match: Simplify `a != C1 ? abs(a) : C2` when C2 == abs(C1) [PR111957]

This adds a match pattern for `a != C1 ? abs(a) : C2` which gets simplified
to `abs(a)`. if C1 was originally *_MIN then change it over to use absu instead
of abs.

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

	PR tree-optimization/111957

gcc/ChangeLog:

	* match.pd (`a != C1 ? abs(a) : C2`): New pattern.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi-opt-40.c: New test.

diff --git a/gcc/match.pd b/gcc/match.pd
index f725a685863dce2b1f7ba295d32fa9ba092bf961..5f6aeb07ac015ba3237f8d126927cb4b9dca61ad 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -5611,6 +5611,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  (if (wi::eq_p (wi::bit_not (wi::to_wide (@1)), wi::to_wide (@2)))
   @3))
 
+/* X != C1 ? abs(X) : C2 simplifies to abs(x) when abs(C1) == C2. */
+(for op (abs absu)
+ (simplify
+  (cond (ne @0 INTEGER_CST@1) (op@3 @0) INTEGER_CST@2)
+  (if (wi::abs (wi::to_wide (@1)) == wi::to_wide (@2))
+   (if (op != ABSU_EXPR && wi::only_sign_bit_p (wi::to_wide (@1)))
+    (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
+     (convert (absu:utype @0)))
+    @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-40.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
new file mode 100644 (file)
index 0000000..a9011ce
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-phiopt" } */
+/* PR tree-optimization/111957 */
+
+int f(int a)
+{
+  if (a)
+    return a > 0 ? a : -a;
+  return 0;
+}
+
+int f1(int x)
+{
+  int intmin = (-1u >> 1);
+  intmin = -intmin - 1;
+  if (x != intmin)
+    return x > 0 ? x : -x;
+  return intmin;
+}
+
+/* { dg-final { scan-tree-dump-times "if " 1 "phiopt1" } } */
+/* { dg-final { scan-tree-dump-not "if " "phiopt2" } } */
+/* { dg-final { scan-tree-dump-times "ABS_EXPR <" 2 "phiopt1" } } */
+/* { dg-final { scan-tree-dump-times "ABS_EXPR <" 1 "phiopt2" } } */
+/* { dg-final { scan-tree-dump-times "ABSU_EXPR <" 1 "phiopt2" } } */