Improve positions tracking inside the HGraphBuilder.

src/hydrogen-instructions.h

 // 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 526 matching lines @@
 
   HValue* base_;
   int offset_;
   int scale_;
 };
 
 
 typedef EnumSet<GVNFlag, int64_t> GVNFlagSet;
 
 
+// This class encapsulates encoding and decoding of sources positions from
+// which hydrogen values originated.
+// When FLAG_track_hydrogen_positions is set this object encodes the
+// identifier of the inlining and absolute offset from the start of the
+// inlined function.
+// When the flag is not set we simply track absolute offset from the
+// script start.
+class HSourcePosition {
+ public:
+  HSourcePosition(const HSourcePosition& other) : value_(other.value_) { }
+
+  static HSourcePosition Unknown() {
+    return HSourcePosition(RelocInfo::kNoPosition);
+  }
+
+  bool IsUnknown() const { return value_ == RelocInfo::kNoPosition; }
+
+  int position() const { return PositionField::decode(value_); }
+  void set_position(int position) {
+    if (FLAG_hydrogen_track_positions) {
+      value_ = static_cast<int>(PositionField::update(value_, position));
+    } else {
+      value_ = position;
+    }
+  }
+
+  int inlining_id() const { return InliningIdField::decode(value_); }
+  void set_inlining_id(int inlining_id) {
+    if (FLAG_hydrogen_track_positions) {
+      value_ = static_cast<int>(InliningIdField::update(value_, inlining_id));
+    }
+  }
+
+  int raw() const { return value_; }
+
+  void PrintTo(FILE* f);
+
+ private:
+  typedef BitField<int, 0, 9> InliningIdField;
+
+  // Offset from the start of the inlined function.
+  typedef BitField<int, 9, 23> PositionField;
+
+  // On HPositionInfo can use this constructor.
+  explicit HSourcePosition(int value) : value_(value) { }
+
+  friend class HPositionInfo;
+
+  // If FLAG_hydrogen_track_positions is set contains bitfields InliningIdField
+  // and PositionField.
+  // Otherwise contains absolute offset from the script start.
+  int value_;
+};
+
+
 class HValue : public ZoneObject {
  public:
   static const int kNoNumber = -1;
 
   enum Flag {
     kFlexibleRepresentation,
     kCannotBeTagged,
     // Participate in Global Value Numbering, i.e. elimination of
     // unnecessary recomputations. If an instruction sets this flag, it must
     // implement DataEquals(), which will be used to determine if other
@@ skipping 73 matching lines @@
 
   HValue(HType type = HType::Tagged())
       : block_(NULL),
         id_(kNoNumber),
         type_(type),
         use_list_(NULL),
         range_(NULL),
         flags_(0) {}
   virtual ~HValue() {}
 
-  virtual int position() const { return RelocInfo::kNoPosition; }
-  virtual int operand_position(int index) const { return position(); }
+  virtual HSourcePosition position() const {
+    return HSourcePosition::Unknown();
+  }
+  virtual HSourcePosition operand_position(int index) const {
+    return position();
+  }
 
   HBasicBlock* block() const { return block_; }
   void SetBlock(HBasicBlock* block);
 
   // Note: Never call this method for an unlinked value.
   Isolate* isolate() const;
 
   int id() const { return id_; }
   void set_id(int id) { id_ = id; }
 
@@ skipping 449 matching lines @@
   }
 
 
 // A helper class to represent per-operand position information attached to
 // the HInstruction in the compact form. Uses tagging to distinguish between
 // case when only instruction's position is available and case when operands'
 // positions are also available.
 // In the first case it contains intruction's position as a tagged value.
 // In the second case it points to an array which contains instruction's
 // position and operands' positions.
 // TODO(vegorov): what we really want to track here is a combination of

[Yang, 2014/02/12 17:32:06]

Is this still a TODO?

[Vyacheslav Egorov (Chromium), 2014/02/13 16:17:43]

Done.

