[heap] Untangle Marking and friends from heap dependencies.

src/heap/marking.h

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_MARKING_H
+#define V8_MARKING_H
+
+#include "src/utils.h"
+
+namespace v8 {
+namespace internal {
+
+class MarkBit {
+ public:
+  typedef uint32_t CellType;
+
+  inline MarkBit(CellType* cell, CellType mask) : cell_(cell), mask_(mask) {}
+
+#ifdef DEBUG
+  bool operator==(const MarkBit& other) {
+    return cell_ == other.cell_ && mask_ == other.mask_;
+  }
+#endif
+
+ private:
+  inline CellType* cell() { return cell_; }
+  inline CellType mask() { return mask_; }
+
+  inline MarkBit Next() {
+    CellType new_mask = mask_ << 1;
+    if (new_mask == 0) {
+      return MarkBit(cell_ + 1, 1);
+    } else {
+      return MarkBit(cell_, new_mask);
+    }
+  }
+
+  inline void Set() { *cell_ |= mask_; }
+  inline bool Get() { return (*cell_ & mask_) != 0; }
+  inline void Clear() { *cell_ &= ~mask_; }
+
+  CellType* cell_;
+  CellType mask_;
+
+  friend class IncrementalMarking;
+  friend class Marking;
+};
+
+// Bitmap is a sequence of cells each containing fixed number of bits.
+class Bitmap {
+ public:
+  static const uint32_t kBitsPerCell = 32;
+  static const uint32_t kBitsPerCellLog2 = 5;
+  static const uint32_t kBitIndexMask = kBitsPerCell - 1;
+  static const uint32_t kBytesPerCell = kBitsPerCell / kBitsPerByte;
+  static const uint32_t kBytesPerCellLog2 = kBitsPerCellLog2 - kBitsPerByteLog2;
+
+  static const size_t kLength = (1 << kPageSizeBits) >> (kPointerSizeLog2);
+
+  static const size_t kSize = (1 << kPageSizeBits) >>
+                              (kPointerSizeLog2 + kBitsPerByteLog2);
+
+  static int CellsForLength(int length) {
+    return (length + kBitsPerCell - 1) >> kBitsPerCellLog2;
+  }
+
+  int CellsCount() { return CellsForLength(kLength); }
+
+  static int SizeFor(int cells_count) {
+    return sizeof(MarkBit::CellType) * cells_count;
+  }
+
+  INLINE(static uint32_t IndexToCell(uint32_t index)) {
+    return index >> kBitsPerCellLog2;
+  }
+
+  V8_INLINE static uint32_t IndexInCell(uint32_t index) {
+    return index & kBitIndexMask;
+  }
+
+  INLINE(static uint32_t CellToIndex(uint32_t index)) {
+    return index << kBitsPerCellLog2;
+  }
+
+  INLINE(static uint32_t CellAlignIndex(uint32_t index)) {
+    return (index + kBitIndexMask) & ~kBitIndexMask;
+  }
+
+  INLINE(MarkBit::CellType* cells()) {
+    return reinterpret_cast<MarkBit::CellType*>(this);
+  }
+
+  INLINE(Address address()) { return reinterpret_cast<Address>(this); }
+
+  INLINE(static Bitmap* FromAddress(Address addr)) {
+    return reinterpret_cast<Bitmap*>(addr);
+  }
+
+  inline MarkBit MarkBitFromIndex(uint32_t index) {
+    MarkBit::CellType mask = 1u << IndexInCell(index);
+    MarkBit::CellType* cell = this->cells() + (index >> kBitsPerCellLog2);
+    return MarkBit(cell, mask);
+  }
+
+  void Clear() {
+    for (int i = 0; i < CellsCount(); i++) cells()[i] = 0;
+  }
+
+  void SetAllBits() {
+    for (int i = 0; i < CellsCount(); i++) cells()[i] = 0xffffffff;
+  }
+
+  static void PrintWord(uint32_t word, uint32_t himask = 0) {
+    for (uint32_t mask = 1; mask != 0; mask <<= 1) {
+      if ((mask & himask) != 0) PrintF("[");
+      PrintF((mask & word) ? "1" : "0");
+      if ((mask & himask) != 0) PrintF("]");
+    }
+  }
+
+  class CellPrinter {
+   public:
+    CellPrinter() : seq_start(0), seq_type(0), seq_length(0) {}
+
+    void Print(uint32_t pos, uint32_t cell) {
+      if (cell == seq_type) {
+        seq_length++;
+        return;
+      }
+
+      Flush();
+
+      if (IsSeq(cell)) {
+        seq_start = pos;
+        seq_length = 0;
+        seq_type = cell;
+        return;
+      }
+
+      PrintF("%d: ", pos);
+      PrintWord(cell);
+      PrintF("\n");
+    }
+
+    void Flush() {
+      if (seq_length > 0) {
+        PrintF("%d: %dx%d\n", seq_start, seq_type == 0 ? 0 : 1,
+               seq_length * kBitsPerCell);
+        seq_length = 0;
+      }
+    }
+
+    static bool IsSeq(uint32_t cell) { return cell == 0 || cell == 0xFFFFFFFF; }
+
+   private:
+    uint32_t seq_start;
+    uint32_t seq_type;
+    uint32_t seq_length;
+  };
+
+  void Print() {
+    CellPrinter printer;
+    for (int i = 0; i < CellsCount(); i++) {
+      printer.Print(i, cells()[i]);
+    }
+    printer.Flush();
+    PrintF("\n");
+  }
+
+  bool IsClean() {
+    for (int i = 0; i < CellsCount(); i++) {
+      if (cells()[i] != 0) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  // Clears all bits starting from {cell_base_index} up to and excluding
+  // {index}. Note that {cell_base_index} is required to be cell aligned.
