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

src/register-configuration.h

Index: src/register-configuration.h
diff --git a/src/register-configuration.h b/src/register-configuration.h
index f12bc7c07c6dfb4beb79477f5a88ce16502b4c71..bd162cc82457ff067001218a77b0fca22ff8b587 100644
--- a/src/register-configuration.h
+++ b/src/register-configuration.h
@@ -34,13 +34,25 @@ class RegisterConfiguration {
   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 {