Wolfgang Jeltsch pushed to branch wip/jeltsch/system-io-implementation-into-base at Glasgow Haskell Compiler / GHC Commits: 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. - - - - - bef14b41 by Wolfgang Jeltsch at 2026-03-23T22:02:25+02:00 Move most of the `System.IO` implementation into `base` Metric Increase: T12227 T12707 T5642 - - - - - 186 changed files: - .gitlab-ci.yml - .gitlab/generate-ci/flake.lock - .gitlab/generate-ci/gen_ci.hs - .gitlab/jobs.yaml - .gitlab/rel_eng/fetch-gitlab-artifacts/fetch_gitlab.py - .gitlab/rel_eng/mk-ghcup-metadata/mk_ghcup_metadata.py - compiler/CodeGen.Platform.h - compiler/GHC/Builtin/Names.hs - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/Cmm/CommonBlockElim.hs - compiler/GHC/Cmm/Expr.hs - compiler/GHC/Cmm/Opt.hs - compiler/GHC/Cmm/Parser.y - compiler/GHC/Cmm/Type.hs - compiler/GHC/Cmm/Utils.hs - compiler/GHC/CmmToAsm/AArch64/CodeGen.hs - compiler/GHC/CmmToAsm/AArch64/Instr.hs - compiler/GHC/CmmToAsm/AArch64/Ppr.hs - compiler/GHC/CmmToAsm/AArch64/Regs.hs - compiler/GHC/CmmToAsm/LA64/CodeGen.hs - compiler/GHC/CmmToAsm/LA64/Ppr.hs - compiler/GHC/CmmToAsm/LA64/Regs.hs - compiler/GHC/CmmToAsm/PPC/CodeGen.hs - compiler/GHC/CmmToAsm/PPC/Ppr.hs - compiler/GHC/CmmToAsm/PPC/Regs.hs - compiler/GHC/CmmToAsm/RV64/CodeGen.hs - compiler/GHC/CmmToAsm/RV64/Ppr.hs - compiler/GHC/CmmToAsm/RV64/Regs.hs - compiler/GHC/CmmToAsm/Reg/Graph/TrivColorable.hs - compiler/GHC/CmmToAsm/Wasm/FromCmm.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToAsm/X86/Ppr.hs - compiler/GHC/CmmToAsm/X86/Regs.hs - compiler/GHC/CmmToC.hs - compiler/GHC/CmmToLlvm/CodeGen.hs - compiler/GHC/CmmToLlvm/Data.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Make.hs - compiler/GHC/Core/Opt/ConstantFold.hs - compiler/GHC/Driver/Config/StgToCmm.hs - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/Foreign/C.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Pmc.hs - compiler/GHC/HsToCore/Pmc/Solver/Types.hs - + compiler/GHC/Platform/Tag.hs - compiler/GHC/Stg/Unarise.hs - compiler/GHC/StgToByteCode.hs - compiler/GHC/StgToCmm/Closure.hs - compiler/GHC/StgToCmm/Expr.hs - compiler/GHC/StgToCmm/Lit.hs - compiler/GHC/StgToCmm/Prim.hs - compiler/GHC/StgToJS/Literal.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Instance/Class.hs - compiler/GHC/Tc/TyCl/Build.hs - compiler/GHC/Tc/Types/Origin.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/Literal.hs - + compiler/GHC/Types/Literal/Floating.hs - compiler/GHC/Types/RepType.hs - compiler/GHC/Utils/Binary.hs - compiler/ghc.cabal.in - docs/users_guide/9.16.1-notes.rst - docs/users_guide/utils.py - ghc/GHCi/UI.hs - ghc/Main.hs - hadrian/cabal.project - hadrian/src/Settings/Flavours/GhcInGhci.hs - hadrian/src/Settings/Flavours/Validate.hs - hadrian/src/Settings/Packages.hs - libraries/base/src/Control/Concurrent.hs - libraries/base/src/GHC/IO/Handle.hs - libraries/base/src/Prelude.hs - libraries/base/src/System/IO.hs - libraries/base/src/Text/Printf.hs - libraries/ghc-experimental/ghc-experimental.cabal.in - + libraries/ghc-experimental/src/GHC/Stack/Decode/Experimental.hs - libraries/ghc-internal/src/GHC/Internal/Conc/IO.hs - libraries/ghc-internal/src/GHC/Internal/Event/Control.hs - libraries/ghc-internal/src/GHC/Internal/Event/KQueue.hsc - libraries/ghc-internal/src/GHC/Internal/Float.hs - libraries/ghc-internal/src/GHC/Internal/Float/RealFracMethods.hs - libraries/ghc-internal/src/GHC/Internal/IO/FD.hs - libraries/ghc-internal/src/GHC/Internal/Int.hs - libraries/ghc-internal/src/GHC/Internal/RTS/Flags.hsc - libraries/ghc-internal/src/GHC/Internal/RTS/Flags/Test.hsc - libraries/ghc-internal/src/GHC/Internal/System/Environment.hs - libraries/ghc-internal/src/GHC/Internal/System/Environment/Blank.hsc - libraries/ghc-internal/src/GHC/Internal/System/IO.hs - libraries/ghc-internal/src/GHC/Internal/System/Posix/Internals.hs - libraries/ghc-internal/src/GHC/Internal/TopHandler.hs - libraries/ghci/GHCi/Message.hs - libraries/ghci/GHCi/ResolvedBCO.hs - libraries/ghci/GHCi/Run.hs - libraries/ghci/GHCi/Server.hs - 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