MemoryManager: Remove grayBitmap

We're not using gray items anywhere. There is no need to waste the
memory for the bitmap.

Change-Id: I26983cbc005531184ed955cea6026b9a8c5be910
Reviewed-by: Sami Shalayel <sami.shalayel@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

4 files changed, 1 insertions, 75 deletions

diff --git a/src/qml/memory/qv4heap_p.h b/src/qml/memory/qv4heap_p.h
index b4bd3c4cd6..41150fd9e1 100644
--- a/src/qml/memory/qv4heap_p.h
+++ b/src/qml/memory/qv4heap_p.h
@@ -77,12 +77,6 @@ struct Q_QML_EXPORT Base {
         Q_ASSERT(!Chunk::testBit(c->extendsBitmap, h - c->realBase()));
         return Chunk::setBit(c->blackBitmap, h - c->realBase());
     }
-    inline void setGrayBit() {
-        const HeapItem *h = reinterpret_cast<const HeapItem *>(this);
-        Chunk *c = h->chunk();
-        Q_ASSERT(!Chunk::testBit(c->extendsBitmap, h - c->realBase()));
-        return Chunk::setBit(c->grayBitmap, h - c->realBase());
-    }
 
     inline bool inUse() const {
         const HeapItem *h = reinterpret_cast<const HeapItem *>(this);
diff --git a/src/qml/memory/qv4mm.cpp b/src/qml/memory/qv4mm.cpp
index 3add05b95e..a7892e9729 100644
--- a/src/qml/memory/qv4mm.cpp
+++ b/src/qml/memory/qv4mm.cpp
@@ -24,7 +24,6 @@
 #include "qv4profiling_p.h"
 #include "qv4mapobject_p.h"
 #include "qv4setobject_p.h"
-#include "qv4writebarrier_p.h"
 
 //#define MM_STATS
 
@@ -272,9 +271,6 @@ bool Chunk::sweep(ExecutionEngine *engine)
     HeapItem *o = realBase();
     bool lastSlotFree = false;
     for (uint i = 0; i < Chunk::EntriesInBitmap; ++i) {
-#if WRITEBARRIER(none)
-        Q_ASSERT((grayBitmap[i] | blackBitmap[i]) == blackBitmap[i]); // check that we don't have gray only objects
-#endif
         quintptr toFree = objectBitmap[i] ^ blackBitmap[i];
         Q_ASSERT((toFree & objectBitmap[i]) == toFree); // check all black objects are marked as being used
         quintptr e = extendsBitmap[i];
@@ -318,7 +314,6 @@ bool Chunk::sweep(ExecutionEngine *engine)
                                                       - (blackBitmap[i] | e)) * Chunk::SlotSize,
                              Profiling::SmallItem);
         objectBitmap[i] = blackBitmap[i];
-        grayBitmap[i] = 0;
         hasUsedSlots |= (blackBitmap[i] != 0);
         extendsBitmap[i] = e;
         lastSlotFree = !((objectBitmap[i]|extendsBitmap[i]) >> (sizeof(quintptr)*8 - 1));
@@ -368,7 +363,6 @@ void Chunk::freeAll(ExecutionEngine *engine)
         Q_V4_PROFILE_DEALLOC(engine, (qPopulationCount(objectBitmap[i]|extendsBitmap[i])
                              - qPopulationCount(e)) * Chunk::SlotSize, Profiling::SmallItem);
         objectBitmap[i] = 0;
-        grayBitmap[i] = 0;
         extendsBitmap[i] = e;
         o += Chunk::Bits;
     }
@@ -380,36 +374,6 @@ void Chunk::resetBlackBits()
     memset(blackBitmap, 0, sizeof(blackBitmap));
 }
 
-void Chunk::collectGrayItems(MarkStack *markStack)
-{
-    //    DEBUG << "sweeping chunk" << this << (*freeList);
-    HeapItem *o = realBase();
-    for (uint i = 0; i < Chunk::EntriesInBitmap; ++i) {
-#if WRITEBARRIER(none)
-        Q_ASSERT((grayBitmap[i] | blackBitmap[i]) == blackBitmap[i]); // check that we don't have gray only objects
-#endif
-        quintptr toMark = blackBitmap[i] & grayBitmap[i]; // correct for a Steele type barrier
-        Q_ASSERT((toMark & objectBitmap[i]) == toMark); // check all black objects are marked as being used
-        //        DEBUG << hex << "   index=" << i << toFree;
-        while (toMark) {
-            uint index = qCountTrailingZeroBits(toMark);
-            quintptr bit = (static_cast<quintptr>(1) << index);
-
-            toMark ^= bit; // mask out marked slot
-            //            DEBUG << "       index" << hex << index << toFree;
-
-            HeapItem *itemToFree = o + index;
-            Heap::Base *b = *itemToFree;
-            Q_ASSERT(b->inUse());
-            markStack->push(b);
-        }
-        grayBitmap[i] = 0;
-        o += Chunk::Bits;
-    }
-    //    DEBUG << "swept chunk" << this << "freed" << slotsFreed << "slots.";
-
-}
-
 void Chunk::sortIntoBins(HeapItem **bins, uint nBins)
 {
 //    qDebug() << "sortIntoBins:";
@@ -622,13 +586,6 @@ void BlockAllocator::resetBlackBits()
         c->resetBlackBits();
 }
 
