match.pd: Improve conditional_replacement for x ? 0 : -1 [PR796232]

As mentioned in the PR, for boolean x we currently optimize
in phiopt x ? 0 : -1 into -(int)!x but it can be optimized as
(int) x - 1 which is one less operation both in GIMPLE and in x86 assembly.

This patch optimizes it in match.pd, by optimizing -(type)!x when
x has boolean range into (type)x - 1.

2020-12-06  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/96232
	* match.pd (-(type)!A -> (type)A - 1): New optimization.

	* gcc.dg/tree-ssa/pr96232-1.c: New test.

diff --git a/gcc/match.pd b/gcc/match.pd
index 68201ff2e07af069102e0bf6be68a8577e9c321e..43bacb4f68e2cb5b4557a45ab4ca42f0d2b473c3 100644 (file)
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3812,6 +3812,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (cnd (logical_inverted_value truth_valued_p@0) @1 @2)
   (cnd @0 @2 @1)))
 
+/* -(type)!A -> (type)A - 1.  */
+(simplify
+ (negate (convert?:s (logical_inverted_value:s @0)))
+ (if (INTEGRAL_TYPE_P (type)
+      && TREE_CODE (type) != BOOLEAN_TYPE
+      && TYPE_PRECISION (type) > 1
+      && TREE_CODE (@0) == SSA_NAME
+      && ssa_name_has_boolean_range (@0))
+  (plus (convert:type @0) { build_all_ones_cst (type); })))
+
 /* A + (B vcmp C ? 1 : 0) -> A - (B vcmp C ? -1 : 0), since vector comparisons
    return all -1 or all 0 results.  */
 /* ??? We could instead convert all instances of the vec_cond to negate,

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96232-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96232-1.c
new file mode 100644 (file)
index 0000000..3170ffd
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96232-1.c
@@ -0,0 +1,11 @@
+/* PR tree-optimization/96232 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump " \\+ -1;" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "~x_\[0-9]*\\\(D\\\)" "optimized" } } */
+
+int
+foo (_Bool x)
+{
+  return x ? 0 : -1;
+}