Track global cells as special side effects in GVN.

src/hydrogen-gvn.h

 // 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 40 matching lines @@
   bool IsEmpty() const { return bits_ == 0; }
   bool ContainsFlag(GVNFlag flag) const {
     return (bits_ & MaskFlag(flag)) != 0;
   }
   bool ContainsSpecial(int special) const {
     return (bits_ & MaskSpecial(special)) != 0;
   }
   bool ContainsAnyOf(SideEffects set) const { return (bits_ & set.bits_) != 0; }
   void Add(SideEffects set) { bits_ |= set.bits_; }
   void AddSpecial(int special) { bits_ |= MaskSpecial(special); }
-  void AddAllSpecial() { bits_ |= ~static_cast<uint64_t>(0) << kNumberOfFlags; }
   void RemoveFlag(GVNFlag flag) { bits_ &= ~MaskFlag(flag); }
   void RemoveAll() { bits_ = 0; }
   uint64_t ToIntegral() const { return bits_; }
   void PrintTo(StringStream* stream) const;
 
  private:
   uint64_t MaskFlag(GVNFlag flag) const {
     return static_cast<uint64_t>(1) << static_cast<unsigned>(flag);
   }
   uint64_t MaskSpecial(int special) const {
     ASSERT(special >= 0);
     ASSERT(special < kNumberOfSpecials);
     return static_cast<uint64_t>(1) << static_cast<unsigned>(
         special + kNumberOfFlags);
   }
 
   uint64_t bits_;
 };
 
 
-// Tracks inobject field loads/stores in a fine grained fashion, and represents
-// them using the "special" dynamic side effects of the SideEffects class (see
-// above). This way unrelated inobject field stores don't prevent hoisting and
-// merging of inobject field loads.
+// Tracks global variable and inobject field loads/stores in a fine grained
+// fashion, and represents them using the "special" dynamic side effects of the
+// SideEffects class (see above). This way unrelated global variable/inobject
+// field stores don't prevent hoisting and merging of global variable/inobject
+// field loads.
 class SideEffectsTracker V8_FINAL BASE_EMBEDDED {
  public:
-  SideEffectsTracker() : num_inobject_fields_(0) {}
+  SideEffectsTracker() : num_global_vars_(0), num_inobject_fields_(0) {}
   SideEffects ComputeChanges(HInstruction* instr);
   SideEffects ComputeDependsOn(HInstruction* instr);
   void PrintSideEffectsTo(StringStream* stream, SideEffects side_effects) const;
 
  private:
+  bool ComputeGlobalVar(Unique<Cell> cell, int* index);
   bool ComputeInobjectField(HObjectAccess access, int* index);
 
-  HObjectAccess inobject_fields_[SideEffects::kNumberOfSpecials];
+  static int GlobalVar(int index) {
+    ASSERT(index >= 0);
+    ASSERT(index < kNumberOfGlobalVars);
+    return index;
+  }
+  static int InobjectField(int index) {
+    ASSERT(index >= 0);
+    ASSERT(index < kNumberOfInobjectFields);
+    return index + kNumberOfGlobalVars;
+  }
+
+  // Track up to four global vars.
+  static const int kNumberOfGlobalVars = 4;
+  Unique<Cell> global_vars_[kNumberOfGlobalVars];
+  int num_global_vars_;
+
+  // Track up to n inobject fields.
+  static const int kNumberOfInobjectFields =
+      SideEffects::kNumberOfSpecials - kNumberOfGlobalVars;
+  HObjectAccess inobject_fields_[kNumberOfInobjectFields];
   int num_inobject_fields_;
 };
 
 
 // Perform common subexpression elimination and loop-invariant code motion.
 class HGlobalValueNumberingPhase V8_FINAL : public HPhase {
  public:
   explicit HGlobalValueNumberingPhase(HGraph* graph);
 
   void Run();
@@ skipping 23 matching lines @@
   // Used when collecting side effects on paths from dominator to
   // dominated.
   BitVector visited_on_paths_;
 
   DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_GVN_H_