[Bug libc/13753] [2.15 backport] Really fix AVX tests

["allan at archlinux dot org" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=13753

--- Comment #6 from Allan McRae <allan at archlinux dot org> 2012-05-10 22:02:58 UTC ---
@Jeff: I have access to a Xen system to test these issues, so if you post a
link to the patch I can test.

Note that with the two original patches I still get issues in strcasecmp() with
illegal instructions with AVX:

#0  0x00007ffff76cd0ff in __strcasecmp_l_avx () from ./lib/libc.so.6

   0x00007ffff76cd0f7 <+23>:    and    $0x3f,%rcx
   0x00007ffff76cd0fb <+27>:    and    $0x3f,%rax
=> 0x00007ffff76cd0ff <+31>:    vmovdqa 0x46979(%rip),%xmm4        #
0x7ffff7713a80
   0x00007ffff76cd107 <+39>:    vmovdqa 0x469a1(%rip),%xmm5        #
0x7ffff7713ab0
   0x00007ffff76cd10f <+47>:    vmovdqa 0x46989(%rip),%xmm6        #
0x7ffff7713aa0

I will test with the additional patches linked in this bug report.


BTW, just to confirm how this should be done, the intel manual [1] states:
1) Detect CPUID.1:ECX.OSXSAVE[bit 27] = 1 (XGETBV enabled for application use1)
2) Issue XGETBV and verify that XCR0[2:1] = ‘11b’ (XMM state and YMM state are
enabled by OS).
3) detect CPUID.1:ECX.AVX[bit 28] = 1 (AVX instructions supported).
(Step 3 can be done in any order relative to 1 and 2)

http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-manual-325462-rmver.html
- section 13.5

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