[Zlib-devel] [PATCH 02/13] For x86, add CPUID check.

[Mike Frysinger]

On Monday 25 November 2013 17:21:38 Jim Kukunas wrote:
> --- /dev/null
> +++ b/x86.c
> @@ -0,0 +1,21 @@
> +#include "x86.h"

all files really should have a comment block at the top.  a simple one line 
explanation, short copyright/license blurb/etc...

> +int x86_cpu_has_sse2;
> +int x86_cpu_has_sse42;
> +int x86_cpu_has_pclmulqdq;
> +
> +void x86_check_features(void)
> +{
> +    unsigned eax, ebx, ecx, edx;
> +
> +    eax = 1;
> +    __asm__ __volatile__ (
> +        "cpuid\n\t"
> +    : "+a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
> +    );

pretty sure this won't compile under PIC.  it'll complain about ebx being 
clobbered.  this one will always work:
	__asm__ __volatile__ (
		"xchg %%ebx, %%esi;"
		"cpuid;"
		"xchg %%esi, %%ebx;"
		: "=S" (ebx), "=a" (eax), "=c" (ecx), "=d" (edx)
		: "a" (1));
-mike
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