Partial refactoring of subgraphs.

Change the interface to the Hydrogen graph builder to appear like it
directly holds a current basic block and a current environment.
Remove some direct accesses to the current subgraph, and remove
subgraph accessors that simply forwarded to the exit block.

Review URL: http://codereview.chromium.org/6532088

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6887 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.h

@@ -200,13 +200,12 @@ class HSubgraph: public ZoneObject {
   }
 
   HGraph* graph() const { return graph_; }
-  HEnvironment* environment() const {
-    ASSERT(HasExit());
-    return exit_block_->last_environment();
+  HBasicBlock* entry_block() const { return entry_block_; }
+  HBasicBlock* exit_block() const { return exit_block_; }
+  void set_exit_block(HBasicBlock* block) {
+    exit_block_ = block;
   }
 
-  bool HasExit() const { return exit_block_ != NULL; }
-
   void PreProcessOsrEntry(IterationStatement* statement);
 
   void AppendJoin(HSubgraph* then_graph, HSubgraph* else_graph, AstNode* node);
@@ -237,17 +236,6 @@ class HSubgraph: public ZoneObject {
     entry_block_ = block;
     exit_block_ = block;
   }
-  HBasicBlock* entry_block() const { return entry_block_; }
-  HBasicBlock* exit_block() const { return exit_block_; }
-  void set_exit_block(HBasicBlock* block) {
-    exit_block_ = block;
-  }
-
-  void ConnectExitTo(HBasicBlock* other, bool include_stack_check = false) {
-    if (HasExit()) {
-      exit_block()->Goto(other, include_stack_check);
-    }
-  }
 
  protected:
   HGraph* graph_;  // The graph this is a subgraph of.
@@ -657,8 +645,13 @@ class HGraphBuilder: public AstVisitor {
   BreakAndContinueScope* break_scope() const { return break_scope_; }
   void set_break_scope(BreakAndContinueScope* head) { break_scope_ = head; }
 
-  HEnvironment* environment() const { return subgraph()->environment(); }
-  HBasicBlock* CurrentBlock() const { return subgraph()->exit_block(); }
+  HBasicBlock* current_block() const { return subgraph()->exit_block(); }
+  void set_current_block(HBasicBlock* block) {
+    subgraph()->set_exit_block(block);
+  }
+  HEnvironment* environment() const {
+    return current_block()->last_environment();
+  }
 
   // Adding instructions.
   HInstruction* AddInstruction(HInstruction* instr);