[Git][ghc/ghc][wip/backports-9.12.4] 70 commits: Allow users to customise the collection of exception annotations

Zubin pushed to branch wip/backports-9.12.4 at Glasgow Haskell Compiler / GHC Commits: f3cb6ffa by fendor at 2026-03-03T16:34:59+05:30 Allow users to customise the collection of exception annotations Add a global `CollectExceptionAnnotationMechanism` which determines how `ExceptionAnnotation`s are collected upon throwing an `Exception`. This API is exposed via `ghc-experimental`. By overriding how we collect `Backtraces`, we can control how the `Backtraces` are displayed to the user by newtyping `Backtraces` and giving a different instance for `ExceptionAnnotation`. A concrete use-case for this feature is allowing us to experiment with alternative stack decoders, without having to modify `base`, which take additional information from the stack frames. This commit does not modify how `Backtraces` are currently collected or displayed. (cherry picked from commit dee28cdd794652a3ebc271184e2ab3c866b5e219) - - - - - f34b8530 by fendor at 2026-03-03T16:34:59+05:30 Expose Backtraces internals from ghc-experimental Additionally, expose the same API `base:Control.Exception.Backtrace` to make it easier to use as a drop-in replacement. (cherry picked from commit 6602472273e1cdffcdb7753c9133047e571896bd) - - - - - 0469b8d0 by Zubin Duggal at 2026-03-03T16:34:59+05:30 testsuite: Be more permissive when filtering out GNU_PROPERTY_TYPE linker warnings The warning text is slightly different with ld.bfd. Fixes #26249 (cherry picked from commit 51c701fef034e2062809eed5de3a51bb0a4243ba) - - - - - 1608afe0 by Cheng Shao at 2026-03-03T16:34:59+05:30 hadrian: enforce have_llvm=False for wasm32/js This patch fixes hadrian to always pass have_llvm=False to the testsuite driver for wasm32/js targets. These targets don't really support the LLVM backend, and the optllvm test way doesn't work. We used to special-case wasm32/js to avoid auto-adding optllvm way in testsuite/config/ghc, but this is still problematic if someone writes a new LLVM-related test and uses something like when(have_llvm(), extra_ways(["optllvm"])). So better just enforce have_llvm=False for these targets here. (cherry picked from commit 1cdc6f46c4168dd92a8f5ea0c398b67fc59449a9) - - - - - 317f1d4f by Cheng Shao at 2026-03-03T16:34:59+05:30 libffi: update to 3.5.2 Bumps libffi submodule. (cherry picked from commit 45dbfa23f508f221b6aeb667783a928511a7654e) - - - - - 04cddfe3 by Cheng Shao at 2026-03-03T16:34:59+05:30 wasm: ensure setKeepCAFs() is called in ghci This patch is a critical bugfix for #26106, see comment and linked issue for details. (cherry picked from commit 10f06163d9adcb3b6e6438f1524faaca3bf6c3b2) - - - - - 19040130 by sheaf at 2026-03-03T16:34:59+05:30 Use tcMkScaledFunTys in matchExpectedFunTys We should use tcMkScaledFunTys rather than mkScaledFunTys in GHC.Tc.Utils.Unify.matchExpectedFunTys, as the latter crashes when the kind of the result type is a bare metavariable. We know the result is always Type-like, so we don't need scaledFunTys to try to rediscover that from the kind. Fixes #26277 (cherry picked from commit 624afa4a65caa8ec23f85e70574dfb606f90c173) - - - - - acf1860c by sheaf at 2026-03-03T16:34:59+05:30 Improve Notes about disambiguating record updates This commit updates the notes [Disambiguating record updates] and [Type-directed record disambiguation], in particular adding more information about the deprecation status of type-directed disambiguation of record updates. (cherry picked from commit a2d9d7c2073867ee0cabb8d49f93246d95ec0b09) - - - - - 9cd8faa5 by sheaf at 2026-03-03T16:34:59+05:30 Add test for #26216 (cherry picked from commit 2e73f3426ab6e3cf1938b53831005593f3fd351c) - - - - - 0ae0a7db by Vladislav Zavialov at 2026-03-03T16:34:59+05:30 Fix PREP_MAYBE_LIBRARY in prep_target_file.m4 This change fixes a configure error introduced in: commit 8235dd8c4945db9cb03e3be3c388d729d576ed1e ghc-toolchain: Move UseLibdw to per-Target file Now the build no longer fails with: acghc-toolchain: Failed to read a valid Target value from hadrian/cfg/default.target (cherry picked from commit 1480872af6b80db1b035a44409188416df041048) - - - - - 8bedc98f by Cheng Shao at 2026-03-03T16:34:59+05:30 rts: remove obsolete CC_SUPPORTS_TLS logic This patch removes