libFLAC/cpu.c: Fixes for MSVC

MSVC is strange and perverse.

src/libFLAC/cpu.c

@@ -35,6 +35,7 @@
 #endif
 
 #include "private/cpu.h"
+#include "share/compat.h"
 #include <stdlib.h>
 #include <memory.h>
 
@@ -453,6 +454,21 @@ void FLAC__cpu_info (FLAC__CPUInfo *info)
 
 #if (defined FLAC__CPU_IA32 || defined FLAC__CPU_X86_64) && FLAC__HAS_X86INTRIN
 
+#if defined _MSC_VER || defined __INTEL_COMPILER
+static inline void
+cpu_id_ex (int *cpuinfo, int result)
+{
+// Stupid MSVC doesn't know how to optimise out:
+//     if (FLAC_AVC_SUPPORTER)
+//         	__cpuidex(cpuinfo, level, 0); /* for AVX2 detection */
+#if FLAC__AVX_SUPPORTED
+	__cpuidex(cpuinfo, result, 0); /* for AVX2 detection */
+#else
+	__cpuid(cpuinfo, result); /* some old compilers don't support __cpuidex */
+#endif
+}
+#endif
+
 void FLAC__cpu_info_x86(FLAC__uint32 level, FLAC__uint32 *eax, FLAC__uint32 *ebx, FLAC__uint32 *ecx, FLAC__uint32 *edx)
 {
 #if defined _MSC_VER || defined __INTEL_COMPILER
@@ -463,10 +479,8 @@ void FLAC__cpu_info_x86(FLAC__uint32 level, FLAC__uint32 *eax, FLAC__uint32 *ebx
 		*eax = *ebx = *ecx = *edx = 0;
 		return;
 	}
-    if (FLAC__AVX_SUPPORTED)
-		__cpuidex(cpuinfo, level, 0); /* for AVX2 detection */
-	else
-		__cpuid(cpuinfo, level); /* some old compilers don't support __cpuidex */
+
+    cpu_id_ex (cpuinfo, ext);
 
 	*eax = cpuinfo[0]; *ebx = cpuinfo[1]; *ecx = cpuinfo[2]; *edx = cpuinfo[3];
 #elif defined __GNUC__ && defined HAVE_CPUID_H