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x86: cpu: clean up check for cpuid instruction support

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This adds macros for accessing the EFLAGS register and uses
these instead of coding the entire check in inline asm.

Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Mans Rullgard 2012-06-24 12:29:28 +01:00 committed by Michael Niedermayer
parent 96890c001f
commit e346176de9
1 changed files with 15 additions and 19 deletions
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34
libavutil/x86/cpu.c
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@ -37,6 +37,16 @@
#define xgetbv(index, eax, edx) \
__asm__ (".byte 0x0f, 0x01, 0xd0" : "=a"(eax), "=d"(edx) : "c" (index))
#define get_eflags(x) \
__asm__ volatile ("pushfl \n" \
"pop %0 \n" \
: "=r"(x))
#define set_eflags(x) \
__asm__ volatile ("push %0 \n" \
"popfl \n" \
:: "r"(x))
/* Function to test if multimedia instructions are supported... */
int ff_get_cpu_flags_x86(void)
{
@ -48,26 +58,12 @@ int ff_get_cpu_flags_x86(void)
#if ARCH_X86_32
x86_reg a, c;
__asm__ volatile (
/* See if CPUID instruction is supported ... */
/* ... Get copies of EFLAGS into eax and ecx */
"pushfl\n\t"
"pop %0\n\t"
"mov %0, %1\n\t"
/* ... Toggle the ID bit in one copy and store */
/* to the EFLAGS reg */
"xor $0x200000, %0\n\t"
"push %0\n\t"
"popfl\n\t"
/* ... Get the (hopefully modified) EFLAGS */
"pushfl\n\t"
"pop %0\n\t"
: "=a" (a), "=c" (c)
:
: "cc"
);
/* Check if CPUID is supported by attempting to toggle the ID bit in
* the EFLAGS register. */
get_eflags(a);
set_eflags(a ^ 0x200000);
get_eflags(c);
if (a == c)
return 0; /* CPUID not supported */