On Sun, 24 Jun 2012, Mans Rullgard wrote:
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 <[email protected]>
---
libavutil/x86/cpu.c | 36 ++++++++++++++++--------------------
1 file changed, 16 insertions(+), 20 deletions(-)
diff --git a/libavutil/x86/cpu.c b/libavutil/x86/cpu.c
index b87d3a3..5c3af1f 100644
--- a/libavutil/x86/cpu.c
+++ b/libavutil/x86/cpu.c
@@ -38,6 +38,16 @@
#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)
{
@@ -49,26 +59,12 @@ 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 */
--
1.7.10.2
Looks sensible to me and seems like a nice cleanup.
// Martin
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