C++ PolyWord::IsDataPtr方法代码示例

// Process a value within the stack.
PolyWord ScanAddress::ScanStackAddress(PolyWord val, StackSpace *stack, bool isCode)
{
    PolyWord *base = stack->bottom;
    PolyWord *end = stack->top;

    // If isCode is set we definitely have a code address.  It may have the
    // bottom bit set or it may be word aligned.
    if (isCode || val.IsCodePtr())
    {
        /* Find the start of the code segment */
        PolyObject *oldObject = ObjCodePtrToPtr(val.AsCodePtr());
        // Calculate the byte offset of this value within the code object.
        POLYUNSIGNED offset = val.AsCodePtr() - (byte*)oldObject;
        PolyObject *newObject = ScanObjectAddress(oldObject);
        return PolyWord::FromCodePtr((byte*)newObject + offset);
    }

    else if (val.IsTagged() || val == PolyWord::FromUnsigned(0) || 
                 (val.AsAddress() > base && val.AsAddress() <= end))
            /* We don't need to process tagged integers (now we've checked it isn't
               a code address) and we don't need to process addresses within the
               current stack. */
            /* N.B. We have "<= end" rather than "< end" because it is possible for
               the stack to be completely empty on a terminated thread. */
           return val;

    else
    {
        ASSERT(val.IsDataPtr());
        return ScanObjectAddress(val.AsObjPtr());
    }
}

// Returns the new address if the argument is the address of an object that
// has moved, otherwise returns the original.
PolyWord SaveFixupAddress::GetNewAddress(PolyWord old)
{
    if (old.IsTagged() || old == PolyWord::FromUnsigned(0) || gMem.IsIOPointer(old.AsAddress()))
        return old; //  Nothing to do.

    // When we are updating addresses in the stack or in code segments we may have
    // code pointers.
    if (old.IsCodePtr())
    {
        // Find the start of the code segment
        PolyObject *oldObject = ObjCodePtrToPtr(old.AsCodePtr());
        // Calculate the byte offset of this value within the code object.
        POLYUNSIGNED offset = old.AsCodePtr() - (byte*)oldObject;
        PolyWord newObject = GetNewAddress(oldObject);
        return PolyWord::FromCodePtr(newObject.AsCodePtr() + offset);
    }

    ASSERT(old.IsDataPtr());

    PolyObject *obj = old.AsObjPtr();
    
    if (obj->ContainsForwardingPtr()) // tombstone is a pointer to a moved object
    {
        PolyObject *newp = obj->GetForwardingPtr();
        ASSERT (newp->ContainsNormalLengthWord());
        return newp;
    }
    
    ASSERT (obj->ContainsNormalLengthWord()); // object is not moved
    return old;
}

bool GetSharing::TestForScan(PolyWord *pt)
{
    PolyObject *obj;

    // This may be a forwarding pointer left over from a minor GC that did
    // not complete or it may be a sharing chain pointer that we've set up.
    while (1)
    {
        PolyWord p = *pt;
        ASSERT(p.IsDataPtr());
        obj = p.AsObjPtr();
        PolyWord *lengthWord = ((PolyWord*)obj) - 1;
        LocalMemSpace *space = gMem.LocalSpaceForAddress(lengthWord);
        if (space == 0)
            return false; // Ignore it if it points to a permanent area

        if (space->bitmap.TestBit(space->wordNo(lengthWord)))
            return false;

        // Wasn't marked - must be a forwarding pointer.
        if (obj->ContainsForwardingPtr())
        {
            obj = obj->GetForwardingPtr();
            *pt = obj;
        }
        else break;
    }

    ASSERT(obj->ContainsNormalLengthWord());

    totalVisited += 1;
    totalSize += obj->Length() + 1;

    return true;
}

void ProcessEnvModule::GarbageCollect(ScanAddress *process)
/* Ensures that all the objects are retained and their addresses updated. */
{
    if (at_exit_list.IsDataPtr())
    {
        PolyObject *obj = at_exit_list.AsObjPtr();
        process->ScanRuntimeAddress(&obj, ScanAddress::STRENGTH_STRONG);
        at_exit_list = obj;
    }
}

void DoCheckPointer (const PolyWord pt)
{
    if (pt == PolyWord::FromUnsigned(0)) return;

    if (OBJ_IS_AN_INTEGER(pt)) return;

    DoCheck (pt);

    if (pt.IsDataPtr())
    {
        PolyObject *obj = pt.AsObjPtr();
        DoCheckObject (obj, obj->LengthWord());
    }
}

// Returns the new address if the argument is the address of an object that
// has moved, otherwise returns the original.
PolyWord ProcessFixupAddress::GetNewAddress(PolyWord old)
{
    if (old.IsTagged() || old == PolyWord::FromUnsigned(0) || gMem.IsIOPointer(old.AsAddress()))
        return old; //  Nothing to do.