-void BlockAllocator::collectGrayItems(MarkStack *markStack)
-{
-    for (auto c : chunks)
-        c->collectGrayItems(markStack);
-
-}
-
 HeapItem *HugeItemAllocator::allocate(size_t size) {
     MemorySegment *m = nullptr;
     Chunk *c = nullptr;
@@ -698,18 +655,6 @@ void HugeItemAllocator::resetBlackBits()
         Chunk::clearBit(c.chunk->blackBitmap, c.chunk->first() - c.chunk->realBase());
 }
 
-void HugeItemAllocator::collectGrayItems(MarkStack *markStack)
-{
-    for (auto c : chunks)
-        // Correct for a Steele type barrier
-        if (Chunk::testBit(c.chunk->blackBitmap, c.chunk->first() - c.chunk->realBase()) &&
-            Chunk::testBit(c.chunk->grayBitmap, c.chunk->first() - c.chunk->realBase())) {
-            HeapItem *i = c.chunk->first();
-            Heap::Base *b = *i;
-            b->mark(markStack);
-        }
-}
-
 void HugeItemAllocator::freeAll()
 {
     for (auto &c : chunks) {
diff --git a/src/qml/memory/qv4mm_p.h b/src/qml/memory/qv4mm_p.h
index cb1d2567b3..378b36369d 100644
--- a/src/qml/memory/qv4mm_p.h
+++ b/src/qml/memory/qv4mm_p.h
@@ -22,10 +22,6 @@
 #include <private/qv4mmdefs_p.h>
 #include <QVector>
 
-#define QV4_MM_MAXBLOCK_SHIFT "QV4_MM_MAXBLOCK_SHIFT"
-#define QV4_MM_MAX_CHUNK_SIZE "QV4_MM_MAX_CHUNK_SIZE"
-#define QV4_MM_STATS "QV4_MM_STATS"
-
 #define MM_DEBUG 0
 
 QT_BEGIN_NAMESPACE
@@ -67,7 +63,6 @@ struct BlockAllocator {
     void sweep();
     void freeAll();
     void resetBlackBits();
-    void collectGrayItems(MarkStack *markStack);
 
     // bump allocations
     HeapItem *nextFree = nullptr;
@@ -89,7 +84,6 @@ struct HugeItemAllocator {
     void sweep(ClassDestroyStatsCallback classCountPtr);
     void freeAll();
     void resetBlackBits();
-    void collectGrayItems(MarkStack *markStack);
 
     size_t usedMem() const {
         size_t used = 0;
diff --git a/src/qml/memory/qv4mmdefs_p.h b/src/qml/memory/qv4mmdefs_p.h
index c873bfd5f8..a7fc7bb7cb 100644
--- a/src/qml/memory/qv4mmdefs_p.h
+++ b/src/qml/memory/qv4mmdefs_p.h
@@ -59,7 +59,7 @@ struct Chunk {
         SlotSizeShift = 5,
         NumSlots = ChunkSize/SlotSize,
         BitmapSize = NumSlots/8,
-        HeaderSize = 4*BitmapSize,
+        HeaderSize = 3*BitmapSize,
         DataSize = ChunkSize - HeaderSize,
         AvailableSlots = DataSize/SlotSize,
 #if QT_POINTER_SIZE == 8
@@ -71,7 +71,6 @@ struct Chunk {
 #endif
         EntriesInBitmap = BitmapSize/sizeof(quintptr)
     };
-    quintptr grayBitmap[BitmapSize/sizeof(quintptr)];
     quintptr blackBitmap[BitmapSize/sizeof(quintptr)];
     quintptr objectBitmap[BitmapSize/sizeof(quintptr)];
     quintptr extendsBitmap[BitmapSize/sizeof(quintptr)];
@@ -152,7 +151,6 @@ struct Chunk {
 
     bool sweep(ClassDestroyStatsCallback classCountPtr);
     void resetBlackBits();
-    void collectGrayItems(QV4::MarkStack *markStack);
     bool sweep(ExecutionEngine *engine);
     void freeAll(ExecutionEngine *engine);
 
@@ -176,11 +174,6 @@ struct HeapItem {
         return reinterpret_cast<Chunk *>(reinterpret_cast<quintptr>(this) >> Chunk::ChunkShift << Chunk::ChunkShift);
     }
 
-    bool isGray() const {
-        Chunk *c = chunk();
-        std::ptrdiff_t index = this - c->realBase();
-        return Chunk::testBit(c->grayBitmap, index);
-    }
     bool isBlack() const {
         Chunk *c = chunk();
         std::ptrdiff_t index = this - c->realBase();