Revert of Reland: Remove register index/code indirection

src/compiler/linkage.cc

 // 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.
 
 #include "src/code-stubs.h"
 #include "src/compiler.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/frame.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/node.h"
 #include "src/compiler/osr.h"
 #include "src/compiler/pipeline.h"
 #include "src/scopes.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 namespace {
 LinkageLocation regloc(Register reg) {
-  return LinkageLocation::ForRegister(reg.code());
+  return LinkageLocation::ForRegister(Register::ToAllocationIndex(reg));
 }
 
 
 MachineType reptyp(Representation representation) {
   switch (representation.kind()) {
     case Representation::kInteger8:
       return kMachInt8;
     case Representation::kUInteger8:
       return kMachUint8;
     case Representation::kInteger16:
@@ skipping 493 matching lines @@
     return LinkageLocation::ForCalleeFrameSlot(spill_index);
   } else {
     // Parameter. Use the assigned location from the incoming call descriptor.
     int parameter_index = 1 + index;  // skip index 0, which is the target.
     return incoming_->GetInputLocation(parameter_index);
   }
 }
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8