[PATCH] Move ~X | X -> -1 folding

[Marek Polacek <polacek at redhat dot com>]

This moves a simple optimization.  Here it's plain to see how :c
removes the need to duplicate code to handle commutativity.

I put some more converts into the pattern, but then it's turned
out that I also need the tree_nop_conversion_p (otherwise we'd
regress binop-notor2.c that uses booleans).

I did a regtest with the patterns in fold-const.c removed to see
whether we have some testing for this folding -- and there were
no regressions, so I had to write a test.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2015-06-29  Marek Polacek  <polacek@redhat.com>

	* fold-const.c (fold_binary_loc): Move ~X | X folding ...
	* match.pd: ... here.

	* gcc.dg/fold-ior-2.c: New test.

diff --git gcc/fold-const.c gcc/fold-const.c
index a447452..caba0cf 100644
--- gcc/fold-const.c
+++ gcc/fold-const.c
@@ -10928,24 +10928,6 @@ fold_binary_loc (location_t loc,
 
     case BIT_IOR_EXPR:
     bit_ior:
-      /* ~X | X is -1.  */
-      if (TREE_CODE (arg0) == BIT_NOT_EXPR
-	  && operand_equal_p (TREE_OPERAND (arg0, 0), arg1, 0))
-	{
-	  t1 = build_zero_cst (type);
-	  t1 = fold_unary_loc (loc, BIT_NOT_EXPR, type, t1);
-	  return omit_one_operand_loc (loc, type, t1, arg1);
-	}
-
-      /* X | ~X is -1.  */
-      if (TREE_CODE (arg1) == BIT_NOT_EXPR
-	  && operand_equal_p (arg0, TREE_OPERAND (arg1, 0), 0))
-	{
-	  t1 = build_zero_cst (type);
-	  t1 = fold_unary_loc (loc, BIT_NOT_EXPR, type, t1);
-	  return omit_one_operand_loc (loc, type, t1, arg0);
-	}
-
       /* Canonicalize (X & C1) | C2.  */
       if (TREE_CODE (arg0) == BIT_AND_EXPR
 	  && TREE_CODE (arg1) == INTEGER_CST
diff --git gcc/match.pd gcc/match.pd
index 0cf3d21..5dcbc1a 100644
--- gcc/match.pd
+++ gcc/match.pd
@@ -283,6 +283,12 @@ along with GCC; see the file COPYING3.  If not see
   (bit_and @0 integer_zerop@1)
   @1)
 
+/* ~x | x -> -1 */
+(simplify
+ (bit_ior:c (convert? @0) (convert? (bit_not @0)))
+ (if (tree_nop_conversion_p (type, TREE_TYPE (@0)))
+  { build_all_ones_cst (type); }))
+
 /* x ^ x -> 0 */
 (simplify
   (bit_xor @0 @0)
diff --git gcc/testsuite/gcc.dg/fold-ior-2.c gcc/testsuite/gcc.dg/fold-ior-2.c
index e69de29..6abac9e 100644
--- gcc/testsuite/gcc.dg/fold-ior-2.c
+++ gcc/testsuite/gcc.dg/fold-ior-2.c
@@ -0,0 +1,47 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-cddce1" } */
+
+int
+fn1 (int x)
+{
+  return ~x | x;
+}
+
+int
+fn2 (int x)
+{
+  return x | ~x;
+}
+
+unsigned int
+fn3 (unsigned int x)
+{
+  return ~x | x;
+}
+
+unsigned int
+fn4 (unsigned int x)
+{
+  return ~x | x;
+}
+
+int
+fn5 (int x)
+{
+  return ~x | (unsigned) x;
+}
+
+int
+fn6 (int x)
+{
+  return (unsigned) ~x | x;
+}
+
+int
+fn7 (int x)
+{
+  return ~(unsigned) x | x;
+}
+
+/* { dg-final { scan-tree-dump-not "~" "cddce1" } } */
+/* { dg-final { scan-tree-dump-not " \\| " "cddce1" } } */

	Marek