
  CLC proposal: https://github.com/haskell/core-libraries-committee/issues/383
  
  Fixes #26751
  

• ef35e3ea
  by Teo Camarasu at 2026-01-27T21:52:46-05:00

  ghc-internal: move all Data instances to Data.Data
  
  Most instances of Data are defined in GHC.Internal.Data.Data.
  Let's move all remaining instance there.
  
  This moves other modules down in the dependency hierarchy allowing for
  more parallelism, and it decreases the likelihood that we would need to
  load this heavy .hi file if we don't actually need it.
  
  Resolves #26830
  
  Metric Decrease:
      T12227
      T16875
  

• 5e0ec555
  by sheaf at 2026-01-28T06:56:38-05:00

  Add test case for #25679
  
  This commit adds the T25679 test case. The test now passes, thanks to
  commit 1e53277af36d3f0b6ad5491f70ffc5593a49dcfd.
  
  Fixes #25679
  

• f1cd1611
  by sheaf at 2026-01-28T06:56:38-05:00

  Improve defaulting of representational equalities
  
  This commit makes the defaulting of representational equalities, introduced
  in 1e53277a, a little bit more robust. Now, instead of calling the eager
  unifier, it calls the full-blown constraint solver, which means that it can
  handle some subtle situations, e.g. involving functional dependencies and
  type-family injectivity annotations, such as:
  
    type family F a = r | r -> a
    type instance F Int = Bool
  
    [W] F beta ~R Bool
  

• 25edf516
  by sheaf at 2026-01-28T06:56:38-05:00

  Improve errors for unsolved representational equalities
  
  This commit adds a new field of CtLoc, CtExplanations, which allows the
  typechecker to leave some information about what it has done. For the moment,
  it is only used to improve error messages for unsolved representational
  equalities. The typechecker will now accumulate, when unifying at
  representational role:
  
    - out-of-scope newtype constructors,
    - type constructors that have nominal role in a certain argument,
    - over-saturated type constructors,
    - AppTys, e.g. `c a ~R# c b`, to report that we must assume that 'c' has
      nominal role in its parameters,
    - data family applications that do not reduce, potentially preventing
      newtype unwrapping.
  
  Now, instead of having to re-construct the possible errors after the fact,
  we simply consult the CtExplanations field.
  
  Additionally, this commit modifies the typechecker error messages that
  concern out-of-scope newtype constructors. The error message now depends
  on whether we have an import suggestion to provide to the user:
  
    - If we have an import suggestion for the newtype constructor,
      the message will be of the form:
  
        The data constructor MkN of the newtype N is out of scope
        Suggested fix: add 'MkN' to the import list in the import of 'M'
  
    - If we don't have any import suggestions, the message will be
      of the form:
  
        NB: The type 'N' is an opaque newtype, whose constructor is hidden
  
  Fixes #15850, #20289, #20468, #23731, #25949, #26137
  

• 4d0e6da1
  by Simon Peyton Jones at 2026-01-28T06:57:19-05:00

  Fix two bugs in short-cut constraint solving
  
  There are two main changes here:
  
  * Use `isSolvedWC` rather than `isEmptyWC` in `tryShortCutSolver`
    The residual constraint may have some fully-solved, but
    still-there implications, and we don't want them to abort short
    cut solving!  That bug caused #26805.
  
  * In the short-cut solver, we abandon the fully-solved residual
    constraint; but we may thereby lose track of Givens that are
    needed, and either report them as redundant or prune evidence
    bindings that are in fact needed.
  
    This bug stopped the `constraints` package from compiling;
    see the trail in !15389.
  
  The second bug led me to (another) significant refactoring
  of the mechanism for tracking needed EvIds.   See the new
     Note [Tracking needed EvIds] in GHC.Tc.Solver.Solve
  It's simpler and much less head-scratchy now.
  
  Some particulars:
  
  * An EvBindsVar now tracks NeededEvIds
  
  * We deal with NeededEvIds for an implication only when it is
    fully solved.  Much simpler!
  
  * `tryShortCutTcS` now takes a `TcM WantedConstraints` rather than
    `TcM Bool`, so that is can plumb the needed EvIds correctly.
  
  * Remove `ic_need` and `ic_need_implic` from Implication (hooray),
    and add `ics_dm` and `ics_non_dm` to `IC_Solved`.
  
