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

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index 76ba3818c253fb48aa7df828bd0979c34dd5b034..df935796200683fee616554ce1815df758fdbe3c 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -14,6 +14,7 @@
 #include "base/at_exit.h"
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "base/cpu.h"
 #include "base/debug/trace_event.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
@@ -971,6 +972,19 @@ int ChromeBrowserMainParts::PreMainMessageLoopRunImpl() {
   StartMetricsRecording();
 #endif
 
+#if defined(ARCH_CPU_X86_FAMILY)

[apatrick_chromium, 2013/01/25 19:06:30]

Consider extracting this code to a function defined in another file and calling
it from here.

+  base::CPU cpu;
+  int arch = 0;
+  if (cpu.has_sse()) arch = 1;

[apatrick_chromium, 2013/01/25 19:06:30]

style nit: Drop body to its own line.

Also can you use an enum, make the last field be the number of fields (currently
8) and comment the enum with a warning that it must not be reordered and that it
must be kept in sync with histograms.xml?

+  if (cpu.has_sse2()) arch = 2;
+  if (cpu.has_sse3()) arch = 3;
+  if (cpu.has_ssse3()) arch = 4;
+  if (cpu.has_sse41()) arch = 5;
+  if (cpu.has_sse42()) arch = 6;
+  if (cpu.has_avx()) arch = 7;
+  UMA_HISTOGRAM_ENUMERATION("Platform.IntelMaxuArchSupport", arch, 8);

[apatrick_chromium, 2013/01/25 19:06:30]

A search for "Intel Maxu Arch" yields nothing. What is "Maxu"? Is it "Max"?

[whunt, 2013/01/30 23:53:11]

uArch is a very common (at least at Intel...) abbreviation for micro
architecture (following the m, u <- greek mu, p convention for mili, micro,
pico)  It doen't really work if you capitalize it.  I'll make Micro more
explicit.

+#endif // defined(ARCH_CPU_X86_FAMILY)
+
   // Create watchdog thread after creating all other threads because it will
   // watch the other threads and they must be running.
   browser_process_->watchdog_thread();