[FFmpeg-devel] [PATCH] read_time() for SPARC

[Michael Niedermayer]

On Fri, Sep 10, 2010 at 10:46:45AM +0100, M?ns Rullg?rd wrote:
[...]
> >>>>$ sparc-unknown-linux-gnu-gcc -m32 -mcpu=v9 -mno-v8plus -dM -E -xc /dev/null | grep -E 'arch|sparc'
> >>>>#define sparc 1
> >>>>#define __sparc__ 1
> >>>>#define __sparc 1
> >>>>#define __sparc_v9__ 1
> >>>
> >>> This is as right as xor rax,rax in an i386 binary built with -march=core2.
> >>
> >>Yes, that instruction would be invalid there.  In a pure 32-bit
> >>environment, you can't use the high half of 64-bit registers, even if
> >>they are physically present.  Consider what happens on a context switch.
> >
> > An ancient kernel will not preserve the sse registers as well. Anyway, there
> > is no such problem on Sparc. Anything else?
> 
> A 32-bit kernel on Sparc will only preserve the low 32 bits of the
> registers.  How could it possibly do otherwise?  Or is such a system
> impossible for some reason?

i dont know about sparc but a cpu surely could provide means to save and
restore future registers. that could be by instructions that just do the
save and restore or by a function in rom of teh cpu somewhere that one can
call
id even say a well designed cpu should do that unless the additional
complexity is an issue

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

There will always be a question for which you do not know the correct awnser.
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