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| author | Richard Guenther <rguenther@suse.de> | 2012-05-08 12:50:18 +0000 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2012-05-08 12:50:18 +0000 |
| commit | ad9fc55abd20a1501ab649693818a93b1538f375 (patch) | |
| tree | 1fdd185372150a013ed29ccd9e618fe1a9495380 /gcc/fold-const.c | |
| parent | 04d170d214ae0a801ccfc4f66bf11531d19e75a8 (diff) | |
| download | gcc-ad9fc55abd20a1501ab649693818a93b1538f375.tar.gz | |
fold-const.c (fold_binary_loc): Fold (X * CST1) & CST2 to zero or to (X * CST1) & CST2' when...
2012-05-08 Richard Guenther <rguenther@suse.de>
* fold-const.c (fold_binary_loc): Fold (X * CST1) & CST2
to zero or to (X * CST1) & CST2' when CST1 has trailing zeros.
* gcc.dg/fold-bitand-4.c: New testcase.
From-SVN: r187280
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index f8b31b7d113..5bb75d490d9 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -11449,6 +11449,30 @@ fold_binary_loc (location_t loc, return fold_convert_loc (loc, type, arg0); } + /* Fold (X * CST1) & CST2 to zero if we can, or drop known zero + bits from CST2. */ + if (TREE_CODE (arg1) == INTEGER_CST + && TREE_CODE (arg0) == MULT_EXPR + && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST) + { + int arg1tz + = double_int_ctz (tree_to_double_int (TREE_OPERAND (arg0, 1))); + if (arg1tz > 0) + { + double_int arg1mask, masked; + arg1mask = double_int_not (double_int_mask (arg1tz)); + arg1mask = double_int_ext (arg1mask, TYPE_PRECISION (type), + TYPE_UNSIGNED (type)); + masked = double_int_and (arg1mask, tree_to_double_int (arg1)); + if (double_int_zero_p (masked)) + return omit_two_operands_loc (loc, type, build_zero_cst (type), + arg0, arg1); + else if (!double_int_equal_p (masked, tree_to_double_int (arg1))) + return fold_build2_loc (loc, code, type, op0, + double_int_to_tree (type, masked)); + } + } + /* For constants M and N, if M == (1LL << cst) - 1 && (N & M) == M, ((A & N) + B) & M -> (A + B) & M Similarly if (N & M) == 0, |