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Re: Patch RFA: Move x86 _mm_pause out of pragma target("sse") scope


Hello Ian, UroÅ,
On 30 May 09:19, Uros Bizjak wrote:
> Hello!
> 
> > This error is because _mm_pause is defined in the scope of #pragma GCC
> > target("sse").  But _mm_pause, which simply generates the pause
> > instruction, does not require SSE support.  The pause instruction has
> > nothing really to do with SSE, and it works on all x86 processors (on
> > processors that do not explicitly recognize it, it is a nop).
> >
> > I propose the following patch, which moves _mm_pause out of the pragma
> > target scope.
> >
> > I know that x86intrin.h provides a similar intrinsic, __pause, but I
> > think it's worth making _mm_pause work reasonably as well.
> >
> > I'm running a full testsuite run.  OK for mainline if it passes?
> >
> > gcc/ChangeLog:
> >
> > 2014-05-29  Ian Lance Taylor  <iant@google.com>
> >
> > * config/i386/xmmintrin.h (_mm_pause): Move out of scope of pragma
> > target("sse").
> >
> > gcc/testsuite/ChangeLog:
> >
> > 2014-05-29  Ian Lance Taylor  <iant@google.com>
> >
> > * gcc.target/i386/pause-2.c: New test.
> 
> The patch looks OK to me, but please wait a day or two for possible
> comments (compatibility, etc) from Kirill.
That is definetely a bug and I see no compatibility issues in the fix.

The only nit I see: maybe it'd be better to put this cpuid-less intrinsic
into immintin.h? xmmintrin.h serves for SSE.

--
Thanks, K


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