Sebastian Graf pushed to branch wip/sg/first-class-strict at Glasgow Haskell Compiler / GHC Commits: 8fadf2e0 by I-Al-Istannen at 2026-06-27T12:09:51+02:00 Strict: add the wired-in unlifted box type Adds the wired-in type Strict :: Type -> UnliftedType with its single strict constructor MkStrict, an evaluated-and-properly-tagged box for strict fields, and the isStrictTy predicate. See Note [The Strict type]. Co-authored-by: Sebastian Graf - - - - - 1f961f09 by I-Al-Istannen at 2026-06-27T12:09:52+02:00 Strict: make demand analysis and CPR transparent to the box Demand and CPR analysis look through Strict/MkStrict so that a product demand on Strict a is passed to the wrapped field and CPR information flows likewise, and exprIsTrivial / unfolding sizing treat MkStrict on a value as trivial. Accepts the resulting signature churn in the test suite. Co-authored-by: Sebastian Graf - - - - - 8a89b9ef by I-Al-Istannen at 2026-06-27T12:09:52+02:00 Strict: unbox strict arguments through the box in worker/wrapper Worker/wrapper marks each strictified worker argument with Strict, so the wrapper passes an evaluated value and the worker need not re-force it, and unboxes the wrapped type when profitable. Co-authored-by: Sebastian Graf - - - - - 0eaa66ed by I-Al-Istannen at 2026-06-27T12:09:52+02:00 Desugar: only reconstruct constructor fields used by the body Co-authored-by: Sebastian Graf - - - - - 4165000f by I-Al-Istannen at 2026-06-27T12:09:52+02:00 CorePrep: erase MkStrict via a representational cast MkStrict is erased in CorePrep: a producer becomes the field cast to Strict a with a heterogeneous representational coercion, forcing the field first when it is not already a value; a consumer match becomes the scrutinee cast back. Core Lint tolerates the resulting out-of-scope type variables and the Strict coercion. See Note [The Strict type]. Co-authored-by: Sebastian Graf - - - - - 7d62101e by I-Al-Istannen at 2026-06-27T12:09:52+02:00 Strict: STG representation and code generation Treats Strict a as a single unlifted heap pointer through RepType, unarisation, STG lint, tag inference and StgToCmm: an unlifted box is already evaluated and properly tagged, so it is returned directly unless applied as a function. An STG Lint check flags an evaluated binder lowered to an updatable indirection. Co-authored-by: Sebastian Graf - - - - - 335c17b6 by Sebastian Graf at 2026-06-27T12:09:52+02:00 Strict: add a should_run test for the strict-field machinery StrictBox exercises a strict value field built from a thunk (forced to an evaluated, properly-tagged value), a strict field of function type that is applied, worker/wrapper unboxing of a strict argument, and a strict field holding another boxed value. Run with -dtag-inference-checks so that a strict field that is not properly tagged aborts at runtime. - - - - - 64 changed files: - compiler/GHC/Builtin/Names.hs - compiler/GHC/Builtin/PrimOps/Casts.hs - compiler/GHC/Builtin/Types.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Opt/CprAnal.hs - compiler/GHC/Core/Opt/DmdAnal.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/SimpleOpt.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/Unfold.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToStg.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/Driver/Config/Core/Lint/Interactive.hs - compiler/GHC/Driver/Config/CoreToStg/Prep.hs - compiler/GHC/Driver/Main/Interactive.hs - compiler/GHC/Driver/Main/Passes.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Pmc/Solver/Types.hs - compiler/GHC/HsToCore/Utils.hs - compiler/GHC/Stg/Lint.hs - compiler/GHC/Stg/Unarise.hs - compiler/GHC/StgToCmm/Closure.hs - compiler/GHC/StgToCmm/Expr.hs - compiler/GHC/StgToCmm/TagCheck.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/RepType.hs - libraries/ghc-internal/src/GHC/Internal/Types.hs - testsuite/tests/backpack/cabal/bkpcabal08/bkpcabal08.stdout - testsuite/tests/codeGen/should_compile/T25166.stdout-ws-64 - + testsuite/tests/codeGen/should_run/StrictBox.hs - + testsuite/tests/codeGen/should_run/StrictBox.stdout - testsuite/tests/codeGen/should_run/all.T - testsuite/tests/core-to-stg/T24124.stderr - testsuite/tests/cpranal/should_compile/T18109.stderr - testsuite/tests/cpranal/should_compile/T18174.stderr - testsuite/tests/dmdanal/should_compile/T10482.stderr - testsuite/tests/dmdanal/should_compile/T10482a.stderr - testsuite/tests/dmdanal/sigs/T16197b.stderr - testsuite/tests/dmdanal/sigs/T16859.stderr - testsuite/tests/dmdanal/sigs/T17932.stderr - testsuite/tests/dmdanal/sigs/T22241.stderr - testsuite/tests/ghci.debugger/scripts/T13825-debugger.stdout - testsuite/tests/ghci.debugger/scripts/print007.stdout - testsuite/tests/ghci.debugger/scripts/print022.stdout - testsuite/tests/interface-stability/base-exports.stdout - testsuite/tests/interface-stability/ghc-experimental-exports.stdout - testsuite/tests/interface-stability/ghc-prim-exports.stdout - + testsuite/tests/perf/should_run/StrictBuilderFusion.hs - + testsuite/tests/perf/should_run/StrictBuilderFusion.stdout - testsuite/tests/perf/should_run/all.T - testsuite/tests/profiling/should_compile/prof-late-cc3.stderr - testsuite/tests/simplCore/should_compile/T18013.stderr - testsuite/tests/simplCore/should_compile/T22309.stderr - testsuite/tests/simplCore/should_compile/T24359a.stderr - testsuite/tests/simplCore/should_compile/T26615.stderr - testsuite/tests/simplCore/should_compile/T4081.stderr - testsuite/tests/simplStg/should_compile/T15226b.stderr The diff was not included because it is too large. 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