Fix worst-case behavior of MergeRemovableSimulates().

src/hydrogen-instructions.cc

 // Copyright 2012 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 667 matching lines @@
 
 void HValue::Kill() {
   // Instead of going through the entire use list of each operand, we only
   // check the first item in each use list and rely on the tail() method to
   // skip dead items, removing them lazily next time we traverse the list.
   SetFlag(kIsDead);
   for (int i = 0; i < OperandCount(); ++i) {
     HValue* operand = OperandAt(i);
     if (operand == NULL) continue;
     HUseListNode* first = operand->use_list_;
-    if (first != NULL && first->value() == this && first->index() == i) {
+    if (first != NULL && first->value()->CheckFlag(kIsDead)) {
       operand->use_list_ = first->tail();
     }
   }
 }
 
 
 void HValue::SetBlock(HBasicBlock* block) {
   ASSERT(block_ == NULL || block == NULL);
   block_ = block;
   if (id_ == kNoNumber && block != NULL) {
@@ skipping 1274 matching lines @@
 }
 
 
 void HPhi::AddIndirectUsesTo(int* dest) {
   for (int i = 0; i < Representation::kNumRepresentations; i++) {
     dest[i] += indirect_uses_[i];
   }
 }
 
 
-void HSimulate::MergeInto(HSimulate* other) {
-  for (int i = 0; i < values_.length(); ++i) {
-    HValue* value = values_[i];
-    if (HasAssignedIndexAt(i)) {
-      other->AddAssignedValue(GetAssignedIndexAt(i), value);
-    } else {
-      if (other->pop_count_ > 0) {
-        other->pop_count_--;
+void HSimulate::MergeWith(ZoneList<HSimulate*>* list) {
+  if (list->is_empty()) return;
+  for (int j = list->length() - 1; j >= 0; --j) {
+    HSimulate* from = list->at(j);
+    ZoneList<HValue*>* from_values = &from->values_;
+    for (int i = 0; i < from_values->length(); ++i) {
+      if (from->HasAssignedIndexAt(i)) {
+        AddAssignedValue(from->GetAssignedIndexAt(i),
+                         from_values->at(i));
       } else {
-        other->AddPushedValue(value);
+        if (pop_count_ > 0) {
+          pop_count_--;
+        } else {
+          AddPushedValue(from_values->at(i));
+        }
       }
     }
+    pop_count_ += from->pop_count_;
+    list->at(j)->DeleteAndReplaceWith(NULL);

[Jakob Kummerow, 2013/04/04 17:12:22]

nit: s/list->at(j)/from/

   }
-  other->pop_count_ += pop_count();
+  list->Clear();
 }
 
 
 void HSimulate::PrintDataTo(StringStream* stream) {
   stream->Add("id=%d", ast_id().ToInt());
   if (pop_count_ > 0) stream->Add(" pop %d", pop_count_);
   if (values_.length() > 0) {
     if (pop_count_ > 0) stream->Add(" /");
     for (int i = values_.length() - 1; i >= 0; --i) {
       if (i > 0) stream->Add(",");
@@ skipping 1524 matching lines @@
 
 
 void HCheckFunction::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal