The following adds a pattern to optimize MAX (a, -a) to abs (a).
Bootstrap / regtest pending on x86_64-unknown-linux-gnu.
Richard.
2016-09-28 Richard Biener <rguent...@suse.de>
PR middle-end/55152
* match.pd: Add max(a,-a) -> abs(a) pattern.
* gcc.dg/pr55152.c: New testcase.
Index: gcc/match.pd
===================================================================
--- gcc/match.pd (revision 240565)
+++ gcc/match.pd (working copy)
@@ -1271,6 +1284,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(simplify
(max:c (min:c @0 @1) @1)
@1)
+/* max(a,-a) -> abs(a). */
+(simplify
+ (max:c @0 (negate @0))
+ (if (TREE_CODE (type) != COMPLEX_TYPE
+ && (! ANY_INTEGRAL_TYPE_P (type)
+ || TYPE_OVERFLOW_UNDEFINED (type)))
+ (abs @0)))
(simplify
(min @0 @1)
(switch
Index: gcc/testsuite/gcc.dg/pr55152.c
===================================================================
--- gcc/testsuite/gcc.dg/pr55152.c (revision 0)
+++ gcc/testsuite/gcc.dg/pr55152.c (working copy)
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O -ffinite-math-only -fstrict-overflow
-fdump-tree-optimized" } */
+
+double g (double a)
+{
+ return (a>=-a)?a:-a;
+}
+int f(int a)
+{
+ return (a>=-a)?a:-a;
+}
+
+/* { dg-final { scan-tree-dump-times "ABS_EXPR" 2 "optimized" } } */