  Pure refactor
  * Shorten data constructor `CoercionHole` to `CH`, following
    general practice in GHC.
  * Rename `EvBindMap` to `EvBindsMap` for consistency
  

• 662480b7
  by Cheng Shao at 2026-01-28T06:58:00-05:00

  ci: use debian validate bindists instead of fedora release bindists in testing stage
  
  This patch changes the `abi-test`, `hadrian-multi` and `perf` jobs in
  the full-ci pipeline testing stage to use debian validate bindists
  instead of fedora release bindists, to increase pipeline level
  parallelism and allow full-ci pipelines to complete earlier. Closes #26818.
  

• 39581ec6
  by Cheng Shao at 2026-01-28T06:58:40-05:00

  ci: run perf test with -j$cores
  
  This patch makes the perf ci job compile Cabal with -j$cores to speed
  up the job.
  

• 607b287b
  by Wolfgang Jeltsch at 2026-01-28T15:41:53+02:00

  Remove `GHC.Desugar` from `base`
  
  `GHC.Desugar` was deprecated and should have been removed in GHC 9.14.
  However, the removal was forgotten, although there was a code block that
  was intended to trigger a compilation error when the GHC version in use
  was 9.14 or later. This code sadly didn’t work, because the
  `__GLASGOW_HASKELL__` macro was misspelled as `__GLASGOW_HASKELL`.
  

• e8f5a45d
  by sterni at 2026-01-29T04:19:18-05:00

  users_guide: fix runtime error during build with Sphinx 9.1.0
  
  Appears that pathto is stricter about what it accepts now.
  Tested Sphinx 8.2.3 and 9.1.0 on the ghc-9.10 branch.
  
  Resolves #26810.
  
  Co-authored-by: Martin Weinelt <hexa@darmstadt.ccc.de>
  

• ce2d62fb
  by Jessica Clarke at 2026-01-29T19:48:51-05:00

  PPC NCG: Use libcall for 64-bit cmpxchg on 32-bit PowerPC
  
  There is no native instruction for this, and even if there were a
  register pair version we could use, the implementation here is assuming
  the values fit in a single register, and we end up only using / defining
  the low halves of the registers.
  
  Fixes: b4d39adbb5 ("PrimOps: Add CAS op for all int sizes")
  Fixes: #23969
  

• 43d97761
  by Michael Karcher at 2026-01-29T19:49:43-05:00

  NCG for PPC: add pattern for CmmRegOff to iselExpr64
  
  Closes #26828

• aeeb4a20
  by Matthew Pickering at 2026-01-30T11:42:47-05:00

  determinism: Use deterministic map for Strings in TyLitMap
  
  When generating typeable evidence the types we need evidence for all
  cached in a TypeMap, the order terms are retrieved from a type map
  determines the order the bindings appear in the program.
  
  A TypeMap is quite diligent to use deterministic maps, apart from in the
  TyLitMap, which uses a UniqFM for storing strings, whose ordering
  depends on the Unique of the FastString.
  
  This can cause non-deterministic .hi and .o files.
  
  An unexpected side-effect is the error message but RecordDotSyntaxFail8
  changing. I looked into this with Sam and this change caused the
  constraints to be solved in a different order which results in a
  slightly different error message. I have accepted the new test, since
  the output before was non-deterministic and the new output is consistent
  with the other messages in that file.
  
  Fixes #26846
  

• 9e4d70c2
  by Andrew Lelechenko at 2026-01-30T11:43:29-05:00

  Upgrade text submodule to 2.1.4
  

• 631fa5ae
  by Recursion Ninja at 2026-01-31T22:30:11+00:00

  Decouple `L.S.H.Decls` from importing `GHC.Types.Basic`
  
  Data-types within `GHC.Types.Basic` which describe components of
  the AST are migrated to `Language.Haskell.Syntax.Basic`. Related
  function definitions are also moved.
  
  Types moved to L.H.S. because they are part of the AST:
    * TopLevelFlag
    * RuleName
  
  Types moved from L.H.S. to GHC.Hs. because they are not needed in the AST:
    * TyConFlavour
    * TypeOrData
    * NewOrData
  
  Migrated instances:
    * `Outputable` instances moved to in `GHC.Utils.Outputable`
    * `Binary` instance of `Boxity` moved to to `GHC.Utils.Binary`
    * Other `Binary` instances are orphans to be migrated later.
  
  The `OverlapMode` data-type is given a TTG extension point.
  The `OverlapFlag` data-type, which depends on `OverlapMode`,
  is updated to support `OverlapMode` with a GHC "pass" type paramerter.
  In order to avoid module import cycles, `OverlapMode` and `OverlapFlag`
  are migrated to new modules (no way around this).
  
