[turbofan] Implement proper caching of heap constants in the JSGraph.

With the handle canonicalization we can now easily cache heap constant
nodes based on the location of the HeapObject handle location.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1523323005

Cr-Commit-Position: refs/heads/master@{#32876}

src/compiler/common-node-cache.cc

@@ -16,6 +16,11 @@ Node** CommonNodeCache::FindExternalConstant(ExternalReference value) {
 }
 
 
+Node** CommonNodeCache::FindHeapConstant(Handle<HeapObject> value) {
+  return heap_constants_.Find(zone(), bit_cast<intptr_t>(value.location()));
+}
+
+
 void CommonNodeCache::GetCachedNodes(ZoneVector<Node*>* nodes) {
   int32_constants_.GetCachedNodes(nodes);
   int64_constants_.GetCachedNodes(nodes);
@@ -23,6 +28,7 @@ void CommonNodeCache::GetCachedNodes(ZoneVector<Node*>* nodes) {
   float64_constants_.GetCachedNodes(nodes);
   external_constants_.GetCachedNodes(nodes);
   number_constants_.GetCachedNodes(nodes);
+  heap_constants_.GetCachedNodes(nodes);
 }
 
 }  // namespace compiler

src/compiler/common-node-cache.h

@@ -12,6 +12,9 @@ namespace internal {
 
 // Forward declarations.
 class ExternalReference;
+class HeapObject;
+template <typename>
+class Handle;
 
 
 namespace compiler {
@@ -47,6 +50,8 @@ class CommonNodeCache final {
     return number_constants_.Find(zone(), bit_cast<int64_t>(value));
   }
 
+  Node** FindHeapConstant(Handle<HeapObject> value);
+
   // Return all nodes from the cache.
   void GetCachedNodes(ZoneVector<Node*>* nodes);
 
@@ -59,7 +64,8 @@ class CommonNodeCache final {
   Int64NodeCache float64_constants_;
   IntPtrNodeCache external_constants_;
   Int64NodeCache number_constants_;
-  Zone* zone_;
+  IntPtrNodeCache heap_constants_;
+  Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(CommonNodeCache);
 };

src/compiler/js-graph.cc

@@ -11,12 +11,6 @@ namespace v8 {
 namespace internal {
 namespace compiler {
 
-Node* JSGraph::ImmovableHeapConstant(Handle<HeapObject> value) {
-  // TODO(bmeurer): Flatten cons strings here before we canonicalize them?
-  return graph()->NewNode(common()->HeapConstant(value));
-}
-
-
 #define CACHED(name, expr) \
   cached_nodes_[name] ? cached_nodes_[name] : (cached_nodes_[name] = (expr))
 
@@ -24,43 +18,40 @@ Node* JSGraph::ImmovableHeapConstant(Handle<HeapObject> value) {
 Node* JSGraph::CEntryStubConstant(int result_size) {
   if (result_size == 1) {
     return CACHED(kCEntryStubConstant,
-                  ImmovableHeapConstant(CEntryStub(isolate(), 1).GetCode()));
+                  HeapConstant(CEntryStub(isolate(), 1).GetCode()));
   }
-  return ImmovableHeapConstant(CEntryStub(isolate(), result_size).GetCode());
+  return HeapConstant(CEntryStub(isolate(), result_size).GetCode());
 }
 
 
 Node* JSGraph::EmptyFixedArrayConstant() {
   return CACHED(kEmptyFixedArrayConstant,
-                ImmovableHeapConstant(factory()->empty_fixed_array()));
+                HeapConstant(factory()->empty_fixed_array()));
 }
 
 
 Node* JSGraph::UndefinedConstant() {
-  return CACHED(kUndefinedConstant,
-                ImmovableHeapConstant(factory()->undefined_value()));
+  return CACHED(kUndefinedConstant, HeapConstant(factory()->undefined_value()));
 }
 
 
 Node* JSGraph::TheHoleConstant() {
-  return CACHED(kTheHoleConstant,
-                ImmovableHeapConstant(factory()->the_hole_value()));
+  return CACHED(kTheHoleConstant, HeapConstant(factory()->the_hole_value()));
 }
 
 
 Node* JSGraph::TrueConstant() {
-  return CACHED(kTrueConstant, ImmovableHeapConstant(factory()->true_value()));
+  return CACHED(kTrueConstant, HeapConstant(factory()->true_value()));
 }
 
 
 Node* JSGraph::FalseConstant() {
-  return CACHED(kFalseConstant,
-                ImmovableHeapConstant(factory()->false_value()));
+  return CACHED(kFalseConstant, HeapConstant(factory()->false_value()));
 }
 
 
 Node* JSGraph::NullConstant() {
-  return CACHED(kNullConstant, ImmovableHeapConstant(factory()->null_value()));
+  return CACHED(kNullConstant, HeapConstant(factory()->null_value()));
 }
 
 
@@ -81,11 +72,12 @@ Node* JSGraph::NaNConstant() {
 
 
 Node* JSGraph::HeapConstant(Handle<HeapObject> value) {
-  // TODO(turbofan): canonicalize heap constants using <magic approach>.
-  // 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 ImmovableHeapConstant(value);
+  // TODO(bmeurer): Flatten cons strings here before we canonicalize them?
+  Node** loc = cache_.FindHeapConstant(value);
+  if (*loc == nullptr) {
+    *loc = graph()->NewNode(common()->HeapConstant(value));
+  }
+  return *loc;
 }
 
 

src/compiler/js-graph.h

@@ -158,7 +158,6 @@ class JSGraph : public ZoneObject {
   CommonNodeCache cache_;
   Node* cached_nodes_[kNumCachedNodes];
 
-  Node* ImmovableHeapConstant(Handle<HeapObject> value);
   Node* NumberConstant(double value);
 
   DISALLOW_COPY_AND_ASSIGN(JSGraph);