x86/cpu: implement support for cpuid through intrinsics

Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -1061,6 +1061,7 @@ HAVE_LIST="
     cbrtf
     closesocket
     cmov
+    cpuid
     dcbzl
     dev_bktr_ioctl_bt848_h
     dev_bktr_ioctl_meteor_h
@@ -2744,6 +2745,7 @@ elif enabled sparc; then
 elif enabled x86; then
 
     check_code ld immintrin.h "__xgetbv(0)" && enable xgetbv
+    check_code ld intrin.h "int info[4]; __cpuid(info, 0)" && enable cpuid
     check_code ld intrin.h "__rdtsc()" && enable rdtsc
 
     check_code ld mmintrin.h "_mm_empty()" && enable mm_empty

libavutil/x86/cpu.c

@@ -25,6 +25,7 @@
 #include "libavutil/x86_cpu.h"
 #include "libavutil/cpu.h"
 
+#if HAVE_INLINE_ASM
 /* ebx saving is necessary for PIC. gcc seems unable to see it alone */
 #define cpuid(index, eax, ebx, ecx, edx)                        \
     __asm__ volatile (                                          \
@@ -33,6 +34,19 @@
         "xchg   %%"REG_b", %%"REG_S                             \
         : "=a" (eax), "=S" (ebx), "=c" (ecx), "=d" (edx)        \
         : "0" (index))
+#elif HAVE_CPUID
+#include <intrin.h>
+
+#define cpuid(index, eax, ebx, ecx, edx)        \
+    do {                                        \
+        int info[4];                            \
+        __cpuid(info, index);                   \
+        eax = info[0];                          \
+        ebx = info[1];                          \
+        ecx = info[2];                          \
+        edx = info[3];                          \
+    } while (0)
+#endif /* HAVE_CPUID */
 
 #if HAVE_INLINE_ASM
 #define xgetbv(index, eax, edx)                                 \