obsolete CC_SUPPORTS_TLS logic throughout the rts, given __thread is now uniformly supported by C toolchains of all platforms we currently support. (cherry picked from commit 0f034942724233e1457549123b46880f7b93e805) - - - - - 2799bcb4 by Cheng Shao at 2026-03-03T16:34:59+05:30 rts: remove obsolete HAS_VISIBILITY_HIDDEN logic This patch removes obsolete HAS_VISIBILITY_HIDDEN logic throughout the rts, given __attribute__((visibility("hidden"))) is uniformly supported by C toolchains of all platforms we currently support. (cherry picked from commit ef7056554df5603ec4d1e33193abe953970e6ab3) - - - - - 80f04f24 by Cheng Shao at 2026-03-03T16:35:00+05:30 rts: remove -O3 pragma hack in Hash.c This patch removes an obsolete gcc pragma to specify -O3 in Hash.c. Hadrian already passes the right flag. (cherry picked from commit 9fdc1f7d855cc61f90de909875f6ae0d6798dca7) - - - - - a7ed406a by Cheng Shao at 2026-03-03T16:35:00+05:30 wasm: fix dyld handling for forward declared GOT.func items This patch fixes wasm shared linker's handling of forward declared GOT.func items, see linked issue for details. Also adds T26430 test to witness the fix. Fixes #26430. Co-authored-by: Codex (cherry picked from commit 867c26755e8855c6df949e65df0c2aebc9da64c3) - - - - - 1d0e59b5 by Cheng Shao at 2026-03-03T16:35:00+05:30 rts: remove obsolete __GNUC__ related logic This patch removes obsolete `__GNUC__` related logic, given on any currently supported platform and toolchain, `__GNUC__ >= 4` is universally true. Also pulls some other weeds and most notably, use `__builtin___clear_cache` for clang as well, since clang has supported this gcc intrinsic since 2014, see https://github.com/llvm/llvm-project/commit/c491a8d4577052bc6b3b4c72a7db6a7c.... (cherry picked from commit 67de53a6ced23caad640d2c7421089242f0dfb76) - - - - - f09d6f18 by Cheng Shao at 2026-03-03T16:35:00+05:30 hadrian: fix GHC.Platform.Host generation for cross stage1 This patch fixes incorrectly GHC.Platform.Host generation logic for cross stage1 in hadrian (#26449). Also adds T26449 test case to witness the fix. Co-authored-by: Codex (cherry picked from commit 8cbe006ad09d5a64e4a3cdf4c91a8b81ff1511be) - - - - - 4d1f030f by Luite Stegeman at 2026-03-03T16:35:00+05:30 rts: Fix lost wakeups in threadPaused for threads blocked on black holes The lazy blackholing code in threadPaused could overwrite closures that were already eagerly blackholed, and as such wouldn't have a marked update frame. If the black hole was overwritten by its original owner, this would lead to an undetected collision, and the contents of any existing blocking queue being lost. This adds a check for eagerly blackholed closures and avoids overwriting their contents. Fixes #26324 (cherry picked from commit a1de535f762bc23d4cf23a5b1853591dda12cdc9) - - - - - 52da5ad6 by Luite Stegeman at 2026-03-03T16:35:00+05:30 rts: push the correct update frame in stg_AP_STACK The frame contains an eager black hole (__stg_EAGER_BLACKHOLE_info) so we should push an stg_bh_upd_frame_info instead of an stg_upd_frame_info. (cherry picked from commit b7e21e498d39e0ee764e3237544b4c39ddf98467) - - - - - 166e7016 by Cheng Shao at 2026-03-03T16:35:00+05:30 testsuite: remove unused expected output files This patch removes unused expected output files in the testsuites on platforms that we no longer support. (cherry picked from commit 6992ac097b9da989f125f896afe21b75dba8b4c9) - - - - - 4df0eeb0 by Ben Gamari at 2026-03-03T16:35:00+05:30 rts/posix: Enforce iteration limit on heap reservation logic Previously we could loop indefinitely when attempting to get an address space reservation for our heap. Limit the logic to 8 iterations to ensure we instead issue a reasonable error message. Addresses #26151. (cherry picked from commit ff1650c96c61af02e193854312a9ccd303968e47) - - - - - 9d41ca6e by Ben Gamari at 2026-03-03T16:35:00+05:30 rts/posix: Hold on to low reservations when reserving heap Previously when the OS gave us an address space reservation in low memory we would immediately release it and try again. However, on some platforms this meant that we would get the same allocation again in the next iteration (since mmap's `hint` argument is just that, a hint). Instead we now hold on to low reservations until we have found a suitable heap reservation. Fixes #26151. (cherry picked from commit 0184455728f841a699648f879fdb29128081fc6b) - - - - - dd07582d by Julian Ospald at 2026-03-03T16:35:00+05:30 ghc-toolchain: Drop `ld.gold` from merge object command It's deprecated. Also see #25716 (cherry picked from commit c58f9a615f05e9d43629f6e846ae22cad2a6163d) - - - - - 2fb93a78 by Ben Gamari at 2026-03-03T16:35:00+05:30 gitlab-ci: Make RELEASE_JOB an input Rather than an undocumented variable. (cherry picked from commit f9790ca81deb8b14ff2eabf701aecbcfd6501963) - - - - - b5c445b4 by Cheng Shao at 2026-03-03T16:35:00+05:30 testsuite: fix T3586 for non-SSE3 platforms `T3586.hs` contains `-fvia-C -optc-msse3` which I think is a best-effort basis to harvest the C compiler's auto vectorization optimizations via the C backend back when the test was added. The `-fvia-C` part is now a deprecated no-op because GHC can't fall back to the C backend on a non-unregisterised build, and `-optc-msse3` might actually cause the test to fail on non x86/x64 platforms, e.g. recent builds of wasi-sdk would report `wasm32-wasi-clang: error: unsupported option '-msse3' for target 'wasm32-unknown-wasi'`. So this patch cleans up this historical cruft. `-fvia-C` is removed, and `-optc-msse3` is only passed when cpuid contains `pni` (which indicates support of SSE3). (cherry picked from commit 70ee825a516bcf7aac762bfedb4a017d35f8dcf3) - - - - - 8836b947 by Julian Ospald at 2026-03-03T16:35:00+05:30 Improve error handling in 'getPackageArchives' When the library dirs in the package conf files are not set up correctly, the JS linker will happily ignore such packages and not link against them, although they're part of the link plan. Fixes #26383 (cherry picked from commit 91b6be10bd58c2bfc1c7c22e81b06ab3be583228) - - - - - 6d883ca9 by Ben Gamari at 2026-03-03T16:35:00+05:30 rts: Annotate BCOs with their Name This introduces a new bytecode instruction, `BCO_NAME`, to aid in debugging bytecode execution. This instruction is injected by `mkProtoBCO` and captures the Haskell name of the BCO. It is then printed by the disassembler, allowing ready correlation with STG dumps. (cherry picked from commit 5192a75fe9b272e8b1ef290fa834714c81bd1f79) - - - - - 3dde94cd by sheaf at 2026-03-03T16:35:00+05:30 Bad record update msg: allow out-of-scope datacons This commit ensures that, when we encounter an invalid record update (because no constructor exists which contains all of the record fields mentioned in the record update), we graciously handle the situation in which the constructors themselves are not in scope. In that case, instead of looking up the constructors in the GlobalRdrEnv, directly look up their GREInfo using the lookupGREInfo function. Fixes #26391 (cherry picked from commit cef8938f3c0d22583f01d5ea29e6109bccd36040) - - - - - e7fcece4 by Cheng Shao at 2026-03-03T16:35:00+05:30 rts: remove obsolete COMPILING_WINDOWS_DLL logic This patch removes obsolete COMPILING_WINDOWS_DLL logic throughout the rts. They were once used for compiling to win32 DLLs, but we haven't been able to compile Haskell units to win32 DLLs for many years now, due to PE format's restriction of no more than 65536 exported symbols in a single DLL. (cherry picked from commit b8cfa8f741729ef123569fb321c4b2ab4a1a941c) - - - - - f22b7309 by Julian Ospald at 2026-03-03T16:35:00+05:30 Skip uniques test if sources are not available (cherry picked from commit 5dc2e9eaf60fd72771bf2e8112aec182665461a1) - - - - - cfdb79bf by Julian Ospald at 2026-03-03T16:35:00+05:30 rts: remove unneccesary cabal flags We perform those checks via proper autoconf macros instead that do the right thing and then add those libs to the rts buildinfo. (cherry picked from commit 643ce801a8b559071683cad0e5adbc26b9fc8385) - - - - - 42fd7682 by Wang Xin at 2026-03-03T16:35:00+05:30 Add -mcmodel=medium moduleflag to generated LLVM IR on LoongArch platform With the Medium code model, the jump range of the generated jump instruction is larger than that of the Small code model. It's a temporary fix of the problem descriped in https://gitlab.haskell .org/ghc/ghc/-/issues/25495. This commit requires that the LLVM used contains the code of commit 9dd1d451d9719aa91b3bdd59c0c6679 83e1baf05, i.e., version 8.0 and later. Actually we should not rely on LLVM, so the only way to solve this problem is to implement