Add the concept of FloatRegister for all platforms.

src/x87/assembler-x87.h

Index: src/x87/assembler-x87.h
diff --git a/src/x87/assembler-x87.h b/src/x87/assembler-x87.h
index 69dab9c98b27bbbdc13cabf817563495230aad07..057201a637990402d96fe0ca5c69bba55efea521 100644
--- a/src/x87/assembler-x87.h
+++ b/src/x87/assembler-x87.h
@@ -74,6 +74,8 @@ namespace internal {
   V(stX_6)                  \
   V(stX_7)
 
+#define FLOAT_REGISTERS DOUBLE_REGISTERS
+
 #define ALLOCATABLE_DOUBLE_REGISTERS(V) \
   V(stX_0)                              \
   V(stX_1)                              \
@@ -145,8 +147,7 @@ GENERAL_REGISTERS(DECLARE_REGISTER)
 #undef DECLARE_REGISTER
 const Register no_reg = {Register::kCode_no_reg};
 
-
-struct DoubleRegister {
+struct X87Register {
   enum Code {
 #define REGISTER_CODE(R) kCode_##R,
     DOUBLE_REGISTERS(REGISTER_CODE)
@@ -158,8 +159,8 @@ struct DoubleRegister {
   static const int kMaxNumRegisters = Code::kAfterLast;
   static const int kMaxNumAllocatableRegisters = 6;
 
-  static DoubleRegister from_code(int code) {
-    DoubleRegister result = {code};
+  static X87Register from_code(int code) {
+    X87Register result = {code};
     return result;
   }
 
@@ -171,24 +172,26 @@ struct DoubleRegister {
     return reg_code;
   }
 
-  bool is(DoubleRegister reg) const { return reg_code == reg.reg_code; }
+  bool is(X87Register reg) const { return reg_code == reg.reg_code; }
 
   const char* ToString();
 
   int reg_code;
 };
 
+typedef X87Register FloatRegister;
+
+typedef X87Register DoubleRegister;
+
+// TODO(x87) Define SIMD registers.
+typedef X87Register Simd128Register;
+
 #define DECLARE_REGISTER(R) \
   const DoubleRegister R = {DoubleRegister::kCode_##R};
 DOUBLE_REGISTERS(DECLARE_REGISTER)
 #undef DECLARE_REGISTER
 const DoubleRegister no_double_reg = {DoubleRegister::kCode_no_reg};
 
-typedef DoubleRegister X87Register;
-
-// TODO(x87) Define SIMD registers.
-typedef DoubleRegister Simd128Register;
-
 enum Condition {
   // any value < 0 is considered no_condition
   no_condition  = -1,