    * Migrated `OverlapMode` to new module `Language.Haskell.Syntax.Overlap`
    * Migrated `OverlapFlag` to new module `GHC.Hs.Decls.Overlap`
  

• 9769cc03
  by Simon Hengel at 2026-02-01T04:21:03-05:00

  Update the documentation for MultiWayIf (fixes #25376)
  
  (so that it matches the implementation)
  

• 5fc9442a
  by Peter Trommler at 2026-02-01T04:21:44-05:00

  hadrian: Fix dependency generation for assembler
  
  Assembler files allow # for comments unless in column 1. A modern
  cpp for C treats those a preprocessor directives. We tell gcc that
  a .S file is assembler with cpp and not C.
  
  Fixes #26819
  

• 269c4087
  by Simon Peyton Jones at 2026-02-01T19:38:10-05:00

  Include current phase in the range for rule/unfoldings
  
  This MR fixes a bad loop in the compiler: #26826.
  
  The fix is to add (WAR2) to
     Note [What is active in the RHS of a RULE or unfolding?]
  in GHC.Core.Opt.Simplify.Utils
  

• ddf1434f
  by Vladislav Zavialov at 2026-02-01T19:38:52-05:00

  Refactor: merge HsMultilineString into HsString (#26860)
  
  Before this patch, HsLit defined two separate constructors to represent
  single-line and multi-line strings:
  
  	data HsLit x
  	  ...
  	  | HsString (XHsString x) FastString
  	  | HsMultilineString (XHsMultilineString x) FastString
  
  I found this to be an unnecessary complication and an obstacle to unifying
  HsLit with HsTyLit. Now we use HsString for both kinds of literals.
  
  One user-facing change here is `ppr (HsString st s)` behaving differently for
  single-line strings containing newlines:
  
  	x = "first line \
  	    \asdf\n\
  	    \second line"
  
  Previously, the literal was fed to `ftext` with its newlines, producing an
  ill-formed SDoc. This issue is now addressed by using `split` for both
  single-line and multi-line strings:
  
  	vcat $ map text $ split '\n' (unpackFS src)
  
  See the parser/should_fail/T26860ppr test.
  
  In addition (and unrelatedly to the main payload of this patch),
  drop the unused pmPprHsLit helper.
  

• 2b4f463c
  by Simon Peyton Jones at 2026-02-02T17:32:32+00:00

  Remove exprIsCheap from doFloatFromRhs
  
  See #26854 and Note [Float when expandable]
  
  This patch simplifies the code, by removing an extra unnecessary test.
  

• 9db7f21f
  by Brandon Chinn at 2026-02-03T09:15:10-05:00

  Refactor: make function patterns exhaustive
  
  Also added missing (==) logic for:
    * HsMultilineString
    * HsInt{8,16,32}
    * HsWord{8,16,32}
  

• aa9c5e2c
  by Hécate Kleidukos at 2026-02-03T15:58:35-05:00

  driver: Hide source paths at verbosity level 1 by default
  

• c64cca1e
  by mangoiv at 2026-02-03T15:59:29-05:00

  ExplicitLevelImports: check staging for types just like for values
  
  Previously, imported types were entirely exempted from staging checks as
  the implicit stage persistance assumed to be all imported types to be
  well staged. ExplicitLevelImports' change specification, however, does
  not do such an exemption. Thus we want to introduce such a check, just
  like we have for values.
  ExplicitLevelImports does not, however, talk about local names - from
  its perspective, we could theoretically keep treating locally introduced
  types specially - e.g. an ill-staged used in a quote would only emit a
  warning, not an error. To allow for a potential future migration away
  from such wrinkles as the staging check in notFound
  (see  Note [Out of scope might be a staging error]) we consistently do
  the strict staging check that we also do for value if ExplicitLevelImports
  is on.
  
  Closes #26098
  

• 5f0dbeb6
  by Simon Hengel at 2026-02-03T16:00:12-05:00

  Use Haddock formatting in deprecation message of `initNameCache`

• 01ecb612
  by Andreas Klebinger at 2026-02-04T09:56:25-05:00

  testsuite: Explicitly use utf-8 encoding in rts-includes linter.
  
  Not doing so caused failures on windows, as python failed to pick a
  reasonable encoding even with locale set.
  
  Fixes #26850
  

• ea0d1317
  by Zubin Duggal at 2026-02-04T09:57:06-05:00

  Bump transformers submodule to 0.6.3.0
  
  Fixes #26790
  

• cbe4300e
  by Simon Peyton Jones at 2026-02-05T04:31:04-05:00

  Fix subtle bug in GHC.Core.Utils.mkTick
  
  This patch fixes a decade-old bug in `mkTick`, which
  could generate type-incorrect code!  See the diagnosis
  in #26772.
  
