use a worklist in HGraph::InsertRepresentationChanges

src/hydrogen.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1861 matching lines @@
 
 
 void HGraph::InsertRepresentationChanges() {
   HPhase phase("Insert representation changes", this);
 
 
   // Compute truncation flag for phis: Initially assume that all
   // int32-phis allow truncation and iteratively remove the ones that
   // are used in an operation that does not allow a truncating
   // conversion.
-  // TODO(fschneider): Replace this with a worklist-based iteration.
-  for (int i = 0; i < phi_list()->length(); i++) {
+  int truncating_phis = 0;
+  for (int i = 0; i < phi_list()->length(); ++i) {
     HPhi* phi = phi_list()->at(i);
     if (phi->representation().IsInteger32()) {
+      ++truncating_phis;
       phi->SetFlag(HValue::kTruncatingToInt32);
     }
   }
-  bool change = true;
-  while (change) {
-    change = false;
-    for (int i = 0; i < phi_list()->length(); i++) {
-      HPhi* phi = phi_list()->at(i);
-      if (!phi->CheckFlag(HValue::kTruncatingToInt32)) continue;
+  
+  ZoneList<HPhi*> worklist(truncating_phis);
+  for (int i = 0; i < phi_list()->length(); ++i) {
+    HPhi* phi = phi_list()->at(i);
+    if (phi->CheckFlag (HValue::kTruncatingToInt32)) {
       for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
         HValue* use = it.value();
         if (!use->CheckFlag(HValue::kTruncatingToInt32)) {
           phi->ClearFlag(HValue::kTruncatingToInt32);
-          change = true;
+          worklist.Add (phi);
           break;
         }
       }
     }
   }
+  
+  while (!worklist.is_empty()) {
+    HPhi* phi = worklist.RemoveLast();
+    for (int i = 0; i < phi->OperandCount(); ++i) {
+      HValue *v = phi->OperandAt(i);
+      if (v->IsPhi() && v->CheckFlag(HValue::kTruncatingToInt32)) {
+        v->ClearFlag(HValue::kTruncatingToInt32);
+        worklist.Add(HPhi::cast(v));
+      }
+    }
+  }
 
   for (int i = 0; i < blocks_.length(); ++i) {
     // Process phi instructions first.
     const ZoneList<HPhi*>* phis = blocks_[i]->phis();
     for (int j = 0; j < phis->length(); j++) {
       InsertRepresentationChangesForValue(phis->at(j));
     }
 
     // Process normal instructions.
     HInstruction* current = blocks_[i]->first();
@@ skipping 4816 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify();
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal