cpuid ifdefs fixed to remove some duplicate code cases.

BUG=none
TESTED=local windows build
R=tpsiaki@google.com

Review URL: https://webrtc-codereview.appspot.com/47619004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@1332 16f28f9a-4ce2-e073-06de-1de4eb20be90

source/cpu_id.cc

@@ -43,17 +43,17 @@ extern "C" {
 #define SAFEBUFFERS
 #endif
 
-// Low level cpuid for X86. Returns zeros on other CPUs.
-#if !defined(__pnacl__) && !defined(__CLR_VER) && \
-    (defined(_M_IX86) || defined(_M_X64) || \
-    defined(__i386__) || defined(__x86_64__))
+// Low level cpuid for X86.
+#if (defined(_M_IX86) || defined(_M_X64) || \
+    defined(__i386__) || defined(__x86_64__)) && \
+    !defined(__pnacl__) && !defined(__CLR_VER)
 LIBYUV_API
 void CpuId(uint32 info_eax, uint32 info_ecx, uint32* cpu_info) {
 #if defined(_MSC_VER) && !defined(__clang__)
+// Visual C version uses intrinsic or inline x86 assembly.
 #if (_MSC_FULL_VER >= 160040219)
   __cpuidex((int*)(cpu_info), info_eax, info_ecx);
-#endif
-#if defined(_M_IX86)
+#elif defined(_M_IX86)
   __asm {
     mov        eax, info_eax
     mov        ecx, info_ecx
@@ -71,7 +71,8 @@ void CpuId(uint32 info_eax, uint32 info_ecx, uint32* cpu_info) {
     cpu_info[3] = cpu_info[2] = cpu_info[1] = cpu_info[0] = 0;
   }
 #endif
-#else  // defined(_MSC_VER)
+// GCC version uses inline x86 assembly.
+#else  // defined(_MSC_VER) && !defined(__clang__)
   uint32 info_ebx, info_edx;
   asm volatile (  // NOLINT
 #if defined( __i386__) && defined(__PIC__)
@@ -89,36 +90,37 @@ void CpuId(uint32 info_eax, uint32 info_ecx, uint32* cpu_info) {
   cpu_info[1] = info_ebx;
   cpu_info[2] = info_ecx;
   cpu_info[3] = info_edx;
-#endif  // defined(_MSC_VER)
+#endif  // defined(_MSC_VER) && !defined(__clang__)
+}
+#else  // (defined(_M_IX86) || defined(_M_X64) ...
+LIBYUV_API
+void CpuId(uint32 eax, uint32 ecx, uint32* cpu_info) {
+  cpu_info[0] = cpu_info[1] = cpu_info[2] = cpu_info[3] = 0;
 }
+#endif
 
-#if !defined(__native_client__)
+// TODO(fbarchard): Enable xgetbv when validator supports it.
+#if (defined(_M_IX86) || defined(_M_X64) || \
+    defined(__i386__) || defined(__x86_64__)) && \
+    !defined(__pnacl__) && !defined(__CLR_VER) && !defined(__native_client__)
 #define HAS_XGETBV
 // X86 CPUs have xgetbv to detect OS saves high parts of ymm registers.
 int TestOsSaveYmm() {
   uint32 xcr0 = 0u;
 #if defined(_MSC_VER) && (_MSC_FULL_VER >= 160040219)
   xcr0 = (uint32)(_xgetbv(0));  // VS2010 SP1 required.
-#endif
-#if defined(_M_IX86) && defined(_MSC_VER)
+#elif defined(_M_IX86) && defined(_MSC_VER) && !defined(__clang__)
   __asm {
     xor        ecx, ecx    // xcr 0
     _asm _emit 0x0f _asm _emit 0x01 _asm _emit 0xd0  // For VS2010 and earlier.
     mov        xcr0, eax
   }
-#endif
-#if defined(__i386__) || defined(__x86_64__)
+#elif defined(__i386__) || defined(__x86_64__)
   asm(".byte 0x0f, 0x01, 0xd0" : "=a" (xcr0) : "c" (0) : "%edx");
-#endif  // defined(_MSC_VER)
+#endif  // defined(__i386__) || defined(__x86_64__)
   return((xcr0 & 6) == 6);  // Is ymm saved?
 }
-#endif  // !defined(__native_client__)
-#else
-LIBYUV_API
-void CpuId(uint32 eax, uint32 ecx, uint32* cpu_info) {
-  cpu_info[0] = cpu_info[1] = cpu_info[2] = cpu_info[3] = 0;
-}
-#endif
+#endif  // defined(_M_IX86) || defined(_M_X64) ..
 
 // based on libvpx arm_cpudetect.c
 // For Arm, but public to allow testing on any CPU