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| author | Roger Sayle <roger@eyesopen.com> | 2006-02-25 22:27:54 +0000 |
|---|---|---|
| committer | Roger Sayle <sayle@gcc.gnu.org> | 2006-02-25 22:27:54 +0000 |
| commit | eb8dffe0fbff242efc573fba9eff7a1da7eb893f (patch) | |
| tree | 33a222942c6e3c0053613f0b378d977c6e36e141 /gcc/fold-const.c | |
| parent | d349482e965a1f68edcc6cbac12aa52c5cc95196 (diff) | |
| download | gcc-eb8dffe0fbff242efc573fba9eff7a1da7eb893f.zip gcc-eb8dffe0fbff242efc573fba9eff7a1da7eb893f.tar.gz gcc-eb8dffe0fbff242efc573fba9eff7a1da7eb893f.tar.bz2 | |
re PR middle-end/23673 (fold does not fold (a^b) != 0 to a != b)
PR middle-end/23673
* fold-const.c (fold_binary) <EQ_EXPR>: Fold (X^Y) == 0 as X == Y
and (X^Y) != 0 as X != Y. Fold (X^Y) == Y as X == 0, and some
symmetry related transformations. Fold (X^C1) == C2 as
X == (C1^C2).
* gcc.dg/fold-eqxor-1.c: New test case.
* gcc.dg/fold-eqxor-2.c: Likewise.
* gcc.dg/fold-eqxor-3.c: Likewise.
From-SVN: r111442
Diffstat (limited to 'gcc/fold-const.c')
| -rw-r--r-- | gcc/fold-const.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/gcc/fold-const.c b/gcc/fold-const.c index 04a8fab..3c3852b 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -9767,6 +9767,32 @@ fold_binary (enum tree_code code, tree type, tree op0, tree op1) } } + /* (X ^ Y) == 0 becomes X == Y, and (X ^ Y) != 0 becomes X != Y. */ + if (integer_zerop (arg1) + && TREE_CODE (arg0) == BIT_XOR_EXPR) + return fold_build2 (code, type, TREE_OPERAND (arg0, 0), + TREE_OPERAND (arg0, 1)); + + /* (X ^ Y) == Y becomes X == 0. We know that Y has no side-effects. */ + if (TREE_CODE (arg0) == BIT_XOR_EXPR + && operand_equal_p (TREE_OPERAND (arg0, 1), arg1, 0)) + return fold_build2 (code, type, TREE_OPERAND (arg0, 0), + build_int_cst (TREE_TYPE (arg1), 0)); + /* Likewise (X ^ Y) == X becomes Y == 0. X has no side-effects. */ + if (TREE_CODE (arg0) == BIT_XOR_EXPR + && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0) + && reorder_operands_p (TREE_OPERAND (arg0, 1), arg1)) + return fold_build2 (code, type, TREE_OPERAND (arg0, 1), + build_int_cst (TREE_TYPE (arg1), 0)); + + /* (X ^ C1) op C2 can be rewritten as X op (C1 ^ C2). */ + if (TREE_CODE (arg0) == BIT_XOR_EXPR + && TREE_CODE (arg1) == INTEGER_CST + && TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST) + return fold_build2 (code, type, TREE_OPERAND (arg0, 0), + fold_build2 (BIT_XOR_EXPR, TREE_TYPE (arg1), + TREE_OPERAND (arg0, 1), arg1)); + if (integer_zerop (arg1) && tree_expr_nonzero_p (arg0)) { |