Tighten the interface to the optimized code map

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index bef6dba7932e0297f3471f22b7829395c6379a24..8b6afc36bb09463c51921ad344ac81ffc4df1000 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -11989,7 +11989,7 @@ void SharedFunctionInfo::AddSharedCodeToOptimizedCodeMap(
 }
 
 
-void SharedFunctionInfo::AddToOptimizedCodeMap(
+void SharedFunctionInfo::AddToOptimizedCodeMapInternal(
     Handle<SharedFunctionInfo> shared, Handle<Context> native_context,
     Handle<HeapObject> code, Handle<LiteralsArray> literals,
     BailoutId osr_ast_id) {
@@ -12001,6 +12001,7 @@ void SharedFunctionInfo::AddToOptimizedCodeMap(
          Code::cast(*code)->kind() == Code::OPTIMIZED_FUNCTION);
   DCHECK(native_context->IsNativeContext());
   STATIC_ASSERT(kEntryLength == 4);
+  Handle<FixedArray> old_code_map(shared->optimized_code_map(), isolate);
   Handle<FixedArray> new_code_map;
   int entry;
 
@@ -12010,19 +12011,21 @@ void SharedFunctionInfo::AddToOptimizedCodeMap(
                       SKIP_WRITE_BARRIER);
     entry = kEntriesStart;
   } else {
-    Handle<FixedArray> old_code_map(shared->optimized_code_map(), isolate);
     entry = shared->SearchOptimizedCodeMapEntry(*native_context, osr_ast_id);
     if (entry > kSharedCodeIndex) {
-      // Found an existing context-specific entry, it must not contain any code.
-      DCHECK(WeakCell::cast(old_code_map->get(entry + kCachedCodeOffset))
+      // Found an existing context-specific entry. If the user provided valid
+      // code, it must not contain any code.
+      DCHECK(code->IsUndefined() ||
+             WeakCell::cast(old_code_map->get(entry + kCachedCodeOffset))
                  ->cleared());
+
       // Just set the code and literals to the entry.
-      Handle<WeakCell> code_cell = code->IsUndefined()
-                                       ? isolate->factory()->empty_weak_cell()
-                                       : isolate->factory()->NewWeakCell(code);
+      if (!code->IsUndefined()) {
+        Handle<WeakCell> code_cell = isolate->factory()->NewWeakCell(code);
+        old_code_map->set(entry + kCachedCodeOffset, *code_cell);
+      }
       Handle<WeakCell> literals_cell =
           isolate->factory()->NewWeakCell(literals);
-      old_code_map->set(entry + kCachedCodeOffset, *code_cell);
       old_code_map->set(entry + kLiteralsOffset, *literals_cell);
       return;
     }
@@ -12051,15 +12054,20 @@ void SharedFunctionInfo::AddToOptimizedCodeMap(
     }
   }
 
-  Handle<WeakCell> code_cell = code->IsUndefined()
-                                   ? isolate->factory()->empty_weak_cell()
-                                   : isolate->factory()->NewWeakCell(code);
-  Handle<WeakCell> literals_cell = isolate->factory()->NewWeakCell(literals);
   WeakCell* context_cell = native_context->self_weak_cell();
-
   new_code_map->set(entry + kContextOffset, context_cell);
-  new_code_map->set(entry + kCachedCodeOffset, *code_cell);
+
+  bool created_new_map = !old_code_map.is_identical_to(new_code_map);
+  if (!code->IsUndefined() || created_new_map) {
+    Handle<WeakCell> code_cell = code->IsUndefined()
+                                     ? isolate->factory()->empty_weak_cell()
+                                     : isolate->factory()->NewWeakCell(code);
+    new_code_map->set(entry + kCachedCodeOffset, *code_cell);
+  }
+
+  Handle<WeakCell> literals_cell = isolate->factory()->NewWeakCell(literals);
   new_code_map->set(entry + kLiteralsOffset, *literals_cell);
+
   new_code_map->set(entry + kOsrAstIdOffset, Smi::FromInt(osr_ast_id.ToInt()));
 
 #ifdef DEBUG
@@ -12076,8 +12084,7 @@ void SharedFunctionInfo::AddToOptimizedCodeMap(
   }
 #endif
 
-  FixedArray* old_code_map = shared->optimized_code_map();
-  if (old_code_map != *new_code_map) {
+  if (created_new_map) {
     shared->set_optimized_code_map(*new_code_map);
   }
 }