  The new code is simpler and easier to understand.
  (As #26772 says, I think it could be improved further.)
  

• a193a8da
  by Simon Peyton Jones at 2026-02-05T04:31:04-05:00

  Modify a debug-trace in the Simplifier
  
  ...just to show a bit more information.
  

• b579dfdc
  by Simon Peyton Jones at 2026-02-05T04:31:04-05:00

  Fix long-standing interaction between ticks and casts
  
  The code for Note [Eliminate Identity Cases] was simply wrong when
  ticks and casts interacted.  This patch fixes the interaction.
  
  It was shown up when validating #26772, although it's not the exactly
  the bug that's reported by #26772.  Nor is it easy to reproduce, hence
  no regression test.
  

• fac0de1e
  by Cheng Shao at 2026-02-05T04:31:49-05:00

  libraries: bump Cabal submodule to 3.16.1.0
  

• 00589122
  by Cheng Shao at 2026-02-05T04:31:49-05:00

  libraries: bump deepseq submodule to 1.5.2.0
  
  Also:
  
  - Get rid of usage of deprecated `NFData` function instance in the
    compiler
  - `T21391` still relies on `NFData` function instance, add
    `-Wno-deprecations` for the time being.
  

• 84474c71
  by Cheng Shao at 2026-02-05T04:31:50-05:00

  libraries: bump directory submodule to 1.3.10.1
  

• 1a9f4662
  by Cheng Shao at 2026-02-05T04:31:50-05:00

  libraries: bump exceptions submodule to 0.10.12
  

• 2e39a340
  by Peng Fan at 2026-02-07T03:42:01-05:00

  NCG/LA64: adjust register usage to avoid src-register being clobbered
  

• 9faf1b35
  by Teo Camarasu at 2026-02-07T03:42:43-05:00

  ghc-internal: Delete unnecessary GHC.Internal.Data.Ix
  
  This module merely re-exports GHC.Internal.Ix. It was copied from
  `base` when `ghc-internal` was split, but there is no reason to have
  this now. So, let's delete it.
  
  Resolves #26848
  

• d112b440
  by Sven Tennie at 2026-02-07T10:47:56-05:00

  Add cabal.project file to generate-ci
  
  This fixes the HLS setup for our CI code generation script
  (generate-ci).
  
  The project file simply makes `generate-ci` of the cabal file
  discoverable.
  

• 5339f6f0
  by Andreas Klebinger at 2026-02-07T10:48:40-05:00

  CI: Don't collapse test results.
  
  This puts test output back into the primary test log instead of a
  subsection removing the need to expand a section to see test results.
  
  While the intention was good in practice the old behaviour mostly wastes time
  by requiring expansion of the section.
  
  Fixes #26882
  

• 0e1cd2e0
  by Evan Piro at 2026-02-08T10:35:16-08:00

  Linker.MacOS reduce dynflags import
  

• 1c79a4cd
  by Michael Alan Dorman at 2026-02-09T08:11:51-05:00

  Remove `extra_src_files` variable from `testsuite/driver/testlib.py`
  
  While reading through the test harness code, I noticed this variable
  with a TODO attached that referenced #12223.  Although that bug is
  closed, it strongly implied that this special-case variable that only
  affected a single test was expected to be removed at some point.
  
  I also looked at 3415bcaa0b1903b5e12dfaadb5b774718e406eab---where it
  was added---whose commit message suggested that it would have been
  desirable to remove it, but that there were special circumstances that
  meant it had to remain (though it doesn't elucidate what those special
  circumstances are).
  
  However, the special circumstances were mentioned as if the test was
  in a different location than is currently is, so I decided to try
  changing the test to use the standard `extra_files` mechanism, which
  works in local testing.
  
  This also seems like a reasonable time to remove the script that was
  originally used in the transition, since it doesn't really serve a
  purpose anymore.
  

• 0020e38a
  by Matthew Pickering at 2026-02-09T17:29:14-05:00

  determinism: Use a stable sort in WithHsDocIdentifiers binary instance
  
  `WithHsDocIdentifiers` is defined as
  
  ```
   71 data WithHsDocIdentifiers a pass = WithHsDocIdentifiers
   72   { hsDocString      :: !a
   73   , hsDocIdentifiers :: ![Located (IdP pass)]
   74   }
  ```
  
  This list of names is populated from `rnHsDocIdentifiers`, which calls
  `lookupGRE`, which calls `lookupOccEnv_AllNameSpaces`, which calls
  `nonDetEltsUFM` and returns the results in an order depending on
  uniques.
  
