On Sun, May 19, 2019, 3:33 PM Olaf van der Spek <ml@xxxxxxxxxx> wrote:
On Sun, May 19, 2019 at 2:31 PM tedheadster <tedheadster@xxxxxxxxx> wrote:
>
> On Sun, May 19, 2019 at 7:31 AM Olaf van der Spek <ml@xxxxxxxxxx> wrote:
> >
> > What's eax after cpuid function 0?
>
> After calling cpuid function 0x0, %eax returns the expected 0x1.
>
> Here is the output of 'cpuid -r'.
>
> # cpuid -r
> CPU 0:
> 0x00000000 0x00: eax=0x00000001 ebx=0x746e6543 ecx=0x736c7561 edx=0x48727561
> 0x00000001 0x00: eax=0x00000585 ebx=0x746e6543 ecx=0x00000000 edx=0x008001b5
ecx does contain 0 doesn't it? Or is this the wrong line?
Olaf
I was fooled by that too. The /usr/bin/cpuid program is not the same as the gcc cpuid.h calls. I inserted debugging code and found that the %ecx register still had its part of the vendor string 'auls' in it (from 'CentaurHauls') from the earlier call to cpuid() with eax = 0.
I posted a patch to the gcc-patches mailing list.
- Matthew
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