On Thu, Sep 29, 2016 at 8:23 PM, Richard Biener <rguent...@suse.de> wrote:
> On Thu, 29 Sep 2016, Richard Biener wrote:
>
>> On Wed, 28 Sep 2016, Joseph Myers wrote:
>>
>> > On Wed, 28 Sep 2016, Richard Biener wrote:
>> >
>> > > Index: gcc/testsuite/gcc.dg/pr55152.c
>> > > ===================================================================
>> > > --- gcc/testsuite/gcc.dg/pr55152.c (revision 0)
>> > > +++ gcc/testsuite/gcc.dg/pr55152.c (working copy)
>> > > @@ -0,0 +1,13 @@
>> > > +/* { dg-do compile } */
>> > > +/* { dg-options "-O -ffinite-math-only -fstrict-overflow
>> > > -fdump-tree-optimized" } */
>> > > +
>> > > +double g (double a)
>> > > +{
>> > > + return (a>=-a)?a:-a;
>> >
>> > You should need -fno-signed-zeros for this (that is, for the
>> > transformation to MAX_EXPR), not -ffinite-math-only. For a == -0, that
>> > function should return -0, but abs would produce +0.
>>
>> This means that tree-ssa-phiopt.c has a bug:
>>
>> static bool
>> minmax_replacement (basic_block cond_bb, basic_block middle_bb,
>> edge e0, edge e1, gimple *phi,
>> tree arg0, tree arg1)
>> {
>> ...
>> /* The optimization may be unsafe due to NaNs. */
>> if (HONOR_NANS (type))
>> return false;
>>
>> and it should check HONOR_SIGNED_ZEROS as well.
>>
>> I'll fix that as a followup.
>
> Committed as follows.
>
> Bootstrapped / tested on x86_64-unknown-linux-gnu.
>
> Richard.
>
> 2016-09-29 Richard Biener <rguent...@suse.de>
>
> PR middle-end/55152
> * match.pd: Add max(a,-a) -> abs(a) pattern.
Hmm, shouldn't we also do "min(a, -a) -> - abs(a)" ?
Thanks,
Andrew Pinski
> * tree-ssa-phiopt.c (minmax_replacement): Disable for
> HONOR_SIGNED_ZEROS types.
>
> * gcc.dg/pr55152.c: New testcase.
> * gcc.dg/tree-ssa/phi-opt-5.c: Adjust.
>
> Index: gcc/match.pd
> ===================================================================
> --- gcc/match.pd (revision 240565)
> +++ gcc/match.pd (working copy)
> @@ -1271,6 +1284,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (simplify
> (max:c (min:c @0 @1) @1)
> @1)
> +/* max(a,-a) -> abs(a). */
> +(simplify
> + (max:c @0 (negate @0))
> + (if (TREE_CODE (type) != COMPLEX_TYPE
> + && (! ANY_INTEGRAL_TYPE_P (type)
> + || TYPE_OVERFLOW_UNDEFINED (type)))
> + (abs @0)))
> (simplify
> (min @0 @1)
> (switch
> Index: gcc/tree-ssa-phiopt.c
> ===================================================================
> --- gcc/tree-ssa-phiopt.c (revision 240565)
> +++ gcc/tree-ssa-phiopt.c (working copy)
> @@ -1075,7 +1075,7 @@ minmax_replacement (basic_block cond_bb,
> type = TREE_TYPE (PHI_RESULT (phi));
>
> /* The optimization may be unsafe due to NaNs. */
> - if (HONOR_NANS (type))
> + if (HONOR_NANS (type) || HONOR_SIGNED_ZEROS (type))
> return false;
>
> cond = as_a <gcond *> (last_stmt (cond_bb));
> Index: gcc/testsuite/gcc.dg/pr55152.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/pr55152.c (revision 0)
> +++ gcc/testsuite/gcc.dg/pr55152.c (working copy)
> @@ -0,0 +1,13 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -ffinite-math-only -fno-signed-zeros -fstrict-overflow
> -fdump-tree-optimized" } */
> +
> +double g (double a)
> +{
> + return (a>=-a)?a:-a;
> +}
> +int f(int a)
> +{
> + return (a>=-a)?a:-a;
> +}
> +
> +/* { dg-final { scan-tree-dump-times "ABS_EXPR" 2 "optimized" } } */
> Index: gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c (revision 240612)
> +++ gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c (working copy)
> @@ -1,5 +1,5 @@
> /* { dg-do compile } */
> -/* { dg-options "-O1 -ffinite-math-only -fdump-tree-phiopt1" } */
> +/* { dg-options "-O1 -ffinite-math-only -fno-signed-zeros
> -fdump-tree-phiopt1" } */
>
> float repl1 (float varx)
> {