 // source position and a script id because cross script inlining can easily
 // result in optimized functions composed of several scripts.
 class HPositionInfo {
  public:
   explicit HPositionInfo(int pos) : data_(TagPosition(pos)) { }
 
-  int position() const {
+  HSourcePosition position() const {
     if (has_operand_positions()) {
-      return static_cast<int>(operand_positions()[kInstructionPosIndex]);
+      return operand_positions()[kInstructionPosIndex];
     }
-    return static_cast<int>(UntagPosition(data_));
+    return HSourcePosition(static_cast<int>(UntagPosition(data_)));
   }
 
-  void set_position(int pos) {
+  void set_position(HSourcePosition pos) {
     if (has_operand_positions()) {
       operand_positions()[kInstructionPosIndex] = pos;
     } else {
-      data_ = TagPosition(pos);
+      data_ = TagPosition(pos.raw());
     }
   }
 
   void ensure_storage_for_operand_positions(Zone* zone, int operand_count) {
     if (has_operand_positions()) {
       return;
     }
 
     const int length = kFirstOperandPosIndex + operand_count;
-    intptr_t* positions =
-        zone->NewArray<intptr_t>(length);
+    HSourcePosition* positions =
+        zone->NewArray<HSourcePosition>(length);
     for (int i = 0; i < length; i++) {
-      positions[i] = RelocInfo::kNoPosition;
+      positions[i] = HSourcePosition::Unknown();
     }
 
-    const int pos = position();
+    const HSourcePosition pos = position();
     data_ = reinterpret_cast<intptr_t>(positions);
     set_position(pos);
 
     ASSERT(has_operand_positions());
   }
 
-  int operand_position(int idx) const {
+  HSourcePosition operand_position(int idx) const {
     if (!has_operand_positions()) {
       return position();
     }
-    return static_cast<int>(*operand_position_slot(idx));
+    return *operand_position_slot(idx);
   }
 
-  void set_operand_position(int idx, int pos) {
+  void set_operand_position(int idx, HSourcePosition pos) {
     *operand_position_slot(idx) = pos;
   }
 
  private:
   static const intptr_t kInstructionPosIndex = 0;
   static const intptr_t kFirstOperandPosIndex = 1;
 
-  intptr_t* operand_position_slot(int idx) const {
+  HSourcePosition* operand_position_slot(int idx) const {
     ASSERT(has_operand_positions());
     return &(operand_positions()[kFirstOperandPosIndex + idx]);
   }
 
   bool has_operand_positions() const {
     return !IsTaggedPosition(data_);
   }
 
-  intptr_t* operand_positions() const {
+  HSourcePosition* operand_positions() const {
     ASSERT(has_operand_positions());
-    return reinterpret_cast<intptr_t*>(data_);
+    return reinterpret_cast<HSourcePosition*>(data_);
   }
 
   static const intptr_t kPositionTag = 1;
   static const intptr_t kPositionShift = 1;
   static bool IsTaggedPosition(intptr_t val) {
     return (val & kPositionTag) != 0;
   }
   static intptr_t UntagPosition(intptr_t val) {
     ASSERT(IsTaggedPosition(val));
     return val >> kPositionShift;
   }
   static intptr_t TagPosition(intptr_t val) {
     const intptr_t result = (val << kPositionShift) | kPositionTag;

[Yang, 2014/02/12 17:32:06]

The way the bit fields in HSourcePosition are defined, all of the 32 bits are
used. So on a 32-bit platform, won't we lose the most significant bit through
tagging?

[Vyacheslav Egorov (Chromium), 2014/02/13 16:17:43]

Good catch!

I was using 31 bits originally to avoid loosing any, but then I was cleaning up
some code and ended up with 32 bits in HSourcePosition. I will fix it.

