diff options
| -rw-r--r-- | compiler/GHC/Core/Coercion.hs | 22 | ||||
| -rw-r--r-- | compiler/GHC/Core/Opt/Arity.hs | 8 |
2 files changed, 17 insertions, 13 deletions
diff --git a/compiler/GHC/Core/Coercion.hs b/compiler/GHC/Core/Coercion.hs index b364091958..ccf5ef1f11 100644 --- a/compiler/GHC/Core/Coercion.hs +++ b/compiler/GHC/Core/Coercion.hs @@ -72,7 +72,7 @@ module GHC.Core.Coercion ( isReflCoVar_maybe, isGReflMCo, mkGReflLeftMCo, mkGReflRightMCo, mkCoherenceRightMCo, - coToMCo, mkTransMCo, mkTransMCoL, mkCastTyMCo, mkSymMCo, isReflMCo, + mkMCo, mkTransMCo, mkTransMCoL, mkTransMCoR, mkCastTyMCo, mkSymMCo, isReflMCo, -- ** Coercion variables mkCoVar, isCoVar, coVarName, setCoVarName, setCoVarUnique, @@ -305,11 +305,13 @@ tidyCoAxBndrsForUser init_env tcvs * * ********************************************************************* -} -coToMCo :: Coercion -> MCoercion --- Convert a coercion to a MCoercion, --- It's not clear whether or not isReflexiveCo would be better here -coToMCo co | isReflCo co = MRefl - | otherwise = MCo co +mkMCo :: Coercion -> MCoercion +-- Convert a coercion to a MCoercion +-- I'm using isReflexiveCo to check whether the coercion is reflexive, +-- because it makes a gigantic difference in T18223, and does little +-- harm otherwise (#19815) +mkMCo co | isReflexiveCo co = MRefl + | otherwise = MCo co -- | Tests if this MCoercion is obviously generalized reflexive -- Guaranteed to work very quickly. @@ -329,11 +331,15 @@ mkGReflCo r ty mco mkTransMCo :: MCoercion -> MCoercion -> MCoercion mkTransMCo MRefl co2 = co2 mkTransMCo co1 MRefl = co1 -mkTransMCo (MCo co1) (MCo co2) = MCo (mkTransCo co1 co2) +mkTransMCo (MCo co1) (MCo co2) = mkMCo (mkTransCo co1 co2) mkTransMCoL :: MCoercion -> Coercion -> MCoercion mkTransMCoL MRefl co2 = MCo co2 -mkTransMCoL (MCo co1) co2 = MCo (mkTransCo co1 co2) +mkTransMCoL (MCo co1) co2 = mkMCo (mkTransCo co1 co2) + +mkTransMCoR :: Coercion -> MCoercion -> MCoercion +mkTransMCoR co1 MRefl = MCo co1 +mkTransMCoR co1 (MCo co2) = mkMCo (mkTransCo co1 co2) -- | Get the reverse of an 'MCoercion' mkSymMCo :: MCoercion -> MCoercion diff --git a/compiler/GHC/Core/Opt/Arity.hs b/compiler/GHC/Core/Opt/Arity.hs index 36a2535c09..aa0b936058 100644 --- a/compiler/GHC/Core/Opt/Arity.hs +++ b/compiler/GHC/Core/Opt/Arity.hs @@ -1672,11 +1672,9 @@ pushCoValArg co -- then co1 :: tyL1 ~ tyR1 -- co2 :: tyL2 ~ tyR2 = ASSERT2( isFunTy tyR, ppr co $$ ppr arg ) - Just (coToMCo (mkSymCo co1), coToMCo co2) - -- Critically, coToMCo to checks for ReflCo; the whole coercion may not - -- be reflexive, but either of its components might be - -- We could use isReflexiveCo, but it's not clear if the benefit - -- is worth the cost, and it makes no difference in #18223 + Just (mkMCo (mkSymCo co1), mkMCo co2) + -- Critically, mkMCo to checks for isReflexiveCo; the whole coercion + -- may not be reflexive, but either of its components might be | otherwise = Nothing |