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Date: Tue, 7 Jun 2022 15:44:26 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: HAO CHEN GUI <guihaoc@linux.ibm.com>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>, David <dje.gcc@gmail.com>,
 "Kewen.Lin" <linkw@linux.ibm.com>, Peter Bergner <bergner@linux.ibm.com>
Subject: Re: [PATCH v3,
 rs6000] Implemented f[min/max]_optab by xs[min/max]dp [PR103605]
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Hi!

On Tue, Jun 07, 2022 at 09:51:43AM +0800, HAO CHEN GUI wrote:
> On 2/6/2022 上午 5:01, Segher Boessenkool wrote:
> > On Wed, May 18, 2022 at 04:52:26PM +0800, HAO CHEN GUI wrote:
> >>    const double __builtin_vsx_xsmaxdp (double, double);
> >> -    XSMAXDP smaxdf3 {}
> >> +    XSMAXDP fmaxdf3 {}
> >>
> >>    const double __builtin_vsx_xsmindp (double, double);
> >> -    XSMINDP smindf3 {}
> >> +    XSMINDP fmindf3 {}
> > 
> > Are s{min,max}df3 still used after this?
> 
> Expands reduc_s[min|max]_scal are still using s[min|max]df3.

Ah, and reduction is undefined for float unless fast-math anyway.  Okay.

> Also we could implement reduc_f[min|max]_scal after committing
> this patch.

Because fmin and fmax treat NaNs as missing data.  But you have to be
careful with SNaNs here, probably just skip most of this when
-fsignaling-nans is used.  It also still needs -fno-signed-zeros btw,
but not full -ffast-math indeed.


Segher