  Sorting the list with a stable sort before returning the interface makes
  the output deterministic and follows the approach taken by other fields
  in `Docs`.
  
  Fixes #26858
  

• 89898ce6
  by echoumcp1 at 2026-02-09T17:30:01-05:00

  Replace putstrln with logMsg in handleSeqHValueStatus
  
  Fixes #26549
  

• 7c52c4f9
  by John Paul Adrian Glaubitz at 2026-02-10T13:52:43-05:00

  rts: Switch prim to use modern atomic compiler builtins
  
  The __sync_*() atomic compiler builtins have been deprecated in GCC
  for a while now and also don't provide variants for 64-bit values
  such as __sync_fetch_and_add_8().
  
  Thus, replace them with the modern __atomic_*() compiler builtins and
  while we're at it, also drop the helper macro CAS_NAND() which is now
  no longer needed since we stopped using the __sync_*() compiler builtins
  altogether.
  
  Co-authored-by: Ilias Tsitsimpis <iliastsi@debian.org>
  
  Fixes #26729
  

• cf60850a
  by Recursion Ninja at 2026-02-10T13:53:27-05:00

  Decoupling L.H.S.Decls from GHC.Types.ForeignCall
  
    - Adding TTG extension point for 'CCallTarget'
    - Adding TTG extension point for 'CType'
    - Adding TTG extension point for 'Header'
    - Moving ForeignCall types that do not need extension
      to new L.H.S.Decls.Foreign module
    - Replacing 'Bool' parameters with descriptive data-types
      to increase clairty and prevent "Boolean Blindness"
  

• 11a04cbb
  by Eric Lee at 2026-02-11T09:20:46-05:00

  Derive Semigroup/Monoid for instances believed could be derived in #25871
  

• 15d9ce44
  by Eric Lee at 2026-02-11T09:20:46-05:00

  add Ghc.Data.Pair deriving
  

• c85dc170
  by Evan Piro at 2026-02-11T09:21:45-05:00

  Linker.MacOS reduce options import
  

• a541dd83
  by Chris Wendt at 2026-02-11T16:06:41-05:00

  Initialize plugins for `:set +c` in GHCi
  
  Fixes #23110.
  

• 0f5a73bc
  by Cheng Shao at 2026-02-11T16:07:27-05:00

  compiler: add Binary Text instance
  
  This patch adds `Binary` instance for strict `Text`, in preparation of
  making `Text` usable in certain GHC API use cases (e.g. haddock). This
  also introduces `text` as a direct dependency of the `ghc` package.
  

• 9e58b8a1
  by Cheng Shao at 2026-02-11T16:08:10-05:00

  ghc-toolchain: add C11 check
  
  This patch partially reverts commit
  b8307eab80c5809df5405d76c822bf86877f5960 that removed C99 check in
  autoconf/ghc-toolchain. Now we:
  
  - No longer re-implement `FP_SET_CFLAGS_C11` similar to
    `FP_SET_CFLAGS_C99` in the past, since autoconf doesn't provide a
    convenient `AC_PROG_CC_C11` function. ghc-toolchain will handle it
    anyway.
  - The Cmm CPP C99 check is relanded and repurposed for C11.
  - The C99 logic in ghc-toolchain is relanded and repurposed for C11.
  - The C99 check in Stg.h is corrected to check for C11. The obsolete
    _ISOC99_SOURCE trick is dropped.
  - Usages of `-std=gnu99` in the testsuite are corrected to use
    `-std=gnu11`.
  
  Closes #26908.
  

• d4d51ac4
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Eliminate STM_AWOKEN
  
  It was used as nullary closure for the block_info.closure in the case of
  a thread being awoken after an STM transaction.
  
  However, while it was written, it was never read, so contributed nothing
  to the behaviour. Furthermore, in the only place it was set (in
  tryWakeupThread) the why_blocked was immediately overwritten by the
  NotBlocked status, and the block_info was updated accordingly (by
  appendToRunQueue).
  
  So it didn't even serve a purpose of clarifying an intermediate state,
  there really was no such intermediate state.
  
  Cleaning this up will allow the BlockedOnSTM case to follow the same
  pattern as the other why_blocked cases that do not use the block_info,
  and in turn this reduces the number of different categories.
  

