[FFmpeg-devel] [RFC] clobbers for XMM registers

[Michael Niedermayer]

On Tue, Sep 28, 2010 at 01:26:35PM +0100, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> 
> > On Tue, Sep 28, 2010 at 08:00:28AM +0100, M?ns Rullg?rd wrote:
> >> Michael Niedermayer <michaelni at gmx.at> writes:
> >> 
> >> > On Mon, Sep 27, 2010 at 09:15:24PM -0400, Ronald S. Bultje wrote:
> >> >> Hi,
> >> >> 
> >> >> 2010/9/27 M?ns Rullg?rd <mans at mansr.com>:
> >> >> > Michael Niedermayer <michaelni at gmx.at> writes:
> >> >> >> On Tue, Sep 28, 2010 at 01:51:33AM +0200, Michael Niedermayer wrote:
> >> >> >>> On Sat, May 29, 2010 at 08:27:58PM +0200, Reimar D?ffinger wrote:
> >> >> >>> > Hello, this is not suitable by far (among other things,
> >> >> >>> > ugly parts, split asm code where a clobber is likely to
> >> >> >>> > introduce bugs, only tested to compile,
> >> >> >>>
> >> >> >>> > did not find a nice "dummy" clobber constraint -
> >> >> >>> > particularly important since
> >> >> >>>
> >> >> >>> try "%esp" ;)
> >> >> >>>
> >> >> >>>
> >> >> >>> > I suspect older gccs won't accept %xmm clobbers, ...).
> >> >> >>>
> >> >> >>> the oldest i have here is 3.3 and it supports it
> >> >> >>
> >> >> >> has someone tested xmm clobbers on fate alraedy?
> >> >> >> if not i think we should commit one and see what fails
> >> >> >> then we can decide if we need a macro wraping them at all
> >> >> >
> >> >> > We tested. ?It failed.
> >> >> 
> >> >> See r24931 and r24934 in vp3dsp_sse2.c.
> >> >> 
> >> >> http://archives.free.net.ph/message/20100825.195706.b4de9543.en.html
> >> >> http://archives.free.net.ph/message/20100825.203635.00f52a36.en.html
> >> >
> >> > do you happen to remember the error messages and which compiler version
> >> > was affected?
> >> 
> >> All BSD and all Windows.  See for example
> >> http://fate.ffmpeg.org/x86_32-dragonflybsd-gcc-4.1.2/20100825202620
> >> http://fate.ffmpeg.org/i686-pc-mingw32-gcc-4.2/20100825201526
> >> 
> >> libavcodec/x86/vp3dsp_sse2.c:165: error: unknown register name '%xmm7' in 'asm'
> >
> > could be a build system bug, aka missing -msse
> 
> -msse will create an executable that doesn't work on pre-SSE CPUs.

you want to execute code from vp3dsp_sse2.c on a pre SSE cpu?


> Need I remind you of the flame war we had over that.

probably as i dont remember flaming you about passing wrong flags to gcc
and then pretending that there was a problem with inline asm

you arent really expecting gcc to compile SSE code if its explicitly told
not to

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When you are offended at any man's fault, turn to yourself and study your
own failings. Then you will forget your anger. -- Epictetus
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