Replace DeoptimizeOnUndefined with whitelisting AllowUndefinedAsNan

src/hydrogen.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 1568 matching lines @@
 
   HValue* element =
       AddInstruction(new(zone()) HLoadKeyed(from_elements, key, NULL,
                                             from_elements_kind,
                                             ALLOW_RETURN_HOLE));
 
   ElementsKind holey_kind = IsFastSmiElementsKind(to_elements_kind)
       ? FAST_HOLEY_ELEMENTS : to_elements_kind;
   HInstruction* holey_store = AddInstruction(
       new(zone()) HStoreKeyed(to_elements, key, element, holey_kind));
-  holey_store->ClearFlag(HValue::kDeoptimizeOnUndefined);
+  holey_store->SetFlag(HValue::kAllowUndefinedAsNaN);

[danno, 2013/05/29 15:33:16]

Maybe a comment, e.g. "Allow NaN hole values to be converted to their tagged
counterparts."  Also, maybe add an if? e.g.

if (IsFastHoleyDoubleElementsKind(to_element_kind)) {
  holey_store->SetFlag(HValue::kAllowUndefinedAsNaN);
}

[Toon Verwaest, 2013/05/29 16:19:58]

Done.

 
   builder.EndBody();
 
   if (!pre_fill_with_holes && length != capacity) {
     // Fill unused capacity with the hole.
     BuildFillElementsWithHole(context, to_elements, to_elements_kind,
                               key, capacity);
   }
 }
 
@@ skipping 1493 matching lines @@
     next = use_value->block()->predecessors()->at(use_index)->end();
   } else {
     next = HInstruction::cast(use_value);
   }
   // For constants we try to make the representation change at compile
   // time. When a representation change is not possible without loss of
   // information we treat constants like normal instructions and insert the
   // change instructions for them.
   HInstruction* new_value = NULL;
   bool is_truncating = use_value->CheckFlag(HValue::kTruncatingToInt32);
-  bool deoptimize_on_undefined =
-      use_value->CheckFlag(HValue::kDeoptimizeOnUndefined);
+  bool allow_undefined_as_nan =
+      use_value->CheckFlag(HValue::kAllowUndefinedAsNaN);
   if (value->IsConstant()) {
     HConstant* constant = HConstant::cast(value);
     // Try to create a new copy of the constant with the new representation.
     new_value = (is_truncating && to.IsInteger32())
         ? constant->CopyToTruncatedInt32(zone())
         : constant->CopyToRepresentation(to, zone());
   }
 
   if (new_value == NULL) {
     new_value = new(zone()) HChange(value, to,
-                                    is_truncating, deoptimize_on_undefined);
+                                    is_truncating, allow_undefined_as_nan);
   }
 
   new_value->InsertBefore(next);
   use_value->SetOperandAt(use_index, new_value);
 }
 
 
 void HGraph::InsertRepresentationChangesForValue(HValue* value) {
   Representation r = value->representation();
   if (r.IsNone()) return;
@@ skipping 86 matching lines @@
     while (current != NULL) {
       HInstruction* next = current->next();
       InsertRepresentationChangesForValue(current);
       current = next;
     }
   }
 }
 
 
 void HGraph::RecursivelyMarkPhiDeoptimizeOnUndefined(HPhi* phi) {
-  if (phi->CheckFlag(HValue::kDeoptimizeOnUndefined)) return;
-  phi->SetFlag(HValue::kDeoptimizeOnUndefined);
+  if (!phi->CheckFlag(HValue::kAllowUndefinedAsNaN)) return;
+  phi->ClearFlag(HValue::kAllowUndefinedAsNaN);
   for (int i = 0; i < phi->OperandCount(); ++i) {
     HValue* input = phi->OperandAt(i);
     if (input->IsPhi()) {
       RecursivelyMarkPhiDeoptimizeOnUndefined(HPhi::cast(input));
     }
   }
 }
 
 
 void HGraph::MarkDeoptimizeOnUndefined() {
   HPhase phase("H_MarkDeoptimizeOnUndefined", this);
   // Compute DeoptimizeOnUndefined flag for phis.
   // Any phi that can reach a use with DeoptimizeOnUndefined set must
   // have DeoptimizeOnUndefined set.  Currently only HCompareIDAndBranch, with
   // double input representation, has this flag set.
   // The flag is used by HChange tagged->double, which must deoptimize
   // if one of its uses has this flag set.
   for (int i = 0; i < phi_list()->length(); i++) {
     HPhi* phi = phi_list()->at(i);
-    if (phi->representation().IsDouble()) {
+    if (phi->representation().IsTagged() || phi->representation().IsDouble()) {
       for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
-        int use_index = it.index();
         HValue* use_value = it.value();
-        Representation req = use_value->RequiredInputRepresentation(use_index);
-        if (!req.IsDouble() ||
-            use_value->CheckFlag(HValue::kDeoptimizeOnUndefined)) {
+        if (!use_value->CheckFlag(HValue::kAllowUndefinedAsNaN)) {
           RecursivelyMarkPhiDeoptimizeOnUndefined(phi);
           break;
         }
       }
     }
   }
 }
 
 
 // Discover instructions that can be marked with kUint32 flag allowing
@@ skipping 6842 matching lines @@
   HInstruction* boilerplate_elements = AddInstruction(new(zone) HConstant(
       elements, Representation::Tagged()));
   int elements_length = elements->length();
   for (int i = 0; i < elements_length; i++) {
     HValue* key_constant = AddInstruction(new(zone) HConstant(i));
     HInstruction* value_instruction =
         AddInstruction(new(zone) HLoadKeyed(
             boilerplate_elements, key_constant, NULL, kind, ALLOW_RETURN_HOLE));
     HInstruction* store = AddInstruction(new(zone) HStoreKeyed(
         object_elements, key_constant, value_instruction, kind));
-    store->ClearFlag(HValue::kDeoptimizeOnUndefined);
+    store->SetFlag(HValue::kAllowUndefinedAsNaN);

[danno, 2013/05/29 15:33:16]

Are you sure you need this? Since there is no change involved, I don't see why
this flag needs to be cleared.

[Toon Verwaest, 2013/05/29 16:19:58]

Done.

   }
 }
 
 
 void HOptimizedGraphBuilder::BuildEmitFixedArray(
     Handle<FixedArrayBase> elements,
     Handle<FixedArrayBase> original_elements,
     ElementsKind kind,
     HValue* object_elements,
     HInstruction* target,
@@ skipping 1375 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal