[flac-dev] FLAC__SSE_OS change

[Erik de Castro Lopo]

lvqcl wrote:

> Dave Yeo wrote:
> 
> >>> >on other OSes:
> >>> >      --enable-sse:
> >>> >          add -msse2 to the compiler switches
> >>> >          test SSE OS support  (why?)
> 
> >>> >It's a bit contradictory: why test whether *BSD etc support SSE or not
> >>> >but at the same time allow compiler to use SSE/SSE2 unconditionally?
> >> Yes, that needs to be fixed. I think the way it works on Linux makes
> >> the most sense.
> >>
> >
> > Doesn't SSE support imply SSE2+ support?
> 
> There's no point to test OS SSE support if a compiler already
> inserted SSE/SSE2 instructions everywhere (because of -msse2 switch).
> 
> > The problem is that the OS has
> > to preserve the XMMS registers when doing a context switch. Once the
> > kernel is preserving the XMMS registers, I'd assume that all SSEx
> > instructions should work.
> 
> If the OS doesn't support SSE instructions but -msse2 option was used
> then libFLAC will crash: it cannot disable the use of SSE/SSE2
> instructions that were generated by the compiler.

Ok, thanks for the info.

Erik
-- 
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Erik de Castro Lopo
http://www.mega-nerd.com/