diff options
Diffstat (limited to 'compiler/codeGen/StgCmmCon.hs')
| -rw-r--r-- | compiler/codeGen/StgCmmCon.hs | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/compiler/codeGen/StgCmmCon.hs b/compiler/codeGen/StgCmmCon.hs index 745dd720eb..04257dd991 100644 --- a/compiler/codeGen/StgCmmCon.hs +++ b/compiler/codeGen/StgCmmCon.hs @@ -43,6 +43,7 @@ import PrelInfo import Outputable import Platform import Util +import MonadUtils (mapMaybeM) import Control.Monad import Data.Char @@ -258,12 +259,18 @@ bindConArgs (DataAlt con) base args -- The binding below forces the masking out of the tag bits -- when accessing the constructor field. - bind_arg :: (NonVoid Id, VirtualHpOffset) -> FCode LocalReg - bind_arg (arg, offset) - = do emit $ mkTaggedObjectLoad dflags (idToReg dflags arg) base offset tag - bindArgToReg arg - mapM bind_arg args_w_offsets + bind_arg :: (NonVoid Id, VirtualHpOffset) -> FCode (Maybe LocalReg) + bind_arg (arg@(NonVoid b), offset) + | isDeadBinder b = + -- Do not load unused fields from objects to local variables. + -- (CmmSink can optimize this, but it's cheap and common enough + -- to handle here) + return Nothing + | otherwise = do + emit $ mkTaggedObjectLoad dflags (idToReg dflags arg) base offset tag + Just <$> bindArgToReg arg + + mapMaybeM bind_arg args_w_offsets bindConArgs _other_con _base args = ASSERT( null args ) return [] - |