Simon Peyton Jones pushed to branch wip/T27994 at Glasgow Haskell Compiler / GHC Commits: ac870ad5 by Simon Jakobi at 2026-10-28T04:40:42-04:00 X86 NCG: use 32-bit POPCNT for sub-word popcounts A 32-bit write zero-extends the result to the full register, so we don't need to emit additional code for this. We also skip emitting zero-extension instructions for the argument when it is already visibly zero-extended. For the byte-wise popcount loop from #24813, this shrinks the popcount sequence from 5 instructions to 3. Assisted-by: Claude Fable 5.1 - - - - - 53087373 by Facundo Domínguez at 2026-10-28T04:41:32-04:00 Use a ShortByteString in Serialized instead of [Word8] This makes the in-memory representation 40x more compact for all values stored in annotations. A test is added to measure the representation size of annotations specified in the compiler input. The GHC API is modified. All functions that previously handled annotations in [Word8] form now use ShortByteString. The following definitions have modified types: * GHC.findGlobalAnns * GHC.Tc.Gen.Splice.getAnnotationsByTypeRep * GHC.Core.Opt.Monad.getAnnotations * GHC.Core.Opt.Monad.getFirstAnnotations * GHC.Types.Annotations.deserializeAnns * GHC.Types.Annotations.findAnns * GHC.Types.Annotations.findAnnsByTypeRep * GHC.Serialized.Serialized * GHC.Serialized.toSerialized * GHC.Serialized.fromSerialized * GHC.Serialized.serializeWithData * GHC.Serialized.deserializeWithData * GHCi.Message.ReifyAnnotations Fixes #28002. - - - - - 1581cecc by Simon Peyton Jones at 2026-10-28T23:37:30+00:00 Simplify a tc-trace which could crash the compiler The trace formatted an error message, which prematurely read the ExpType in a FunResCtxt. Solution: don't put call the error message formatting when tc-tracing. - - - - - d0e160be by Simon Peyton Jones at 2026-10-28T23:37:30+00:00 Tiny comment change to uniqAway - - - - - 50de89a1 by Simon Peyton Jones at 2026-10-28T23:45:06+00:00 Make niFixSubst idempotent I discovered (when fixing #27994) that `niFixSubst` didn't actually generate an idempotent subsitution despite its claims. It could return a substitution that mentions domain variables on in its range, when those variables are hidden inside the kind of a type variable occurrence. As a result it can generate ill-kinded types. Boo! The fix is simple, and uses deep substitution. See Note [Finding the substitution fixpoint] I don't think it actually /caused/ any bugs, so there is no regression test. - - - - - 6af2da8d by Simon Peyton Jones at 2026-10-28T23:51:45+00:00 Fix a nasty bug in fundeps This MR fixes #27994, which turned out to be very tricky. See Note [Exploiting closed type famililes], especially (CF7). I was ending up with TyVars (not TcTyVars) in the solver, because the substitution computed in `getRelevantBranches` mixed the two. The code was just too clever. I ended up simplifying it quite a bit, eliminating fancy footwork in a function `trim_qtvs`. I left behind Historical Note [trim_qtvs] to explain. This patch also fixes one other buglet in the same code. * Over-saturated type families were being mis-handled. See the new use of `saturatedFamApp_maybe`. - - - - - 35 changed files: - + changelog.d/T28002 - + changelog.d/T28002-api - + changelog.d/ncg-x86-subword-popcnt - compiler/GHC.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/Core/Coercion/Axiom.hs - compiler/GHC/Core/Opt/Monad.hs - compiler/GHC/Core/Predicate.hs - compiler/GHC/Core/TyCo/FVs.hs - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/Tc/Gen/Splice.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Solver/FunDeps.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Types/Annotations.hs - compiler/GHC/Types/Var/Env.hs - compiler/GHC/Utils/Outputable.hs - libraries/ghc-boot/GHC/Serialized.hs - libraries/ghci/GHCi/Message.hs - libraries/ghci/GHCi/TH.hs - libraries/ghci/GHCi/TH/Binary.hs - testsuite/tests/annotations/should_run/Makefile - + testsuite/tests/annotations/should_run/T16841.hs - + testsuite/tests/annotations/should_run/T16841.stdout - testsuite/tests/annotations/should_run/all.T - + testsuite/tests/codeGen/should_gen_asm/T24813.asm - + testsuite/tests/codeGen/should_gen_asm/T24813.cmm - testsuite/tests/codeGen/should_gen_asm/all.T - testsuite/tests/plugins/T26761Plugin.hs - testsuite/tests/plugins/all.T - + testsuite/tests/typecheck/should_compile/T27994.hs - + testsuite/tests/typecheck/should_compile/T27994a.hs - testsuite/tests/typecheck/should_compile/all.T The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/0b7cebad3132bbb556b367910a8df4e... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/0b7cebad3132bbb556b367910a8df4e... You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help