• 7f7e51ee
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Add a proper mapping from internal to external thread event stop codes
  
  See issue #9003 for what goes wrong when we mess this up.
  
  In that ticket, people note that we should really not require the
  internal tso->why_blocked codes to leak into the external eventlog
  thread stop codes.
  
  This change properly separates them, and explicitly maps between them
  using a (compact, constant) table. This table is at most 20 bytes big,
  and will soon shrink (and has no alignment constraints) so it seems a
  sensible tradeoff.
  
  This will allow us to renumber the internal why_blockd codes without
  breaking the eventlog output.
  

• e5386cb8
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Remove unused tso->block_info.wakeup member.
  
  Presumably it was used once, but not now.
  

• c1151241
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Document StgTSOBlockInfo to say what cases use what members
  
  In principle, tso->why_blocked is the tag for the StgTSOBlockInfo union,
  so we should be able to say for each union member the why_blocked cases
  that use that member.
  

• f2f9dd71
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Add a tso->block_info.mvar member and use it
  
  in preference to the generic block_info.closure union member, with
  casts.
  
  The plan is that when we know what case we're in (via tso->why_blocked)
  then we can always access the correct union member, and so we will only
  need to access block_info.closure for generic cases where we don't know
  or don't care.
  

• 55f5ed61
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Add a tso->block_info.unused member and use it
  
  in preference to the generic block_info.closure union member, with
  casts.
  
  The plan is that when we know what case we're in (via tso->why_blocked)
  then we can always access the correct union member, and so we will only
  need to access block_info.closure for generic cases where we don't know
  or don't care.
  

• b08e0ec0
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Avoid storing to tso->block_info.closure
  
  In one case we can use a specific union member (.prev) instead. In
  several cases the stores were in fact redundant because of subsequent
  overwrites.
  
  In scavengeTSO we replace setting tso->block_info.closure to a valid
  closure, with an assertion that the block_info.unused is already set to
  END_TSO_QUEUE which is a valid (static) closure.
  

• 85df83bd
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Renumber the tso->why_blocked constants
  
  We can do this now because we have separated the internal values from
  the external ones used in the eventlog.
  
  This lets us put them back into a deliberate order and consolodate some
  gaps.
  
  More importantly, it is a prepation for a slightly more sophisticated
  encoding.
  

• cad2d298
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Define constants for the existing stg_threadStatuszh return codes
  
  The stg_threadStatuszh reuses the internal tso->why_blocked codes but
  also extends them with a couple previously magic values. This is awkward
  since we need to know what those magic values are so we don't
  accidentally use those values to mean something else. By pulling a
  definition up to where the why_blocked codes are defined we will be able
  to avoid mistakenly assining those codes some meaning (or just changing
  the BlockedThreadComplete, BlockedThreadKilled code if necessary).
  

• 805126c9
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Extend the tso->why_blocked encoding to indicate block_info closures
  
  We use some bit tricks to cheaply and generically test if a
  tso->why_blocked tag implies that the corresponding tso->block_info will
  contain a non-trivial valid closure (i.e. not just block_info.unused set
  to END_TSO_QUEUE).
  
  In particular we arrange for most why_blocked values to naturally have a
  distinguishing bit, but for the BlockedOn{Read,Write,Delay} cases, they
  can come in either non-closure or closure forms. We allow an additional
  bit to distinguish these cases. The non-closure forms are only from
  legacy I/O managers: select and win32-legacy. So this extra bit
  mechanism will be able to be retired once the legacy I/O managers are
  themselves retired.
  
  This means in a few places we need to untag the why_blocked value before
  inspecting it, but in most places we do not.
  

• 76a905e1
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Use BlockInfoForceNonClosure in the select I/O manager
  

• 2315521b
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Use BlockInfoForceNonClosure in the win32-legacy I/O manager
  
  for the BlockedOn{Read,Write} since these use the non-heap allocated
  StgAsyncIOResult.
  

• 3216922b
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Enforce the why_blocked and block_info rules in checkTSO
  
  We now check the cases wher IsBlockInfoClosure should hold, the cases
  that are supposed to use block_info.unused == END_TSO_QUEUE, and which
  cases are allowed to use BlockInfoForceNonClosure.
  
  This partially enforces the use of why_blocked as a tag for the
  block_info union. We could be stricter and check for the correct
  expected info table for the closure cases.
  

• 61d3b3b3
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Use IsBlockInfoClosure to simplify several tests
  
  In GC and generic traversal we need to know if we should look at the
  block_info.closure or not. Now we can do just that using a cheap bit
  test on the why_blocked tag.
  