the LoongArch backend. Add new type for codemodel (cherry picked from commit e70d41406b5d5638b42c4d8222cd03e76bbfeb86) - - - - - 9dd4278e by Peng Fan at 2026-03-03T16:35:00+05:30 Pass the mcmodel=medium parameter to CC via GHC Ensure that GHC-driver builds default to mcmodel=medium, so that GHC passes this default parameter to CC without having to add it to the compiled project. Commit e70d41406b5d5638b42c4d8222cd03e76bbfeb86 does not ensure that all GHC-built object files have a default model of medium, and will raise an R_LARCH_B26 overflow error. (cherry picked from commit 1a3f11314cc7b8dbf9af03dd2ae2cb066a998d63) - - - - - 845258e5 by Ben Gamari at 2026-03-03T16:35:00+05:30 gitlab-ci: Run ghcup-metadata jobs on OpenCape runners This significantly reduces our egress traffic and makes the jobs significantly faster. (cherry picked from commit ff3f0d09bce1c261638b572af2bac1d87f1f6df7) - - - - - 27474eb7 by Luite Stegeman at 2026-03-03T16:35:00+05:30 rts: fix eager black holes: record mutated closure and fix assertion This fixes two problems with handling eager black holes, introduced by a1de535f762bc23d4cf23a5b1853591dda12cdc9. - the closure mutation must be recorded even for eager black holes, since the mutator has mutated it before calling threadPaused - The assertion that an unmarked eager black hole must be owned by the TSO calling threadPaused is incorrect, since multiple threads can race to claim the black hole. fixes #26495 (cherry picked from commit 3ba3d9f9db784c903ebe8fd617447ce62d30b7d3) - - - - - f2a5ec52 by ARATA Mizuki at 2026-03-03T16:35:00+05:30 LLVM backend: Pass the +evex512 attribute to LLVM 18+ if -mavx512f is set The newer LLVM requires the +evex512 attribute to enable use of ZMM registers. LLVM exhibits a backward-compatible behavior if the cpu is `x86-64`, but not if `penryn`. Therefore, on macOS, where the cpu is set to `penryn`, we need to explicitly pass +evex512. Fixes #26410 (cherry picked from commit b22777d4b7182f40a31eb430fa27f5fb9ef0f292) - - - - - e0b35b99 by Matthew Pickering at 2026-03-03T16:35:00+05:30 hadrian: Use a response file to invoke GHC for dep gathering. In some cases we construct an argument list too long for GHC to handle directly on windows. This happens when we generate the dependency file because the command line will contain references to a large number of .hs files. To avoid this we now invoke GHC using a response file when generating dependencies to sidestep length limitations. Note that we only pass the actual file names in the dependency file. Why? Because this side-steps #26560 (cherry picked from commit 9d371d23c526fd160d7e99bef2bc7da825cf3c0f) - - - - - af0b5f1e by Andreas Klebinger at 2026-03-03T16:35:00+05:30 Add hpc to release script (cherry picked from commit 64ec82ffa7f48399e18fcec43051d2b7ddcb7cc2) - - - - - 25d1768c by Matthew Pickering at 2026-03-03T16:35:00+05:30 rts: Fix a deadlock with eventlog flush interval and RTS shutdown The ghc_ticker thread attempts to flush at the eventlog tick interval, this requires waiting to take all capabilities. At the same time, the main thread is shutting down, the schedule is stopped and then we wait for the ticker thread to finish. Therefore we are deadlocked. The solution is to use `newBoundTask/exitMyTask`, so that flushing can cooperate with the scheduler shutdown. Fixes #26573 (cherry picked from commit b7fe744598b4569cd0236268e4f6f5b9d27e12b7) - - - - - e91c3d94 by Julian Ospald at 2026-03-03T16:35:00+05:30 rts: Fix object file format detection in loadArchive Commit 76d1041dfa4b96108cfdd22b07f2b3feb424dcbe seems to have introduced this bug, ultimately leading to failure of test T11788. I can only theorize that this test isn't run in upstream's CI, because they don't build a static GHC. The culprit is that we go through the thin archive, trying to follow the members on the filesystem, but don't re-identify the new object format of the member. This pins `object_fmt` to `NotObject` from the thin archive. Thanks to @angerman for spotting this. (cherry picked from commit fc958fc9eb6f6f4db473cdda23c381da8f32163d) - - - - - bf30088c by Simon Peyton Jones at 2026-03-03T16:35:00+05:30 Add missing InVar->OutVar lookup in SetLevels As #26681 showed, the SetLevels pass was failing to map an InVar to an OutVar. Very silly! I'm amazed it