[turbofan] Properly merge compatible field access infos.

src/compiler/access-info.cc

 // Copyright 2015 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 <ostream>
 
 #include "src/accessors.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-info.h"
 #include "src/compiler/type-cache.h"
@@ skipping 127 matching lines @@
                                AccessMode access_mode, Zone* zone) {
   if (this->kind_ != that->kind_) return false;
   if (this->holder_.address() != that->holder_.address()) return false;
 
   switch (this->kind_) {
     case kInvalid:
       break;
 
     case kDataField:
     case kDataConstantField: {
-      // Check if we actually access the same field.
-      if (this->kind_ == that->kind_ &&
-          this->field_index_ == that->field_index_) {
+      // Check if we actually access the same field (we use the
+      // GetFieldAccessStubKey method here just like the ICs do
+      // since that way we only compare the relevant bits of the
+      // field indices).
+      if (this->field_index_.GetFieldAccessStubKey() ==
+          that->field_index_.GetFieldAccessStubKey()) {
         switch (access_mode) {
           case AccessMode::kLoad: {
             if (this->field_representation_ != that->field_representation_) {
               if (!IsAnyTagged(this->field_representation_) ||
                   !IsAnyTagged(that->field_representation_)) {
                 return false;
               }
               this->field_representation_ = MachineRepresentation::kTagged;
             }
             if (this->field_map_.address() != that->field_map_.address()) {
@@ skipping 486 matching lines @@
   }
   return false;
 }
 
 
 Factory* AccessInfoFactory::factory() const { return isolate()->factory(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8