[PATCH] match.pd: Optimize (x & y) == x into (x & ~y) == 0 [PR94589]

[Jakub Jelinek <jakub@redhat.com>]

On Thu, May 06, 2021 at 09:42:41PM +0200, Marc Glisse wrote:
> We can probably do it in 2 steps, first something like
> 
> (for cmp (eq ne)
>  (simplify
>   (cmp (bit_and:c @0 @1) @0)
>   (cmp (@0 (bit_not! @1)) { build_zero_cst (TREE_TYPE (@0)); })))
> 
> to get rid of the double use, and then simplify X&C==0 to X<=~C if C is a
> mask 111...000 (I thought we already had a function to detect such masks, or
> the 000...111, but I can't find them anymore).

Ok, here is the first step then.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Or should it have cmp:c too given that == and != are commutative too?

2021-05-11  Jakub Jelinek  <jakub@redhat.com>
	    Marc Glisse  <marc.glisse@inria.fr>

	PR tree-optimization/94589
	* match.pd ((X & Y) == Y -> (X & ~Y) == 0,
	(X | Y) == Y -> (X & ~Y) == 0): New GIMPLE simplifications.

	* gcc.dg/tree-ssa/pr94589-1.c: New test.

--- gcc/match.pd.jj	2021-04-27 14:46:56.583716888 +0200
+++ gcc/match.pd	2021-05-10 22:31:49.726870421 +0200
@@ -4764,6 +4764,18 @@ (define_operator_list COND_TERNARY
   (cmp:c (bit_xor:c @0 @1) @0)
   (cmp @1 { build_zero_cst (TREE_TYPE (@1)); }))
 
+#if GIMPLE
+ /* (X & Y) == X becomes (X & ~Y) == 0.  */
+ (simplify
+  (cmp (bit_and:c @0 @1) @0)
+  (cmp (bit_and @0 (bit_not! @1)) { build_zero_cst (TREE_TYPE (@0)); }))
+
+ /* (X | Y) == Y becomes (X & ~Y) == 0.  */
+ (simplify
+  (cmp (bit_ior:c @0 @1) @1)
+  (cmp (bit_and @0 (bit_not! @1)) { build_zero_cst (TREE_TYPE (@0)); }))
+#endif
+
  /* (X ^ C1) op C2 can be rewritten as X op (C1 ^ C2).  */
  (simplify
   (cmp (convert?@3 (bit_xor @0 INTEGER_CST@1)) INTEGER_CST@2)
--- gcc/testsuite/gcc.dg/tree-ssa/pr94589-1.c.jj	2021-05-10 22:36:10.574130179 +0200
+++ gcc/testsuite/gcc.dg/tree-ssa/pr94589-1.c	2021-05-10 22:36:17.789054362 +0200
@@ -0,0 +1,21 @@
+/* PR tree-optimization/94589 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int
+foo (int x)
+{
+  return (x & 23) == x;
+/* { dg-final { scan-tree-dump " & -24;" "optimized" } } */
+/* { dg-final { scan-tree-dump-not " & 23;" "optimized" } } */
+/* { dg-final { scan-tree-dump " == 0" "optimized" } } */
+}
+
+int
+bar (int x)
+{
+  return (x | 137) != 137;
+/* { dg-final { scan-tree-dump " & -138;" "optimized" } } */
+/* { dg-final { scan-tree-dump-not " \\| 137;" "optimized" } } */
+/* { dg-final { scan-tree-dump " != 0" "optimized" } } */
+}


	Jakub