diff options
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 f8b31b7..5bb75d4 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, |