Refactor construction of switch statements to avoid subgraphs.

Refactor construction of switch statements so it doesn't use class
HSubgraph.

There are also a few improvements.  We do not use an auxiliary list of
comparisons because they're embedded as a linked list in the graph
under construction.  We share a common break block for all breaks from
the same switch.  We do not insert empty blocks unless necessary to
maintain edge-split form.

There is also a bug fix.  The entry to a clause body is a potential
join and must have a join ID set, otherwise deoptimization within the
body can go to an unpredictable place in the unoptimized code.

Review URL: http://codereview.chromium.org/6650021

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7099 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/full-codegen-arm.cc

@@ -878,6 +878,7 @@ void FullCodeGenerator::VisitSwitchStatement(SwitchStatement* stmt) {
     Comment cmnt(masm_, "[ Case body");
     CaseClause* clause = clauses->at(i);
     __ bind(clause->body_target()->entry_label());
+    PrepareForBailoutForId(clause->EntryId(), NO_REGISTERS);
     VisitStatements(clause->statements());
   }
 

src/ast.cc

@@ -1062,6 +1062,8 @@ CaseClause::CaseClause(Expression* label,
     : label_(label),
       statements_(statements),
       position_(pos),
-      compare_type_(NONE) {}
+      compare_type_(NONE),
+      entry_id_(AstNode::GetNextId()) {
+}
 
 } }  // namespace v8::internal

src/ast.h

@@ -175,6 +175,8 @@ class AstNode: public ZoneObject {
   static unsigned current_id_;
   static unsigned count_;
   unsigned id_;
+
+  friend class CaseClause;  // Generates AST IDs.
 };
 
 
@@ -694,6 +696,8 @@ class CaseClause: public ZoneObject {
   int position() { return position_; }
   void set_position(int pos) { position_ = pos; }
 
+  int EntryId() { return entry_id_; }
+
   // Type feedback information.
   void RecordTypeFeedback(TypeFeedbackOracle* oracle);
   bool IsSmiCompare() { return compare_type_ == SMI_ONLY; }
@@ -706,6 +710,7 @@ class CaseClause: public ZoneObject {
   int position_;
   enum CompareTypeFeedback { NONE, SMI_ONLY, OBJECT_ONLY };
   CompareTypeFeedback compare_type_;
+  int entry_id_;
 };
 
 

src/hydrogen.h

@@ -794,7 +794,6 @@ class HGraphBuilder: public AstVisitor {
 #undef DECLARE_VISIT
 
   HBasicBlock* CreateBasicBlock(HEnvironment* env);
-  HSubgraph* CreateEmptySubgraph();
   HBasicBlock* CreateLoopHeaderBlock();
 
   // Helpers for flow graph construction.
@@ -887,10 +886,6 @@ class HGraphBuilder: public AstVisitor {
                                                  HValue* val,
                                                  Expression* expr);
 
-  HCompare* BuildSwitchCompare(HSubgraph* subgraph,
-                               HValue* switch_value,
-                               CaseClause* clause);
-
   HValue* BuildContextChainWalk(Variable* var);
 
   void AddCheckConstantFunction(Call* expr,

src/ia32/full-codegen-ia32.cc

@@ -825,6 +825,7 @@ void FullCodeGenerator::VisitSwitchStatement(SwitchStatement* stmt) {
     Comment cmnt(masm_, "[ Case body");
     CaseClause* clause = clauses->at(i);
     __ bind(clause->body_target()->entry_label());
+    PrepareForBailoutForId(clause->EntryId(), NO_REGISTERS);
     VisitStatements(clause->statements());
   }
 

src/x64/full-codegen-x64.cc

@@ -837,6 +837,7 @@ void FullCodeGenerator::VisitSwitchStatement(SwitchStatement* stmt) {
     Comment cmnt(masm_, "[ Case body");
     CaseClause* clause = clauses->at(i);
     __ bind(clause->body_target()->entry_label());
+    PrepareForBailoutForId(clause->EntryId(), NO_REGISTERS);
     VisitStatements(clause->statements());
   }