cpu_id cleanup. no functional change.

source/cpu_id.cc

 /*
  *  Copyright 2011 The LibYuv Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS. All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 50 matching lines @@
     cpuid
     mov        [edi], eax
     mov        [edi + 4], ebx
     mov        [edi + 8], ecx
     mov        [edi + 12], edx
   }
 #else  // Visual C but not x86
   if (info_ecx == 0) {
     __cpuid((int*)(cpu_info), info_eax);
   } else {
-    cpu_info[3] = cpu_info[2] = cpu_info[1] = cpu_info[0] = 0;
+    cpu_info[3] = cpu_info[2] = cpu_info[1] = cpu_info[0] = 0u;
   }
 #endif
 // GCC version uses inline x86 assembly.
 #else  // defined(_MSC_VER)
   uint32 info_ebx, info_edx;
   asm volatile (
 #if defined( __i386__) && defined(__PIC__)
     // Preserve ebx for fpic 32 bit.
     "mov %%ebx, %%edi                          \n"
     "cpuid                                     \n"
@@ skipping 25 matching lines @@
 //    mov        xcr0, eax
 //  }
 // For VS2013 and earlier 32 bit, the _xgetbv(0) optimizer produces bad code.
 // https://code.google.com/p/libyuv/issues/detail?id=529
 #if defined(_M_IX86) && (_MSC_VER < 1900)
 #pragma optimize("g", off)
 #endif
 #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 GetXCR0() {
   uint32 xcr0 = 0u;
 #if defined(_MSC_FULL_VER) && (_MSC_FULL_VER >= 160040219)
   xcr0 = (uint32)(_xgetbv(0));  // VS2010 SP1 required.
 #elif defined(__i386__) || defined(__x86_64__)
   asm(".byte 0x0f, 0x01, 0xd0" : "=a" (xcr0) : "c" (0) : "%edx");
 #endif  // defined(__i386__) || defined(__x86_64__)
   return xcr0;
 }
+#else
+// xgetbv unavailable to query for OSSave support.  Return 0.
+#define GetXCR0() 0
 #endif  // defined(_M_IX86) || defined(_M_X64) ..
 // Return optimization to previous setting.
 #if defined(_M_IX86) && (_MSC_VER < 1900)
 #pragma optimize("g", on)
 #endif
 
 // based on libvpx arm_cpudetect.c
 // For Arm, but public to allow testing on any CPU
 LIBYUV_API SAFEBUFFERS
 int ArmCpuCaps(const char* cpuinfo_name) {
@@ skipping 73 matching lines @@
   return LIBYUV_FALSE;
 }
 #else  // nacl does not support getenv().
 static LIBYUV_BOOL TestEnv(const char*) {
   return LIBYUV_FALSE;
 }
 #endif
 
 LIBYUV_API SAFEBUFFERS
 int InitCpuFlags(void) {
-  // TODO(fbarchard): swap kCpuInit logic so 0 means uninitialized.
   int cpu_info = 0;
 #if !defined(__pnacl__) && !defined(__CLR_VER) && defined(CPU_X86)
   uint32 cpu_info0[4] = { 0, 0, 0, 0 };
   uint32 cpu_info1[4] = { 0, 0, 0, 0 };
   uint32 cpu_info7[4] = { 0, 0, 0, 0 };
   CpuId(0, 0, cpu_info0);
   CpuId(1, 0, cpu_info1);
   if (cpu_info0[0] >= 7) {
     CpuId(7, 0, cpu_info7);
   }
   cpu_info = kCpuHasX86 |
              ((cpu_info1[3] & 0x04000000) ? kCpuHasSSE2 : 0) |
              ((cpu_info1[2] & 0x00000200) ? kCpuHasSSSE3 : 0) |
              ((cpu_info1[2] & 0x00080000) ? kCpuHasSSE41 : 0) |
              ((cpu_info1[2] & 0x00100000) ? kCpuHasSSE42 : 0) |
              ((cpu_info7[1] & 0x00000200) ? kCpuHasERMS : 0);
 
-#ifdef HAS_XGETBV
-  // AVX requires CPU has AVX, XSAVE and OSXSave for xgetbv
+  // AVX requires OS saves YMM registers.
   if (((cpu_info1[2] & 0x1c000000) == 0x1c000000) &&  // AVX and OSXSave
       ((GetXCR0() & 6) == 6)) {  // Test OS saves YMM registers
     cpu_info |= kCpuHasAVX |
                 ((cpu_info7[1] & 0x00000020) ? kCpuHasAVX2 : 0) |
                 ((cpu_info1[2] & 0x00001000) ? kCpuHasFMA3 : 0) |
                 ((cpu_info1[2] & 0x20000000) ? kCpuHasF16C : 0);
 
     // Detect AVX512bw
     if ((GetXCR0() & 0xe0) == 0xe0) {
       cpu_info |= (cpu_info7[1] & 0x40000000) ? kCpuHasAVX3 : 0;
     }
   }
-#endif
 
   // Environment variable overrides for testing.
   if (TestEnv("LIBYUV_DISABLE_X86")) {
     cpu_info &= ~kCpuHasX86;
   }
   if (TestEnv("LIBYUV_DISABLE_SSE2")) {
     cpu_info &= ~kCpuHasSSE2;
   }
   if (TestEnv("LIBYUV_DISABLE_SSSE3")) {
     cpu_info &= ~kCpuHasSSSE3;
@@ skipping 71 matching lines @@
 // Note that use of this function is not thread safe.
 LIBYUV_API
 void MaskCpuFlags(int enable_flags) {
   cpu_info_ = InitCpuFlags() & enable_flags;
 }
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif