Introduce HTransitionElementsKind instruction.

src/hydrogen.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4083 matching lines @@
   AddInstruction(HCheckInstanceType::NewIsSpecObject(object));
   SmallMapList* maps = prop->GetReceiverTypes();
   bool todo_external_array = false;
 
   static const int kNumElementTypes = kElementsKindCount;
   bool type_todo[kNumElementTypes];
   for (int i = 0; i < kNumElementTypes; ++i) {
     type_todo[i] = false;
   }
 
-  for (int i = 0; i < maps->length(); ++i) {
-    ASSERT(maps->at(i)->IsMap());
-    type_todo[maps->at(i)->elements_kind()] = true;
-    if (maps->at(i)->elements_kind()
-        >= FIRST_EXTERNAL_ARRAY_ELEMENTS_KIND) {
-      todo_external_array = true;
+  // Elements_kind transition support.
+  MapList transition_target(maps->length());
+  if (is_store) {
+    // Collect possible transition targets.
+    MapList possible_transitioned_maps(maps->length());
+    for (int i = 0; i < maps->length(); ++i) {
+      Handle<Map> map = maps->at(i);
+      ElementsKind elements_kind = map->elements_kind();
+      if (elements_kind == FAST_DOUBLE_ELEMENTS ||
+          elements_kind == FAST_ELEMENTS) {
+        possible_transitioned_maps.Add(*map);
+      }
+    }
+    // Get transition target for each map (NULL == no transition).
+    for (int i = 0; i < maps->length(); ++i) {
+      Handle<Map> map = maps->at(i);
+      Map* transitioned_map =
+          map->FindTransitionedMap(&possible_transitioned_maps);
+      transition_target.Add(transitioned_map);
     }
   }
 
+  for (int i = 0; i < maps->length(); ++i) {
+    Handle<Map> map = maps->at(i);
+    ASSERT(map->IsMap());
+    ASSERT(!is_store || (transition_target.length() == maps->length()));
+    if (is_store && transition_target.at(i) != NULL) {
+      object = AddInstruction(new(zone()) HTransitionElementsKind(
+          object, map, Handle<Map>(transition_target.at(i))));
+    } else {
+      type_todo[map->elements_kind()] = true;
+      if (map->elements_kind() >= FIRST_EXTERNAL_ARRAY_ELEMENTS_KIND) {
+        todo_external_array = true;
+      }
+    }
+  }
+
   HBasicBlock* join = graph()->CreateBasicBlock();
 
   HInstruction* elements_kind_instr =
       AddInstruction(new(zone()) HElementsKind(object));
   HCompareConstantEqAndBranch* elements_kind_branch = NULL;
   HInstruction* elements = AddInstruction(new(zone()) HLoadElements(object));
   HLoadExternalArrayPointer* external_elements = NULL;
   HInstruction* checked_key = NULL;
 
   // Generated code assumes that FAST_SMI_ONLY_ELEMENTS, FAST_ELEMENTS,
@@ skipping 2816 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal