Implement fixpoint iteration for escape analysis.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/23533003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17235 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -313,6 +313,8 @@ DEFINE_bool(inline_construct, true, "inline constructor calls")
 DEFINE_bool(inline_arguments, true, "inline functions with arguments object")
 DEFINE_bool(inline_accessors, true, "inline JavaScript accessors")
 DEFINE_int(loop_weight, 1, "loop weight for representation inference")
+DEFINE_int(escape_analysis_iterations, 1,
+           "maximum number of escape analysis fix-point iterations")
 
 DEFINE_bool(optimize_for_in, true,
             "optimize functions containing for-in loops")

src/hydrogen-escape-analysis.cc

@@ -306,7 +306,7 @@ void HEscapeAnalysisPhase::PerformScalarReplacement() {
     number_of_objects_++;
     block_states_.Clear();
 
-    // Perform actual analysis steps.
+    // Perform actual analysis step.
     AnalyzeDataFlow(allocate);
 
     cumulative_values_ += number_of_values_;
@@ -320,8 +320,13 @@ void HEscapeAnalysisPhase::Run() {
   // TODO(mstarzinger): We disable escape analysis with OSR for now, because
   // spill slots might be uninitialized. Needs investigation.
   if (graph()->has_osr()) return;
-  CollectCapturedValues();
-  PerformScalarReplacement();
+  int max_fixpoint_iteration_count = FLAG_escape_analysis_iterations;
+  for (int i = 0; i < max_fixpoint_iteration_count; i++) {
+    CollectCapturedValues();
+    if (captured_.is_empty()) break;
+    PerformScalarReplacement();
+    captured_.Clear();
+  }
 }
 
 

src/hydrogen-instructions.cc

@@ -2396,6 +2396,12 @@ void HCapturedObject::ReplayEnvironment(HEnvironment* env) {
 }
 
 
+void HCapturedObject::PrintDataTo(StringStream* stream) {
+  stream->Add("#%d ", capture_id());
+  HDematerializedObject::PrintDataTo(stream);
+}
+
+
 void HEnterInlined::RegisterReturnTarget(HBasicBlock* return_target,
                                          Zone* zone) {
   ASSERT(return_target->IsInlineReturnTarget());

src/hydrogen-instructions.h

@@ -3317,6 +3317,8 @@ class HCapturedObject V8_FINAL : public HDematerializedObject {
   // Replay effects of this instruction on the given environment.
   void ReplayEnvironment(HEnvironment* env);
 
+  virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
+
   DECLARE_CONCRETE_INSTRUCTION(CapturedObject)
 
  private: