Experimental parser: merge to r19637

src/hydrogen-load-elimination.cc

 // Copyright 2013 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 58 matching lines @@
   // The main processing of instructions.
   HLoadEliminationTable* Process(HInstruction* instr, Zone* zone) {
     switch (instr->opcode()) {
       case HValue::kLoadNamedField: {
         HLoadNamedField* l = HLoadNamedField::cast(instr);
         TRACE((" process L%d field %d (o%d)\n",
                instr->id(),
                FieldOf(l->access()),
                l->object()->ActualValue()->id()));
         HValue* result = load(l);
-        if (result != instr) {
+        if (result != instr &&
+            result->type().Equals(instr->type()) &&
+            result->representation().Equals(instr->representation())) {
           // The load can be replaced with a previous load or a value.
           TRACE(("  replace L%d -> v%d\n", instr->id(), result->id()));
           instr->DeleteAndReplaceWith(result);
         }
         break;
       }
       case HValue::kStoreNamedField: {
         HStoreNamedField* s = HStoreNamedField::cast(instr);
         TRACE((" process S%d field %d (o%d) = v%d\n",
                instr->id(),
                FieldOf(s->access()),
                s->object()->ActualValue()->id(),
                s->value()->id()));
         HValue* result = store(s);
         if (result == NULL) {
           // The store is redundant. Remove it.
           TRACE(("  remove S%d\n", instr->id()));
           instr->DeleteAndReplaceWith(NULL);
         }
         break;
       }
+      case HValue::kTransitionElementsKind: {
+        HTransitionElementsKind* t = HTransitionElementsKind::cast(instr);
+        HValue* object = t->object()->ActualValue();
+        KillFieldInternal(object, FieldOf(JSArray::kElementsOffset), NULL);
+        KillFieldInternal(object, FieldOf(JSObject::kMapOffset), NULL);
+        break;
+      }
       default: {
-        if (instr->CheckGVNFlag(kChangesInobjectFields)) {
+        if (instr->CheckChangesFlag(kInobjectFields)) {
           TRACE((" kill-all i%d\n", instr->id()));
           Kill();
           break;
         }
-        if (instr->CheckGVNFlag(kChangesMaps)) {
+        if (instr->CheckChangesFlag(kMaps)) {
           TRACE((" kill-maps i%d\n", instr->id()));
           KillOffset(JSObject::kMapOffset);
         }
-        if (instr->CheckGVNFlag(kChangesElementsKind)) {
+        if (instr->CheckChangesFlag(kElementsKind)) {
           TRACE((" kill-elements-kind i%d\n", instr->id()));
           KillOffset(JSObject::kMapOffset);
           KillOffset(JSObject::kElementsOffset);
         }
-        if (instr->CheckGVNFlag(kChangesElementsPointer)) {
+        if (instr->CheckChangesFlag(kElementsPointer)) {
           TRACE((" kill-elements i%d\n", instr->id()));
           KillOffset(JSObject::kElementsOffset);
         }
-        if (instr->CheckGVNFlag(kChangesOsrEntries)) {
+        if (instr->CheckChangesFlag(kOsrEntries)) {
           TRACE((" kill-osr i%d\n", instr->id()));
           Kill();
         }
       }
       // Improvements possible:
       // - learn from HCheckMaps for field 0
       // - remove unobservable stores (write-after-write)
       // - track cells
       // - track globals
       // - track roots
     }
     return this;
   }
 
-  // Support for global analysis with HFlowEngine: Copy state to sucessor block.
-  HLoadEliminationTable* Copy(HBasicBlock* succ, Zone* zone) {
+  // Support for global analysis with HFlowEngine: Merge given state with
+  // the other incoming state.
+  static HLoadEliminationTable* Merge(HLoadEliminationTable* succ_state,
+                                      HBasicBlock* succ_block,
+                                      HLoadEliminationTable* pred_state,
+                                      HBasicBlock* pred_block,
+                                      Zone* zone) {
+    ASSERT(pred_state != NULL);
+    if (succ_state == NULL) {
+      return pred_state->Copy(succ_block, pred_block, zone);
+    } else {
+      return succ_state->Merge(succ_block, pred_state, pred_block, zone);
+    }
+  }
+
+  // Support for global analysis with HFlowEngine: Given state merged with all
+  // the other incoming states, prepare it for use.
+  static HLoadEliminationTable* Finish(HLoadEliminationTable* state,
+                                       HBasicBlock* block,
+                                       Zone* zone) {
+    ASSERT(state != NULL);
+    return state;
+  }
+
+ private:
+  // Copy state to successor block.
+  HLoadEliminationTable* Copy(HBasicBlock* succ, HBasicBlock* from_block,
+                              Zone* zone) {
     HLoadEliminationTable* copy =
         new(zone) HLoadEliminationTable(zone, aliasing_);
     copy->EnsureFields(fields_.length());
     for (int i = 0; i < fields_.length(); i++) {
       copy->fields_[i] = fields_[i]->Copy(zone);
     }
     if (FLAG_trace_load_elimination) {
       TRACE((" copy-to B%d\n", succ->block_id()));
       copy->Print();
     }
     return copy;
   }
 
