Allocation folding integrated into the GVN phase.

src/hydrogen.cc

 // Copyright 2013 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 645 matching lines @@
   }                                                                            \
   return constant_##name##_.get();                                             \
 }
 
 
 DEFINE_GET_CONSTANT(True, true, HType::Boolean(), true)
 DEFINE_GET_CONSTANT(False, false, HType::Boolean(), false)
 DEFINE_GET_CONSTANT(Hole, the_hole, HType::Tagged(), false)
 DEFINE_GET_CONSTANT(Null, null, HType::Tagged(), false)
 
+HConstant* HGraph::GetConstantFreeSpaceMap() {
+  if (!constant_free_space_map_.is_set()) {
+    HConstant* constant = new(zone()) HConstant(
+        isolate()->factory()->free_space_map(),
+        UniqueValueId(isolate()->heap()->free_space_map()),
+        Representation::None(),
+        HType::Tagged(),
+        false,
+        true,
+        false,
+        false);
+    constant->InsertAfter(GetConstantUndefined());
+    constant_free_space_map_.set(constant);
+  }
+  return constant_free_space_map_.get();
+}
+
 
 #undef DEFINE_GET_CONSTANT
 
 
 HConstant* HGraph::GetInvalidContext() {
   return GetConstant(&constant_invalid_context_, 0xFFFFC0C7);
 }
 
 
 bool HGraph::IsStandardConstant(HConstant* constant) {
@@ skipping 2757 matching lines @@
 bool HGraph::Optimize(SmartArrayPointer<char>* bailout_reason) {
   *bailout_reason = SmartArrayPointer<char>();
   OrderBlocks();
   AssignDominators();
 
   // We need to create a HConstant "zero" now so that GVN will fold every
   // zero-valued constant in the graph together.
   // The constant is needed to make idef-based bounds check work: the pass
   // evaluates relations with "zero" and that zero cannot be created after GVN.
   GetConstant0();
+  GetConstantFreeSpaceMap();
 
 #ifdef DEBUG
   // Do a full verify after building the graph and computing dominators.
   Verify(true);
 #endif
 
   if (FLAG_analyze_environment_liveness && maximum_environment_size() != 0) {
     Run<HEnvironmentLivenessAnalysisPhase>();
   }
 
@@ skipping 7384 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal