match: `a CMP nonnegative ? a : ABS<a>` simplified to just `ABS<a>` [PR112392]

We can optimize `a == nonnegative ? a : ABS<a>`, `a > nonnegative ? a : ABS<a>`
and `a >= nonnegative ? a : ABS<a>` into `ABS<a>`. This allows removal of
some extra comparison and extra conditional moves in some cases.
I don't remember where I had found though but it is simple to add so
let's add it.

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

Note I have a secondary pattern for the equal case as either a or nonnegative
could be used.

	PR tree-optimization/112392

gcc/ChangeLog:

	* match.pd (`x CMP nonnegative ? x : ABS<x>`): New pattern;
	where CMP is ==, > and >=.
	(`x CMP nonnegative@y ? y : ABS<x>`): New pattern.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi-opt-41.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

2 files changed, 49 insertions, 0 deletions

diff --git a/gcc/match.pd b/gcc/match.pd
index 03a03c3..07e743a 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -5876,6 +5876,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
      (convert (absu:utype @0)))
     @3))))
 
+/* X >  Positive ? X : ABS(X) -> ABS(X) */
+/* X >= Positive ? X : ABS(X) -> ABS(X) */
+/* X == Positive ? X : ABS(X) -> ABS(X) */
+(for cmp (eq gt ge)
+ (simplify
+  (cond (cmp:c @0 tree_expr_nonnegative_p@1) @0 (abs@3 @0))
+  (if (INTEGRAL_TYPE_P (type))
+   @3)))
+
+/* X == Positive ? Positive : ABS(X) -> ABS(X) */
+(simplify
+ (cond (eq:c @0 tree_expr_nonnegative_p@1) @1 (abs@3 @0))
+ (if (INTEGRAL_TYPE_P (type))
+  @3))
+
 /* (X + 1) > Y ? -X : 1 simplifies to X >= Y ? -X : 1 when
    X is unsigned, as when X + 1 overflows, X is -1, so -X == 1.  */
 (simplify
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
new file mode 100644
index 0000000..9774e28
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-41.c
@@ -0,0 +1,34 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-phiopt1" } */
+/* PR tree-optimization/112392 */
+
+int feq_1(int a, unsigned char b)
+{
+  int absb = b;
+  if (a == absb)  return absb;
+  return a > 0 ? a : -a;
+}
+int feq_2(int a, unsigned char b)
+{
+  int absb = b;
+  if (a == absb)  return a;
+  return a > 0 ? a : -a;
+}
+
+int fgt(int a, unsigned char b)
+{
+  int absb = b;
+  if (a > absb)  return a;
+  return a > 0 ? a : -a;
+}
+
+int fge(int a, unsigned char b)
+{
+  int absb = b;
+  if (a >= absb)  return a;
+  return a > 0 ? a : -a;
+}
+
+
+/* { dg-final { scan-tree-dump-not "if " "phiopt1" } } */
+/* { dg-final { scan-tree-dump-times "ABS_EXPR <" 4 "phiopt1" } } */