Add code for CPU feature detection and use it to detect SSE3 and SSE 4.1.

runtime/vm/assembler_ia32.cc

Index: runtime/vm/assembler_ia32.cc
===================================================================
--- runtime/vm/assembler_ia32.cc	(revision 12828)
+++ runtime/vm/assembler_ia32.cc	(working copy)
@@ -16,8 +16,60 @@
 DEFINE_FLAG(bool, print_stop_message, true, "Print stop message.");
 DEFINE_FLAG(bool, code_comments, false,
             "Include comments into code and disassembly");
+DEFINE_FLAG(bool, use_sse41, true, "Use SSE 4.1 if available");
 
 
+bool CPUFeatures::sse3_supported_ = false;
+bool CPUFeatures::sse4_1_supported_ = false;
+#ifdef DEBUG
+bool CPUFeatures::initialized_ = false;
+#endif
+
+bool CPUFeatures::sse3_supported() {
+  DEBUG_ASSERT(initialized_);
+  return sse3_supported_;
+}
+
+
+bool CPUFeatures::sse4_1_supported() {
+  DEBUG_ASSERT(initialized_);
+  return sse4_1_supported_;
+}
+
+
+#define __ assembler.
+
+void CPUFeatures::InitOnce() {
+  Assembler assembler;
+  __ pushl(EBP);
+  __ pushl(EBX);
+  __ movl(EBP, ESP);
+  // Get feature information in ECX:EDX and return it in EDX:EAX.
+  __ movl(EAX, Immediate(1));
+  __ cpuid();
+  __ movl(EAX, EDX);
+  __ movl(EDX, ECX);
+  __ movl(ESP, EBP);
+  __ popl(EBX);
+  __ popl(EBP);
+  __ 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())();
+  sse3_supported_ = (features & kSSE3BitMask) != 0;
+  sse4_1_supported_ = (features & kSSE4_1BitMask) != 0;
+#ifdef DEBUG
+  initialized_ = true;
+#endif
+}
+
+#undef __
+
+
 class DirectCallRelocation : public AssemblerFixup {
  public:
   void Process(const MemoryRegion& region, int position) {
@@ -1307,6 +1359,13 @@
 }
 
 
+void Assembler::cpuid() {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitUint8(0x0F);
+  EmitUint8(0xA2);
+}
+
+
 void Assembler::CompareRegisters(Register a, Register b) {
   cmpl(a, b);
 }