  This fixes issue 26717, where the problem was that some GC modes did not
  know when to look at block_info.closure, because the poll I/O manager
  uses a closure for BlockedOn{Read,Write} while the select I/O manager
  uses a non-closure. Now this information is in the why_blocked tag
  itself.
  

• 50e12c45
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Remove the now-unused scavengeTSOIOManager
  
  The GC no longer has to delegate to the I/O manager, since it can use
  IsBlockInfoClosure to decide things itself.
  

• deb4ecd9
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Remove duplicate assertion
  

• 07b3d2c1
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  Follow atomic access rules more consistently for tso->why_blocked
  
  The rule is this:
  
  store block_info *before* why_blocked
  store why_blocked using store release
  
  load why_blocked using load acquire
  load block_info *after* why_blocked
  
  This is a an atomic store release / load acquire pair and (if the reads
  are in a separate thread to the writes, and the read receives the value
  stored) then this guarantees a full "happens before" relationship of
  these stores and loads.
  
  In some cases, we do not need a full load acquire, because we don't read
  the block_info at all and so do not need any ordering. In this case we
  just need an atomic relaxed load.
  
  This was being followed in most places, but not all. If there's good
  reason in any case that we don't need atomic access, then we should
  document that in a comment. In the absence of that I think it's easier
  to follow the rule everywhere.
  

• ed8bbd96
  by Duncan Coutts at 2026-02-11T23:41:52+00:00

  FIXUP for Use BlockInfoForceNonClosure in the select I/O manager

438 changed files:

