Preserve optimized code map during GCs weakly.

src/mark-compact.cc

 // Copyright 2012 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 1036 matching lines @@
     isolate_->heap()->mark_compact_collector()->
         RecordSlot(code_slot, code_slot, *code_slot);
 
     candidate = next_candidate;
   }
 
   shared_function_info_candidates_head_ = NULL;
 }
 
 
+void CodeFlusher::ProcessOptimizedCodeMaps() {
+  static const int kEntriesStart = SharedFunctionInfo::kEntriesStart;
+  static const int kEntryLength = SharedFunctionInfo::kEntryLength;
+  STATIC_ASSERT(kEntryLength == 3);
+
+  SharedFunctionInfo* holder = optimized_code_map_holder_head_;
+  SharedFunctionInfo* next_holder;
+  while (holder != NULL) {
+    next_holder = GetNextCodeMap(holder);
+    ClearNextCodeMap(holder);
+
+    FixedArray* code_map = FixedArray::cast(holder->optimized_code_map());
+    int new_length = kEntriesStart;
+    int old_length = code_map->length();
+    for (int i = kEntriesStart; i < old_length; i += kEntryLength) {
+      Code* code = Code::cast(code_map->get(i + 1));

[Hannes Payer (out of office), 2013/05/15 13:11:25]

Can we use a constant like kCodeOffset = 1 here? The same comment would apply
for the the code_map->get calls below. I think it improves readability.

[Michael Starzinger, 2013/05/15 15:09:57]

Done.

+      MarkBit code_mark = Marking::MarkBitFrom(code);
+      if (!code_mark.Get()) {
+        continue;
+      }
+
+      // Update and record the context slot in the optimized code map.
+      Object** context_slot = HeapObject::RawField(code_map,
+          FixedArray::OffsetOfElementAt(new_length));
+      code_map->set(new_length++, code_map->get(i));

[Hannes Payer (out of office), 2013/05/15 13:11:25]

kContextOffset = 0

[Michael Starzinger, 2013/05/15 15:09:57]

Done.

+      ASSERT(Marking::IsBlack(
+          Marking::MarkBitFrom(HeapObject::cast(*context_slot))));
+      isolate_->heap()->mark_compact_collector()->
+          RecordSlot(context_slot, context_slot, *context_slot);
+
+      // Update and record the code slot in the optimized code map.
+      Object** code_slot = HeapObject::RawField(code_map,
+          FixedArray::OffsetOfElementAt(new_length));
+      code_map->set(new_length++, code_map->get(i + 1));

[Hannes Payer (out of office), 2013/05/15 13:11:25]

kCodeOffset = 1

[Michael Starzinger, 2013/05/15 15:09:57]

Done.

+      ASSERT(Marking::IsBlack(
+          Marking::MarkBitFrom(HeapObject::cast(*code_slot))));
+      isolate_->heap()->mark_compact_collector()->
+          RecordSlot(code_slot, code_slot, *code_slot);
+
+      // Update and record the literals slot in the optimized code map.
+      Object** literals_slot = HeapObject::RawField(code_map,
+          FixedArray::OffsetOfElementAt(new_length));
+      code_map->set(new_length++, code_map->get(i + 2));

[Hannes Payer (out of office), 2013/05/15 13:11:25]

kLiteralsOffset = 2

[Michael Starzinger, 2013/05/15 15:09:57]

Done.

+      ASSERT(Marking::IsBlack(
+          Marking::MarkBitFrom(HeapObject::cast(*literals_slot))));
+      isolate_->heap()->mark_compact_collector()->
+          RecordSlot(literals_slot, literals_slot, *literals_slot);
+    }
+
+    // Trim the optimized code map if entries have been removed.
+    if (new_length < old_length) {
+      holder->TrimOptimizedCodeMap(old_length - new_length);
+    }
+
+    holder = next_holder;
+  }
+
+  optimized_code_map_holder_head_ = NULL;
+}
+
+
 void CodeFlusher::EvictCandidate(SharedFunctionInfo* shared_info) {
   // Make sure previous flushing decisions are revisited.
   isolate_->heap()->incremental_marking()->RecordWrites(shared_info);
 
   SharedFunctionInfo* candidate = shared_function_info_candidates_head_;
   SharedFunctionInfo* next_candidate;
   if (candidate == shared_info) {
     next_candidate = GetNextCandidate(shared_info);
     shared_function_info_candidates_head_ = next_candidate;
     ClearNextCandidate(shared_info);
@@ skipping 38 matching lines @@
         ClearNextCandidate(function, undefined);
         break;
       }
 
       candidate = next_candidate;
     }
   }
 }
 
 
+void CodeFlusher::EvictOptimizedCodeMap(SharedFunctionInfo* code_map_holder) {
+  ASSERT(!FixedArray::cast(code_map_holder->optimized_code_map())->
+         get(SharedFunctionInfo::kNextMapIndex)->IsUndefined());
+
+  // Make sure previous flushing decisions are revisited.
+  isolate_->heap()->incremental_marking()->RecordWrites(code_map_holder);
+
+  SharedFunctionInfo* holder = optimized_code_map_holder_head_;
+  SharedFunctionInfo* next_holder;
+  if (holder == code_map_holder) {
+    next_holder = GetNextCodeMap(code_map_holder);
+    optimized_code_map_holder_head_ = next_holder;
+    ClearNextCodeMap(code_map_holder);
+  } else {
+    while (holder != NULL) {
+      next_holder = GetNextCodeMap(holder);
+
+      if (next_holder == code_map_holder) {
+        next_holder = GetNextCodeMap(code_map_holder);
+        SetNextCodeMap(holder, next_holder);
+        ClearNextCodeMap(code_map_holder);
+        break;
+      }
+
+      holder = next_holder;
+    }
+  }

[Hannes Payer (out of office), 2013/05/15 13:11:25]

A follow-up CL could refactor the list handling code.

[Michael Starzinger, 2013/05/15 15:09:57]

Agreed. If have two ideas for cleanup:
1) Come up with a OptimizedCodeMap class to handle all accesses.
2) Factor out the weak slot handling in the code-flusher and other places.

+}
+
+
 void CodeFlusher::EvictJSFunctionCandidates() {
   JSFunction* candidate = jsfunction_candidates_head_;
   JSFunction* next_candidate;
   while (candidate != NULL) {
     next_candidate = GetNextCandidate(candidate);
     EvictCandidate(candidate);
     candidate = next_candidate;
   }
   ASSERT(jsfunction_candidates_head_ == NULL);
 }
 
 
 void CodeFlusher::EvictSharedFunctionInfoCandidates() {
   SharedFunctionInfo* candidate = shared_function_info_candidates_head_;
   SharedFunctionInfo* next_candidate;
   while (candidate != NULL) {
     next_candidate = GetNextCandidate(candidate);
     EvictCandidate(candidate);
     candidate = next_candidate;
   }
   ASSERT(shared_function_info_candidates_head_ == NULL);
 }
 
 
+void CodeFlusher::EvictOptimizedCodeMaps() {
+  SharedFunctionInfo* holder = optimized_code_map_holder_head_;
+  SharedFunctionInfo* next_holder;
+  while (holder != NULL) {
+    next_holder = GetNextCodeMap(holder);
+    EvictOptimizedCodeMap(holder);
+    holder = next_holder;
+  }
+  ASSERT(optimized_code_map_holder_head_ == NULL);
+}
+
+
 void CodeFlusher::IteratePointersToFromSpace(ObjectVisitor* v) {
   Heap* heap = isolate_->heap();
 
   JSFunction** slot = &jsfunction_candidates_head_;
   JSFunction* candidate = jsfunction_candidates_head_;
   while (candidate != NULL) {
     if (heap->InFromSpace(candidate)) {
       v->VisitPointer(reinterpret_cast<Object**>(slot));
     }
     candidate = GetNextCandidate(*slot);
@@ skipping 2799 matching lines @@
 
   if (enable) {
     if (code_flusher_ != NULL) return;
     code_flusher_ = new CodeFlusher(isolate());
   } else {
     if (code_flusher_ == NULL) return;
     code_flusher_->EvictAllCandidates();
     delete code_flusher_;
     code_flusher_ = NULL;
   }
+
+  if (FLAG_trace_code_flushing) {
+    PrintF("[code-flushing is now %s]\n", enable ? "on" : "off");
+  }
 }
 
 
 // TODO(1466) ReportDeleteIfNeeded is not called currently.
 // Our profiling tools do not expect intersections between
 // code objects. We should either reenable it or change our tools.
 void MarkCompactCollector::ReportDeleteIfNeeded(HeapObject* obj,
                                                 Isolate* isolate) {
 #ifdef ENABLE_GDB_JIT_INTERFACE
   if (obj->IsCode()) {
@@ skipping 165 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal