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| author | Simon Marlow <marlowsd@gmail.com> | 2010-02-11 13:15:43 +0000 |
|---|---|---|
| committer | Simon Marlow <marlowsd@gmail.com> | 2010-02-11 13:15:43 +0000 |
| commit | ca10c79f28cfc0c29d02d0f2c0ea111093bd2b37 (patch) | |
| tree | e53454cdecb90216243b33fb9b17bc9093b754c0 /compiler/prelude/PrelRules.lhs | |
| parent | d259dd70d7f5b1981b522b5a9317fbf22840450b (diff) | |
| download | haskell-ca10c79f28cfc0c29d02d0f2c0ea111093bd2b37.tar.gz | |
don't constant fold division that would result in negative zero (#3676)
Diffstat (limited to 'compiler/prelude/PrelRules.lhs')
| -rw-r--r-- | compiler/prelude/PrelRules.lhs | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/compiler/prelude/PrelRules.lhs b/compiler/prelude/PrelRules.lhs index bc8c9b81bc..4ca4462e50 100644 --- a/compiler/prelude/PrelRules.lhs +++ b/compiler/prelude/PrelRules.lhs @@ -293,7 +293,9 @@ floatOp2 _ _ _ = Nothing floatOp2Z :: (Rational -> Rational -> Rational) -> Literal -> Literal -> Maybe (Expr CoreBndr) floatOp2Z op (MachFloat f1) (MachFloat f2) - | f2 /= 0 = Just (mkFloatVal (f1 `op` f2)) + | (f1 /= 0 || f2 > 0) -- see Note [negative zero] + && f2 /= 0 -- avoid NaN and Infinity/-Infinity + = Just (mkFloatVal (f1 `op` f2)) floatOp2Z _ _ _ = Nothing -------------------------- @@ -306,7 +308,13 @@ doubleOp2 _ _ _ = Nothing doubleOp2Z :: (Rational -> Rational -> Rational) -> Literal -> Literal -> Maybe (Expr CoreBndr) doubleOp2Z op (MachDouble f1) (MachDouble f2) - | f2 /= 0 = Just (mkDoubleVal (f1 `op` f2)) + | (f1 /= 0 || f2 > 0) -- see Note [negative zero] + && f2 /= 0 -- avoid NaN and Infinity/-Infinity + = Just (mkDoubleVal (f1 `op` f2)) + -- Note [negative zero] Avoid (0 / -d), otherwise 0/(-1) reduces to + -- zero, but we might want to preserve the negative zero here which + -- is representable in Float/Double but not in (normalised) + -- Rational. (#3676) Perhaps we should generate (0 :% (-1)) instead? doubleOp2Z _ _ _ = Nothing |