Add flags for write barrier elimination and local allocation folding.

src/hydrogen-instructions.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 3366 matching lines @@
 
   // Try to fold allocations together with their dominating allocations.
   if (!dominator->IsAllocate()) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s)\n",
           id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
     }
     return;
   }
 
+  // Check whether we are folding within the same block for local folding.
+  if (FLAG_use_local_allocation_folding && dominator->block() != block()) {
+    if (FLAG_trace_allocation_folding) {
+      PrintF("#%d (%s) cannot fold into #%d (%s), crosses basic blocks\n",
+          id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
+    }
+    return;
+  }
+
   HAllocate* dominator_allocate = HAllocate::cast(dominator);
   HValue* dominator_size = dominator_allocate->size();
   HValue* current_size = size();
 
   // TODO(hpayer): Add support for non-constant allocation in dominator.
   if (!current_size->IsInteger32Constant() ||
       !dominator_size->IsInteger32Constant()) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s), dynamic allocation size\n",
           id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
@@ skipping 1019 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal