[Pixman] [Mesa-stable] [PATCH] configure.ac: fix test for SSE4.1 assembler support

Oded Gabbay oded.gabbay at gmail.com
Wed Dec 9 03:39:30 PST 2015

On Wed, Dec 9, 2015 at 1:09 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> On 9 December 2015 at 05:37, Jonathan Gray <jsg at jsg.id.au> wrote:
>> Change the __m128i variables to be volatile so gcc 4.9 won't optimise
>> all of them out with -O1 or greater.  The _mm_set1_epi32/pinsrd calls
>> still get optimised out but now there is at least one SSE4.1 instruction
>> generated via _mm_max_epu32/pmaxud.  When all of the sse4.1 instructions
>> got optimised out the configure test would incorrectly pass when the
>> compiler supported the intrinsics and the assembler didn't support the
>> instructions.
> Must admit that I was not expecting that one. Looks like pixman (the
> inspiration for this check) is missing volatile as well. Does that one
> build/run fine on OpenBSD ?
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91806
>> Signed-off-by: Jonathan Gray <jsg at jsg.id.au>
>> Cc: "11.0 11.1" <mesa-stable at lists.freedesktop.org>
> Reviewed-by: Emil Velikov <emil.velikov at collabora.com>
> I'll pick this in a couple of days (barring any objections).
> Thanks
> Emil

Adding pixman ML.
I must admit ignorance on this one.
I looked at configure.ac of pixman and I don't see any SSE4.1
reference, and AFAIK, we don't use those instructions (only SSE2 and
Is the above patch relevant for those as well ? because the tests in
configure.ac does *not* contain volatile.


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