diff options
| author | rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4> | 2006-08-11 07:44:45 +0000 |
|---|---|---|
| committer | rguenth <rguenth@138bc75d-0d04-0410-961f-82ee72b054a4> | 2006-08-11 07:44:45 +0000 |
| commit | 3cea28d762bf7cd8d486d9add64299b8d3a4ee45 (patch) | |
| tree | ab98ba9561a282ffc55741231132e99c53814c2a /gcc/simplify-rtx.c | |
| parent | 61179c97e8930e0cd465d29f7aff7390b7b88140 (diff) | |
| download | gcc-3cea28d762bf7cd8d486d9add64299b8d3a4ee45.tar.gz | |
2006-08-11 Richard Guenther <rguenther@suse.de>
PR middle-end/28651
* simplify-rtx.c (simplify_const_relational_operation):
Simplify A CMP B to A - B CMP 0 only for EQ and NE comparison
codes.
* gcc.c-torture/execute/pr28651.c: New testcase.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@116079 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'gcc/simplify-rtx.c')
| -rw-r--r-- | gcc/simplify-rtx.c | 17 |
1 files changed, 8 insertions, 9 deletions
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c index 3f627e5308a..8c437e483df 100644 --- a/gcc/simplify-rtx.c +++ b/gcc/simplify-rtx.c @@ -3733,19 +3733,18 @@ simplify_const_relational_operation (enum rtx_code code, a register or a CONST_INT, this can't help; testing for these cases will prevent infinite recursion here and speed things up. - If CODE is an unsigned comparison, then we can never do this optimization, - because it gives an incorrect result if the subtraction wraps around zero. - ANSI C defines unsigned operations such that they never overflow, and - thus such cases can not be ignored; but we cannot do it even for - signed comparisons for languages such as Java, so test flag_wrapv. */ + We can only do this for EQ and NE comparisons as otherwise we may + lose or introduce overflow which we cannot disregard as undefined as + we do not know the signedness of the operation on either the left or + the right hand side of the comparison. */ - if (!flag_wrapv && INTEGRAL_MODE_P (mode) && trueop1 != const0_rtx + if (INTEGRAL_MODE_P (mode) && trueop1 != const0_rtx + && (code == EQ || code == NE) && ! ((REG_P (op0) || GET_CODE (trueop0) == CONST_INT) && (REG_P (op1) || GET_CODE (trueop1) == CONST_INT)) && 0 != (tem = simplify_binary_operation (MINUS, mode, op0, op1)) - /* We cannot do this for == or != if tem is a nonzero address. */ - && ((code != EQ && code != NE) || ! nonzero_address_p (tem)) - && code != GTU && code != GEU && code != LTU && code != LEU) + /* We cannot do this if tem is a nonzero address. */ + && ! nonzero_address_p (tem)) return simplify_const_relational_operation (signed_condition (code), mode, tem, const0_rtx); |