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List:       kde-multimedia
Subject:    Re: configure check for SSE support in the assembler (#29700)
From:       Malte Starostik <malte () kde ! org>
Date:       2001-07-27 15:21:54
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On Freitag, 27. Juli 2001 17:07, Charles Samuels wrote:
> On Friday 27 July 2001 07:56 am, Malte Starostik wrote:
> > On Freitag, 27. Juli 2001 16:17, Charles Samuels wrote:
> > > On Friday 27 July 2001 05:52 am, Malte Starostik wrote:
> > > > Please review, if it's okay, I'll do the same for kdemultimedia and
> > > > where it's used in noatun etc.
> > >
> > > What's this for? I thought the whole reason we had the runtime check
> > > was so that SSE would always be used, even if the user is using
> > > binaries compiled on a non-sse system..?
> >
> > There seem to be quite a few users with old GNU as that doesn't
> > understand those opcodes regardless of what the hardware supports. They
> > simply get compile errors now...
>
> Is this a workaround for _that_ problem, or are you only allowing it on SSE
> systems?  Perhaps a --disable-sse option or something of the likes?
All it does is to #define HAVE_X86_SSE according to whether the assembler 
groks SSE insns. The symbol will still be defined if the build machine is a 
386, and the actual use of SSE is left to the runtime check.
If the CPU and kernel can use it is not subject of this test, it's just to 
avoid compile errors on setups with an old assembler. I even had a report 
from a gcc 3.0 user who got

/tmp/ccKUmE00.s: Assembler messages:
/tmp/ccKUmE00.s:160: Error: no such 386 instruction: `movups'
make[4]: *** [cpuinfo.lo] Error 1

due to using as 2.9.1 which simply doesn't know about SSE.
Of course a binutils upgrade would have helped, too, but as long as these 
__asm__ blocks are everything that fails with that version it might not be 
that nice to require an upgrade as stw pointed out :)

-- 
Malte Starostik
PGP: 1024D/D2F3C787 [C138-2121-FAF3-410A-1C2A-27CD-5431-7745-D2F3-C787]
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