https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90356
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2019-05-06
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
Ever confirmed|0 |1
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Untested fix:
--- gcc/match.pd.jj 2019-05-03 15:22:07.370401908 +0200
+++ gcc/match.pd 2019-05-06 11:26:04.701663020 +0200
@@ -152,6 +152,28 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(if (fold_real_zero_addition_p (type, @1, 1))
(non_lvalue @0)))
+/* Even if the fold_real_zero_addition_p can't simplify X + 0.0
+ into X, we can optimize (X + 0.0) + 0.0 or (X + 0.0) - 0.0
+ or (X - 0.0) + 0.0 into X + 0.0 and (X - 0.0) - 0.0 into X - 0.0
+ if not -frounding-math. For sNaNs the first operation would raise
+ exceptions but turn the result into qNan, so the second operation
+ would not raise it. */
+(for inner_op (plus minus)
+ (for outer_op (plus minus)
+ (simplify
+ (outer_op (inner_op @0 real_zerop@1) real_zerop@2)
+ (if (TREE_CODE (@1) == REAL_CST
+ && TREE_CODE (@2) == REAL_CST
+ && HONOR_SIGNED_ZEROS (element_mode (type))
+ && !HONOR_SIGN_DEPENDENT_ROUNDING (element_mode (type)))
+ (with { bool plus1 = ((inner_op == PLUS_EXPR)
+ ^ REAL_VALUE_MINUS_ZERO (TREE_REAL_CST (@1)));
+ bool plus2 = ((outer_op == PLUS_EXPR)
+ ^ REAL_VALUE_MINUS_ZERO (TREE_REAL_CST (@2))); }
+ (if (plus2 && !plus1)
+ (outer_op @0 @2)
+ (inner_op @0 @1)))))))
+
/* Simplify x - x.
This is unsafe for certain floats even in non-IEEE formats.
In IEEE, it is unsafe because it does wrong for NaNs.
