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| author | Richard Guenther <rguenther@suse.de> | 2006-10-21 13:21:06 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2006-10-21 13:21:06 +0000 |
| commit | 8a1eca08037f5a936526485f1056385708dc5c7c (patch) | |
| tree | 4cf583b76df07ca2a2dedcc508f861ce8f54ba4f /gcc/fold-const.c | |
| parent | 5a4171a01d9f9041175a6b7c473ed43a623bea0b (diff) | |
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re PR middle-end/26898 (Fold does not fold signed + CST1 CMP signed + CST2)
2006-10-21 Richard Guenther <rguenther@suse.de>
PR middle-end/26898
* fold-const.c (fold_comparison): Fold signed comparisons
of the form X +- C1 CMP Y +- C2.
* gcc.dg/torture/pr26898-1.c: New testcase.
* gcc.dg/torture/pr26898-2.c: Likewise.
From-SVN: r117931
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 30efccd..b04022e 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -7835,6 +7835,48 @@ fold_comparison (enum tree_code code, tree type, tree op0, tree op1) } } + /* Transform comparisons of the form X +- C1 CMP Y +- C2 to + X CMP Y +- C2 +- C1 for signed X, Y. This is valid if + the resulting offset is smaller in absolute value than the + original one. */ + if (!(flag_wrapv || flag_trapv) + && !TYPE_UNSIGNED (TREE_TYPE (arg0)) + && (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR) + && (TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST + && !TREE_OVERFLOW (TREE_OPERAND (arg0, 1))) + && (TREE_CODE (arg1) == PLUS_EXPR || TREE_CODE (arg1) == MINUS_EXPR) + && (TREE_CODE (TREE_OPERAND (arg1, 1)) == INTEGER_CST + && !TREE_OVERFLOW (TREE_OPERAND (arg1, 1)))) + { + tree const1 = TREE_OPERAND (arg0, 1); + tree const2 = TREE_OPERAND (arg1, 1); + tree variable1 = TREE_OPERAND (arg0, 0); + tree variable2 = TREE_OPERAND (arg1, 0); + tree cst; + + /* Put the constant on the side where it doesn't overflow and is + of lower absolute value than before. */ + cst = int_const_binop (TREE_CODE (arg0) == TREE_CODE (arg1) + ? MINUS_EXPR : PLUS_EXPR, + const2, const1, 0); + if (!TREE_OVERFLOW (cst) + && tree_int_cst_compare (const2, cst) == tree_int_cst_sgn (const2)) + return fold_build2 (code, type, + variable1, + fold_build2 (TREE_CODE (arg1), TREE_TYPE (arg1), + variable2, cst)); + + cst = int_const_binop (TREE_CODE (arg0) == TREE_CODE (arg1) + ? MINUS_EXPR : PLUS_EXPR, + const1, const2, 0); + if (!TREE_OVERFLOW (cst) + && tree_int_cst_compare (const1, cst) == tree_int_cst_sgn (const1)) + return fold_build2 (code, type, + fold_build2 (TREE_CODE (arg0), TREE_TYPE (arg0), + variable1, cst), + variable2); + } + if (FLOAT_TYPE_P (TREE_TYPE (arg0))) { tree targ0 = strip_float_extensions (arg0); |