Make maps in monomorphic IC stubs weak.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index f04a8bcb9a64105a496b8e4926cc833d06b7bc3a..69021095e30c13903b940e09d3e6fea2ae6b80ce 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -449,7 +449,7 @@ void MarkCompactCollector::CollectGarbage() {
 
 #ifdef VERIFY_HEAP
   if (heap()->weak_embedded_objects_verification_enabled()) {
-    VerifyWeakEmbeddedObjectsInOptimizedCode();
+    VerifyWeakEmbeddedObjectsInCode();
   }
   if (FLAG_collect_maps && FLAG_omit_map_checks_for_leaf_maps) {
     VerifyOmittedMapChecks();
@@ -510,13 +510,13 @@ void MarkCompactCollector::VerifyMarkbitsAreClean() {
 }
 
 
-void MarkCompactCollector::VerifyWeakEmbeddedObjectsInOptimizedCode() {
+void MarkCompactCollector::VerifyWeakEmbeddedObjectsInCode() {
   HeapObjectIterator code_iterator(heap()->code_space());
   for (HeapObject* obj = code_iterator.Next();
        obj != NULL;
        obj = code_iterator.Next()) {
     Code* code = Code::cast(obj);
-    if (code->kind() != Code::OPTIMIZED_FUNCTION) continue;
+    if (!code->is_optimized_code() && !code->is_weak_stub()) continue;
     if (WillBeDeoptimized(code)) continue;
     code->VerifyEmbeddedObjectsDependency();
   }
@@ -2582,9 +2582,11 @@ void MarkCompactCollector::ClearNonLiveReferences() {
 
     if (map_mark.Get()) {
       ClearNonLiveDependentCode(map->dependent_code());
+      ClearNonLiveDependentIC(map);
     } else {
       ClearAndDeoptimizeDependentCode(map->dependent_code());
       map->set_dependent_code(DependentCode::cast(heap()->empty_fixed_array()));
+      ClearAndInvalidateDependentIC(map);
     }
   }
 
@@ -2765,6 +2767,32 @@ void MarkCompactCollector::ClearNonLiveDependentCode(DependentCode* entries) {
 }
 
 
+void MarkCompactCollector::ClearAndInvalidateDependentIC(Map* map) {
+  Object* current = map->dependent_ic();
+  Object* undefined = heap()->undefined_value();
+  while (current != undefined) {
+    Code* code = Code::cast(current);
+    if (IsMarked(code)) {
+      ASSERT(code->is_weak_stub());
+      IC::InvalidateMaps(code);
+    }
+    current = code->next_code_link();
+    code->set_next_code_link(undefined);
+  }
+  map->set_dependent_ic(undefined);
+}
+
+
+void MarkCompactCollector::ClearNonLiveDependentIC(Map* map) {
+  MarkCompactWeakObjectRetainer retainer;
+  Object* head =
+      VisitWeakList<Code>(heap(), map->dependent_ic(), &retainer, true);
+  map->set_dependent_ic(head);
+  Object** slot = HeapObject::RawField(map, Map::kDependentICOffset);
+  RecordSlot(slot, slot, head);
+}
+
+
 void MarkCompactCollector::ProcessWeakCollections() {
   GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_WEAKCOLLECTION_PROCESS);
   Object* weak_collection_obj = encountered_weak_collections();
@@ -3409,7 +3437,7 @@ void MarkCompactCollector::InvalidateCode(Code* code) {
 
 // Return true if the given code is deoptimized or will be deoptimized.
 bool MarkCompactCollector::WillBeDeoptimized(Code* code) {
-  return code->marked_for_deoptimization();
+  return code->is_optimized_code() && code->marked_for_deoptimization();
 }