[PATCH] match.pd: Add (-(X < 0) | 1) * X -> abs (X) etc. simplifications [PR94785]

[Jakub Jelinek via Gcc-patches]

Hi!

The following patch adds two simplifications to recognize idioms
for ABS_EXPR resp. ABSU_EXPR.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2020-12-31  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/94785
        * match.pd ((-(X < 0) | 1) * X -> abs (X)): New simplification.
        ((-(X < 0) | 1U) * X -> absu (X)): Likewise.

        * gcc.dg/tree-ssa/pr94785.c: New test.

--- gcc/match.pd.jj     2020-12-15 22:43:39.254276743 +0100
+++ gcc/match.pd        2020-12-30 12:00:00.924301784 +0100
@@ -1374,6 +1374,22 @@ (define_operator_list COND_TERNARY
  (absu tree_expr_nonnegative_p@0)
  (convert @0))
 
+/* Simplify (-(X < 0) | 1) * X into abs (X).  */
+(simplify
+ (mult:c (bit_ior (negate (convert? (lt @0 integer_zerop))) integer_onep) @0)
+ (if (INTEGRAL_TYPE_P (type) && !TYPE_UNSIGNED (type))
+  (abs @0)))
+
+/* Similarly (-(X < 0) | 1U) * X into absu (X).  */
+(simplify
+ (mult:c (bit_ior (nop_convert (negate (convert? (lt @0 integer_zerop))))
+                 integer_onep) (nop_convert @0))
+ (if (INTEGRAL_TYPE_P (type)
+      && TYPE_UNSIGNED (type)
+      && INTEGRAL_TYPE_P (TREE_TYPE (@0))
+      && !TYPE_UNSIGNED (TREE_TYPE (@0)))
+  (absu @0)))
+
 /* A few cases of fold-const.c negate_expr_p predicate.  */
 (match negate_expr_p
  INTEGER_CST
--- gcc/testsuite/gcc.dg/tree-ssa/pr94785.c.jj  2020-12-30 12:03:45.693776141 
+0100
+++ gcc/testsuite/gcc.dg/tree-ssa/pr94785.c     2020-12-30 12:04:26.895313170 
+0100
@@ -0,0 +1,36 @@
+/* PR tree-optimization/94785 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times " = ABS_EXPR <v_\[0-9]*\\\(D\\\)>;" 2 
"optimized" } } */
+/* { dg-final { scan-tree-dump-times " = ABSU_EXPR <v_\[0-9]*\\\(D\\\)>;" 2 
"optimized" } } */
+
+int
+f1 (int v)
+{
+  return (1 | -(v < 0)) * v;
+}
+
+unsigned
+f2 (int v)
+{
+  return (1U | -(v < 0)) * v;
+}
+
+int
+f3 (int v)
+{
+  int a = v < 0;
+  int b = -a;
+  int c = 1 | b;
+  return c * v;
+}
+
+unsigned
+f4 (int v)
+{
+  int a = v < 0;
+  int b = -a;
+  unsigned c = b;
+  unsigned d = c | 1;
+  return d * v;
+}

        Jakub