[PATCH] match.pd: Implement missed optimization (x << c) >> c -> -(x & 1) [PR101955]

[Drew Ross <drross@redhat.com>]

	PR middle-end/101955

gcc/ChangeLog:

	* match.pd (x << c) >> c -> -(x & 1): New simplification.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr101955.c: New test.
---
 gcc/match.pd                    |  9 +++++
 gcc/testsuite/gcc.dg/pr101955.c | 62 +++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/pr101955.c

diff --git a/gcc/match.pd b/gcc/match.pd
index 8543f777a28..bf63652e80f 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3766,6 +3766,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
       && (wi::ltu_p (wi::to_wide (@1), element_precision (type))))
   (bit_and @0 (rshift { build_minus_one_cst (type); } @1))))
 
+/* Optimize (X << C) >> C where C = precision(type) - 1 and X is signed
+   into -(X & 1).  */
+(simplify
+ (rshift (lshift @0 INTEGER_CST@1) @@1)
+ (if (ANY_INTEGRAL_TYPE_P (type)
+      && !TYPE_UNSIGNED (type)
+      && wi::eq_p (wi::to_wide (@1), element_precision (type) - 1))
+  (negate (bit_and @0 { build_one_cst (type); }))))
+
 /* Optimize x >> x into 0 */
 (simplify
  (rshift @0 @0)
diff --git a/gcc/testsuite/gcc.dg/pr101955.c b/gcc/testsuite/gcc.dg/pr101955.c
new file mode 100644
index 00000000000..0e233269e21
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr101955.c
@@ -0,0 +1,62 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-dse1 -Wno-psabi" } */
+
+typedef int v4si __attribute__((vector_size(16)));
+
+__attribute__((noipa)) int
+t1 (int x)
+{
+  return (x << 31) >> 31;
+}
+
+__attribute__((noipa)) int
+t2 (int x)
+{
+  int y = x << 31;
+  int z = y >> 31;
+  return z;
+}
+
+__attribute__((noipa)) int
+t3 (int x)
+{
+  int w = 31;
+  int y = x << w;
+  int z = y >> w;
+  return z;
+}
+
+__attribute__((noipa)) long long
+t4 (long long x)
+{
+  return (x << 63) >> 63;
+}
+
+__attribute__((noipa)) long long
+t5 (long long x)
+{
+  long long y = x << 63;
+  long long z = y >> 63;
+  return z;
+}
+
+__attribute__((noipa)) long long
+t6 (long long x)
+{
+  int w = 63;
+  long long y = x << w;
+  long long z = y >> w;
+  return z;
+}
+
+__attribute__((noipa)) v4si
+t7 (v4si x)
+{
+  return (x << 31) >> 31;
+}
+
+/* { dg-final { scan-tree-dump-not " >> " "dse1" } } */
+/* { dg-final { scan-tree-dump-not " << " "dse1" } } */
+/* { dg-final { scan-tree-dump-times " -" 7 "dse1" } } */
+/* { dg-final { scan-tree-dump-times " & " 7 "dse1" } } */
+
-- 
2.39.3