diff mbox series

Add !flag_signaling_nans to simplifcation: (trunc)copysign((extend)a, (extend)b) to copysign (a, b).

Message ID 20211105022024.27921-1-hongtao.liu@intel.com
State New
Headers
Series Add !flag_signaling_nans to simplifcation: (trunc)copysign((extend)a, (extend)b) to copysign (a, b). |

Commit Message

Liu, Hongtao Nov. 5, 2021, 2:20 a.m. UTC 
  > Note that this is not safe with -fsignaling-nans, so needs to be disabled
> for that option (if there isn't already logic somewhere with that effect),
> because the extend will convert a signaling NaN to quiet (raising
> "invalid"), but copysign won't, so this transformation could result in a
> signaling NaN being wrongly returned when the original code would never
> have returned a signaling NaN.
>
> --
> Joseph S. Myers
> joseph@codesourcery.com

Bootstrapped and regtested on x86_64-linux-gnu{-m32,}.
Ok for trunk?

gcc/ChangeLog

	* match.pd
	(Simplifcation (trunc)copysign((extend)a, (extend)b) to
	.COPYSIGN (a, b)): Add !flag_signaling_nans.
---
 gcc/match.pd | 1 +
 1 file changed, 1 insertion(+)

Comments

Richard Biener Nov. 5, 2021, 9:48 a.m. UTC | #1 
On Fri, Nov 5, 2021 at 3:20 AM liuhongt <hongtao.liu@intel.com> wrote:
>
> > Note that this is not safe with -fsignaling-nans, so needs to be disabled
> > for that option (if there isn't already logic somewhere with that effect),
> > because the extend will convert a signaling NaN to quiet (raising
> > "invalid"), but copysign won't, so this transformation could result in a
> > signaling NaN being wrongly returned when the original code would never
> > have returned a signaling NaN.
> >
> > --
> > Joseph S. Myers
> > joseph@codesourcery.com
>
> Bootstrapped and regtested on x86_64-linux-gnu{-m32,}.
> Ok for trunk?
>
> gcc/ChangeLog
>
>         * match.pd
>         (Simplifcation (trunc)copysign((extend)a, (extend)b) to
>         .COPYSIGN (a, b)): Add !flag_signaling_nans.
> ---
>  gcc/match.pd | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index fb1065dc0e6..d6a8dd0dd20 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -6176,6 +6176,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>   (simplify
>    (convert (copysigns (convert@2 @0) (convert @1)))
>     (if (optimize
> +       && !flag_signaling_nans

Please use !HONOR_SNANS (@2)

OK with that change.

>         && types_match (type, TREE_TYPE (@0))
>         && types_match (type, TREE_TYPE (@1))
>         && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (@2))
> --
> 2.18.1
>
diff mbox series

Patch

diff --git a/gcc/match.pd b/gcc/match.pd
index fb1065dc0e6..d6a8dd0dd20 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -6176,6 +6176,7 @@  DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
  (simplify
   (convert (copysigns (convert@2 @0) (convert @1)))
    (if (optimize
+       && !flag_signaling_nans
        && types_match (type, TREE_TYPE (@0))
        && types_match (type, TREE_TYPE (@1))
        && TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (@2))