Re: Why doesn't GCC generate conditional move for COND_EXPR?
On Tue, Oct 25, 2011 at 4:28 AM, Bingfeng Mei wrote: > 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)? I just committed the patch which does the expansion of COND_EXPR to condmov to the trunk. I have more patches which do what ifcvt does but in phiopt (which seems better in general as ifcvt work only over loops). I hope to post those patches in the coming weeks. Thanks, Andrew Pinski > > Cheers, > Bingfeng > >> -Original Message- >> From: Andrew Pinski [mailto:pins...@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 >> wrote: >> > On Mon, Oct 24, 2011 at 2:55 PM, Bingfeng Mei >> 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 >
RE: Why doesn't GCC generate conditional move for COND_EXPR?
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:pins...@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 > wrote: > > On Mon, Oct 24, 2011 at 2:55 PM, Bingfeng Mei > 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
Re: Why doesn't GCC generate conditional move for COND_EXPR?
On Mon, Oct 24, 2011 at 7:00 AM, Richard Guenther wrote: > On Mon, Oct 24, 2011 at 2:55 PM, Bingfeng Mei 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
Re: Why doesn't GCC generate conditional move for COND_EXPR?
On Mon, Oct 24, 2011 at 2:55 PM, Bingfeng Mei 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. > Thanks, > Bingfeng Mei > >
Why doesn't GCC generate conditional move for COND_EXPR?
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. Thanks, Bingfeng Mei