hasn't broken before now. I have improved the type singatures (to mention InVar and OutVar) so it's more obvious what needs to happen. (cherry picked from commit 52d00c05e1d803b36c93295399fe931c871166bf) - - - - - c85a5eb7 by Cheng Shao at 2026-03-03T16:35:00+05:30 compiler: change sectionProtection to take SectionType argument This commit changes `sectionProtection` to only take `SectionType` argument instead of whole `Section`, since it doesn't need the Cmm section content anyway, and it can then be called in parts of NCG where we only have a `SectionType` in scope. (cherry picked from commit 2433e91d41675d56f48f82d22430a8dee915e7a0) - - - - - ceac560b by Cheng Shao at 2026-03-03T16:35:00+05:30 compiler: change isInitOrFiniSection to take SectionType argument This commit changes `isInitOrFiniSection` to only take `SectionType` argument instead of whole `Section`, since it doesn't need the Cmm section content anyway, and it can then be called in parts of NCG where we only have a `SectionType` in scope. Also marks it as exported. (cherry picked from commit e5926fbebf341ee547227d41710d78471eecd09c) - - - - - 16941b01 by Cheng Shao at 2026-03-03T16:35:00+05:30 compiler: fix split sections on windows This patch fixes split sections on windows by emitting the right COMDAT section header in NCG, see added comment for more explanation. Fix #26696 #26494. ------------------------- Metric Decrease: LargeRecord T9675 size_hello_artifact size_hello_artifact_gzip size_hello_unicode size_hello_unicode_gzip Metric Increase: T13035 ------------------------- Co-authored-by: Codex (cherry picked from commit 244d57d79a555dcecc7590287bb14976d561291a) - - - - - 38251395 by Matthew Pickering at 2026-03-03T16:35:00+05:30 rts: Use INFO_TABLE_CONSTR for stg_dummy_ret_closure Since the closure type is CONSTR_NOCAF, we need to use INFO_TABLE_CONSTR to populate the constructor description field (this crashes ghc-debug when decoding AP_STACK frames sometimes) Fixes #26745 (cherry picked from commit 322dd6726b11c7101c28ffb8aeb7cb4cee34ab56) - - - - - 64011deb by Matthew Pickering at 2026-03-03T16:35:00+05:30 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 (cherry picked from commit 94dcd15e54146abecf9b4f5e47d258ca3cd40f1b) - - - - - 4b5668e6 by fendor at 2026-03-03T16:35:00+05:30 Remove `traceId` from ghc-pkg executable (cherry picked from commit d0966e64880e9fa30ce07c0fa5ea28108c6e8ad9) - - - - - fd64a588 by sheaf at 2026-03-03T16:35:00+05:30 Don't re-use stack slots for growing registers This commit avoids re-using a stack slot for a register that has grown but already had a stack slot. For example, suppose we have stack slot assigments %v1 :: FF64 |-> StackSlot 0 %v2 :: FF64 |-> StackSlot 1 Later, we start using %v1 at a larger format (e.g. F64x2) and we need to spill it again. Then we **must not** use StackSlot 0, as a spill at format F64x2 would clobber the data in StackSlot 1. This can cause some fragmentation of the `StackMap`, but that's probably OK. Fixes #26668 (cherry picked from commit 023c301c51e7346af3d4d773c448277ad3645ad2) - - - - - 161aff8b by Cheng Shao at 2026-03-03T16:35:00+05:30 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 (cherry picked from commit b18b2c42c32488ad6d3480a56a1fcd753cad2023) - - - - - 330d8ba5 by Matthew Pickering at 2026-03-03T16:35:00+05:30 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. (cherry picked from commit ee937134aa0ddf35c1a9dc7334c0aec0de13b719) - - - - - d0eb1c85 by Sylvain Henry at 2026-03-03T16:35:01+05:30 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. (cherry picked from commit 0491f08a965df0d6448bd9cd940d2b86fca2db5d) - - - - - ac3b7ef0 by Sylvain Henry at 2026-03-03T16:35:01+05:30 GC: suffix parallel GC with "par" instead of "thr" Avoid some potential confusion (see discussion in !15351). (cherry picked from commit 211a8f5633f0a5069c0689171f60b57719a242be) - - - - - 82071896 by Cheng Shao at 2026-03-03T16:35:01+05:30 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 (cherry picked from commit ca79475f6b4dfba991e2c933bac9c22d54a4950d) - - - - - d70c4204 by Zubin Duggal at 2026-03-03T16:35:01+05:30 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 (cherry picked from commit 1b490f5a7bbdb1441948241e6089b31efba9db45) - - - - - edec419b by Jessica Clarke at 2026-03-03T16:35:01+05:30 