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| author | Ben Gamari <ben@smart-cactus.org> | 2021-11-09 10:44:07 -0500 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-12-02 18:13:30 -0500 |
| commit | 9c65197e0aec9a4ee11e377dac52f459ac64067a (patch) | |
| tree | 2fe7456cb0264192cff507e2e3382db1523b9374 | |
| parent | 7094f4faeb78a3ffda98c44700b4addba3f5b951 (diff) | |
| download | haskell-9c65197e0aec9a4ee11e377dac52f459ac64067a.tar.gz | |
cmm/opt: Fold away shifts larger than shiftee width
This is necessary for lint-correctness since we no longer allow such
shifts in Cmm.
| -rw-r--r-- | compiler/GHC/Cmm/Opt.hs | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/compiler/GHC/Cmm/Opt.hs b/compiler/GHC/Cmm/Opt.hs index e9615c3a15..131267e352 100644 --- a/compiler/GHC/Cmm/Opt.hs +++ b/compiler/GHC/Cmm/Opt.hs @@ -72,6 +72,16 @@ cmmMachOpFoldM _ op [CmmLit (CmmInt x rep)] _ -> panic $ "cmmMachOpFoldM: unknown unary op: " ++ show op +-- Eliminate shifts that are wider than the shiftee +cmmMachOpFoldM _ op [_shiftee, CmmLit (CmmInt shift _)] + | Just width <- isShift op + , shift >= fromIntegral (widthInBits width) + = Just $! CmmLit (CmmInt 0 width) + where + isShift (MO_Shl w) = Just w + isShift (MO_U_Shr w) = Just w + isShift (MO_S_Shr w) = Just w + isShift _ = Nothing -- Eliminate conversion NOPs cmmMachOpFoldM _ (MO_SS_Conv rep1 rep2) [x] | rep1 == rep2 = Just x @@ -137,9 +147,9 @@ cmmMachOpFoldM platform mop [CmmLit (CmmInt x xrep), CmmLit (CmmInt y _)] MO_Or r -> Just $! CmmLit (CmmInt (x .|. y) r) MO_Xor r -> Just $! CmmLit (CmmInt (x `xor` y) r) - MO_Shl r -> Just $! CmmLit (CmmInt (x `shiftL` fromIntegral y) r) + MO_Shl r -> Just $! CmmLit (CmmInt (x `shiftL` fromIntegral y) r) MO_U_Shr r -> Just $! CmmLit (CmmInt (x_u `shiftR` fromIntegral y) r) - MO_S_Shr r -> Just $! CmmLit (CmmInt (x `shiftR` fromIntegral y) r) + MO_S_Shr r -> Just $! CmmLit (CmmInt (x `shiftR` fromIntegral y) r) _ -> Nothing |