Improve inobject field tracking during GVN.

src/hydrogen-gvn.h

Index: src/hydrogen-gvn.h
diff --git a/src/hydrogen-gvn.h b/src/hydrogen-gvn.h
index 30333cca61045d7292496cece8aa3235c173e7fb..3da3ecfbf085a5e940b7f432a4db323a3079f503 100644
--- a/src/hydrogen-gvn.h
+++ b/src/hydrogen-gvn.h
@@ -36,15 +36,76 @@
 namespace v8 {
 namespace internal {
 
+// This class extends GVNFlagSet with additional "special" dynamic side effects,
+// which can be used to represent side effects that cannot be expressed using
+// the GVNFlags of an HInstruction. These special side effects are tracked by a
+// SideEffectsTracker (see below).
+class SideEffects V8_FINAL {
+ public:
+  static const int kNumberOfSpecials = 64 - kNumberOfFlags;
+
+  SideEffects() : bits_(0) {}
+  explicit SideEffects(GVNFlagSet flags) : bits_(flags.ToIntegral()) {}
+  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_;
+  STATIC_ASSERT(kNumberOfFlags + kNumberOfSpecials == sizeof(bits_) * CHAR_BIT);
+};
+
+
+// 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.
+class SideEffectsTracker V8_FINAL BASE_EMBEDDED {
+ public:
+  SideEffectsTracker() : num_inobject_fields_(0) {}
+  SideEffects ComputeChanges(HInstruction* instr);
+  SideEffects ComputeDependsOn(HInstruction* instr);
+  void PrintSideEffectsTo(StringStream* stream, SideEffects side_effects) const;
+
+ private:
+  bool ComputeInobjectField(HObjectAccess access, int* index);
+
+  HObjectAccess inobject_fields_[SideEffects::kNumberOfSpecials];
+  int num_inobject_fields_;
+};
+
+
 // Perform common subexpression elimination and loop-invariant code motion.
-class HGlobalValueNumberingPhase : public HPhase {
+class HGlobalValueNumberingPhase V8_FINAL : public HPhase {
  public:
   explicit HGlobalValueNumberingPhase(HGraph* graph);
 
   void Run();
 
  private:
-  GVNFlagSet CollectSideEffectsOnPathsToDominatedBlock(
+  SideEffects CollectSideEffectsOnPathsToDominatedBlock(
       HBasicBlock* dominator,
       HBasicBlock* dominated);
   void AnalyzeGraph();
@@ -52,17 +113,18 @@ class HGlobalValueNumberingPhase : public HPhase {
   void LoopInvariantCodeMotion();
   void ProcessLoopBlock(HBasicBlock* block,
                         HBasicBlock* before_loop,
-                        GVNFlagSet loop_kills);
+                        SideEffects loop_kills);
   bool AllowCodeMotion();
   bool ShouldMove(HInstruction* instr, HBasicBlock* loop_header);
 
+  SideEffectsTracker side_effects_tracker_;
   bool removed_side_effects_;
 
   // A map of block IDs to their side effects.
-  ZoneList<GVNFlagSet> block_side_effects_;
+  ZoneList<SideEffects> block_side_effects_;
 
   // A map of loop header block IDs to their loop's side effects.
-  ZoneList<GVNFlagSet> loop_side_effects_;
+  ZoneList<SideEffects> loop_side_effects_;
 
   // Used when collecting side effects on paths from dominator to
   // dominated.
@@ -71,7 +133,6 @@ class HGlobalValueNumberingPhase : public HPhase {
   DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
 };
 
-
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_GVN_H_