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 (cherry picked from commit ce2d62fba69d2ea0c74c46c50628feb8b81719d2) - - - - - 67eae519 by John Paul Adrian Glaubitz at 2026-03-03T16:35:01+05:30 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 Fixes #26729 (cherry picked from commit 7c52c4f9bc8d6ae6404039ec02efe48fbf7a4778) - - - - - f0723f59 by sterni at 2026-03-03T16:35:01+05:30 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 (cherry picked from commit e8f5a45de561ec80c88cd3da2c66502deb32d4c3) - - - - - 667cc709 by Michael Karcher at 2026-03-03T16:35:01+05:30 NCG for PPC: add pattern for CmmRegOff to iselExpr64 Closes #26828 (cherry picked from commit 43d977619de65c0cf87695fa5d86f1a3ff3176c3) - - - - - 5661cc49 by Matthew Pickering at 2026-03-03T16:35:01+05:30 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 (cherry picked from commit aeeb4a2034e80e26503eb88f5abde85e87a82f7b) - - - - - b2c5f223 by Andrew Lelechenko at 2026-03-03T16:35:01+05:30 Upgrade text submodule to 2.1.4 (cherry picked from commit 9e4d70c2764d117c5cf753127f93056d66e4f0d7) - - - - - 8e257c26 by Zubin Duggal at 2026-03-03T16:35:01+05:30 Bump transformers submodule to 0.6.3.0 Fixes #26790 (cherry picked from commit ea0d1317a630799a6b7bea12b24ef7e1ea6ed512) - - - - - 1f9c98a8 by Matthew Pickering at 2026-03-03T16:35:01+05:30 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 (cherry picked from commit 0020e38a021b5f0371c48fe73cddf8987acb1eb1) - - - - - 8eabffd3 by Simon Peyton Jones at 2026-03-03T16:35:01+05:30 Fix subtle bug in cast worker/wrapper See (CWw4) in Note [Cast worker/wrapper]. The true payload is in the change to the definition of GHC.Types.Id.Info.hasInlineUnfolding Everthing else is just documentation. There is a 2% compile time decrease for T13056; I'll take the win! Metric Decrease: T13056 (cherry picked from commit 99d8c146c12146e1e21b1f2d31809845d4afe9d4) - - - - - 54bae547 by Cheng Shao at 2026-03-03T16:35:01+05:30 wasm: use import.meta.main for proper distinction of nodejs main modules This patch uses `import.meta.main` for proper distinction of nodejs main modules, especially when the main module might be installed as a symlink. Fixes #26916. (cherry picked from commit 039f19778e35b193af0de2a2c6ed89556038627a) - - - - - 4dd0cb12 by Simon Peyton Jones at 2026-03-03T16:35:01+05:30 Report solid equality errors before custom errors This MR fixes #26255 by * Reporting solid equality errors like Int ~ Bool before "custom type errors". See comments in `report1` in `reportWanteds` * Suppressing errors that arise from superclasses of Wanteds. See (SCE1) in Note [Suppressing confusing errors] More details in #26255. (cherry picked from commit ba210d981b0812aea604f884d3c0aada4c8ca75c) - - - - - 6b4b8374 by Simon Peyton Jones at 2026-03-03T16:35:01+05:30 Fix a horrible shadowing bug in implicit parameters Fixes #26451. The change is in GHC.Tc.Solver.Monad.updInertDicts where we now do /not/ delete /Wanted/ implicit-parameeter constraints. This bug has been in GHC since 9.8! But it's quite hard to provoke; I contructed a tests in T26451, but it was hard to do so. (cherry picked from commit c052c724d2dfc994994b6548545836969aee8ed8) - - - - - 561cf2e3 by Simon Peyton Jones at 2026-03-03T16:35:01+05:30 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.) (cherry picked from commit cbe4300ef586c8bee1800426624db12e0237c6b5) - - - - - 439ddc80 by Simon Peyton Jones at 2026-03-03T16:35:01+05:30 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. (cherry picked from commit b579dfdc614e288b0fd754ac69ae7ff723d808be) - - - - - 61987e71 by sheaf at 2026-03-03T16:35:01+05:30 NamedDefaults: require the class to be standard We now only default type variables if they only appear in constraints of the form `C v`, where `C` is either a standard class or a class with an in-scope default declaration. This rectifies an oversight in the original implementation of the NamedDefault extensions that was remarked in #25775; that implementation allowed type variables to appear in unary constraints which had arbitrary classes at the head. See the rewritten Note [How type-class constraints are defaulted] for details of the implementation. Fixes #25775 Fixes #25778 (cherry picked from commit f1acdd2c2b664ad0bdcaae4064b50e84aa7bc599) - - - - - 0e0cd635 