Revert of Remove register index/code indirection

src/mips64/macro-assembler-mips64.h

Index: src/mips64/macro-assembler-mips64.h
diff --git a/src/mips64/macro-assembler-mips64.h b/src/mips64/macro-assembler-mips64.h
index f138179f39c1ff7dcef9dc8f7a4b852b7d0c2da3..3d1cbe35f21119323e39574babbb7c7eb9cc5227 100644
--- a/src/mips64/macro-assembler-mips64.h
+++ b/src/mips64/macro-assembler-mips64.h
@@ -13,17 +13,17 @@
 namespace internal {
 
 // Give alias names to registers for calling conventions.
-const Register kReturnRegister0 = {Register::kCode_v0};
-const Register kReturnRegister1 = {Register::kCode_v1};
-const Register kJSFunctionRegister = {Register::kCode_a1};
-const Register kContextRegister = {Register::kCpRegister};
-const Register kInterpreterAccumulatorRegister = {Register::kCode_v0};
-const Register kInterpreterRegisterFileRegister = {Register::kCode_a7};
-const Register kInterpreterBytecodeOffsetRegister = {Register::kCode_t0};
-const Register kInterpreterBytecodeArrayRegister = {Register::kCode_t1};
-const Register kInterpreterDispatchTableRegister = {Register::kCode_t2};
-const Register kRuntimeCallFunctionRegister = {Register::kCode_a1};
-const Register kRuntimeCallArgCountRegister = {Register::kCode_a0};
+const Register kReturnRegister0 = {kRegister_v0_Code};
+const Register kReturnRegister1 = {kRegister_v1_Code};
+const Register kJSFunctionRegister = {kRegister_a1_Code};
+const Register kContextRegister = {kRegister_s7_Code};
+const Register kInterpreterAccumulatorRegister = {kRegister_v0_Code};
+const Register kInterpreterRegisterFileRegister = {kRegister_a7_Code};
+const Register kInterpreterBytecodeOffsetRegister = {kRegister_t0_Code};
+const Register kInterpreterBytecodeArrayRegister = {kRegister_t1_Code};
+const Register kInterpreterDispatchTableRegister = {kRegister_t2_Code};
+const Register kRuntimeCallFunctionRegister = {kRegister_a1_Code};
+const Register kRuntimeCallArgCountRegister = {kRegister_a0_Code};
 
 // Forward declaration.
 class JumpTarget;