+  void ClearRange(uint32_t cell_base_index, uint32_t index) {
+    DCHECK_EQ(IndexInCell(cell_base_index), 0u);
+    DCHECK_GE(index, cell_base_index);
+    uint32_t start_cell_index = IndexToCell(cell_base_index);
+    uint32_t end_cell_index = IndexToCell(index);
+    DCHECK_GE(end_cell_index, start_cell_index);
+    // Clear all cells till the cell containing the last index.
+    for (uint32_t i = start_cell_index; i < end_cell_index; i++) {
+      cells()[i] = 0;
+    }
+    // Clear all bits in the last cell till the last bit before index.
+    uint32_t clear_mask = ~((1u << IndexInCell(index)) - 1);
+    cells()[end_cell_index] &= clear_mask;
+  }
+};
+
+class Marking : public AllStatic {
+ public:
+  // Impossible markbits: 01
+  static const char* kImpossibleBitPattern;
+  INLINE(static bool IsImpossible(MarkBit mark_bit)) {
+    return !mark_bit.Get() && mark_bit.Next().Get();
+  }
+
+  // Black markbits: 11
+  static const char* kBlackBitPattern;
+  INLINE(static bool IsBlack(MarkBit mark_bit)) {
+    return mark_bit.Get() && mark_bit.Next().Get();
+  }
+
+  // White markbits: 00 - this is required by the mark bit clearer.
+  static const char* kWhiteBitPattern;
+  INLINE(static bool IsWhite(MarkBit mark_bit)) {
+    DCHECK(!IsImpossible(mark_bit));
+    return !mark_bit.Get();
+  }
+
+  // Grey markbits: 10
+  static const char* kGreyBitPattern;
+  INLINE(static bool IsGrey(MarkBit mark_bit)) {
+    return mark_bit.Get() && !mark_bit.Next().Get();
+  }
+
+  // IsBlackOrGrey assumes that the first bit is set for black or grey
+  // objects.
+  INLINE(static bool IsBlackOrGrey(MarkBit mark_bit)) { return mark_bit.Get(); }
+
+  INLINE(static void MarkBlack(MarkBit mark_bit)) {
+    mark_bit.Set();
+    mark_bit.Next().Set();
+  }
+
+  INLINE(static void MarkWhite(MarkBit mark_bit)) {
+    mark_bit.Clear();
+    mark_bit.Next().Clear();
+  }
+
+  INLINE(static void BlackToWhite(MarkBit markbit)) {
+    DCHECK(IsBlack(markbit));
+    markbit.Clear();
+    markbit.Next().Clear();
+  }
+
+  INLINE(static void GreyToWhite(MarkBit markbit)) {
+    DCHECK(IsGrey(markbit));
+    markbit.Clear();
+    markbit.Next().Clear();
+  }
+
+  INLINE(static void BlackToGrey(MarkBit markbit)) {
+    DCHECK(IsBlack(markbit));
+    markbit.Next().Clear();
+  }
+
+  INLINE(static void WhiteToGrey(MarkBit markbit)) {
+    DCHECK(IsWhite(markbit));
+    markbit.Set();
+  }
+
+  INLINE(static void WhiteToBlack(MarkBit markbit)) {
+    DCHECK(IsWhite(markbit));
+    markbit.Set();
+    markbit.Next().Set();
+  }
+
+  INLINE(static void GreyToBlack(MarkBit markbit)) {
+    DCHECK(IsGrey(markbit));
+    markbit.Next().Set();
+  }
+
+  INLINE(static void AnyToGrey(MarkBit markbit)) {
+    markbit.Set();
+    markbit.Next().Clear();
+  }
+
+#ifdef DEBUG
+  enum ObjectColor {
+    BLACK_OBJECT,
+    WHITE_OBJECT,
+    GREY_OBJECT,
+    IMPOSSIBLE_COLOR
+  };
+
+  static const char* ColorName(ObjectColor color) {
+    switch (color) {
+      case BLACK_OBJECT:
+        return "black";
+      case WHITE_OBJECT:
+        return "white";
+      case GREY_OBJECT:
+        return "grey";
+      case IMPOSSIBLE_COLOR:
+        return "impossible";
+    }
+    return "error";
+  }
+
+  static ObjectColor Color(MarkBit mark_bit) {
+    if (IsBlack(mark_bit)) return BLACK_OBJECT;
+    if (IsWhite(mark_bit)) return WHITE_OBJECT;
+    if (IsGrey(mark_bit)) return GREY_OBJECT;
+    UNREACHABLE();
+    return IMPOSSIBLE_COLOR;
+  }
+#endif
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(Marking);
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_MARKING_H_