[turbofan] Initial version of ValueNumberingReducer.

src/compiler/js-graph.cc

 // Copyright 2014 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/js-graph.h"
 #include "src/compiler/node-properties-inl.h"
 #include "src/compiler/typer.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 86 matching lines @@
 Node* JSGraph::HeapConstant(PrintableUnique<Object> value) {
   // TODO(turbofan): canonicalize heap constants using Unique<T>
   return NewNode(common()->HeapConstant(value));
 }
 
 
 Node* JSGraph::HeapConstant(Handle<Object> value) {
   // TODO(titzer): We could also match against the addresses of immortable
   // immovables here, even without access to the heap, thus always
   // canonicalizing references to them.
-  return HeapConstant(
-      PrintableUnique<Object>::CreateUninitialized(zone(), value));
+  // return HeapConstant(
+  //    PrintableUnique<Object>::CreateUninitialized(zone(), value));
+  // TODO(turbofan): This is a work-around to make Unique::HashCode() work for
+  // value numbering. We need some sane way to compute a unique hash code for
+  // arbitrary handles here.
+  PrintableUnique<Object> unique(
+      zone(), reinterpret_cast<Address>(*value.location()), value);
+  return HeapConstant(unique);
 }
 
 
 Node* JSGraph::Constant(Handle<Object> value) {
   // Dereference the handle to determine if a number constant or other
   // canonicalized node can be used.
   if (value->IsNumber()) {
     return Constant(value->Number());
   } else if (value->IsUndefined()) {
     return UndefinedConstant();
@@ skipping 55 matching lines @@
 Node* JSGraph::ExternalConstant(ExternalReference reference) {
   Node** loc = cache_.FindExternalConstant(reference);
   if (*loc == NULL) {
     *loc = NewNode(common()->ExternalConstant(reference));
   }
   return *loc;
 }
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8