    // When we are updating addresses in the stack or in code segments we may have
    // code pointers.
    if (old.IsCodePtr())
    {
        // Find the start of the code segment
        PolyObject *oldObject = ObjCodePtrToPtr(old.AsCodePtr());
        // Calculate the byte offset of this value within the code object.
        POLYUNSIGNED offset = old.AsCodePtr() - (byte*)oldObject;
        PolyWord newObject = GetNewAddress(oldObject);
        return PolyWord::FromCodePtr(newObject.AsCodePtr() + offset);
    }

    ASSERT(old.IsDataPtr());

    PolyObject *obj = old.AsObjPtr();
    POLYUNSIGNED L = obj->LengthWord();

    // Generally each address will point to an object processed at a lower depth.
    // The exception is if we have a cycle and have assigned the rest of the
    // structure to a higher depth.
    // N.B. We return the original address here but this could actually share
    // with something else and not be retained.
    if (OBJ_IS_DEPTH(L))
        return old;

    if (obj->ContainsForwardingPtr()) // tombstone is a pointer to a shared object
    {
        PolyObject *newp = obj->GetForwardingPtr();
//        ASSERT (newp->ContainsNormalLengthWord());
        return newp;
    }

    ASSERT (obj->ContainsNormalLengthWord()); // object is not shared
    return old;
}

// Deal with weak objects
void MTGCCheckWeakRef::ScanAddressesInObject(PolyObject *obj, POLYUNSIGNED L)
{
    if (! OBJ_IS_WEAKREF_OBJECT(L)) return;
    ASSERT(OBJ_IS_MUTABLE_OBJECT(L)); // Should be a mutable.
    ASSERT(OBJ_IS_WORD_OBJECT(L)); // Should be a plain object.
    // See if any of the SOME objects contain unreferenced refs.
    POLYUNSIGNED length = OBJ_OBJECT_LENGTH(L);
    PolyWord *baseAddr = (PolyWord*)obj;
    for (POLYUNSIGNED i = 0; i < length; i++)
    {
        PolyWord someAddr = baseAddr[i];
        if (someAddr.IsDataPtr())
        {
            LocalMemSpace *someSpace = gMem.LocalSpaceForAddress(someAddr.AsAddress());
            if (someSpace != 0)
            {
                PolyObject *someObj = someAddr.AsObjPtr();
                // If this is a weak object the SOME value may refer to an unreferenced
                // ref.  If so we have to set this entry to NONE.  For safety we also
                // set the contents of the SOME to TAGGED(0).
                ASSERT(someObj->Length() == 1 && someObj->IsWordObject()); // Should be a SOME node.
                PolyWord refAddress = someObj->Get(0);
                LocalMemSpace *space = gMem.LocalSpaceForAddress(refAddress.AsAddress());
                if (space != 0)
                    // If the ref is permanent it's always there.
                {
                    POLYUNSIGNED new_bitno = space->wordNo(refAddress.AsStackAddr());
                    if (! space->bitmap.TestBit(new_bitno))
                    {
                        // It wasn't marked so it's otherwise unreferenced.
                        baseAddr[i] = TAGGED(0); // Set it to NONE.
                        someObj->Set(0, TAGGED(0)); // For safety.
                        convertedWeak = true;
                    }
                }
            }
        }
    }
}

// This is called via ScanAddressesInRegion to process the permanent mutables.  It is
// also called from ScanObjectAddress to process root addresses.
// It processes all the addresses reachable from the object.
void RecursiveScan::ScanAddressesInObject(PolyObject *obj, POLYUNSIGNED lengthWord)
{
    if (OBJ_IS_BYTE_OBJECT(lengthWord))
    {
        Completed(obj);
        return;
    }

    while (true)
    {
        ASSERT (OBJ_IS_LENGTH(lengthWord));

        // Get the length and base address.  N.B.  If this is a code segment
        // these will be side-effected by GetConstSegmentForCode.
        POLYUNSIGNED length = OBJ_OBJECT_LENGTH(lengthWord);
        PolyWord *baseAddr = (PolyWord*)obj;

        if (OBJ_IS_CODE_OBJECT(lengthWord))
        {
            // It's better to process the whole code object in one go.
            ScanAddress::ScanAddressesInObject(obj, lengthWord);
            length = 0; // Finished
        }
        ASSERT(! OBJ_IS_BYTE_OBJECT(lengthWord)); // Check - remove this later