• .gitignore
• .gitlab-ci.yml
• .gitlab/ci.sh
• .gitlab/darwin/nix/sources.json
• .gitlab/darwin/toolchain.nix
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• .gitmodules
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• compiler/GHC/CmmToAsm/LA64/CodeGen.hs
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• compiler/GHC/CmmToLlvm/Base.hs
• compiler/GHC/CmmToLlvm/CodeGen.hs
• compiler/GHC/Core/Coercion.hs
• compiler/GHC/Core/FamInstEnv.hs
• compiler/GHC/Core/InstEnv.hs
• compiler/GHC/Core/Map/Type.hs
• compiler/GHC/Core/Opt/Arity.hs
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• compiler/GHC/Core/Opt/Simplify/Env.hs
• compiler/GHC/Core/Opt/Simplify/Iteration.hs
• compiler/GHC/Core/Opt/Simplify/Utils.hs
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• compiler/GHC/Core/TyCon.hs
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• compiler/GHC/Core/Unfold.hs
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• compiler/GHC/CoreToStg.hs
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• compiler/GHC/Data/Maybe.hs
• compiler/GHC/Data/Pair.hs
• compiler/GHC/Driver/CodeOutput.hs
• compiler/GHC/Driver/Pipeline/Execute.hs
• compiler/GHC/Driver/Session.hs
• compiler/GHC/Hs/Decls.hs
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• compiler/GHC/Hs/Doc.hs
• compiler/GHC/Hs/Instances.hs
• compiler/GHC/Hs/Lit.hs
• compiler/GHC/Hs/Syn/Type.hs
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• compiler/GHC/Hs/Utils.hs
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• compiler/GHC/HsToCore/Foreign/JavaScript.hs
• compiler/GHC/HsToCore/Foreign/Utils.hs
• compiler/GHC/HsToCore/Foreign/Wasm.hs
• compiler/GHC/HsToCore/Match/Literal.hs
• compiler/GHC/HsToCore/Pmc.hs
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• compiler/GHC/Iface/Ext/Ast.hs
• compiler/GHC/Iface/Syntax.hs
• compiler/GHC/Linker/MacOS.hs
• compiler/GHC/Parser.y
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• compiler/GHC/Rename/HsType.hs
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• compiler/GHC/Stg/EnforceEpt.hs
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• compiler/GHC/StgToByteCode.hs
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• compiler/GHC/Tc/Deriv.hs
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• compiler/GHC/Utils/Outputable.hs
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• compiler/Language/Haskell/Syntax/Extension.hs
• compiler/Language/Haskell/Syntax/Lit.hs
• compiler/ghc.cabal.in
• config.guess
• config.sub
• configure.ac
• distrib/configure.ac.in
• docs/users_guide/9.16.1-notes.rst
• docs/users_guide/exts/multiway_if.rst
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• hadrian/src/Context.hs
• hadrian/src/Flavour.hs
• hadrian/src/Hadrian/Utilities.hs
• hadrian/src/Rules/Compile.hs
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• hadrian/src/Rules/Documentation.hs
• hadrian/src/Rules/Lint.hs
• hadrian/src/Settings/Builders/Cc.hs
• hadrian/src/Settings/Builders/Configure.hs
• hadrian/src/Settings/Builders/Ghc.hs
• hadrian/src/Settings/Builders/Make.hs
• hadrian/src/Settings/Builders/RunTest.hs
• hadrian/src/Settings/Builders/SplitSections.hs
• hadrian/src/Settings/Default.hs
• hadrian/src/Settings/Flavours/Benchmark.hs
• hadrian/src/Settings/Flavours/Development.hs
• hadrian/src/Settings/Flavours/GhcInGhci.hs
• hadrian/src/Settings/Flavours/Performance.hs
• hadrian/src/Settings/Flavours/Quick.hs
• hadrian/src/Settings/Flavours/QuickCross.hs
• hadrian/src/Settings/Flavours/Quickest.hs
• hadrian/src/Settings/Flavours/Validate.hs
• hadrian/src/Settings/Packages.hs
• libraries/Cabal
• libraries/base/base.cabal.in
• libraries/base/changelog.md
• libraries/base/src/Control/Concurrent.hs
• libraries/base/src/Data/Array/Byte.hs
• libraries/base/src/Data/Ix.hs
• − libraries/base/src/GHC/Desugar.hs
• − libraries/base/src/GHC/JS/Prim/Internal/Build.hs
• libraries/base/src/GHC/Num.hs
• − libraries/base/src/GHC/Num/BigNat.hs
• − libraries/base/src/GHC/Num/Integer.hs
• − libraries/base/src/GHC/Num/Natural.hs
• libraries/base/src/System/CPUTime/Utils.hs
• + libraries/base/src/System/IO/OS.hs
• libraries/base/src/System/Timeout.hs
• libraries/base/tests/IO/all.T
• + libraries/base/tests/IO/osHandles001FileDescriptors.hs
• + libraries/base/tests/IO/osHandles001FileDescriptors.stdout
• + libraries/base/tests/IO/osHandles001WindowsHandles.hs
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• libraries/directory
• libraries/exceptions
• libraries/ghc-bignum/ghc-bignum.cabal
• libraries/ghc-compact/tests/all.T
• libraries/ghc-experimental/CHANGELOG.md
• libraries/ghc-experimental/ghc-experimental.cabal.in
• libraries/ghc-experimental/src/GHC/Exception/Backtrace/Experimental.hs
• libraries/ghc-experimental/src/GHC/TypeNats/Experimental.hs
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• libraries/ghc-internal/src/GHC/Internal/CString.hs
• libraries/ghc-internal/src/GHC/Internal/Classes.hs
• + libraries/ghc-internal/src/GHC/Internal/Classes/IP.hs
• libraries/ghc-internal/src/GHC/Internal/Conc/Sync.hs
• libraries/ghc-internal/src/GHC/Internal/Data/Data.hs
• − libraries/ghc-internal/src/GHC/Internal/Data/Ix.hs
• libraries/ghc-internal/src/GHC/Internal/Err.hs
• libraries/ghc-internal/src/GHC/Internal/Exts.hs
• libraries/ghc-internal/src/GHC/Internal/Functor/ZipList.hs
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• libraries/ghc-internal/tests/backtraces/all.T
• libraries/ghc-internal/tests/stack-annotation/all.T
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• libraries/haskeline
• libraries/text
• libraries/transformers
• llvm-targets
• m4/fp_cmm_cpp_cmd_with_args.m4
• rts/AllocArray.c
• rts/AllocArray.h
• rts/ClosureTable.c
• rts/Heap.c
• rts/IOManager.c
• rts/IOManager.h
• rts/PrimOps.cmm
• rts/RaiseAsync.c
• rts/RtsFlags.c
• rts/STM.c
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• rts/StgMiscClosures.cmm
• rts/Threads.c
• rts/Trace.c
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• rts/include/Cmm.h
• rts/include/Stg.h
• rts/include/rts/Constants.h
• rts/include/rts/Flags.h
• rts/include/rts/storage/TSO.h
• rts/include/stg/MiscClosures.h
• rts/include/stg/Ticky.h
• rts/posix/Poll.c
• rts/posix/Select.c
• rts/posix/Timeout.c
• rts/prim/atomic.c
• rts/rts.cabal
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• testsuite/tests/parser/should_fail/all.T
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• testsuite/tests/plugins/all.T
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• utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs
• utils/haddock/haddock-api/src/Haddock/Types.hs

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