Adds AVX detection to CPU and records a histogram of Intel uArch Support

base/cpu.cc

Index: base/cpu.cc
diff --git a/base/cpu.cc b/base/cpu.cc
index cf4f2f1e496346c7ceea9dfcbe46d36f8cc4e48e..0f95c2006208581536a1c3b6d6c27060249a105c 100644
--- a/base/cpu.cc
+++ b/base/cpu.cc
@@ -117,6 +117,7 @@ void CPU::Initialize() {
     has_ssse3_ = (cpu_info[2] & 0x00000200) != 0;
     has_sse41_ = (cpu_info[2] & 0x00080000) != 0;
     has_sse42_ = (cpu_info[2] & 0x00100000) != 0;
+    has_avx_ = (cpu_info[2] & 0x10000000) != 0;
   }
 
   // Get the brand string of the cpu.
@@ -137,4 +138,16 @@ void CPU::Initialize() {
 #endif
 }
 
+CPU::IntelMicroArchitecture CPU::getIntelMicroArchitecture() const {
+  IntelMicroArchitecture arch = Pentium;

[brettw, 2013/01/31 20:08:43]

This seems weird. It looks like if the processor supports all of these things,
you'll execute every one overwriting the result. I guess it's correct but it
looks like a bug. I think it would be clearer to invert and do 

if (has_avx()) return AVX;
if (has_sse42()) return SSE42;
...

+  if (has_sse()) arch = SSE;
+  if (has_sse2()) arch = SSE2;
+  if (has_sse3()) arch = SSE3;
+  if (has_ssse3()) arch = SSSE3;
+  if (has_sse41()) arch = SSE41;
+  if (has_sse42()) arch = SSE42;
+  if (has_avx()) arch = AVX;
+  return arch;
+}
+
 }  // namespace base