Config double register number as 1 for X87 Turbofan.

src/x64/assembler-x64.h

Index: src/x64/assembler-x64.h
diff --git a/src/x64/assembler-x64.h b/src/x64/assembler-x64.h
index cb52541b5690ffbeb4e36ad282d7282a1429be57..3c3590465f8780b8b5f333baaae4e32fc69bb05e 100644
--- a/src/x64/assembler-x64.h
+++ b/src/x64/assembler-x64.h
@@ -208,6 +208,14 @@ struct XMMRegister {
     return NumAllocatableRegisters();
   }
 
+  static int NumAllocatableRegistersForTurbo() {
+    return kMaxNumAllocatableRegisters;
+  }
+
+  static int NumAllocatableAliasedRegistersForTurbo() {
+    return NumAllocatableAliasedRegisters();
+  }
+
   static int ToAllocationIndex(XMMRegister reg) {
     DCHECK(reg.code() != 0);
     return reg.code() - 1;