-  // Support for global analysis with HFlowEngine: Merge this state with
-  // the other incoming state.
-  HLoadEliminationTable* Merge(HBasicBlock* succ,
-      HLoadEliminationTable* that, Zone* zone) {
+  // Merge this state with the other incoming state.
+  HLoadEliminationTable* Merge(HBasicBlock* succ, HLoadEliminationTable* that,
+                               HBasicBlock* that_block, Zone* zone) {
     if (that->fields_.length() < fields_.length()) {
       // Drop fields not in the other table.
       fields_.Rewind(that->fields_.length());
     }
     for (int i = 0; i < fields_.length(); i++) {
       // Merge the field approximations for like fields.
       HFieldApproximation* approx = fields_[i];
       HFieldApproximation* prev = NULL;
       while (approx != NULL) {
         // TODO(titzer): Merging is O(N * M); sort?
         HFieldApproximation* other = that->Find(approx->object_, i);
         if (other == NULL || !Equal(approx->last_value_, other->last_value_)) {
           // Kill an entry that doesn't agree with the other value.
           if (prev != NULL) {
             prev->next_ = approx->next_;
           } else {
             fields_[i] = approx->next_;
           }
           approx = approx->next_;
           continue;
         }
         prev = approx;
         approx = approx->next_;
       }
     }
+    if (FLAG_trace_load_elimination) {
+      TRACE((" merge-to B%d\n", succ->block_id()));
+      Print();
+    }
     return this;
   }
 
   friend class HLoadEliminationEffects;  // Calls Kill() and others.
   friend class HLoadEliminationPhase;
 
  private:
   // Process a load instruction, updating internal table state. If a previous
   // load or store for this object and field exists, return the new value with
   // which the load should be replaced. Otherwise, return {instr}.
   HValue* load(HLoadNamedField* instr) {
+    // There must be no loads from non observable in-object properties.
+    ASSERT(!instr->access().IsInobject() ||
+           instr->access().existing_inobject_property());
+
     int field = FieldOf(instr->access());
     if (field < 0) return instr;
 
     HValue* object = instr->object()->ActualValue();
     HFieldApproximation* approx = FindOrCreate(object, field);
 
     if (approx->last_value_ == NULL) {
       // Load is not redundant. Fill out a new entry.
       approx->last_value_ = instr;
       return instr;
-    } else {
+    } else if (approx->last_value_->block()->EqualToOrDominates(
+        instr->block())) {
       // Eliminate the load. Reuse previously stored value or load instruction.
       return approx->last_value_;
+    } else {
+      return instr;
     }
   }
 
   // Process a store instruction, updating internal table state. If a previous
   // store to the same object and field makes this store redundant (e.g. because
   // the stored values are the same), return NULL indicating that this store
   // instruction is redundant. Otherwise, return {instr}.
   HValue* store(HStoreNamedField* instr) {
+    if (instr->access().IsInobject() &&
+        !instr->access().existing_inobject_property()) {
+      TRACE(("  skipping non existing property initialization store\n"));
+      return instr;
+    }
+
     int field = FieldOf(instr->access());
     if (field < 0) return KillIfMisaligned(instr);
 
     HValue* object = instr->object()->ActualValue();
     HValue* value = instr->value();
 
     if (instr->has_transition()) {
       // A transition introduces a new field and alters the map of the object.
       // Since the field in the object is new, it cannot alias existing entries.
       // TODO(titzer): introduce a constant for the new map and remember it.
@@ skipping 183 matching lines @@
   Zone* zone_;
   ZoneList<HFieldApproximation*> fields_;
   HAliasAnalyzer* aliasing_;
 };
 