by Rodrigo Mesquita at 2026-03-03T16:35:01+05:30 bytecode: Use 32bits for breakpoint index Fixes #26325 (cherry picked from commit e368e24779f8a7bf110a025383db23521b313407) - - - - - ecb62efc by Zubin Duggal at 2026-03-03T16:35:01+05:30 Prepare release 9.12.4 - - - - - 213 changed files: - .gitlab-ci.yml - .gitlab/rel_eng/upload_ghc_libs.py - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/ByteCode/Instr.hs - compiler/GHC/Cmm.hs - compiler/GHC/Cmm/InitFini.hs - compiler/GHC/Cmm/Parser.y - compiler/GHC/CmmToAsm/AArch64/Ppr.hs - compiler/GHC/CmmToAsm/PPC/CodeGen.hs - compiler/GHC/CmmToAsm/Ppr.hs - compiler/GHC/CmmToAsm/Reg/Linear.hs - compiler/GHC/CmmToAsm/Reg/Linear/StackMap.hs - compiler/GHC/CmmToAsm/Wasm/FromCmm.hs - compiler/GHC/CmmToAsm/X86/Ppr.hs - compiler/GHC/CmmToC.hs - compiler/GHC/CmmToLlvm.hs - compiler/GHC/CmmToLlvm/Base.hs - compiler/GHC/CmmToLlvm/Data.hs - compiler/GHC/Core/Map/Type.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - compiler/GHC/Core/Opt/WorkWrap.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Pipeline/Execute.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Doc.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/Rename/Env.hs - compiler/GHC/Rename/Pat.hs - compiler/GHC/StgToByteCode.hs - compiler/GHC/StgToJS/Linker/Linker.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Instance/Class.hs - compiler/GHC/Tc/Solver.hs - compiler/GHC/Tc/Solver/Dict.hs - compiler/GHC/Tc/Types/Constraint.hs - compiler/GHC/Tc/Types/Evidence.hs - compiler/GHC/Tc/Utils/TcType.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Types/DefaultEnv.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Unit/Info.hs - compiler/ghc.cabal.in - + docs/users_guide/9.12.4-notes.rst - docs/users_guide/debugging.rst - docs/users_guide/release-notes.rst - docs/users_guide/rtd-theme/layout.html - hadrian/src/Builder.hs - hadrian/src/Rules/Documentation.hs - hadrian/src/Rules/Generate.hs - hadrian/src/Rules/Rts.hs - hadrian/src/Settings/Builders/Ghc.hs - hadrian/src/Settings/Builders/RunTest.hs - libffi-tarballs - libraries/base/base.cabal.in - libraries/base/changelog.md - libraries/ghc-experimental/ghc-experimental.cabal.in - + libraries/ghc-experimental/src/GHC/Exception/Backtrace/Experimental.hs - libraries/ghc-internal/src/GHC/Internal/Err.hs - libraries/ghc-internal/src/GHC/Internal/Exception.hs - libraries/ghc-internal/src/GHC/Internal/Exception/Backtrace.hs - libraries/ghc-internal/src/GHC/Internal/Exception/Backtrace.hs-boot - + libraries/ghc-internal/tests/Makefile - + libraries/ghc-internal/tests/all.T - + libraries/ghc-internal/tests/backtraces/Makefile - + libraries/ghc-internal/tests/backtraces/T14532a.hs - + libraries/ghc-internal/tests/backtraces/T14532a.stdout - + libraries/ghc-internal/tests/backtraces/T14532b.hs - + libraries/ghc-internal/tests/backtraces/T14532b.stdout - + libraries/ghc-internal/tests/backtraces/all.T - + libraries/ghc-internal/tests/stack-annotation/ann_frame005.hs - + libraries/ghc-internal/tests/stack-annotation/ann_frame005.stdout - libraries/text - libraries/transformers - m4/fp_check_pthreads.m4 - − m4/fp_visibility_hidden.m4 - m4/fptools_set_c_ld_flags.m4 - m4/prep_target_file.m4 - rts/Apply.cmm - rts/BeginPrivate.h - rts/Disassembler.c - rts/EndPrivate.h - rts/Hash.c - rts/Interpreter.c - − rts/RtsDllMain.c - − rts/RtsDllMain.h - rts/RtsStartup.c - rts/RtsSymbols.c - rts/StgMiscClosures.cmm - rts/Task.c - rts/Task.h - rts/ThreadPaused.c - rts/configure.ac - rts/eventlog/EventLog.c - rts/include/Rts.h - rts/include/RtsAPI.h - rts/include/Stg.h - rts/include/rts/OSThreads.h - rts/include/rts/Types.h - rts/include/stg/DLL.h - rts/linker/LoadArchive.c - rts/posix/OSMem.c - rts/posix/OSThreads.c - rts/prim/atomic.c - rts/prim/ctz.c - + rts/rts.buildinfo.in - rts/rts.cabal - rts/sm/BlockAlloc.c - rts/sm/Evac.c - rts/sm/Evac.h - rts/sm/Evac_thr.c → rts/sm/Evac_par.c - rts/sm/GCTDecl.h - rts/sm/GCThread.h - rts/sm/Scav_thr.c → rts/sm/Scav_par.c - rts/sm/Storage.c - rts/win32/OSThreads.c - testsuite/config/ghc - testsuite/driver/cpu_features.py - testsuite/driver/runtests.py - testsuite/driver/testlib.py - testsuite/driver/testutil.py - testsuite/tests/arrows/should_compile/T21301.stderr - + testsuite/tests/bytecode/T26216.hs - + testsuite/tests/bytecode/T26216.script - + testsuite/tests/bytecode/T26216.stdout - + testsuite/tests/bytecode/T26216_aux.hs - testsuite/tests/bytecode/all.T - + testsuite/tests/cross/should_run/T26449.hs - + testsuite/tests/cross/should_run/all.T - testsuite/tests/deSugar/should_fail/DsStrictFail.stderr - testsuite/tests/deSugar/should_run/T20024.stderr - testsuite/tests/deSugar/should_run/dsrun005.stderr - testsuite/tests/deSugar/should_run/dsrun007.stderr - testsuite/tests/deSugar/should_run/dsrun008.stderr - + testsuite/tests/default/T25775.hs - + testsuite/tests/default/T25775.stderr - testsuite/tests/default/all.T - testsuite/tests/deriving/should_run/T9576.stderr - + testsuite/tests/ghc-api/TypeMapStringLiteral.hs - testsuite/tests/ghc-api/all.T - + testsuite/tests/ghci-wasm/Makefile - + testsuite/tests/ghci-wasm/T26430.hs - + testsuite/tests/ghci-wasm/T26430A.c - + testsuite/tests/ghci-wasm/T26430B.c - + testsuite/tests/ghci-wasm/all.T - testsuite/tests/ghci.debugger/scripts/T8487.stdout - testsuite/tests/ghci.debugger/scripts/break011.stdout - testsuite/tests/ghci.debugger/scripts/break017.stdout - testsuite/tests/ghci.debugger/scripts/break025.stdout - testsuite/tests/ghci/scripts/Defer02.stderr - testsuite/tests/ghci/scripts/T15325.stderr - testsuite/tests/interface-stability/ghc-experimental-exports.stdout - testsuite/tests/interface-stability/ghc-experimental-exports.stdout-mingw32 - testsuite/tests/linters/all.T - + testsuite/tests/overloadedrecflds/should_fail/T26391.hs - + testsuite/tests/overloadedrecflds/should_fail/T26391.stderr - testsuite/tests/overloadedrecflds/should_fail/all.T - testsuite/tests/patsyn/should_run/ghci.stderr - testsuite/tests/perf/should_run/T3586.hs - testsuite/tests/perf/should_run/all.T - − testsuite/tests/process/process010.stdout-i386-unknown-solaris2 - testsuite/tests/rts/all.T - − testsuite/tests/rts/linker/T11223/T11223_link_order_a_b_2_fail.stderr-ws-32-mingw32 - − testsuite/tests/rts/linker/T11223/T11223_simple_duplicate_lib.stderr-ws-32-mingw32 - − testsuite/tests/rts/outofmem.stderr-i386-apple-darwin - − testsuite/tests/rts/outofmem.stderr-i386-unknown-mingw32 - − testsuite/tests/rts/outofmem.stderr-powerpc-apple-darwin - testsuite/tests/safeHaskell/safeLanguage/SafeLang15.stderr - testsuite/tests/showIface/DocsInHiFile1.stdout - testsuite/tests/showIface/HaddockSpanIssueT24378.stdout - testsuite/tests/showIface/MagicHashInHaddocks.stdout - + testsuite/tests/simd/should_run/T26410_ffi.hs - + testsuite/tests/simd/should_run/T26410_ffi.stdout - + testsuite/tests/simd/should_run/T26410_ffi_c.c - + testsuite/tests/simd/should_run/T26410_prim.hs - + testsuite/tests/simd/should_run/T26410_prim.stdout - testsuite/tests/simd/should_run/all.T - + testsuite/tests/simplCore/should_compile/T26681.hs - + testsuite/tests/simplCore/should_compile/T26903.hs - + testsuite/tests/simplCore/should_compile/T26903.stderr - testsuite/tests/simplCore/should_compile/all.T - testsuite/tests/th/T10279.hs - testsuite/tests/th/T10279.stderr - testsuite/tests/type-data/should_run/T22332a.stderr - + testsuite/tests/typecheck/should_compile/T26277.hs - + testsuite/tests/typecheck/should_compile/T26451.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/T12921.stderr - testsuite/tests/typecheck/should_fail/T18851.hs - + testsuite/tests/typecheck/should_fail/T26255a.hs - + testsuite/tests/typecheck/should_fail/T26255a.stderr - + testsuite/tests/typecheck/should_fail/T26255b.hs - + testsuite/tests/typecheck/should_fail/T26255b.stderr - + testsuite/tests/typecheck/should_fail/T26255c.hs - + testsuite/tests/typecheck/should_fail/T26255c.stderr - testsuite/tests/typecheck/should_fail/UnliftedNewtypesFamilyKindFail2.stderr - testsuite/tests/typecheck/should_fail/all.T - testsuite/tests/typecheck/should_run/T10284.stderr - testsuite/tests/typecheck/should_run/T13838.stderr - testsuite/tests/typecheck/should_run/T9497a-run.stderr - testsuite/tests/typecheck/should_run/T9497b-run.stderr - testsuite/tests/typecheck/should_run/T9497c-run.stderr - testsuite/tests/unsatisfiable/T23816.stderr - testsuite/tests/unsatisfiable/UnsatDefer.stderr - utils/ghc-pkg/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Tools/MergeObjs.hs - utils/jsffi/dyld.mjs - utils/jsffi/post-link.mjs The diff was not included because it is too large. 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