Perform a fix point iteration for GVN.

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 1496 matching lines @@
     case IS_INTERNALIZED_STRING:
       *mask = kIsNotStringMask | kIsNotInternalizedMask;
       *tag = kInternalizedTag;
       return;
     default:
       UNREACHABLE();
   }
 }
 
 
-void HCheckMaps::HandleSideEffectDominator(GVNFlag side_effect,
+bool HCheckMaps::HandleSideEffectDominator(GVNFlag side_effect,
                                            HValue* dominator) {
   ASSERT(side_effect == kChangesMaps);
   // TODO(mstarzinger): For now we specialize on HStoreNamedField, but once
   // type information is rich enough we should generalize this to any HType
   // for which the map is known.
   if (HasNoUses() && dominator->IsStoreNamedField()) {
     HStoreNamedField* store = HStoreNamedField::cast(dominator);
-    if (!store->has_transition() || store->object() != value()) return;
+    if (!store->has_transition() || store->object() != value()) return false;
     HConstant* transition = HConstant::cast(store->transition());
     if (map_set_.Contains(transition->GetUnique())) {
       DeleteAndReplaceWith(NULL);
-      return;
+      return true;
     }
   }
+  return false;
 }
 
 
 void HCheckMaps::PrintDataTo(StringStream* stream) {
   value()->PrintNameTo(stream);
   stream->Add(" [%p", *map_set_.at(0).handle());
   for (int i = 1; i < map_set_.size(); ++i) {
     stream->Add(",%p", *map_set_.at(i).handle());
   }
   stream->Add("]%s", CanOmitMapChecks() ? "(omitted)" : "");
@@ skipping 1860 matching lines @@
   // If any of the actual input representation is more general than what we
   // have so far but not Tagged, use that representation instead.
   Representation input_rep = value()->representation();
   if (!input_rep.IsTagged()) {
     rep = rep.generalize(input_rep);
   }
   return rep;
 }
 
 
-void HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
+bool HAllocate::HandleSideEffectDominator(GVNFlag side_effect,
                                           HValue* dominator) {
   ASSERT(side_effect == kChangesNewSpacePromotion);
   Zone* zone = block()->zone();
-  if (!FLAG_use_allocation_folding) return;
+  if (!FLAG_use_allocation_folding) return false;
 
   // Try to fold allocations together with their dominating allocations.
   if (!dominator->IsAllocate()) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s)\n",
           id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
     }
-    return;
+    return false;
   }
 
   HAllocate* dominator_allocate = HAllocate::cast(dominator);
   HValue* dominator_size = dominator_allocate->size();
   HValue* current_size = size();
 
   // TODO(hpayer): Add support for non-constant allocation in dominator.
   if (!current_size->IsInteger32Constant() ||
       !dominator_size->IsInteger32Constant()) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s), dynamic allocation size\n",
           id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
     }
-    return;
+    return false;
   }
 
   dominator_allocate = GetFoldableDominator(dominator_allocate);
   if (dominator_allocate == NULL) {
-    return;
+    return false;
   }
 
   ASSERT((IsNewSpaceAllocation() &&
          dominator_allocate->IsNewSpaceAllocation()) ||
          (IsOldDataSpaceAllocation() &&
          dominator_allocate->IsOldDataSpaceAllocation()) ||
          (IsOldPointerSpaceAllocation() &&
          dominator_allocate->IsOldPointerSpaceAllocation()));
 
   // First update the size of the dominator allocate instruction.
@@ skipping 16 matching lines @@
   }
 
   // Since we clear the first word after folded memory, we cannot use the
   // whole Page::kMaxRegularHeapObjectSize memory.
   if (new_dominator_size > Page::kMaxRegularHeapObjectSize - kPointerSize) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s) due to size: %d\n",
           id(), Mnemonic(), dominator_allocate->id(),
           dominator_allocate->Mnemonic(), new_dominator_size);
     }
-    return;
+    return false;
   }
 
   HInstruction* new_dominator_size_constant = HConstant::CreateAndInsertBefore(
       zone,
       context(),
       new_dominator_size,
       Representation::None(),
       dominator_allocate);
   dominator_allocate->UpdateSize(new_dominator_size_constant);
 
@@ skipping 27 matching lines @@
                                  dominator_allocate,
                                  inner_offset,
                                  type());
   dominated_allocate_instr->InsertBefore(this);
   DeleteAndReplaceWith(dominated_allocate_instr);
   if (FLAG_trace_allocation_folding) {
     PrintF("#%d (%s) folded into #%d (%s)\n",
         id(), Mnemonic(), dominator_allocate->id(),
         dominator_allocate->Mnemonic());
   }
+  return true;
 }
 
 
 HAllocate* HAllocate::GetFoldableDominator(HAllocate* dominator) {
   if (!IsFoldable(dominator)) {
     // We cannot hoist old space allocations over new space allocations.
     if (IsNewSpaceAllocation() || dominator->IsNewSpaceAllocation()) {
       if (FLAG_trace_allocation_folding) {
         PrintF("#%d (%s) cannot fold into #%d (%s), new space hoisting\n",
             id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
@@ skipping 928 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal