[PATCH] match.pd: Fold umin(a, 1) | umin(b, 1) into umin(a | b, 1) [PR126646]

[Reshma.Roy]

From: Reshma Roy <reshma....@amd.com>

gcc/ChangeLog:

        PR tree-optimization/126646
        * match.pd: Fold umin(a, 1) | umin(b, 1) into umin(a | b, 1).

gcc/testsuite/ChangeLog:

        * gcc.dg/tree-ssa/pr126646-1.c: New test.
---

Hi,
  This patch fixes the missed optimization opportunity reported in
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126646.
  For the following snippet of code, gcc generates 2 MIN_EXPR.
  unsigned f(unsigned a, unsigned b)
  {
    unsigned t = 1;
    a = a < t ? a : t;
    b = b < t ? b : t;
    return a | b;
  }
 But this can be optimized with just one MIN_EXPR since 
 umin(a,1) | umin(b,1) can be simplified to umin(a|b, 1).

 Bootstrapped and tested on x86_64-linux.

Thanks,
  Reshma

 gcc/match.pd                               |  5 +++++
 gcc/testsuite/gcc.dg/tree-ssa/pr126646-1.c | 15 +++++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr126646-1.c

diff --git a/gcc/match.pd b/gcc/match.pd
index 50e73177022..7347b83ec4f 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -4860,6 +4860,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (bit_not (minmax:cs (bit_not @0) @1))
   (maxmin @0 (bit_not @1))))
 
+/* umin (a, 1) | umin (b, 1) -> umin (a | b, 1).  */
+ (simplify
+  (bit_ior (min @0 integer_onep@2) (min @1 @2))
+    (if (TYPE_UNSIGNED (type))
+     (min (bit_ior @0 @1) @2)))
 /* MIN (X, Y) == X -> X <= Y  */
 /* MIN (X, Y) < X -> X > Y  */
 /* MIN (X, Y) >= X -> X <= Y  */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr126646-1.c 
b/gcc/testsuite/gcc.dg/tree-ssa/pr126646-1.c
new file mode 100644
index 00000000000..447a1739b5f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr126646-1.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+/* The test case should produce only one min expr.  */
+/* umin(a,1) | umin(b,1) -> umin(a|b, 1).  */
+
+unsigned min_or (unsigned a, unsigned b)
+{
+  unsigned t = 1;
+  a = a < t ? a : t;
+  b = b < t ? b : t;
+  return a | b;
+}
+
+/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "optimized" } } */
-- 
2.34.1