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|
module GHC.CmmToAsm.X86.Cond (
Cond(..),
condToUnsigned,
maybeFlipCond,
maybeInvertCond
)
where
import GHC.Prelude
data Cond
= ALWAYS -- What's really used? ToDo
| EQQ
| GE
| GEU
| GTT
| GU
| LE
| LEU
| LTT
| LU
| NE
| NEG
| POS
| CARRY
| OFLO
| PARITY
| NOTPARITY
deriving Eq
condToUnsigned :: Cond -> Cond
condToUnsigned GTT = GU
condToUnsigned LTT = LU
condToUnsigned GE = GEU
condToUnsigned LE = LEU
condToUnsigned x = x
-- | @maybeFlipCond c@ returns @Just c'@ if it is possible to flip the
-- arguments to the conditional @c@, and the new condition should be @c'@.
maybeFlipCond :: Cond -> Maybe Cond
maybeFlipCond cond = case cond of
EQQ -> Just EQQ
NE -> Just NE
LU -> Just GU
GU -> Just LU
LEU -> Just GEU
GEU -> Just LEU
LTT -> Just GTT
GTT -> Just LTT
LE -> Just GE
GE -> Just LE
_other -> Nothing
-- | If we apply @maybeInvertCond@ to the condition of a jump we turn
-- jumps taken into jumps not taken and vice versa.
--
-- Careful! If the used comparison and the conditional jump
-- don't match the above behaviour will NOT hold.
-- When used for FP comparisons this does not consider unordered
-- numbers.
-- Also inverting twice might return a synonym for the original condition.
maybeInvertCond :: Cond -> Maybe Cond
maybeInvertCond cond = case cond of
ALWAYS -> Nothing
EQQ -> Just NE
NE -> Just EQQ
NEG -> Just POS
POS -> Just NEG
GEU -> Just LU
LU -> Just GEU
GE -> Just LTT
LTT -> Just GE
GTT -> Just LE
LE -> Just GTT
GU -> Just LEU
LEU -> Just GU
--GEU "==" NOTCARRY, they are synonyms
--at the assembly level
CARRY -> Just GEU
OFLO -> Nothing
PARITY -> Just NOTPARITY
NOTPARITY -> Just PARITY
|
