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());

[Michael Starzinger, 2014/03/06 15:45:28]

See comment below.

[Benedikt Meurer, 2014/03/07 06:23:58]

Done.

+    }
+  }
   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_);

[Michael Starzinger, 2014/03/06 15:45:28]

Dereferencing the handle here will not work if we are on the compiler thread. We
could print the hashcode of the Unique instead. On the other hand, cells are not
relocated, so we could broaden the assert.

[Benedikt Meurer, 2014/03/07 06:23:58]

Done.

+      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_;