provides a mechanism for optimizing compilers to select the different Register configuration.

src/register-configuration.cc

Index: src/register-configuration.cc
diff --git a/src/register-configuration.cc b/src/register-configuration.cc
index 084e735af1e9c2346af612984f4b9cdb2ac769e5..2a0d6afc56da0cf5b756e0dda4787b40171b5d62 100644
--- a/src/register-configuration.cc
+++ b/src/register-configuration.cc
@@ -44,6 +44,79 @@ class ArchDefaultRegisterConfiguration : public RegisterConfiguration {
             kMaxAllocatableDoubleRegisterCount,
             kMaxAllocatableDoubleRegisterCount,
 #elif V8_TARGET_ARCH_X87
+            kMaxAllocatableGeneralRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+#elif V8_TARGET_ARCH_X64
+            kMaxAllocatableGeneralRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+#elif V8_TARGET_ARCH_ARM
+            FLAG_enable_embedded_constant_pool
+                ? (kMaxAllocatableGeneralRegisterCount - 1)
+                : kMaxAllocatableGeneralRegisterCount,
+            CpuFeatures::IsSupported(VFP32DREGS)
+                ? kMaxAllocatableDoubleRegisterCount
+                : (ALLOCATABLE_NO_VFP32_DOUBLE_REGISTERS(REGISTER_COUNT)0),
+            ALLOCATABLE_NO_VFP32_DOUBLE_REGISTERS(REGISTER_COUNT)0,
+#elif V8_TARGET_ARCH_ARM64
+            kMaxAllocatableGeneralRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+#elif V8_TARGET_ARCH_MIPS
+            kMaxAllocatableGeneralRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+#elif V8_TARGET_ARCH_MIPS64
+            kMaxAllocatableGeneralRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+#elif V8_TARGET_ARCH_PPC
+            kMaxAllocatableGeneralRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+#else
+            GetAllocatableGeneralRegisterCount(),
+            GetAllocatableDoubleRegisterCount(),
+            GetAllocatableAliasedDoubleRegisterCount(),
+#endif
+            GetAllocatableGeneralCodes(), GetAllocatableDoubleCodes(),
+            kGeneralRegisterNames, kDoubleRegisterNames) {
+  }
+
+  const char* general_register_name_table_[Register::kNumRegisters];
+  const char* double_register_name_table_[DoubleRegister::kMaxNumRegisters];
+
+ private:
+  static const int* GetAllocatableGeneralCodes() {
+#define REGISTER_CODE(R) Register::kCode_##R,
+    static const int general_codes[] = {
+        ALLOCATABLE_GENERAL_REGISTERS(REGISTER_CODE)};
+#undef REGISTER_CODE
+    return general_codes;
+  }
+
+  static const int* GetAllocatableDoubleCodes() {
+#define REGISTER_CODE(R) DoubleRegister::kCode_##R,
+    static const int double_codes[] = {
+        ALLOCATABLE_DOUBLE_REGISTERS(REGISTER_CODE)};
+#undef REGISTER_CODE
+    return double_codes;
+  }
+};
+
+
+class ArchDefaultRegisterConfigurationForTurbofan
+    : public RegisterConfiguration {
+ public:
+  ArchDefaultRegisterConfigurationForTurbofan()
+      : RegisterConfiguration(
+            Register::kNumRegisters, DoubleRegister::kMaxNumRegisters,
+#if V8_TARGET_ARCH_IA32
+            kMaxAllocatableGeneralRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+            kMaxAllocatableDoubleRegisterCount,
+#elif V8_TARGET_ARCH_X87
             kMaxAllocatableGeneralRegisterCount, 1, 1,
 #elif V8_TARGET_ARCH_X64
             kMaxAllocatableGeneralRegisterCount,
@@ -107,6 +180,9 @@ class ArchDefaultRegisterConfiguration : public RegisterConfiguration {
 static base::LazyInstance<ArchDefaultRegisterConfiguration>::type
     kDefaultRegisterConfiguration = LAZY_INSTANCE_INITIALIZER;
 
+static base::LazyInstance<ArchDefaultRegisterConfigurationForTurbofan>::type
+    kDefaultRegisterConfigurationForTurbo = LAZY_INSTANCE_INITIALIZER;
+
 }  // namespace
 
 
@@ -114,6 +190,12 @@ const RegisterConfiguration* RegisterConfiguration::ArchDefault() {
   return &kDefaultRegisterConfiguration.Get();
 }
 
+
+const RegisterConfiguration* RegisterConfiguration::ArchDefaultForTurbo() {
+  return &kDefaultRegisterConfiguration.Get();
+}
+
+
 RegisterConfiguration::RegisterConfiguration(
     int num_general_registers, int num_double_registers,
     int num_allocatable_general_registers, int num_allocatable_double_registers,