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| author | Roger Sayle <roger@eyesopen.com> | 2006-12-31 16:17:49 +0000 |
|---|---|---|
| committer | Roger Sayle <sayle@gcc.gnu.org> | 2006-12-31 16:17:49 +0000 |
| commit | 870aa1ebe0d3e05912f763ece1ed4491282d34e2 (patch) | |
| tree | b1cf895f653525f285670f935e58e7beff2a7eef /gcc/fold-const.c | |
| parent | 7c2da05e604c27549afadf4df26c679aead5f414 (diff) | |
| download | gcc-870aa1ebe0d3e05912f763ece1ed4491282d34e2.zip gcc-870aa1ebe0d3e05912f763ece1ed4491282d34e2.tar.gz gcc-870aa1ebe0d3e05912f763ece1ed4491282d34e2.tar.bz2 | |
re PR middle-end/30322 (((-i-1) + i) +1) is turned into ~i + (i+1) and never into 0 on the tree level)
PR middle-end/30322
* fold-const.c (fold_binary): Fold X + ~X and ~X + X into -1 when
we don't care about trapping overflow. Only convert -A - 1 into ~A
when we don't care about trapping overflow.
* gcc.dg/fold-plusnot-1.c: New test case.
From-SVN: r120300
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index dbdc9c2..da9579e 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -8662,6 +8662,26 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1) if (integer_zerop (arg1)) return non_lvalue (fold_convert (type, arg0)); + /* ~X + X is -1. */ + if (TREE_CODE (arg0) == BIT_NOT_EXPR + && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0) + && !TYPE_TRAP_SIGNED (type)) + { + t1 = build_int_cst (type, -1); + t1 = force_fit_type (t1, 0, false, false); + return omit_one_operand (type, t1, arg1); + } + + /* X + ~X is -1. */ + if (TREE_CODE (arg1) == BIT_NOT_EXPR + && operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0) + && !TYPE_TRAP_SIGNED (type)) + { + t1 = build_int_cst (type, -1); + t1 = force_fit_type (t1, 0, false, false); + return omit_one_operand (type, t1, arg0); + } + /* If we are adding two BIT_AND_EXPR's, both of which are and'ing with a constant, and the two constants have no bits in common, we should treat this as a BIT_IOR_EXPR since this may produce more @@ -9002,7 +9022,8 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1) /* Convert -A - 1 to ~A. */ if (INTEGRAL_TYPE_P (type) && TREE_CODE (arg0) == NEGATE_EXPR - && integer_onep (arg1)) + && integer_onep (arg1) + && !TYPE_TRAP_SIGNED (type)) return fold_build1 (BIT_NOT_EXPR, type, fold_convert (type, TREE_OPERAND (arg0, 0))); |