        // else it's a normal object,

        // If there are only two addresses in this cell that need to be
        // followed we follow them immediately and treat this cell as done.
        // If there are more than two we push the address of this cell on
        // the stack, follow the first address and then rescan it.  That way
        // list cells are processed once only but we don't overflow the
        // stack by pushing all the addresses in a very large vector.
        PolyWord *endWord = baseAddr + length;
        PolyObject *firstWord = 0;
        PolyObject *secondWord = 0;

        while (baseAddr != endWord)
        {
            PolyWord wordAt = *baseAddr;

            if (wordAt.IsDataPtr() && wordAt != PolyWord::FromUnsigned(0))
            {
                // Normal address.  We can have words of all zeros at least in the
                // situation where we have a partially constructed code segment where
                // the constants at the end of the code have not yet been filled in.
                if (TestForScan(baseAddr)) // Test value at baseAddr (may side-effect it)
                {
                    PolyObject *wObj = (*baseAddr).AsObjPtr();
                    if (wObj->IsByteObject())
                    {
                        // Can do this now - don't need to push it
                        MarkAsScanning(wObj);
                        Completed(wObj);
                    }
                    else if (firstWord == 0)
                    {
                        firstWord = wObj;
                        // We mark the word immediately.  We can have
                        // two words in an object that are the same
                        // and we don't want to process it again.
                        MarkAsScanning(firstWord);
                    }
                    else if (secondWord == 0)
                        secondWord = wObj;
                    else break;  // More than two words.
                }
            }
            else if (wordAt.IsCodePtr())
            {
                // If we're processing the constant area of a code segment this could
                // be a code address.
                PolyObject *oldObject = ObjCodePtrToPtr(wordAt.AsCodePtr());
                // Calculate the byte offset of this value within the code object.
                POLYUNSIGNED offset = wordAt.AsCodePtr() - (byte*)oldObject;
                wordAt = oldObject;
                bool test = TestForScan(&wordAt);
                // TestForScan may side-effect the word.
                PolyObject *newObject = wordAt.AsObjPtr();
                wordAt = PolyWord::FromCodePtr((byte*)newObject + offset);
                if (wordAt != *baseAddr)
                    *baseAddr = wordAt;
                if (test)
                {
                    if (firstWord == 0)
                    {
                        firstWord = newObject;
                        MarkAsScanning(firstWord);
                    }
                    else if (secondWord == 0)
                        secondWord = newObject;
                    else break;
                }
            }
            baseAddr++;
        }

//.........这里部分代码省略.........

// This is called via ScanAddressesInRegion to process the permanent mutables.  It is
// also called from ScanObjectAddress to process root addresses.
// It processes all the addresses reachable from the object.
void MTGCProcessMarkPointers::ScanAddressesInObject(PolyObject *obj, POLYUNSIGNED lengthWord)
{
    if (OBJ_IS_BYTE_OBJECT(lengthWord))
        return;

    while (true)
    {
        ASSERT (OBJ_IS_LENGTH(lengthWord));

        // Get the length and base address.  N.B.  If this is a code segment
        // these will be side-effected by GetConstSegmentForCode.
        POLYUNSIGNED length = OBJ_OBJECT_LENGTH(lengthWord);

        if (OBJ_IS_WEAKREF_OBJECT(lengthWord))
        {
            // Special case.  
            ASSERT(OBJ_IS_MUTABLE_OBJECT(lengthWord)); // Should be a mutable.
            ASSERT(OBJ_IS_WORD_OBJECT(lengthWord)); // Should be a plain object.
            // We need to mark the "SOME" values in this object but we don't mark
            // the references contained within the "SOME".
            PolyWord *baseAddr = (PolyWord*)obj;
            // Mark every word but ignore the result.
            for (POLYUNSIGNED i = 0; i < length; i++)
                (void)MarkAndTestForScan(baseAddr+i);
            // We've finished with this.
            length = 0;
        }

        else if (OBJ_IS_CODE_OBJECT(lengthWord))
        {
            // It's better to process the whole code object in one go.
            ScanAddress::ScanAddressesInObject(obj, lengthWord);
            length = 0; // Finished
        }

