Revert of [compiler] Load elimination now traverses CheckTaggedPointer.

src/compiler/load-elimination.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/compiler/load-elimination.h"
 
 #include "src/compiler/graph.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/simplified-operator.h"
 #include "src/types.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 LoadElimination::~LoadElimination() {}
 
 Reduction LoadElimination::Reduce(Node* node) {
   switch (node->opcode()) {
     case IrOpcode::kLoadField:
       return ReduceLoadField(node);
     default:
       break;
   }
   return NoChange();
 }
 
-namespace {
-
-// If {node} is a CheckTaggedPointer, follow its input until {node} is no
-// longer a CheckTaggedPointer.
-Node* NormalizeCheckTaggedPointer(Node* node) {
-  while (node->opcode() == IrOpcode::kCheckTaggedPointer) {
-    node = NodeProperties::GetValueInput(node, 0);
-  }
-  return node;
-}
-
-}  // namespace
-
 Reduction LoadElimination::ReduceLoadField(Node* node) {
   DCHECK_EQ(IrOpcode::kLoadField, node->opcode());
   FieldAccess const access = FieldAccessOf(node->op());
   Node* object = NodeProperties::GetValueInput(node, 0);
   for (Node* effect = NodeProperties::GetEffectInput(node);;
        effect = NodeProperties::GetEffectInput(effect)) {
     switch (effect->opcode()) {
       case IrOpcode::kLoadField: {
         FieldAccess const effect_access = FieldAccessOf(effect->op());
         if (object == NodeProperties::GetValueInput(effect, 0) &&
             access == effect_access && effect_access.type->Is(access.type)) {
           Node* const value = effect;
           ReplaceWithValue(node, value);
           return Replace(value);
         }
         break;
       }
       case IrOpcode::kStoreField: {
         if (access == FieldAccessOf(effect->op())) {
-          Node* value_input = NormalizeCheckTaggedPointer(
-              NodeProperties::GetValueInput(effect, 0));
-          if (object == value_input) {
+          if (object == NodeProperties::GetValueInput(effect, 0)) {
             Node* const value = NodeProperties::GetValueInput(effect, 1);
             Type* stored_value_type = NodeProperties::GetType(value);
             Type* load_type = NodeProperties::GetType(node);
             // Make sure the replacement's type is a subtype of the node's
             // type. Otherwise we could confuse optimizations that were
             // based on the original type.
             if (stored_value_type->Is(load_type)) {
               ReplaceWithValue(node, value);
               return Replace(value);
             } else {
               Node* renamed = graph()->NewNode(
                   simplified()->TypeGuard(Type::Intersect(
                       stored_value_type, load_type, graph()->zone())),
                   value, NodeProperties::GetControlInput(node));
               ReplaceWithValue(node, renamed);
               return Replace(renamed);
             }
           }
           // TODO(turbofan): Alias analysis to the rescue?
           return NoChange();
         }
         break;
       }
       case IrOpcode::kBeginRegion:
       case IrOpcode::kStoreBuffer:
       case IrOpcode::kStoreElement: {
         // These can never interfere with field loads.
         break;
       }
-      case IrOpcode::kFinishRegion:
-      case IrOpcode::kCheckTaggedPointer: {
+      case IrOpcode::kFinishRegion: {
         // "Look through" FinishRegion nodes to make LoadElimination capable
         // of looking into atomic regions.
         if (object == effect) object = NodeProperties::GetValueInput(effect, 0);
         break;
       }
       case IrOpcode::kAllocate: {
         // Allocations don't interfere with field loads. In case we see the
         // actual allocation for the {object} we can abort.
         if (object == effect) return NoChange();
         break;
       }
       default: {
         if (!effect->op()->HasProperty(Operator::kNoWrite) ||
             effect->op()->EffectInputCount() != 1) {
           return NoChange();
         }
         break;
       }
     }
   }
   UNREACHABLE();
   return NoChange();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8