 
 // Support for HFlowEngine: collect store effects within loops.
 class HLoadEliminationEffects : public ZoneObject {
  public:
   explicit HLoadEliminationEffects(Zone* zone)
-    : zone_(zone),
-      maps_stored_(false),
-      fields_stored_(false),
-      elements_stored_(false),
-      stores_(5, zone) { }
+    : zone_(zone), stores_(5, zone) { }
 
   inline bool Disabled() {
     return false;  // Effects are _not_ disabled.
   }
 
   // Process a possibly side-effecting instruction.
   void Process(HInstruction* instr, Zone* zone) {
-    switch (instr->opcode()) {
-      case HValue::kStoreNamedField: {
-        stores_.Add(HStoreNamedField::cast(instr), zone_);
-        break;
-      }
-      case HValue::kOsrEntry: {
-        // Kill everything. Loads must not be hoisted past the OSR entry.
-        maps_stored_ = true;
-        fields_stored_ = true;
-        elements_stored_ = true;
-      }
-      default: {
-        fields_stored_ |= instr->CheckGVNFlag(kChangesInobjectFields);
-        maps_stored_ |= instr->CheckGVNFlag(kChangesMaps);
-        maps_stored_ |= instr->CheckGVNFlag(kChangesElementsKind);
-        elements_stored_ |= instr->CheckGVNFlag(kChangesElementsKind);
-        elements_stored_ |= instr->CheckGVNFlag(kChangesElementsPointer);
-      }
+    if (instr->IsStoreNamedField()) {
+      stores_.Add(HStoreNamedField::cast(instr), zone_);
+    } else {
+      flags_.Add(instr->ChangesFlags());
     }
   }
 
   // Apply these effects to the given load elimination table.
   void Apply(HLoadEliminationTable* table) {
-    if (fields_stored_) {
+    // Loads must not be hoisted past the OSR entry, therefore we kill
+    // everything if we see an OSR entry.
+    if (flags_.Contains(kInobjectFields) || flags_.Contains(kOsrEntries)) {
       table->Kill();
       return;
     }
-    if (maps_stored_) {
+    if (flags_.Contains(kElementsKind) || flags_.Contains(kMaps)) {
       table->KillOffset(JSObject::kMapOffset);
     }
-    if (elements_stored_) {
+    if (flags_.Contains(kElementsKind) || flags_.Contains(kElementsPointer)) {
       table->KillOffset(JSObject::kElementsOffset);
     }
 
     // Kill non-agreeing fields for each store contained in these effects.
     for (int i = 0; i < stores_.length(); i++) {
       table->KillStore(stores_[i]);
     }
   }
 
   // Union these effects with the other effects.
   void Union(HLoadEliminationEffects* that, Zone* zone) {
-    maps_stored_ |= that->maps_stored_;
-    fields_stored_ |= that->fields_stored_;
-    elements_stored_ |= that->elements_stored_;
+    flags_.Add(that->flags_);
     for (int i = 0; i < that->stores_.length(); i++) {
       stores_.Add(that->stores_[i], zone);
     }
   }
 
  private:
   Zone* zone_;
-  bool maps_stored_ : 1;
-  bool fields_stored_ : 1;
-  bool elements_stored_ : 1;
+  GVNFlagSet flags_;
   ZoneList<HStoreNamedField*> stores_;
 };
 
 
 // The main routine of the analysis phase. Use the HFlowEngine for either a
 // local or a global analysis.
 void HLoadEliminationPhase::Run() {
   HFlowEngine<HLoadEliminationTable, HLoadEliminationEffects>
     engine(graph(), zone());
   HAliasAnalyzer aliasing;
   HLoadEliminationTable* table =
       new(zone()) HLoadEliminationTable(zone(), &aliasing);
 
   if (GLOBAL) {
     // Perform a global analysis.
     engine.AnalyzeDominatedBlocks(graph()->blocks()->at(0), table);
   } else {
     // Perform only local analysis.
     for (int i = 0; i < graph()->blocks()->length(); i++) {
       table->Kill();
       engine.AnalyzeOneBlock(graph()->blocks()->at(i), table);
     }
   }
 }
 
 } }  // namespace v8::internal