[turbofan] attempt to fix OOM caused by escape analysis

src/compiler/escape-analysis.cc

 // Copyright 2015 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/compiler/escape-analysis.h"
 
 #include <limits>
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
@@ skipping 235 matching lines @@
       changed = true;
       fields_[i] = other.fields_[i];
     }
   }
   return changed;
 }
 
 class VirtualState : public ZoneObject {
  public:
   VirtualState(Node* owner, Zone* zone, size_t size)
-      : info_(size, nullptr, zone), owner_(owner) {}
+      : info_(size, nullptr, zone),
+        initialized_(static_cast<int>(size), zone),
+        owner_(owner) {}
 
   VirtualState(Node* owner, const VirtualState& state)
       : info_(state.info_.size(), nullptr, state.info_.get_allocator().zone()),
+        initialized_(state.initialized_.length(),
+                     state.info_.get_allocator().zone()),
         owner_(owner) {
     for (size_t i = 0; i < info_.size(); ++i) {
       if (state.info_[i]) {
         info_[i] = state.info_[i];
       }
     }
   }
 
   VirtualObject* VirtualObjectFromAlias(size_t alias);
   void SetVirtualObject(Alias alias, VirtualObject* state);
   bool UpdateFrom(VirtualState* state, Zone* zone);
   bool MergeFrom(MergeCache* cache, Zone* zone, Graph* graph,
                  CommonOperatorBuilder* common, Node* at);
   size_t size() const { return info_.size(); }
   Node* owner() const { return owner_; }
   VirtualObject* Copy(VirtualObject* obj, Alias alias);
   void SetCopyRequired() {
     for (VirtualObject* obj : info_) {
       if (obj) obj->SetCopyRequired();
     }
   }
 
  private:
   ZoneVector<VirtualObject*> info_;
+  BitVector initialized_;
   Node* owner_;
 
   DISALLOW_COPY_AND_ASSIGN(VirtualState);
 };
 
 class MergeCache : public ZoneObject {
  public:
   explicit MergeCache(Zone* zone)
       : states_(zone), objects_(zone), fields_(zone) {
     states_.reserve(5);
@@ skipping 75 matching lines @@
   info_[alias] = new_obj;
   return new_obj;
 }
 
 VirtualObject* VirtualState::VirtualObjectFromAlias(size_t alias) {
   return info_[alias];
 }
 
 void VirtualState::SetVirtualObject(Alias alias, VirtualObject* obj) {
   info_[alias] = obj;
+  if (obj) initialized_.Add(alias);
 }
 
 bool VirtualState::UpdateFrom(VirtualState* from, Zone* zone) {
   if (from == this) return false;
   bool changed = false;
   for (Alias alias = 0; alias < size(); ++alias) {
     VirtualObject* ls = VirtualObjectFromAlias(alias);
     VirtualObject* rs = from->VirtualObjectFromAlias(alias);
 
     if (ls == rs || rs == nullptr) continue;
@@ skipping 132 matching lines @@
     size_t fields = std::numeric_limits<size_t>::max();
     for (VirtualState* state : cache->states()) {
       if (VirtualObject* obj = state->VirtualObjectFromAlias(alias)) {
         cache->objects().push_back(obj);
         if (mergeObject == obj) {
           copy_merge_object = true;
         }
         fields = std::min(obj->field_count(), fields);
       }
     }
-    if (cache->objects().size() == cache->states().size()) {
+    if (cache->objects().size() == cache->states().size() &&
+        (mergeObject || !initialized_.Contains(alias))) {
       bool initialMerge = false;
       if (!mergeObject) {
         initialMerge = true;
         VirtualObject* obj = new (zone)
             VirtualObject(cache->objects().front()->id(), this, zone, fields,
                           cache->objects().front()->IsInitialized());
         SetVirtualObject(alias, obj);
         mergeObject = obj;
         changed = true;
       } else if (copy_merge_object) {
@@ skipping 1187 matching lines @@
     }
   }
   return false;
 }
 
 Graph* EscapeAnalysis::graph() const { return status_analysis_->graph(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8