MATCH: Add simplifications of `(a == CST) & a`

`(a == CST) & a` can be either simplified to simplying `a == CST`
or 0 depending on the first bit of the CST.
This is an extension of the already pattern of `X & !X` and allows
us to remove the 2 xfails on gcc.dg/binop-notand1a.c and gcc.dg/binop-notand4a.c.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

	PR tree-optimization/111431

gcc/ChangeLog:

	* match.pd (`(a == CST) & a`): New pattern.

gcc/testsuite/ChangeLog:

	* gcc.dg/binop-notand1a.c: Remove xfail.
	* gcc.dg/binop-notand4a.c: Likewise.
	* gcc.c-torture/execute/pr111431-1.c: New test.
	* gcc.dg/binop-andeq1.c: New test.
	* gcc.dg/binop-andeq2.c: New test.
	* gcc.dg/binop-notand7.c: New test.
	* gcc.dg/binop-notand7a.c: New test.

8 files changed, 99 insertions, 6 deletions

diff --git a/gcc/match.pd b/gcc/match.pd
index 87edf0e..a05d4f0 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -5156,6 +5156,14 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  )
 )
 
+/* `(a == CST) & a` can be simplified to `0` or `(a == CST)` depending
+   on the first bit of the CST.  */
+(simplify
+ (bit_and:c (convert@2 (eq @0 INTEGER_CST@1)) (convert? @0))
+ (if ((wi::to_wide (@1) & 1) != 0)
+  @2
+  { build_zero_cst (type); }))
+
 /* Optimize
    # x_5 in range [cst1, cst2] where cst2 = cst1 + 1
    x_5 ? cstN ? cst4 : cst3
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr111431-1.c b/gcc/testsuite/gcc.c-torture/execute/pr111431-1.c
new file mode 100644
index 0000000..a96dbad
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr111431-1.c
@@ -0,0 +1,39 @@
+int
+foo (int a)
+{
+  int b = a == 0;
+  return (a & b);
+}
+
+#define function(vol,cst) \
+__attribute__((noipa)) \
+_Bool func_##cst##_##vol(vol int a) \
+{ \
+  vol int b = a == cst; \
+  return (a & b); \
+}
+
+#define funcdefs(cst) \
+function(,cst) \
+function(volatile,cst)
+
+#define funcs(f) \
+f(0) \
+f(1) \
+f(5)
+
+funcs(funcdefs)
+
+#define test(cst) \
+do { \
+ if(func_##cst##_(a) != func_##cst##_volatile(a))\
+   __builtin_abort(); \
+} while(0);
+int main(void)
+{
+  for(int a = -10; a <= 10; a++)
+   {
+     funcs(test)
+   }
+}
+
diff --git a/gcc/testsuite/gcc.dg/binop-andeq1.c b/gcc/testsuite/gcc.dg/binop-andeq1.c
new file mode 100644
index 0000000..2a92b8f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/binop-andeq1.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* PR tree-optimization/111431 */
+
+int
+foo (int a)
+{
+  int b = a == 2;
+  return (a & b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/binop-andeq2.c b/gcc/testsuite/gcc.dg/binop-andeq2.c
new file mode 100644
index 0000000..895262f
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/binop-andeq2.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* PR tree-optimization/111431 */
+
+int
+foo (int a)
+{
+  int b = a == 1025;
+  return (a & b);
+}
+
+/* { dg-final { scan-tree-dump-not "return 0"  "optimized" } } */
+/* { dg-final { scan-tree-dump-not " & "  "optimized" } } */
+/* { dg-final { scan-tree-dump-times " == 1025;" 1  "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/binop-notand1a.c b/gcc/testsuite/gcc.dg/binop-notand1a.c
index c7e932b..d94685e 100644
--- a/gcc/testsuite/gcc.dg/binop-notand1a.c
+++ b/gcc/testsuite/gcc.dg/binop-notand1a.c
@@ -7,6 +7,4 @@ foo (char a, unsigned short b)
   return (a & !a) | (b & !b);
 }
 
-/* As long as comparisons aren't boolified and casts from boolean-types
-   aren't preserved, the folding of  X & !X to zero fails.  */
-/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized"  } } */
diff --git a/gcc/testsuite/gcc.dg/binop-notand4a.c b/gcc/testsuite/gcc.dg/binop-notand4a.c
index dce6a5c..bd9c7cc 100644
--- a/gcc/testsuite/gcc.dg/binop-notand4a.c
+++ b/gcc/testsuite/gcc.dg/binop-notand4a.c
@@ -7,6 +7,4 @@ foo (unsigned char a, _Bool b)
   return (!a & a) | (b & !b);
 }
 
-/* As long as comparisons aren't boolified and casts from boolean-types
-   aren't preserved, the folding of  X & !X to zero fails.  */
-/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/binop-notand7.c b/gcc/testsuite/gcc.dg/binop-notand7.c
new file mode 100644
index 0000000..c2bb6a0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/binop-notand7.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* PR tree-optimization/111431 */
+
+int
+foo (int a)
+{
+  int b = !a;
+  return (a & b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/binop-notand7a.c b/gcc/testsuite/gcc.dg/binop-notand7a.c
new file mode 100644
index 0000000..dd50916
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/binop-notand7a.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* PR tree-optimization/111431 */
+
+unsigned
+foo (int a)
+{
+  int b = !a;
+  return (a & b);
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 1 "optimized" } } */