Hi!
The
/* Given (xor (ior (xor A B) C) D), where B, C and D are
constants, simplify to (xor (ior A C) (B&~C)^D), canceling
out bits inverted twice and not set by C. Similarly, given
(xor (and (xor A B) C) D), simplify without inverting C in
the xor operand: (xor (and A C) (B&C)^D).
*/
comment describes the intended optimization correctly, but unfortunately
the code diverges from it, using (xor (and A C) (B&~C)^D)
for the second and (xor (ior A C) (B&C)^D) for the first one.
Fixed thusly, committed as obvious after bootstrapping/regtesting it on
x86_64-linux and i686-linux.
2015-02-06 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/64957
PR debug/64817
* simplify-rtx.c (simplify_binary_operation_1): Use ~cval for
IOR rather than for AND.
* gcc.c-torture/execute/pr64957.c: New test.
--- gcc/simplify-rtx.c.jj 2015-02-04 15:24:20.000000000 +0100
+++ gcc/simplify-rtx.c 2015-02-06 09:41:31.139326554 +0100
@@ -2731,9 +2731,9 @@ simplify_binary_operation_1 (enum rtx_co
HOST_WIDE_INT xcval;
if (op == IOR)
- xcval = cval;
- else
xcval = ~cval;
+ else
+ xcval = cval;
return simplify_gen_binary (XOR, mode,
simplify_gen_binary (op, mode, a, c),
--- gcc/testsuite/gcc.c-torture/execute/pr64957.c.jj 2015-02-06
09:43:12.595616710 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr64957.c 2015-02-06
09:43:26.361384715 +0100
@@ -0,0 +1,23 @@
+/* PR rtl-optimization/64957 */
+
+__attribute__((noinline, noclone)) int
+foo (int b)
+{
+ return (((b ^ 5) | 1) ^ 5) | 1;
+}
+
+__attribute__((noinline, noclone)) int
+bar (int b)
+{
+ return (((b ^ ~5) & ~1) ^ ~5) & ~1;
+}
+
+int
+main ()
+{
+ int i;
+ for (i = 0; i < 16; i++)
+ if (foo (i) != (i | 1) || bar (i) != (i & ~1))
+ __builtin_abort ();
+ return 0;
+}
Jakub
