Ben Gamari pushed to branch wip/backports-9.14 at Glasgow Haskell Compiler / GHC Commits: c7bd98fa by Ben Gamari at 2025-08-18T15:17:53-04:00 compiler: Enable polymorphic-specialisation Fixes #23559, by re-enabling polymorphic specialisation by default as the remaining hazards to soundness have been addressed by #23109. Metric Increase: info_table_map_perf (cherry picked from commit bbe5bb7682c2dbbfc89ad9031c77bb4a1845451a) - - - - - f957d52f by Ben Gamari at 2025-08-18T15:17:53-04:00 users-guide: Release notes formatting wibbles - - - - - 5 changed files: - compiler/GHC/Driver/DynFlags.hs - compiler/GHC/Driver/Flags.hs - docs/users_guide/9.14.1-notes.rst - docs/users_guide/using-optimisation.rst - testsuite/tests/simplCore/should_compile/T8331.stderr Changes: ===================================== compiler/GHC/Driver/DynFlags.hs ===================================== @@ -1250,6 +1250,7 @@ optLevelFlags -- see Note [Documenting optimisation flags] , ([1,2], Opt_CfgBlocklayout) -- Experimental , ([1,2], Opt_Specialise) + , ([1,2], Opt_PolymorphicSpecialisation) , ([1,2], Opt_CrossModuleSpecialise) , ([1,2], Opt_InlineGenerics) , ([1,2], Opt_Strictness) ===================================== compiler/GHC/Driver/Flags.hs ===================================== @@ -907,6 +907,7 @@ optimisationFlags = EnumSet.fromList , Opt_SpecialiseAggressively , Opt_CrossModuleSpecialise , Opt_StaticArgumentTransformation + , Opt_PolymorphicSpecialisation , Opt_CSE , Opt_StgCSE , Opt_StgLiftLams ===================================== docs/users_guide/9.14.1-notes.rst ===================================== @@ -102,7 +102,9 @@ Language Compiler ~~~~~~~~ -- An improved error message is introduced to refer users to the heap-controlling flags of the RTS when there is a heap overflow during compilation. (#25198) +- Polymorphic specialisation has been reenabled by default in optimisation levels 1 and higher (:ghc-ticket:`23559`) + +- An improved error message is introduced to refer users to the heap-controlling flags of the RTS when there is a heap overflow during compilation. (:ghc-ticket:`25198`) - The kind checker now does a better job of finding type family instances for use in the kinds of other declarations in the same module. This fixes a number @@ -116,14 +118,14 @@ Compiler subordinate import lists (:ghc-ticket:`22581`). - A new flag, :ghc-flag:`-Wuseless-specialisations`, controls warnings emitted when GHC - determines that a SPECIALISE pragma would have no effect. + determines that a ``SPECIALISE`` pragma would have no effect. -- A new flag, :ghc-flag:`-Wrule-lhs-equalities`, controls warnings emitted for RULES +- A new flag, :ghc-flag:`-Wrule-lhs-equalities`, controls warnings emitted for ``RULES`` whose left-hand side attempts to quantify over equality constraints that previous GHC versions accepted quantifying over. GHC will now drop such RULES, emitting a warning message controlled by this flag. - This warning is intended to give visibility to the fact that the RULES that + This warning is intended to give visibility to the fact that the ``RULES`` that previous GHC versions generated in such circumstances could never fire. - A new flag, :ghc-flag:`-Wunusable-unpack-pragmas`, controls warnings emitted ===================================== docs/users_guide/using-optimisation.rst ===================================== @@ -1316,10 +1316,7 @@ as such you shouldn't need to set any of them explicitly. A flag :reverse: -fno-polymorphic-specialisation :category: - :default: off - - Warning, this feature is highly experimental and may lead to incorrect runtime - results. Use at your own risk (:ghc-ticket:`23469`, :ghc-ticket:`23109`, :ghc-ticket:`21229`, :ghc-ticket:`23445`). + :default: on Enable specialisation of function calls to known dictionaries with free type variables. The created specialisation will abstract over the type variables free in the dictionary. ===================================== testsuite/tests/simplCore/should_compile/T8331.stderr ===================================== @@ -1,5 +1,148 @@ ==================== Tidy Core rules ==================== +"SPEC $c*> @(ST s) @_" + forall (@s) (@r) ($dApplicative :: Applicative (ST s)). + $fApplicativeReaderT_$c*> @(ST s) @r $dApplicative + = ($fApplicativeReaderT2 @s @r) + `cast` (forall (a :: <*>_N) (b :: <*>_N). + _R + %<'Many>_N ->_R _R + %<'Many>_N ->_R <r>_R %<'Many>_N ->_R Sym (N:ST <s>_N <b>_R) + ; Sym (N:ReaderT <*>_N <r>_R <ST s>_R <b>_N) + :: Coercible + (forall a b. + ReaderT r (ST s) a -> ReaderT r (ST s) b -> r -> STRep s b) + (forall a b. + ReaderT r (ST s) a -> ReaderT r (ST s) b -> ReaderT r (ST s) b)) +"SPEC $c<$ @(ST s) @_" + forall (@s) (@r) ($dFunctor :: Functor (ST s)). + $fFunctorReaderT_$c<$ @(ST s) @r $dFunctor + = ($fApplicativeReaderT6 @s @r) + `cast` (forall (a :: <*>_N) (b :: <*>_N). + <a>_R + %<'Many>_N ->_R _R + %<'Many>_N ->_R <r>_R %<'Many>_N ->_R Sym (N:ST <s>_N <a>_R) + ; Sym (N:ReaderT <*>_N <r>_R <ST s>_R <a>_N) + :: Coercible + (forall a b. a -> ReaderT r (ST s) b -> r -> STRep s a) + (forall a b. a -> ReaderT r (ST s) b -> ReaderT r (ST s) a)) +"SPEC $c<* @(ST s) @_" + forall (@s) (@r) ($dApplicative :: Applicative (ST s)). + $fApplicativeReaderT_$c<* @(ST s) @r $dApplicative + = ($fApplicativeReaderT1 @s @r) + `cast` (forall (a :: <*>_N) (b :: <*>_N). + _R + %<'Many>_N ->_R _R + %<'Many>_N ->_R <r>_R %<'Many>_N ->_R Sym (N:ST <s>_N <a>_R) + ; Sym (N:ReaderT <*>_N <r>_R <ST s>_R <a>_N) + :: Coercible + (forall a b. + ReaderT r (ST s) a -> ReaderT r (ST s) b -> r -> STRep s a) + (forall a b. + ReaderT r (ST s) a -> ReaderT r (ST s) b -> ReaderT r (ST s) a)) +"SPEC $c<*> @(ST s) @_" + forall (@s) (@r) ($dApplicative :: Applicative (ST s)). + $fApplicativeReaderT9 @(ST s) @r $dApplicative + = ($fApplicativeReaderT4 @s @r) + `cast` (forall (a :: <*>_N) (b :: <*>_N). + b)>_R + %<'Many>_N ->_R _R + %<'Many>_N ->_R <r>_R + %<'Many>_N ->_R Sym (N:ST <s>_N <b>_R) + :: Coercible + (forall a b. + ReaderT r (ST s) (a -> b) -> ReaderT r (ST s) a -> r -> STRep s b) + (forall a b. + ReaderT r (ST s) (a -> b) -> ReaderT r (ST s) a -> r -> ST s b)) +"SPEC $c>> @(ST s) @_" + forall (@s) (@r) ($dMonad :: Monad (ST s)). + $fMonadReaderT1 @(ST s) @r $dMonad + = $fMonadAbstractIOSTReaderT_$s$c>> @s @r +"SPEC $c>>= @(ST s) @_" + forall (@s) (@r) ($dMonad :: Monad (ST s)). + $fMonadReaderT2 @(ST s) @r $dMonad + = ($fMonadAbstractIOSTReaderT2 @s @r) + `cast` (forall (a :: <*>_N) (b :: <*>_N). + _R + %<'Many>_N ->_R ReaderT r (ST s) b>_R + %<'Many>_N ->_R <r>_R + %<'Many>_N ->_R Sym (N:ST <s>_N <b>_R) + :: Coercible + (forall a b. + ReaderT r (ST s) a -> (a -> ReaderT r (ST s) b) -> r -> STRep s b) + (forall a b. + ReaderT r (ST s) a -> (a -> ReaderT r (ST s) b) -> r -> ST s b)) +"SPEC $cfmap @(ST s) @_" + forall (@s) (@r) ($dFunctor :: Functor (ST s)). + $fFunctorReaderT_$cfmap @(ST s) @r $dFunctor + = ($fApplicativeReaderT7 @s @r) + `cast` (forall (a :: <*>_N) (b :: <*>_N). + b>_R + %<'Many>_N ->_R _R + %<'Many>_N ->_R <r>_R %<'Many>_N ->_R Sym (N:ST <s>_N <b>_R) + ; Sym (N:ReaderT <*>_N <r>_R <ST s>_R <b>_N) + :: Coercible + (forall a b. (a -> b) -> ReaderT r (ST s) a -> r -> STRep s b) + (forall a b. (a -> b) -> ReaderT r (ST s) a -> ReaderT r (ST s) b)) +"SPEC $cliftA2 @(ST s) @_" + forall (@s) (@r) ($dApplicative :: Applicative (ST s)). + $fApplicativeReaderT_$cliftA2 @(ST s) @r $dApplicative + = ($fApplicativeReaderT3 @s @r) + `cast` (forall (a :: <*>_N) (b :: <*>_N) (c :: <*>_N). + b -> c>_R + %<'Many>_N ->_R _R + %<'Many>_N ->_R _R + %<'Many>_N ->_R <r>_R %<'Many>_N ->_R Sym (N:ST <s>_N <c>_R) + ; Sym (N:ReaderT <*>_N <r>_R <ST s>_R <c>_N) + :: Coercible + (forall a b c. + (a -> b -> c) + -> ReaderT r (ST s) a -> ReaderT r (ST s) b -> r -> STRep s c) + (forall a b c. + (a -> b -> c) + -> ReaderT r (ST s) a -> ReaderT r (ST s) b -> ReaderT r (ST s) c)) +"SPEC $cp1Applicative @(ST s) @_" + forall (@s) (@r) ($dApplicative :: Applicative (ST s)). + $fApplicativeReaderT_$cp1Applicative @(ST s) @r $dApplicative + = $fApplicativeReaderT_$s$fFunctorReaderT @s @r +"SPEC $cp1Monad @(ST s) @_" + forall (@s) (@r) ($dMonad :: Monad (ST s)). + $fMonadReaderT_$cp1Monad @(ST s) @r $dMonad + = $fApplicativeReaderT_$s$fApplicativeReaderT @s @r +"SPEC $cpure @(ST s) @_" + forall (@s) (@r) ($dApplicative :: Applicative (ST s)). + $fApplicativeReaderT_$cpure @(ST s) @r $dApplicative + = ($fApplicativeReaderT5 @s @r) + `cast` (forall (a :: <*>_N). + <a>_R + %<'Many>_N ->_R <r>_R %<'Many>_N ->_R Sym (N:ST <s>_N <a>_R) + ; Sym (N:ReaderT <*>_N <r>_R <ST s>_R <a>_N) + :: Coercible + (forall a. a -> r -> STRep s a) + (forall a. a -> ReaderT r (ST s) a)) +"SPEC $creturn @(ST s) @_" + forall (@s) (@r) ($dMonad :: Monad (ST s)). + $fMonadReaderT_$creturn @(ST s) @r $dMonad + = ($fApplicativeReaderT5 @s @r) + `cast` (forall (a :: <*>_N). + <a>_R + %<'Many>_N ->_R <r>_R %<'Many>_N ->_R Sym (N:ST <s>_N <a>_R) + ; Sym (N:ReaderT <*>_N <r>_R <ST s>_R <a>_N) + :: Coercible + (forall a. a -> r -> STRep s a) + (forall a. a -> ReaderT r (ST s) a)) +"SPEC $fApplicativeReaderT @(ST s) @_" + forall (@s) (@r) ($dApplicative :: Applicative (ST s)). + $fApplicativeReaderT @(ST s) @r $dApplicative + = $fApplicativeReaderT_$s$fApplicativeReaderT @s @r +"SPEC $fFunctorReaderT @(ST s) @_" + forall (@s) (@r) ($dFunctor :: Functor (ST s)). + $fFunctorReaderT @(ST s) @r $dFunctor + = $fApplicativeReaderT_$s$fFunctorReaderT @s @r +"SPEC $fMonadReaderT @(ST s) @_" + forall (@s) (@r) ($dMonad :: Monad (ST s)). + $fMonadReaderT @(ST s) @r $dMonad + = $fMonadAbstractIOSTReaderT_$s$fMonadReaderT @s @r "USPEC useAbstractMonad @(ReaderT Int (ST s))" forall (@s) ($dMonadAbstractIOST :: MonadAbstractIOST (ReaderT Int (ST s))). View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/4a8df35bf60e46affe13dbef3637a6ce55c7afc5...f957d52f50b16f7ed2246d315a2761f037917df4 -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/4a8df35bf60e46affe13dbef3637a6ce55c7afc5...f957d52f50b16f7ed2246d315a2761f037917df4 You're receiving this email because of your account on gitlab.haskell.org.