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

src/register-configuration.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_REGISTER_CONFIGURATION_H_
 #define V8_COMPILER_REGISTER_CONFIGURATION_H_
 
 #include "src/base/macros.h"
 
 namespace v8 {
@@ skipping 16 matching lines @@
                         const int* allocatable_general_codes,
                         const int* allocatable_double_codes,
                         char const* const* general_names,
                         char const* const* double_names);
 
   int num_general_registers() const { return num_general_registers_; }
   int num_double_registers() const { return num_double_registers_; }
   int num_allocatable_general_registers() const {
     return num_allocatable_general_registers_;
   }
-  int num_allocatable_double_registers() const {
+  int num_allocatable_double_registers(bool for_turbo = false) const {
+#if V8_TARGET_ARCH_X87

[titzer, 2015/10/15 16:44:43]

Seems like this check should be moved to the ArchDefault() method.

+    // TODO(X87): Currently Trubofan for X87 uses only one double register.
+    // But crankshaft for X87 has to use more than 1 double register. We
+    // use this temporary solution to return different allocatable double
+    // register number for different compilers and we will unify the number
+    // Turbofan and Crankshaft.
+    return for_turbo ? 1 : num_allocatable_double_registers_;
+#endif
     return num_allocatable_double_registers_;
   }
   // TODO(turbofan): This is a temporary work-around required because our
   // register allocator does not yet support the aliasing of single/double
   // registers on ARM.
-  int num_allocatable_aliased_double_registers() const {
+  int num_allocatable_aliased_double_registers(bool for_turbo = false) const {
+#if V8_TARGET_ARCH_X87
+    // Same reason as num_allocatable_double_registers() function.
+    return for_turbo ? 1 : num_allocatable_aliased_double_registers_;
+#endif
     return num_allocatable_aliased_double_registers_;
   }
   int32_t allocatable_general_codes_mask() const {
     return allocatable_general_codes_mask_;
   }
   int32_t allocatable_double_codes_mask() const {
     return allocatable_double_codes_mask_;
   }
   int GetAllocatableGeneralCode(int index) const {
     return allocatable_general_codes_[index];
@@ skipping 25 matching lines @@
   const int* allocatable_general_codes_;
   const int* allocatable_double_codes_;
   char const* const* general_register_names_;
   char const* const* double_register_names_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_REGISTER_CONFIGURATION_H_