[heap] Remove black pages and use black areas instead.

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 {
@@ skipping 88 matching lines @@
   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;
+  void SetRange(uint32_t start_index, uint32_t end_index) {

[ulan, 2016/07/19 13:23:32]

Let's add a comment describing that it sets bits in range [start_index,
end_index): end is not included.

[Hannes Payer (out of office), 2016/07/19 14:42:53]

Done.

+    unsigned int start_cell_index = start_index >> Bitmap::kBitsPerCellLog2;
+    MarkBit::CellType start_index_mask = 1u << Bitmap::IndexInCell(start_index);
+
+    unsigned int end_cell_index = end_index >> Bitmap::kBitsPerCellLog2;
+    MarkBit::CellType end_index_mask = 1u << Bitmap::IndexInCell(end_index);
+
+    if (start_cell_index != end_cell_index) {
+      // Firstly, fill all bits from the start address to the end of the first
+      // cell with 1s.
+      cells()[start_cell_index] |= ~(start_index_mask - 1);
+      // Then fill all in between cells with 1s.
+      for (unsigned int i = start_cell_index + 1; i < end_cell_index; i++) {
+        cells()[i] = ~0u;
+      }
+      // Finally, fill all bits until the end address in the last cell with 1s.
+      cells()[end_cell_index] |= (end_index_mask - 1);
+    } else {
+      cells()[start_cell_index] |= end_index_mask - start_index_mask;
+    }
+  }
+
+  void ClearRange(uint32_t start_index, uint32_t end_index) {
+    unsigned int start_cell_index = start_index >> Bitmap::kBitsPerCellLog2;
+    MarkBit::CellType start_index_mask = 1u << Bitmap::IndexInCell(start_index);
+
+    unsigned int end_cell_index = end_index >> Bitmap::kBitsPerCellLog2;
+    MarkBit::CellType end_index_mask = 1u << Bitmap::IndexInCell(end_index);
+
+    if (start_cell_index != end_cell_index) {
+      // Firstly, fill all bits from the start address to the end of the first
+      // cell with 0s.
+      cells()[start_cell_index] &= (start_index_mask - 1);
+      // Then fill all in between cells with 0s.
+      for (unsigned int i = start_cell_index + 1; i < end_cell_index; i++) {
+        cells()[i] = 0;
+      }
+      // Finally, set all bits until the end address in the last cell with 0s.
+      cells()[end_cell_index] &= ~(end_index_mask - 1);
+    } else {
+      cells()[start_cell_index] &= ~(end_index_mask - start_index_mask);
+    }
   }
 
   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("]");
     }
   }
 
@@ skipping 47 matching lines @@
   }
 
   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();
   }
 
@@ skipping 98 matching lines @@
   }
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Marking);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_MARKING_H_