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Duncan Coutts pushed to branch wip/dcoutts/posix-ticker at Glasgow Haskell Compiler / GHC

Commits:

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