Use the cpuid instruction to generate the CPU brand string. And

use this string to check whether the cpu is Intel Atom processor.

This change is to make sure the 2D canvas acceleration is enabled
on Atom / windows system.

BUG=151500

Review URL: https://chromiumcodereview.appspot.com/11009011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@160226 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 25 insertions, 10 deletions

diff --git a/base/cpu.cc b/base/cpu.cc
index a077834..cf4f2f1 100644
--- a/base/cpu.cc
+++ b/base/cpu.cc
@@ -6,6 +6,8 @@
 
 #include <string.h>
 
+#include <algorithm>
+
 #include "build/build_config.h"
 
 #if defined(ARCH_CPU_X86_FAMILY)
@@ -84,22 +86,20 @@ void __cpuidex(int cpu_info[4], int info_type, int info_index) {
 void CPU::Initialize() {
 #if defined(ARCH_CPU_X86_FAMILY)
   int cpu_info[4] = {-1};
-  char cpu_string[0x20];
+  char cpu_string[48];
 
   // __cpuid with an InfoType argument of 0 returns the number of
   // valid Ids in CPUInfo[0] and the CPU identification string in
   // the other three array elements. The CPU identification string is
   // not in linear order. The code below arranges the information
-  // in a human readable form.
-  //
-  // More info can be found here:
-  // http://msdn.microsoft.com/en-us/library/hskdteyh.aspx
+  // in a human readable form. The human readable order is CPUInfo[1] |
+  // CPUInfo[3] | CPUInfo[2]. CPUInfo[2] and CPUInfo[3] are swapped
+  // before using memcpy to copy these three array elements to cpu_string.
   __cpuid(cpu_info, 0);
   int num_ids = cpu_info[0];
-  memset(cpu_string, 0, sizeof(cpu_string));
-  *(reinterpret_cast<int*>(cpu_string)) = cpu_info[1];
-  *(reinterpret_cast<int*>(cpu_string+4)) = cpu_info[3];
-  *(reinterpret_cast<int*>(cpu_string+8)) = cpu_info[2];
+  std::swap(cpu_info[2], cpu_info[3]);
+  memcpy(cpu_string, &cpu_info[1], 3 * sizeof(cpu_info[1]));
+  cpu_vendor_.assign(cpu_string, 3 * sizeof(cpu_info[1]));
 
   // Interpret CPU feature information.
   if (num_ids > 0) {
@@ -110,7 +110,6 @@ void CPU::Initialize() {
     type_ = (cpu_info[0] >> 12) & 0x3;
     ext_model_ = (cpu_info[0] >> 16) & 0xf;
     ext_family_ = (cpu_info[0] >> 20) & 0xff;
-    cpu_vendor_ = cpu_string;
     has_mmx_ = (cpu_info[3] & 0x00800000) != 0;
     has_sse_ = (cpu_info[3] & 0x02000000) != 0;
     has_sse2_ = (cpu_info[3] & 0x04000000) != 0;
@@ -119,6 +118,22 @@ void CPU::Initialize() {
     has_sse41_ = (cpu_info[2] & 0x00080000) != 0;
     has_sse42_ = (cpu_info[2] & 0x00100000) != 0;
   }
+
+  // Get the brand string of the cpu.
+  __cpuid(cpu_info, 0x80000000);
+  const int parameter_end = 0x80000004;
+
+  if (cpu_info[0] >= parameter_end) {
+    char* cpu_string_ptr = cpu_string;
+
+    for (int parameter = 0x80000002; parameter <= parameter_end &&
+         cpu_string_ptr < &cpu_string[sizeof(cpu_string)]; parameter++) {
+      __cpuid(cpu_info, parameter);
+      memcpy(cpu_string_ptr, cpu_info, sizeof(cpu_info));
+      cpu_string_ptr += sizeof(cpu_info);
+    }
+    cpu_brand_.assign(cpu_string, cpu_string_ptr - cpu_string);
+  }
 #endif
 }