Refactors CPU feature detection.

runtime/vm/cpu_x64.cc

Index: runtime/vm/cpu_x64.cc
===================================================================
--- runtime/vm/cpu_x64.cc	(revision 31402)
+++ runtime/vm/cpu_x64.cc	(working copy)
@@ -8,13 +8,18 @@
 
 #include "vm/cpu.h"
 
+#include "vm/assembler.h"
 #include "vm/constants_x64.h"
+#include "vm/cpuinfo.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
 #include "vm/object.h"
 
 namespace dart {
 
+DEFINE_FLAG(bool, use_sse41, true, "Use SSE 4.1 if available");
+
+
 void CPU::FlushICache(uword start, uword size) {
   // Nothing to be done here.
 }
@@ -24,6 +29,62 @@
   return "x64";
 }
 
+
+bool CPUFeatures::sse4_1_supported_ = false;
+char CPUFeatures::hardware_[HARDWARE_LEN] = {0};
+#ifdef DEBUG
+bool CPUFeatures::initialized_ = false;
+#endif
+
+
+bool CPUFeatures::sse4_1_supported() {
+  DEBUG_ASSERT(initialized_);
+  return sse4_1_supported_ && FLAG_use_sse41;
+}
+
+
+char* CPUFeatures::hardware() {
+  DEBUG_ASSERT(initialized_);
+  return hardware_;
+}
+
+
+#define __ assembler.
+void CPUFeatures::InitOnce() {
+  Assembler assembler;
+  __ pushq(RBP);
+  __ pushq(RBX);
+  __ movq(RBP, RSP);
+  // Get feature information in ECX:EDX and return it in RAX.
+  // Note that cpuid operates the same in 64-bit and 32-bit mode.
+  __ movq(RAX, Immediate(1));
+  __ cpuid();
+  __ movl(RAX, RCX);  // Zero extended.
+  __ shlq(RAX, Immediate(32));
+  __ movl(RCX, RDX);  // Zero extended.
+  __ orq(RAX, RCX);
+  __ movq(RSP, RBP);
+  __ popq(RBX);
+  __ popq(RBP);
+  __ ret();
+
+  const Code& code =
+      Code::Handle(Code::FinalizeCode("DetectCPUFeatures", &assembler));
+  Instructions& instructions = Instructions::Handle(code.instructions());
+  typedef uint64_t (*DetectCPUFeatures)();
+  uint64_t features =
+      reinterpret_cast<DetectCPUFeatures>(instructions.EntryPoint())();
+  sse4_1_supported_ = (features & kSSE4_1BitMask) != 0;
+
+  CpuInfo::Read();
+  CpuInfo::GetCpuModel(hardware_, HARDWARE_LEN);
+
+#ifdef DEBUG
+  initialized_ = true;
+#endif
+}
+#undef __
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64