Remove write-barriers for stores to new-space objects.

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 1303 matching lines @@
     ASSERT(new_element_pos != kNil);
     free_list_head_ = lists_[free_list_head_].next;
     lists_[new_element_pos].value = value;
     lists_[new_element_pos].next = array_[pos].next;
     ASSERT(array_[pos].next == kNil || lists_[array_[pos].next].value != NULL);
     array_[pos].next = new_element_pos;
   }
 }
 
 
+HSideEffectMap::HSideEffectMap() : count_(0) {
+  memset(data_, 0, kNumberOfTrackedSideEffects * kPointerSize);
+}
+
+
+HSideEffectMap::HSideEffectMap(HSideEffectMap& other) : count_(other.count_) {
+  memcpy(data_, other.data_, kNumberOfTrackedSideEffects * kPointerSize);
+}
+
+
+void HSideEffectMap::Kill(GVNFlagSet flags) {
+  for (int i = 0; i < kNumberOfTrackedSideEffects; i++) {
+    GVNFlag changes_flag = static_cast<GVNFlag>(i * 2);
+    if (flags.Contains(changes_flag)) {
+      if (data_[i] != NULL) count_--;
+      data_[i] = NULL;
+    }
+  }
+}
+
+
+void HSideEffectMap::Store(GVNFlagSet flags, HInstruction* instr) {
+  for (int i = 0; i < kNumberOfTrackedSideEffects; i++) {
+    GVNFlag changes_flag = static_cast<GVNFlag>(i * 2);
+    if (flags.Contains(changes_flag)) {
+      if (data_[i] == NULL) count_++;
+      data_[i] = instr;
+    }
+  }
+}
+
+
 class HStackCheckEliminator BASE_EMBEDDED {
  public:
   explicit HStackCheckEliminator(HGraph* graph) : graph_(graph) { }
 
   void Process();
 
  private:
   HGraph* graph_;
 };
 
@@ skipping 86 matching lines @@
     ASSERT(!info_->isolate()->heap()->allow_allocation(true));
   }
 
   // Returns true if values with side effects are removed.
   bool Analyze();
 
  private:
   GVNFlagSet CollectSideEffectsOnPathsToDominatedBlock(
       HBasicBlock* dominator,
       HBasicBlock* dominated);
-  void AnalyzeBlock(HBasicBlock* block, HValueMap* map);
+  void AnalyzeBlock(HBasicBlock* block,
+                    HValueMap* map,
+                    HSideEffectMap& dominators);
   void ComputeBlockSideEffects();
   void LoopInvariantCodeMotion();
   void ProcessLoopBlock(HBasicBlock* block,
                         HBasicBlock* before_loop,
                         GVNFlagSet loop_kills,
                         GVNFlagSet* accumulated_first_time_depends,
                         GVNFlagSet* accumulated_first_time_changes);
   bool AllowCodeMotion();
   bool ShouldMove(HInstruction* instr, HBasicBlock* loop_header);
 
@@ skipping 17 matching lines @@
 };
 
 
 bool HGlobalValueNumberer::Analyze() {
   removed_side_effects_ = false;
   ComputeBlockSideEffects();
   if (FLAG_loop_invariant_code_motion) {
     LoopInvariantCodeMotion();
   }
   HValueMap* map = new(zone()) HValueMap();
-  AnalyzeBlock(graph_->entry_block(), map);
+  HSideEffectMap side_effect_dominators;
+  AnalyzeBlock(graph_->entry_block(), map, side_effect_dominators);
   return removed_side_effects_;
 }
 
 
 void HGlobalValueNumberer::ComputeBlockSideEffects() {
   // The Analyze phase of GVN can be called multiple times. Clear loop side
   // effects before computing them to erase the contents from previous Analyze
   // passes.
   for (int i = 0; i < loop_side_effects_.length(); ++i) {
     loop_side_effects_[i].RemoveAll();
@@ skipping 174 matching lines @@
         side_effects.Add(loop_side_effects_[block->block_id()]);
       }
       side_effects.Add(CollectSideEffectsOnPathsToDominatedBlock(
           dominator, block));
     }
   }
   return side_effects;
 }
 
 
-void HGlobalValueNumberer::AnalyzeBlock(HBasicBlock* block, HValueMap* map) {
+void HGlobalValueNumberer::AnalyzeBlock(HBasicBlock* block,
+                                        HValueMap* map,
+                                        HSideEffectMap& dominators) {

[Erik Corry, 2012/04/10 12:06:52]

This should be a pointer argument:
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Reference_Argu...

