diff options
Diffstat (limited to 'compiler/GHC')
| -rw-r--r-- | compiler/GHC/Core/Opt/Simplify/Monad.hs | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/compiler/GHC/Core/Opt/Simplify/Monad.hs b/compiler/GHC/Core/Opt/Simplify/Monad.hs index 5c111374c8..3c05549ad5 100644 --- a/compiler/GHC/Core/Opt/Simplify/Monad.hs +++ b/compiler/GHC/Core/Opt/Simplify/Monad.hs @@ -43,6 +43,7 @@ import GHC.Utils.Panic (throwGhcExceptionIO, GhcException (..)) import GHC.Types.Basic ( IntWithInf, treatZeroAsInf, mkIntWithInf ) import Control.Monad ( ap ) import GHC.Core.Multiplicity ( pattern Many ) +import GHC.Exts( oneShot ) {- ************************************************************************ @@ -56,14 +57,25 @@ For the simplifier monad, we want to {\em thread} a unique supply and a counter. -} newtype SimplM result - = SM { unSM :: SimplTopEnv -- Envt that does not change much - -> UniqSupply -- We thread the unique supply because - -- constantly splitting it is rather expensive - -> SimplCount - -> IO (result, UniqSupply, SimplCount)} - -- we only need IO here for dump output + = SM' { unSM :: SimplTopEnv -- Envt that does not change much + -> UniqSupply -- We thread the unique supply because + -- constantly splitting it is rather expensive + -> SimplCount + -> IO (result, UniqSupply, SimplCount)} + -- We only need IO here for dump output deriving (Functor) +pattern SM :: (SimplTopEnv -> UniqSupply -> SimplCount + -> IO (result, UniqSupply, SimplCount)) + -> SimplM result +-- This pattern synonym makes the simplifier monad eta-expand, +-- which as a very beneficial effect on compiler performance +-- (worth a 1-2% reduction in bytes-allocated). See #18202. +-- See Note [The one-shot state monad trick] in GHC.Core.Unify +pattern SM m <- SM' m + where + SM m = SM' (oneShot m) + data SimplTopEnv = STE { st_flags :: DynFlags , st_max_ticks :: IntWithInf -- Max #ticks in this simplifier run |