From: "Bingfeng Mei" <bmei@broadcom.com>
To: "Andrew Pinski" <pinskia@gmail.com>,
"Richard Guenther" <richard.guenther@gmail.com>
Cc: "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: RE: Why doesn't GCC generate conditional move for COND_EXPR?
Date: Tue, 25 Oct 2011 14:10:00 -0000 [thread overview]
Message-ID: <7FB04A5C213E9943A72EE127DB74F0ADD15FEADFF8@SJEXCHCCR02.corp.ad.broadcom.com> (raw)
In-Reply-To: <CA+=Sn1mQ=XHw+J_mtVN=g54T3FNjagGOxNyO6ZPc1tf6_4_DqQ@mail.gmail.com>
Thanks, Andrew. I also implemented a quick patch on our port (based on GCC 4.5).
I noticed it produced better code now for our applications. Maybe eliminating
control flow in earlier stage helps other optimizing passes. Currently, tree
if-conversion pass is not turned on by default (only with tree vectorization
or some other passes). Maybe it is worth to make it default at -O2 (for those
processors support conditional move)?
Cheers,
Bingfeng
> -----Original Message-----
> From: Andrew Pinski [mailto:pinskia@gmail.com]
> Sent: 24 October 2011 17:20
> To: Richard Guenther
> Cc: Bingfeng Mei; gcc@gcc.gnu.org
> Subject: Re: Why doesn't GCC generate conditional move for COND_EXPR?
>
> On Mon, Oct 24, 2011 at 7:00 AM, Richard Guenther
> <richard.guenther@gmail.com> wrote:
> > On Mon, Oct 24, 2011 at 2:55 PM, Bingfeng Mei <bmei@broadcom.com>
> wrote:
> >> Hello,
> >> I noticed that COND_EXPR is not expanded to conditional move
> >> as MIN_EXPR/MAX_EXPR are (assuming movmodecc is available).
> >> I wonder why not?
> >>
> >> I have some loop that fails tree vectorization, but still contains
> >> COND_EXPR from tree ifcvt pass. In the end, the generated code
> >> is worse than if I don't turned -ftree-vectorize on. This
> >> is on our private port.
> >
> > Because nobody touched COND_EXPR expansion since ages.
>
> I have a patch which I will be submitting next week or so that does
> this expansion correctly. In fact I have a few patches which improves
> the generation of COND_EXPR in simple cases (in PHI-OPT).
>
> Thanks,
> Andrew Pinski
next prev parent reply other threads:[~2011-10-25 11:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-24 14:45 Bingfeng Mei
2011-10-24 16:19 ` Richard Guenther
2011-10-25 3:12 ` Andrew Pinski
2011-10-25 14:10 ` Bingfeng Mei [this message]
2012-05-04 21:26 ` Andrew Pinski
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