On Tue, 11 May 2021, Jakub Jelinek via Gcc-patches wrote:
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?
Ah, yes, you are right, good point on the cmp:c, thank you.
2021-05-11 Jakub Jelinek <ja...@redhat.com>
Marc Glisse <marc.gli...@inria.fr>
PR tree-optimization/94589
* match.pd ((X & Y) == Y -> (X & ~Y) == 0,
^
X?
(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
--
Marc Glisse
