Remove class HSubgraph.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index b1b2c32a9a5e5d6ce1e02ebe9f1ebecea5588993..82c9b70e33a2e22068db4bb5a42872dd2402f245 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -557,13 +557,15 @@ void HBasicBlock::FinishExit(HControlInstruction* instruction) {
 
 
 HGraph::HGraph(CompilationInfo* info)
-    : HSubgraph(this),
-      next_block_id_(0),
+    : next_block_id_(0),
+      entry_block_(NULL),
       blocks_(8),
       values_(16),
       phi_list_(NULL) {
   start_environment_ = new HEnvironment(NULL, info->scope(), info->closure());
   start_environment_->set_ast_id(info->function()->id());
+  entry_block_ = CreateBasicBlock();
+  entry_block_->SetInitialEnvironment(start_environment_);
 }
 
 
@@ -785,11 +787,11 @@ void HGraph::EliminateUnreachablePhis() {
 
 
 bool HGraph::CollectPhis() {
-  const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
-  phi_list_ = new ZoneList<HPhi*>(blocks->length());
-  for (int i = 0; i < blocks->length(); ++i) {
-    for (int j = 0; j < blocks->at(i)->phis()->length(); j++) {
-      HPhi* phi = blocks->at(i)->phis()->at(j);
+  int block_count = blocks_.length();
+  phi_list_ = new ZoneList<HPhi*>(block_count);
+  for (int i = 0; i < block_count; ++i) {
+    for (int j = 0; j < blocks_[i]->phis()->length(); ++j) {
+      HPhi* phi = blocks_[i]->phis()->at(j);
       phi_list_->Add(phi);
       // We don't support phi uses of arguments for now.
       if (phi->CheckFlag(HValue::kIsArguments)) return false;
@@ -2080,36 +2082,6 @@ void TestContext::BuildBranch(HValue* value) {
   } while (false)
 
 
-// 'thing' could be an expression, statement, or list of statements.
-#define ADD_TO_SUBGRAPH(graph, thing)       \
-  do {                                      \
-    AddToSubgraph(graph, thing);            \
-    if (HasStackOverflow()) return;         \
-  } while (false)
-
-
-class HGraphBuilder::SubgraphScope BASE_EMBEDDED {
- public:
-  SubgraphScope(HGraphBuilder* builder, HSubgraph* new_subgraph)
-      : builder_(builder) {
-    old_subgraph_ = builder_->current_subgraph_;
-    subgraph_ = new_subgraph;
-    builder_->current_subgraph_ = subgraph_;
-  }
-
-  ~SubgraphScope() {
-    builder_->current_subgraph_ = old_subgraph_;
-  }
-
-  HSubgraph* subgraph() const { return subgraph_; }
-
- private:
-  HGraphBuilder* builder_;
-  HSubgraph* old_subgraph_;
-  HSubgraph* subgraph_;
-};
-
-
 void HGraphBuilder::Bailout(const char* reason) {
   if (FLAG_trace_bailout) {
     SmartPointer<char> name(info()->shared_info()->DebugName()->ToCString());
@@ -2161,13 +2133,10 @@ void HGraphBuilder::VisitExpressions(ZoneList<Expression*>* exprs) {
 
 
 HGraph* HGraphBuilder::CreateGraph() {
-  ASSERT(subgraph() == NULL);
   graph_ = new HGraph(info());
-
   {
     HPhase phase("Block building");
-    graph()->Initialize(CreateBasicBlock(graph()->start_environment()));
-    current_subgraph_ = graph();
+    current_block_ = graph()->entry_block();
 
     Scope* scope = info()->scope();
     if (scope->HasIllegalRedeclaration()) {
@@ -2245,25 +2214,6 @@ HGraph* HGraphBuilder::CreateGraph() {
 }
 
 
-void HGraphBuilder::AddToSubgraph(HSubgraph* graph, Statement* stmt) {
-  SubgraphScope scope(this, graph);
-  Visit(stmt);
-}
-
-
-void HGraphBuilder::AddToSubgraph(HSubgraph* graph, Expression* expr) {
-  SubgraphScope scope(this, graph);
-  VisitForValue(expr);
-}
-
-
-void HGraphBuilder::AddToSubgraph(HSubgraph* graph,
-                                  ZoneList<Statement*>* stmts) {
-  SubgraphScope scope(this, graph);
-  VisitStatements(stmts);
-}
-
-
 HInstruction* HGraphBuilder::AddInstruction(HInstruction* instr) {
   ASSERT(current_block() != NULL);
   current_block()->AddInstruction(instr);