Hello,
we already have the more complicated: x & ~(x & y) -> x & ~y (which I am
reindenting by the way) and the simpler: (~x | y) & x -> x & y, so I am
proposing this one for completeness. Regtested on ppc64le-redhat-linux.
2015-05-15 Marc Glisse <marc.gli...@inria.fr>
gcc/
* match.pd ((x | y) & ~x -> y & ~x, (x & y) | ~x -> y | ~x): New
simplifications.
gcc/testsuite/
* gcc.dg/nand.c: New testcase.
--
Marc GlisseIndex: match.pd
===================================================================
--- match.pd (revision 223217)
+++ match.pd (working copy)
@@ -257,24 +257,32 @@ along with GCC; see the file COPYING3.
/* x + (x & 1) -> (x + 1) & ~1 */
(simplify
(plus:c @0 (bit_and@2 @0 integer_onep@1))
(if (TREE_CODE (@2) != SSA_NAME || has_single_use (@2))
(bit_and (plus @0 @1) (bit_not @1))))
/* x & ~(x & y) -> x & ~y */
/* x | ~(x | y) -> x | ~y */
(for bitop (bit_and bit_ior)
- (simplify
- (bitop:c @0 (bit_not (bitop:c@2 @0 @1)))
- (if (TREE_CODE (@2) != SSA_NAME || has_single_use (@2))
- (bitop @0 (bit_not @1)))))
+ (simplify
+ (bitop:c @0 (bit_not (bitop:c@2 @0 @1)))
+ (if (TREE_CODE (@2) != SSA_NAME || has_single_use (@2))
+ (bitop @0 (bit_not @1)))))
+
+/* (x | y) & ~x -> y & ~x */
+/* (x & y) | ~x -> y | ~x */
+(for bitop (bit_and bit_ior)
+ rbitop (bit_ior bit_and)
+ (simplify
+ (bitop:c (rbitop:c @0 @1) (bit_not@2 @0))
+ (bitop @1 @2)))
(simplify
(abs (negate @0))
(abs @0))
(simplify
(abs tree_expr_nonnegative_p@0)
@0)
/* Try to fold (type) X op CST -> (type) (X op ((type-x) CST))
Index: testsuite/gcc.dg/nand.c
===================================================================
--- testsuite/gcc.dg/nand.c (revision 0)
+++ testsuite/gcc.dg/nand.c (working copy)
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-original" } */
+
+unsigned f(unsigned x, unsigned y){
+ return (x | y) & ~x;
+}
+unsigned g(unsigned x, unsigned y){
+ return ~x & (y | x);
+}
+
+/* { dg-final { scan-tree-dump-times "return ~x & y;" 2 "original" } } */
+/* { dg-final { cleanup-tree-dump "original" } } */