     ASSERT(UntagPosition(result) == val);
     return result;
   }
 
   intptr_t data_;
 };
 
 
 class HInstruction : public HValue {
  public:
   HInstruction* next() const { return next_; }
   HInstruction* previous() const { return previous_; }
 
   virtual void PrintTo(StringStream* stream) V8_OVERRIDE;
   virtual void PrintDataTo(StringStream* stream);
 
   bool IsLinked() const { return block() != NULL; }
   void Unlink();
   void InsertBefore(HInstruction* next);
   void InsertAfter(HInstruction* previous);
 
   // The position is a write-once variable.
-  virtual int position() const V8_OVERRIDE {
-    return position_.position();
+  virtual HSourcePosition position() const V8_OVERRIDE {
+    return HSourcePosition(position_.position());
   }
   bool has_position() const {
-    return position_.position() != RelocInfo::kNoPosition;
+    return !position().IsUnknown();
   }
-  void set_position(int position) {
+  void set_position(HSourcePosition position) {
     ASSERT(!has_position());
-    ASSERT(position != RelocInfo::kNoPosition);
+    ASSERT(!position.IsUnknown());
     position_.set_position(position);
   }
 
-  virtual int operand_position(int index) const V8_OVERRIDE {
-    const int pos = position_.operand_position(index);
-    return (pos != RelocInfo::kNoPosition) ? pos : position();
+  virtual HSourcePosition operand_position(int index) const V8_OVERRIDE {
+    const HSourcePosition pos = position_.operand_position(index);
+    return pos.IsUnknown() ? position() : pos;
   }
-  void set_operand_position(Zone* zone, int index, int pos) {
+  void set_operand_position(Zone* zone, int index, HSourcePosition pos) {
     ASSERT(0 <= index && index < OperandCount());
     position_.ensure_storage_for_operand_positions(zone, OperandCount());
     position_.set_operand_position(index, pos);
   }
 
   bool CanTruncateToInt32() const { return CheckFlag(kTruncatingToInt32); }
 
   virtual LInstruction* CompileToLithium(LChunkBuilder* builder) = 0;
 
 #ifdef DEBUG
@@ skipping 2030 matching lines @@
   virtual HValue* OperandAt(int index) const V8_OVERRIDE {
     return inputs_[index];
   }
   HValue* GetRedundantReplacement();
   void AddInput(HValue* value);
   bool HasRealUses();
 
   bool IsReceiver() const { return merged_index_ == 0; }
   bool HasMergedIndex() const { return merged_index_ != kInvalidMergedIndex; }
 
-  virtual int position() const V8_OVERRIDE;
+  virtual HSourcePosition position() const V8_OVERRIDE;
 
   int merged_index() const { return merged_index_; }
 
   InductionVariableData* induction_variable_data() {
     return induction_variable_data_;
   }
   bool IsInductionVariable() {
     return induction_variable_data_ != NULL;
   }
   bool IsLimitedInductionVariable() {
@@ skipping 516 matching lines @@
 
   virtual bool IsCommutative() const { return false; }
 
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
 
   virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
     if (index == 0) return Representation::Tagged();
     return representation();
   }
 
-  void SetOperandPositions(Zone* zone, int left_pos, int right_pos) {
+  void SetOperandPositions(Zone* zone,
+                           HSourcePosition left_pos,
+                           HSourcePosition right_pos) {
     set_operand_position(zone, 1, left_pos);
     set_operand_position(zone, 2, right_pos);
   }
 
   DECLARE_ABSTRACT_INSTRUCTION(BinaryOperation)
 
  private:
   bool IgnoreObservedOutputRepresentation(Representation current_rep);
 
   Representation observed_input_representation_[2];
@@ skipping 419 matching lines @@
       HInferRepresentationPhase* h_infer) V8_OVERRIDE;
 
   virtual Representation RequiredInputRepresentation(int index) V8_OVERRIDE {
     return representation();
   }
   virtual Representation observed_input_representation(int index) V8_OVERRIDE {
     return observed_input_representation_[index];
   }
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
 
-  void SetOperandPositions(Zone* zone, int left_pos, int right_pos) {
+  void SetOperandPositions(Zone* zone,
+                           HSourcePosition left_pos,
+                           HSourcePosition right_pos) {
     set_operand_position(zone, 0, left_pos);
     set_operand_position(zone, 1, right_pos);
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CompareNumericAndBranch)
 
  private:
   HCompareNumericAndBranch(HValue* left,
                            HValue* right,
                            Token::Value token,
@@ skipping 3286 matching lines @@
   virtual bool IsDeletable() const V8_OVERRIDE { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_