Allow merging of monomorphic accesses to tracked fields.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 075fb1bb93e4b66b6f2228e284b675389e961923..7094cab29ea5acd180025e2b4148d524a9ba8c9c 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -6144,8 +6144,22 @@ class HLoadNamedField V8_FINAL : public HTemplateInstruction<2> {
  public:
   DECLARE_INSTRUCTION_FACTORY_P3(HLoadNamedField, HValue*, HValue*,
                                  HObjectAccess);
-  DECLARE_INSTRUCTION_FACTORY_P4(HLoadNamedField, HValue*, HValue*,
-                                 HObjectAccess, Handle<Map>);
+  static HLoadNamedField* New(Zone* zone, HValue* context,
+                              HValue* object, HValue* dependency,
+                              HObjectAccess access, SmallMapList* maps,
+                              CompilationInfo* info) {
+    HLoadNamedField* load_named_field = HLoadNamedField::New(
+        zone, context, object, dependency, access);
+    for (int i = 0; i < maps->length(); ++i) {
+      Handle<Map> map(maps->at(i));
+      load_named_field->map_set_.Add(Unique<Map>(map), zone);
+      if (map->CanTransition()) {
+        Map::AddDependentCompilationInfo(
+            map, DependentCode::kPrototypeCheckGroup, info);
+      }
+    }
+    return load_named_field;
+  }
 
   HValue* object() { return OperandAt(0); }
   HValue* dependency() {
@@ -6158,7 +6172,7 @@ class HLoadNamedField V8_FINAL : public HTemplateInstruction<2> {
       return access_.representation();
   }
 
-  Unique<Map> map() const { return map_; }
+  UniqueSet<Map> map_set() const { return map_set_; }
 
   virtual bool HasEscapingOperandAt(int index) V8_OVERRIDE { return false; }
   virtual bool HasOutOfBoundsAccess(int size) V8_OVERRIDE {
@@ -6179,7 +6193,7 @@ class HLoadNamedField V8_FINAL : public HTemplateInstruction<2> {
  protected:
   virtual bool DataEquals(HValue* other) V8_OVERRIDE {
     HLoadNamedField* b = HLoadNamedField::cast(other);
-    return access_.Equals(b->access_) && map_ == b->map_;
+    return access_.Equals(b->access_) && this->map_set_.Equals(&b->map_set_);
   }
 
  private:
@@ -6187,7 +6201,7 @@ class HLoadNamedField V8_FINAL : public HTemplateInstruction<2> {
                   HValue* dependency,
                   HObjectAccess access,
                   Handle<Map> map = Handle<Map>::null())
-      : access_(access), map_(map) {
+      : access_(access) {
     ASSERT(object != NULL);
     SetOperandAt(0, object);
     SetOperandAt(1, dependency != NULL ? dependency : object);
@@ -6221,7 +6235,7 @@ class HLoadNamedField V8_FINAL : public HTemplateInstruction<2> {
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 
   HObjectAccess access_;
-  Unique<Map> map_;
+  UniqueSet<Map> map_set_;
 };