match.pd: Optimize (x & y) ^ (x | y)

[Marek Polacek]

On Thu, Jun 11, 2015 at 01:08:41PM +0200, Richard Biener wrote:
> If the pattern doesn't exist in fold-const.c (obviously it doesn't)
> then I think it makes sense to only add testcases to match this on
> GIMPLE (because in the long run we'd like to _not_ transform things
> in GENERIC, at least not without -O).
> 
> Thus sth like
> 
> > +int
> > +fn1 (signed int x, signed int y)
> > +{
>    signed int tem1 = x & y;
>    singed int tem2 = x | y;
> > +  return tem1 ^ tem2;
> > +}
> 
> and scanning the first DCE dump (cddec1) for the applied transform.
 
Makes sense.  Fixed.

> Otherwise the patch is of course ok.  (take the suggestion above
> for followup patches)

I'll commit the following version if testing passes then, thanks.

2015-06-11  Marek Polacek  <polacek@redhat.com>

	* match.pd ((x & y) ^ (x | y) -> x ^ y): New pattern.

	* gcc.dg/fold-xor-3.c: New test.

diff --git gcc/match.pd gcc/match.pd
index 33fa717..9a1317e 100644
--- gcc/match.pd
+++ gcc/match.pd
@@ -320,6 +320,12 @@ along with GCC; see the file COPYING3.  If not see
   (bitop:c (rbitop:c @0 @1) (bit_not@2 @0))
   (bitop @1 @2)))
 
+/* (x & y) ^ (x | y) -> x ^ y */
+(simplify
+ (bit_xor:c (bit_and@2 @0 @1) (bit_ior@3 @0 @1))
+  (if (single_use (@2) && single_use (@3))
+   (bit_xor @0 @1)))
+
 (simplify
  (abs (negate @0))
  (abs @0))
diff --git gcc/testsuite/gcc.dg/fold-xor-3.c gcc/testsuite/gcc.dg/fold-xor-3.c
index e69de29..c2c0af6 100644
--- gcc/testsuite/gcc.dg/fold-xor-3.c
+++ gcc/testsuite/gcc.dg/fold-xor-3.c
@@ -0,0 +1,37 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-cddce1" } */
+
+int
+fn1 (signed int x, signed int y)
+{
+  signed int tem1 = x & y;
+  signed int tem2 = x | y;
+  return tem1 ^ tem2;
+}
+
+unsigned int
+fn2 (unsigned int x, unsigned int y)
+{
+  unsigned int tem1 = x & y;
+  unsigned int tem2 = x | y;
+  return tem1 ^ tem2;
+}
+
+int
+fn3 (signed int x, signed int y)
+{
+  signed int tem1 = x & y;
+  signed int tem2 = x | y;
+  return tem2 ^ tem1;
+}
+
+unsigned int
+fn4 (unsigned int x, unsigned int y)
+{
+  unsigned int tem1 = x & y;
+  unsigned int tem2 = x | y;
+  return tem2 ^ tem1;
+}
+
+/* { dg-final { scan-tree-dump-not " & " "cddce1" } } */
+/* { dg-final { scan-tree-dump-not " \\| " "cddce1" } } */

	Marek