use a worklist in HGraph::InsertRepresentationChanges

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index a6205ecdf5a6de3e10dbd6cd219a6faef1010434..56a24c8cd96d124557c81425f0de106ba7565ae3 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -1879,29 +1879,40 @@ void HGraph::InsertRepresentationChanges() {
   // 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.