Simon Peyton Jones pushed to branch wip/T27862 at Glasgow Haskell Compiler / GHC Commits: 54cf3c1e by sheaf at 2026-11-03T07:00:23-05:00 Consolidate all CPU feature handling This commit introduces GHC.Platform.CpuFeatures which consolidates all of the logic for implications between CPU feature flags (mainly X86): - DynFlags now only records the set of -m<feature> flags that were passed, as an EnumSet CpuFeature. That keeps it a simple record of the flags the user passed, with no post-processing. - GHC.Platform.CpuFeatures.initCpuFeatures turns this set into a CpuFeatures value, applying all implications and the per-architecture baseline. This is the single home for all of the feature implication logic. Some datatypes were reworked to better reflect the implication structure in the types, e.g. SseAvxVersion has a strategically placed 'FMA' boolean. - The NCG, LLVM backend, StgToCmm, CPP defines and LLVM -mattr flags all consult CpuFeatures, via targetCpuFeatures. See Note [CPU features], which replaces Note [Implications between X86 CPU feature flags]. Behaviour changes: - x86 feature flags (-msse3, -mavx, -mavx512*, -mgfni, ...) passed when targeting a non-x86 architecture no longer cause x86 CPP macros (__SSE3__, __AVX512BW__, __GFNI__, ...) to be defined, nor x86 attributes to be passed to LLVM. - Error messages reported when required CPU features are not enabled now print out the minimal set of flags required (e.g. "-mavx512vl" rather than "-mavx512f -mavx512vl"). - - - - - 9af64305 by Luite Stegeman at 2026-11-03T07:01:23-05:00 rts: move stack check to the start of the stg_unpack_cstring thunks fixes a deadlock see #27272 - - - - - a2208b21 by Simon Jakobi at 2026-11-03T07:02:05-05:00 Cmm: exclude the entry block from common block elimination a1d8139054c had fixed #27722 only partially, because it didn't prevent elimination of the entry block in later rounds, where the entry block is no longer guaranteed to come first. To close this loophole, we exclude the entry block from the CBE merge logic. See Note [Retain entry block during common block elimination] for details. This also deletes a misleading comment regarding unreachable blocks: the control-flow optimiser doesn't actually guarantee that no unreachable blocks reach CBE. Fixes #27722. Assisted-by: Claude Fable 5.1 - - - - - 37ad4710 by Alan Zimmerman at 2026-11-03T07:02:46-05:00 EPA: Use AnnList for GADT declarations Continuing the process of using AnnList to capture parser layout - - - - - b2bd7dc2 by Simon Peyton Jones at 2026-11-03T15:12:27+00:00 Better desugaring for bang patterns Ticket #27862 showed that we were desugaring bang patterns in a silly way, which led to bad code. This small fix makes it much better. See Note [Tidying patterns] which has new (TP1) and (TP2) and Note [Grouping equations] especially (GE1) - - - - - 58 changed files: - changelog.d/T27722-cbe-entry-block.md - + changelog.d/T27862 - + changelog.d/caf-deadlock-27272 - compiler/GHC/Cmm/CallConv.hs - compiler/GHC/Cmm/CommonBlockElim.hs - compiler/GHC/CmmToAsm/Config.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToAsm/X86/Instr.hs - compiler/GHC/CmmToLlvm/CodeGen.hs - compiler/GHC/CmmToLlvm/Config.hs - compiler/GHC/Driver/Config/CmmToAsm.hs - compiler/GHC/Driver/Config/CmmToLlvm.hs - compiler/GHC/Driver/Config/StgToCmm.hs - compiler/GHC/Driver/DynFlags.hs - compiler/GHC/Driver/Pipeline/Execute.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/HsToCore/Match.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Monad.hs - compiler/GHC/HsToCore/Pmc.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Platform.hs - + compiler/GHC/Platform/CpuFeatures.hs - compiler/GHC/StgToCmm/Config.hs - compiler/GHC/StgToCmm/Prim.hs - compiler/GHC/SysTools/Cpp.hs - compiler/ghc.cabal.in - rts/StgStdThunks.cmm - testsuite/tests/ado/T22483.stderr - + testsuite/tests/cmm/should_run/T27722.hs - + testsuite/tests/cmm/should_run/T27722_cmm.cmm - testsuite/tests/cmm/should_run/all.T - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/deSugar/should_compile/T27862.hs - + testsuite/tests/deSugar/should_compile/T27862.stderr - + testsuite/tests/deSugar/should_compile/T27862a.hs - + testsuite/tests/deSugar/should_compile/T27862a.stderr - testsuite/tests/deSugar/should_compile/all.T - testsuite/tests/deSugar/should_run/dsrun008.stderr - testsuite/tests/ghc-api/exactprint/Test20239.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T17544.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T17544_kw.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T24221.stderr - testsuite/tests/parser/should_compile/DumpParsedAst.stderr - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/parser/should_compile/T14189.stderr - testsuite/tests/parser/should_compile/T15323.stderr - testsuite/tests/parser/should_compile/T20452.stderr - testsuite/tests/pmcheck/should_compile/T24234.stderr - testsuite/tests/printer/T18791.stderr - + testsuite/tests/rts/T27272.hs - + testsuite/tests/rts/T27272_gen.py - testsuite/tests/rts/all.T - testsuite/tests/typecheck/should_fail/tcfail203a.stderr - utils/check-exact/ExactPrint.hs The diff was not included because it is too large. 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