[Michael Starzinger, 2012/04/11 09:53:08]

Done.

   TraceGVN("Analyzing block B%d%s\n",
            block->block_id(),
            block->IsLoopHeader() ? " (loop header)" : "");
 
   // If this is a loop header kill everything killed by the loop.
   if (block->IsLoopHeader()) {
     map->Kill(loop_side_effects_[block->block_id()]);
   }
 
   // Go through all instructions of the current block.
   HInstruction* instr = block->first();
   while (instr != NULL) {
     HInstruction* next = instr->next();
     GVNFlagSet flags = instr->ChangesFlags();
     if (!flags.IsEmpty()) {
       // Clear all instructions in the map that are affected by side effects.
+      // Store instruction as the dominating one for tracked side effects.
       map->Kill(flags);
+      dominators.Store(flags, instr);
       TraceGVN("Instruction %d kills\n", instr->id());
     }
     if (instr->CheckFlag(HValue::kUseGVN)) {
       ASSERT(!instr->HasObservableSideEffects());
       HValue* other = map->Lookup(instr);
       if (other != NULL) {
         ASSERT(instr->Equals(other) && other->Equals(instr));
         TraceGVN("Replacing value %d (%s) with value %d (%s)\n",
                  instr->id(),
                  instr->Mnemonic(),
                  other->id(),
                  other->Mnemonic());
         if (instr->HasSideEffects()) removed_side_effects_ = true;
         instr->DeleteAndReplaceWith(other);
       } else {
         map->Add(instr);
       }
     }
+    if (instr->CheckFlag(HValue::kTrackSideEffectDominators)) {
+      for (int i = 0; i < kNumberOfTrackedSideEffects; i++) {
+        GVNFlag changes_flag = static_cast<GVNFlag>(i * 2);
+        GVNFlag depends_on_flag = static_cast<GVNFlag>(i * 2 + 1);

[Erik Corry, 2012/04/10 12:06:52]

This would be cleaner with a variable to hold dominators[i] that you can use in
the 4 places below.

[Michael Starzinger, 2012/04/11 09:53:08]

Done.

+        if (instr->DependsOnFlags().Contains(depends_on_flag) &&
+            (dominators[i] != NULL)) {
+          TraceGVN("Side-effect #%d in %d (%s) is dominated by %d (%s)\n",
+                   i,
+                   instr->id(),
+                   instr->Mnemonic(),
+                   dominators[i]->id(),
+                   dominators[i]->Mnemonic());
+          instr->SetSideEffectDominator(changes_flag, dominators[i]);
+        }
+      }
+    }
     instr = next;
   }
 
   // Recursively continue analysis for all immediately dominated blocks.
   int length = block->dominated_blocks()->length();
   for (int i = 0; i < length; ++i) {
     HBasicBlock* dominated = block->dominated_blocks()->at(i);
     // No need to copy the map for the last child in the dominator tree.
     HValueMap* successor_map = (i == length - 1) ? map : map->Copy(zone());
+    HSideEffectMap successor_dominators(dominators);
 
     // Kill everything killed on any path between this block and the
-    // dominated block.
-    // We don't have to traverse these paths if the value map is
-    // already empty.
-    // If the range of block ids (block_id, dominated_id) is empty
-    // there are no such paths.
-    if (!successor_map->IsEmpty() &&
+    // dominated block.  We don't have to traverse these paths if the
+    // value map and the dominators list is already empty.  If the range
+    // of block ids (block_id, dominated_id) is empty there are no such
+    // paths.
+    if ((!successor_map->IsEmpty() || !successor_dominators.IsEmpty()) &&
         block->block_id() + 1 < dominated->block_id()) {
       visited_on_paths_.Clear();
-      successor_map->Kill(CollectSideEffectsOnPathsToDominatedBlock(block,
-                                                                    dominated));
+      GVNFlagSet side_effects_on_all_paths =
+          CollectSideEffectsOnPathsToDominatedBlock(block, dominated);
+      successor_map->Kill(side_effects_on_all_paths);
+      successor_dominators.Kill(side_effects_on_all_paths);
     }
-    AnalyzeBlock(dominated, successor_map);
+    AnalyzeBlock(dominated, successor_map, successor_dominators);
   }
 }
 
 
 class HInferRepresentation BASE_EMBEDDED {
  public:
   explicit HInferRepresentation(HGraph* graph)
       : graph_(graph),
         worklist_(8),
         in_worklist_(graph->GetMaximumValueID(), graph->zone()) { }
@@ skipping 6499 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal