[turbofan] Preserve cached code across GCs.

src/heap/objects-visiting-inl.h

 // 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.
 
 #ifndef V8_OBJECTS_VISITING_INL_H_
 #define V8_OBJECTS_VISITING_INL_H_
 
 #include "src/heap/objects-visiting.h"
 
 namespace v8 {
@@ skipping 401 matching lines @@
       !shared->optimized_code_map()->IsSmi()) {
     // Always flush the optimized code map if requested by flag.
     shared->ClearOptimizedCodeMap();
   }
   MarkCompactCollector* collector = heap->mark_compact_collector();
   if (collector->is_code_flushing_enabled()) {
     if (!shared->optimized_code_map()->IsSmi()) {
       // Add the shared function info holding an optimized code map to
       // the code flusher for processing of code maps after marking.
       collector->code_flusher()->AddOptimizedCodeMap(shared);
-      // Treat all references within the code map weakly by marking the
+      // Treat some references within the code map weakly by marking the
       // code map itself but not pushing it onto the marking deque.
       FixedArray* code_map = FixedArray::cast(shared->optimized_code_map());
-      StaticVisitor::MarkObjectWithoutPush(heap, code_map);
+      MarkOptimizedCodeMap(heap, code_map);
     }
     if (IsFlushable(heap, shared)) {
       // This function's code looks flushable. But we have to postpone
       // the decision until we see all functions that point to the same
       // SharedFunctionInfo because some of them might be optimized.
       // That would also make the non-optimized version of the code
       // non-flushable, because it is required for bailing out from
       // optimized code.
       collector->code_flusher()->AddCandidate(shared);
       // Treat the reference to the code object weakly.
@@ skipping 146 matching lines @@
   }
 
   int num_transitions = TransitionArray::NumberOfTransitions(transitions);
   for (int i = 0; i < num_transitions; ++i) {
     StaticVisitor::VisitPointer(heap, transitions->GetKeySlot(i));
   }
 }
 
 
 template <typename StaticVisitor>
+void StaticMarkingVisitor<StaticVisitor>::MarkOptimizedCodeMap(
+    Heap* heap, FixedArray* code_map) {
+  if (!StaticVisitor::MarkObjectWithoutPush(heap, code_map)) return;
+
+  // Mark the context-independent entry in the optimized code map. Depending on
+  // the age of the code object, we treat it as a strong or a weak reference.
+  Object* shared_object = code_map->get(SharedFunctionInfo::kSharedCodeIndex);
+  if (FLAG_turbo_preserve_shared_code && shared_object->IsCode() &&
+      FLAG_age_code && !Code::cast(shared_object)->IsOld()) {
+    StaticVisitor::VisitPointer(
+        heap,
+        code_map->RawFieldOfElementAt(SharedFunctionInfo::kSharedCodeIndex));
+  }
+}
+
+
+template <typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::MarkInlinedFunctionsCode(Heap* heap,
                                                                    Code* code) {
   // For optimized functions we should retain both non-optimized version
   // of its code and non-optimized version of all inlined functions.
   // This is required to support bailing out from inlined code.
   DeoptimizationInputData* const data =
       DeoptimizationInputData::cast(code->deoptimization_data());
   FixedArray* const literals = data->LiteralArray();
   int const inlined_count = data->InlinedFunctionCount()->value();
   for (int i = 0; i < inlined_count; ++i) {
@@ skipping 233 matching lines @@
 
   RelocIterator it(this, mode_mask);
   for (; !it.done(); it.next()) {
     it.rinfo()->template Visit<StaticVisitor>(heap);
   }
 }
 }
 }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_VISITING_INL_H_