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Re: testsuite run-time test for sse2 support
- From: "Uros Bizjak" <ubizjak at gmail dot com>
- To: "Joel Sherrill" <joel dot sherrill at oarcorp dot com>
- Cc: "GCC Development" <gcc at gcc dot gnu dot org>
- Date: Thu, 13 Mar 2008 15:25:56 +0100
- Subject: Re: testsuite run-time test for sse2 support
- References: <5787cf470803130032u323a4a06ka403f5d6b18eb78@mail.gmail.com> <47D92D98.8090605@oarcorp.com>
On Thu, Mar 13, 2008 at 2:35 PM, Joel Sherrill
<joel.sherrill@oarcorp.com> wrote:
> I hacked on that test program to get the attached
> program. I ran it multiple times on qemu.
>
> ext=0x0 sig=0x756e6547
> 0x781abfd YES on SSE2
>
> I ran the same program natively and got this:
>
> ext=0x0 sig=0x756e6547
> 0xbfebfbff YES on SSE2
>
> I wonder if qemu is just reporting things wrong. :(
> I searched the qemu manual and googled some but
> didn't see anything that jumped out.
>
> Does this look like qemu reporting a bogus cpuid or
> gcc not parsing it correctly?
This all depends on the return value of __get_cpuid_max(). It returns
max value of base cpuid level (5 in my case), and shoould return 0 if
cpuid is not supported. This follows the procedure outlined in
http://download.intel.com/design/processor/applnots/24161832.pdf,
section 2: "Detecting the CPUID Instruction".
It is true, that this is not the most maintained code on the planet,
so some bitrot is possible. The return value of __get_cpuid_max() on
your target will tell...
Thanks,
Uros.