Re: [PATCH] Implement __builtin_issignaling

[Richard Biener <rguenther@suse.de>]

On Tue, 16 Aug 2022, Jakub Jelinek wrote:

> On Tue, Aug 16, 2022 at 11:41:06AM +0000, Richard Biener wrote:
> > Can you also amend the extend.texi documentation?  I think the
> > behavior will be special enough to worth mentioning it (I don't see
> > any of -ffinite-math-only effect on isnan/isinf mentioned though).
> 
> Like this?

Yes.

Thanks,
Richard.

> --- gcc/doc/extend.texi.jj	2022-08-16 13:23:04.227103773 +0200
> +++ gcc/doc/extend.texi	2022-08-16 13:56:01.250769807 +0200
> @@ -13557,6 +13557,8 @@ In the same fashion, GCC provides @code{
>  @code{isinf_sign}, @code{isnormal} and @code{signbit} built-ins used with
>  @code{__builtin_} prefixed.  The @code{isinf} and @code{isnan}
>  built-in functions appear both with and without the @code{__builtin_} prefix.
> +With @code{-ffinite-math-only} option the @code{isinf} and @code{isnan}
> +built-in functions will always return 0.
>  
>  GCC provides built-in versions of the ISO C99 floating-point rounding and
>  exceptions handling functions @code{fegetround}, @code{feclearexcept} and
> @@ -14496,6 +14498,12 @@ Note while the parameter list is an
>  ellipsis, this function only accepts exactly one floating-point
>  argument.  GCC treats this parameter as type-generic, which means it
>  does not do default promotion from float to double.
> +This built-in function can work even without the non-default
> +@code{-fsignaling-nans} option, although if a signaling NaN is computed,
> +stored or passed as argument to some function other than this built-in
> +in the current translation unit, it is safer to use @code{-fsignaling-nans}.
> +With @code{-ffinite-math-only} option this built-in function will always
> +return 0.
>  @end deftypefn
>  
>  @deftypefn {Built-in Function} int __builtin_ffs (int x)
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
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