Track global cells as special side effects in GVN.

src/hydrogen-gvn.cc

Index: src/hydrogen-gvn.cc
diff --git a/src/hydrogen-gvn.cc b/src/hydrogen-gvn.cc
index 6bf5a1b68e4fc3a2a8cdcaf02da63e614c63e1ee..4c98015bee1ef86d9ff7fc2f2c646c4e60e7fd82 100644
--- a/src/hydrogen-gvn.cc
+++ b/src/hydrogen-gvn.cc
@@ -367,15 +367,28 @@ void HSideEffectMap::Store(SideEffects side_effects, HInstruction* instr) {
 
 
 SideEffects SideEffectsTracker::ComputeChanges(HInstruction* instr) {
+  int index;
   SideEffects result(instr->ChangesFlags());
+  if (result.ContainsFlag(kGlobalVars)) {
+    if (instr->IsStoreGlobalCell() &&
+        ComputeGlobalVar(HStoreGlobalCell::cast(instr)->cell(), &index)) {
+      result.RemoveFlag(kGlobalVars);
+      result.AddSpecial(GlobalVar(index));
+    } else {
+      for (index = 0; index < kNumberOfGlobalVars; ++index) {
+        result.AddSpecial(GlobalVar(index));
+      }
+    }
+  }
   if (result.ContainsFlag(kInobjectFields)) {
-    int index;
     if (instr->IsStoreNamedField() &&
         ComputeInobjectField(HStoreNamedField::cast(instr)->access(), &index)) {
       result.RemoveFlag(kInobjectFields);
-      result.AddSpecial(index);
+      result.AddSpecial(InobjectField(index));
     } else {
-      result.AddAllSpecial();
+      for (index = 0; index < kNumberOfInobjectFields; ++index) {
+        result.AddSpecial(InobjectField(index));
+      }
     }
   }
   return result;
@@ -383,15 +396,28 @@ SideEffects SideEffectsTracker::ComputeChanges(HInstruction* instr) {
 
 
 SideEffects SideEffectsTracker::ComputeDependsOn(HInstruction* instr) {
+  int index;
   SideEffects result(instr->DependsOnFlags());
+  if (result.ContainsFlag(kGlobalVars)) {
+    if (instr->IsLoadGlobalCell() &&
+        ComputeGlobalVar(HLoadGlobalCell::cast(instr)->cell(), &index)) {
+      result.RemoveFlag(kGlobalVars);
+      result.AddSpecial(GlobalVar(index));
+    } else {
+      for (index = 0; index < kNumberOfGlobalVars; ++index) {
+        result.AddSpecial(GlobalVar(index));
+      }
+    }
+  }
   if (result.ContainsFlag(kInobjectFields)) {
-    int index;
     if (instr->IsLoadNamedField() &&
         ComputeInobjectField(HLoadNamedField::cast(instr)->access(), &index)) {
       result.RemoveFlag(kInobjectFields);
-      result.AddSpecial(index);
+      result.AddSpecial(InobjectField(index));
     } else {
-      result.AddAllSpecial();
+      for (index = 0; index < kNumberOfInobjectFields; ++index) {
+        result.AddSpecial(InobjectField(index));
+      }
     }
   }
   return result;
@@ -420,8 +446,15 @@ GVN_UNTRACKED_FLAG_LIST(DECLARE_FLAG)
       }
     }
   }
+  for (int index = 0; index < num_global_vars_; ++index) {
+    if (side_effects.ContainsSpecial(GlobalVar(index))) {
+      stream->Add(separator);
+      separator = ", ";
+      stream->Add("[%p]", *global_vars_[index].handle());
+    }
+  }
   for (int index = 0; index < num_inobject_fields_; ++index) {
-    if (side_effects.ContainsSpecial(index)) {
+    if (side_effects.ContainsSpecial(InobjectField(index))) {
       stream->Add(separator);
       separator = ", ";
       inobject_fields_[index].PrintTo(stream);
@@ -431,6 +464,29 @@ GVN_UNTRACKED_FLAG_LIST(DECLARE_FLAG)
 }
 
 
+bool SideEffectsTracker::ComputeGlobalVar(Unique<Cell> cell, int* index) {
+  for (int i = 0; i < num_global_vars_; ++i) {
+    if (cell == global_vars_[i]) {
+      *index = i;
+      return true;
+    }
+  }
+  if (num_global_vars_ < kNumberOfGlobalVars) {
+    if (FLAG_trace_gvn) {
+      HeapStringAllocator allocator;
+      StringStream stream(&allocator);
+      stream.Add("Tracking global var [%p] (mapped to index %d)\n",
+                 *cell.handle(), num_global_vars_);
+      stream.OutputToStdOut();
+    }
+    *index = num_global_vars_;
+    global_vars_[num_global_vars_++] = cell;
+    return true;
+  }
+  return false;
+}
+
+
 bool SideEffectsTracker::ComputeInobjectField(HObjectAccess access,
                                               int* index) {
   for (int i = 0; i < num_inobject_fields_; ++i) {
@@ -439,13 +495,13 @@ bool SideEffectsTracker::ComputeInobjectField(HObjectAccess access,
       return true;
     }
   }
-  if (num_inobject_fields_ < SideEffects::kNumberOfSpecials) {
+  if (num_inobject_fields_ < kNumberOfInobjectFields) {
     if (FLAG_trace_gvn) {
       HeapStringAllocator allocator;
       StringStream stream(&allocator);
       stream.Add("Tracking inobject field access ");
       access.PrintTo(&stream);
-      stream.Add(" (mapped to special index %d)\n", num_inobject_fields_);
+      stream.Add(" (mapped to index %d)\n", num_inobject_fields_);
       stream.OutputToStdOut();
     }
     *index = num_inobject_fields_;