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

[Måns Rullgård]

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

-- 
M?ns Rullg?rd
mans at mansr.com