[heap] Record references in the new code objects in heap::CopyCode.

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/context-slot-cache.h"
 #include "src/base/bits.h"
@@ skipping 3355 matching lines @@
 
   // Relocate the copy.
   DCHECK(IsAligned(bit_cast<intptr_t>(new_code->address()), kCodeAlignment));
   DCHECK(!memory_allocator()->code_range()->valid() ||
          memory_allocator()->code_range()->contains(code->address()) ||
          obj_size <= code_space()->AreaSize());
   new_code->Relocate(new_addr - old_addr);
   // We have to iterate over the object and process its pointers when black
   // allocation is on.
   incremental_marking()->IterateBlackObject(new_code);
+  // Record all references to embedded objects in the new code object.
+  for (RelocIterator it(new_code,

[Michael Lippautz, 2016/08/02 19:07:57]

That works, but ideally we would have fused visitor (together with the code in
IterateBlackObject). In the case that we copy a black object you need to visit
the reloc info twice, which is not ideal. Then again CopyCode might be rare
enough so that it does not matter.

Ulan, wdyt?

[ahaas, 2016/08/03 08:47:42]

I think that this would be an optimization that we should not do unless there
are actual performance reasons for it.

[ulan, 2016/08/03 10:59:32]

Yep, I would prefer decoding reloc info once. But for the sake of simplicity
let's keep it as it is unless benchmarks regress.

In any case, could you please extract new code into RecordWritesIntoCode
function?

+                        RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT));
+       !it.done(); it.next()) {
+    RecordWriteIntoCode(new_code, it.rinfo(), it.rinfo()->target_object());
+  }
   return new_code;
 }
 
 AllocationResult Heap::CopyBytecodeArray(BytecodeArray* bytecode_array) {
   int size = BytecodeArray::SizeFor(bytecode_array->length());
   HeapObject* result = nullptr;
   {
     AllocationResult allocation = AllocateRaw(size, OLD_SPACE);
     if (!allocation.To(&result)) return allocation;
   }
@@ skipping 3066 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8