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

[Richard Biener <rguenther@suse.de>]

On December 5, 2020 11:57:46 AM GMT+01:00, Jakub Jelinek <jakub@redhat.com> wrote:
>On Sat, Dec 05, 2020 at 11:20:11AM +0100, Richard Biener wrote:
>> >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.
>> >
>> >Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>> >
>> >And/or, shall we have a match.pd optimization to turn that -(type)!x
>> >for BOOLEAN_TYPE (or other 1 bit unsigned precision values) into
>> >(type) - 1.
>> 
>> I think that would make sense. Does that then cover the phiopt case
>directly? 
>
>That would be the following then.  Seems it works for that case.
>Ok for trunk if it passes bootstrap/regtest?

Ok. 

Richard. 

>2020-12-05  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.
>
>--- gcc/match.pd.jj	2020-12-02 11:20:24.765486816 +0100
>+++ gcc/match.pd	2020-12-05 11:46:00.554518927 +0100
>@@ -3812,6 +3812,16 @@ (define_operator_list COND_TERNARY
>   (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,
>--- gcc/testsuite/gcc.dg/tree-ssa/pr96232-1.c.jj	2020-12-05
>11:37:27.804332875 +0100
>+++ gcc/testsuite/gcc.dg/tree-ssa/pr96232-1.c	2020-12-05
>11:37:27.804332875 +0100
>@@ -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;
>+}
>
>
>	Jakub