        // else it's a normal object,

        // If there are only two addresses in this cell that need to be
        // followed we follow them immediately and treat this cell as done.
        // If there are more than two we push the address of this cell on
        // the stack, follow the first address and then rescan it.  That way
        // list cells are processed once only but we don't overflow the
        // stack by pushing all the addresses in a very large vector.
        PolyWord *baseAddr = (PolyWord*)obj;
        PolyWord *endWord = baseAddr + length;
        PolyObject *firstWord = 0;
        PolyObject *secondWord = 0;
        PolyWord *restartAddr = 0;

        if (obj == largeObjectCache[locPtr].base)
        {
            baseAddr = largeObjectCache[locPtr].current;
            ASSERT(baseAddr > (PolyWord*)obj && baseAddr < ((PolyWord*)obj)+length);
            if (locPtr == 0) locPtr = LARGECACHE_SIZE-1; else locPtr--;
        }

        while (baseAddr != endWord)
        {
            PolyWord wordAt = *baseAddr;

            if (wordAt.IsDataPtr() && wordAt != PolyWord::FromUnsigned(0))
            {
                // Normal address.  We can have words of all zeros at least in the
                // situation where we have a partially constructed code segment where
                // the constants at the end of the code have not yet been filled in.
                if (TestForScan(baseAddr))
                {
                    if (firstWord == 0)
                        firstWord = baseAddr->AsObjPtr();
                    else if (secondWord == 0)
                    {
                        // If we need to rescan because there are three or more words to do
                        // this is the place we need to restart (or the start of the cell if it's
                        // small).
                        restartAddr = baseAddr;
                        secondWord = baseAddr->AsObjPtr();
                    }
                    else break;  // More than two words.
                }
            }
            else if (wordAt.IsCodePtr())
            {
                // If we're processing the constant area of a code segment this could
                // be a code address.
                // Check that this is actually an address.  If we have had a bad pointer
                // earlier we may treat some length fields as values.
                ASSERT(gMem.SpaceForAddress(wordAt.AsCodePtr()) != 0);
                PolyObject *oldObject = ObjCodePtrToPtr(wordAt.AsCodePtr());
                // Calculate the byte offset of this value within the code object.
                POLYUNSIGNED offset = wordAt.AsCodePtr() - (byte*)oldObject;
                wordAt = oldObject;
                bool test = TestForScan(&wordAt);
                // If we've changed it because we had a left-over forwarding pointer
                // we need to update the original.
                PolyObject *newObject = wordAt.AsObjPtr();
                wordAt = PolyWord::FromCodePtr((byte*)newObject + offset);
                if (wordAt != *baseAddr)
//.........这里部分代码省略.........

// Process one level of the word data.
// N.B.  The length words are updated without any locking.  This is safe
// because all length words are initially chain entries and a chain entry
// can be replaced by another chain entry, a forwarding pointer or a normal
// length word.  Forwarding pointers and normal length words are only ever
// set once.  There is a small chance that we could lose some sharing as a
// result of a race condition if a thread defers an object because it
// contains a pointer with a chain entry and later sees an otherwise
// equal object where another thread has replaced the chain with a
// normal address, adds it to the list for immediate processing and
// so never compares the two.
void SortVector::wordDataTask(GCTaskId*, void *a, void *)
{
    SortVector *s = (SortVector*)a;
    // Partition the objects between those that have pointers to objects that are
    // still to be processed and those that have been processed.
    if (s->baseObject.objList == ENDOFLIST)
        return;
    PolyObject *h = s->baseObject.objList;
    s->baseObject.objList = ENDOFLIST;
    s->baseObject.objCount = 0;
    POLYUNSIGNED words = OBJ_OBJECT_LENGTH(s->lengthWord);
    s->carryOver = 0;

    for (unsigned i = 0; i < 256; i++)
    {
        // Clear the entries in the hash table but not the sharing count.
        s->processObjects[i].objList = ENDOFLIST;
        s->processObjects[i].objCount = 0;
    }

    while (h != ENDOFLIST)
    {
        PolyObject *next = h->GetForwardingPtr();
        bool deferred = false;
        for (POLYUNSIGNED i = 0; i < words; i++)
        {
            PolyWord w = h->Get(i);
            if (w.IsDataPtr())
            {
                PolyObject *p = w.AsObjPtr();
                objectState state = getObjectState(p);
                if (state == FORWARDED)
                {
                    // Update the addresses of objects that have been merged
                    h->Set(i, p->GetForwardingPtr());
                    s->carryOver++;
                    break;
                }
                else if (state == CHAINED)
                {
                    // If it is still to be shared leave it
                    deferred = true;
                    break; // from the loop
                }
            }
        }
        if (deferred)
        {
            // We can't do it yet: add it back to the list
            h->SetForwardingPtr(s->baseObject.objList);
            s->baseObject.objList = h;
            s->baseObject.objCount++;
        }
        else
        {
            // Add it to the hash table.
            unsigned char hash = 0;
            for (POLYUNSIGNED i = 0; i < words*sizeof(PolyWord); i++)
                hash += h->AsBytePtr()[i];
            h->SetForwardingPtr(s->processObjects[hash].objList);
            s->processObjects[hash].objList = h;
            s->processObjects[hash].objCount++;
        }
        h = next;
    }
    s->SortData();
}