[Pixman] [PATCH] mmx: Use MMX2 intrinsics from xmmintrin.h directly.

[Matt Turner]

On Sun, Oct 11, 2015 at 8:59 PM, Matt Turner <mattst88 at gmail.com> wrote:
> We had lots of hacks to handle the inability to include xmmintrin.h
> without compiling with -msse (lest SSE instructions be used in
> pixman-mmx.c). Some recent version of gcc relaxed this restriction.
>
> Change configure.ac to test that xmmintrin.h can be included and that we
> can use some intrinsics from it, and remove the work-around code from
> pixman-mmx.c.
>
> Evidently allows gcc 4.9.3 to optimize better as well:
>
>    text    data     bss     dec     hex filename
>  657078   30848     680  688606   a81de libpixman-1.so.0.33.3 before
>  656710   30848     680  688238   a806e libpixman-1.so.0.33.3 after
>
> Signed-off-by: Matt Turner <mattst88 at gmail.com>
> ---

Ugh. This is apparently not sufficient...

https://bugs.gentoo.org/show_bug.cgi?id=564024

GCC allows you to *include* xmmintrin.h without enabling SSE, but it
still doesn't allow you to use any of the functions:

conftest.c: In function ‘main’:
/usr/lib/gcc/x86_64-pc-linux-gnu/5.1.0/include/xmmintrin.h:1124:1:
error: inlining failed in call to always_inline ‘_mm_mulhi_pu16’:
target specific option mismatch
 _mm_mulhi_pu16 (__m64 __A, __m64 __B)
 ^
conftest.c:12:7: error: called from here
     w = _mm_mulhi_pu16(w, w);

I'm not sure what to do except to revert.

The MMX but no SSE case is important, at least it was in the past
because of OLPC's XO-1.

Suggestions besides reverting this?