C++ FrameEntry::isCopy方法代码示例

void
FrameState::assertValidRegisterState() const
{
    Registers checkedFreeRegs;

    FrameEntry *tos = tosFe();
    for (uint32 i = 0; i < tracker.nentries; i++) {
        FrameEntry *fe = tracker[i];
        if (fe >= tos)
            continue;

        JS_ASSERT(i == fe->trackerIndex());
        JS_ASSERT_IF(fe->isCopy(),
                     fe->trackerIndex() > fe->copyOf()->trackerIndex());
        JS_ASSERT_IF(fe->isCopy(), !fe->type.inRegister() && !fe->data.inRegister());
        JS_ASSERT_IF(fe->isCopy(), fe->copyOf() < tos);
        JS_ASSERT_IF(fe->isCopy(), fe->copyOf()->isCopied());

        if (fe->isCopy())
            continue;
        if (fe->type.inRegister()) {
            checkedFreeRegs.takeReg(fe->type.reg());
            JS_ASSERT(regstate[fe->type.reg()].fe == fe);
        }
        if (fe->data.inRegister()) {
            checkedFreeRegs.takeReg(fe->data.reg());
            JS_ASSERT(regstate[fe->data.reg()].fe == fe);
        }
    }

    JS_ASSERT(checkedFreeRegs == freeRegs);
}

void
FrameState::pushCopyOf(uint32 index)
{
    FrameEntry *backing = entryFor(index);
    FrameEntry *fe = rawPush();
    fe->resetUnsynced();
    if (backing->isConstant()) {
        fe->setConstant(Jsvalify(backing->getValue()));
    } else {
        if (backing->isTypeKnown())
            fe->setType(backing->getKnownType());
        else
            fe->type.invalidate();
        fe->isNumber = backing->isNumber;
        fe->data.invalidate();
        if (backing->isCopy()) {
            backing = backing->copyOf();
            fe->setCopyOf(backing);
        } else {
            fe->setCopyOf(backing);
            backing->setCopied();
        }

        /* Maintain tracker ordering guarantees for copies. */
        JS_ASSERT(backing->isCopied());
        if (fe->trackerIndex() < backing->trackerIndex())
            swapInTracker(fe, backing);
    }
}

void
FrameState::merge(Assembler &masm, Changes changes) const
{
    FrameEntry *tos = tosFe();
    Registers temp(Registers::TempRegs);

    for (uint32 i = 0; i < tracker.nentries; i++) {
        FrameEntry *fe = tracker[i];
        if (fe >= tos)
            continue;

        /* Copies do not have registers. */
        if (fe->isCopy()) {
            JS_ASSERT(!fe->data.inRegister());
            JS_ASSERT(!fe->type.inRegister());
            continue;
        }

        if (fe->data.inRegister() && fe->type.inRegister())
            masm.loadValueAsComponents(addressOf(fe), fe->type.reg(), fe->data.reg());
        else if (fe->data.inRegister())
            masm.loadPayload(addressOf(fe), fe->data.reg());
        else if (fe->type.inRegister())
            masm.loadTypeTag(addressOf(fe), fe->type.reg());
    }
}

void
FrameState::storeLocal(uint32 n, bool popGuaranteed, bool typeChange)
{
    FrameEntry *localFe = getLocal(n);
    bool cacheable = !eval && !escaping[n];

    if (!popGuaranteed && !cacheable) {
        JS_ASSERT_IF(base[localIndex(n)] && (!eval || n < script->nfixed),
                     entries[localIndex(n)].type.inMemory() &&
                     entries[localIndex(n)].data.inMemory());
        Address local(JSFrameReg, sizeof(JSStackFrame) + n * sizeof(Value));
        storeTo(peek(-1), local, false);
        forgetAllRegs(getLocal(n));
        localFe->resetSynced();
        return;
    }

    bool wasSynced = localFe->type.synced();

    /* Detect something like (x = x) which is a no-op. */
    FrameEntry *top = peek(-1);
    if (top->isCopy() && top->copyOf() == localFe) {
        JS_ASSERT(localFe->isCopied());
        return;
    }

    /* Completely invalidate the local variable. */
    if (localFe->isCopied()) {
        uncopy(localFe);
        if (!localFe->isCopied())
            forgetAllRegs(localFe);
    } else {
        forgetAllRegs(localFe);
    }

    localFe->resetUnsynced();

    /* Constants are easy to propagate. */
    if (top->isConstant()) {
        localFe->setCopyOf(NULL);
        localFe->setNotCopied();
        localFe->setConstant(Jsvalify(top->getValue()));
        return;
    }

    /*
     * When dealing with copies, there are two important invariants:
     *
     * 1) The backing store precedes all copies in the tracker.
     * 2) The backing store of a local is never a stack slot, UNLESS the local
     *    variable itself is a stack slot (blocks) that precedes the stack
     *    slot.
     *
     * If the top is a copy, and the second condition holds true, the local
     * can be rewritten as a copy of the original backing slot. If the first
     * condition does not hold, force it to hold by swapping in-place.
     */
    FrameEntry *backing = top;
    if (top->isCopy()) {
        backing = top->copyOf();
        JS_ASSERT(backing->trackerIndex() < top->trackerIndex());

        uint32 backingIndex = indexOfFe(backing);
        uint32 tol = uint32(spBase - base);
        if (backingIndex < tol || backingIndex < localIndex(n)) {
            /* local.idx < backing.idx means local cannot be a copy yet */
            if (localFe->trackerIndex() < backing->trackerIndex())
                swapInTracker(backing, localFe);
            localFe->setNotCopied();
            localFe->setCopyOf(backing);
            if (backing->isTypeKnown())
                localFe->setType(backing->getKnownType());
            else
                localFe->type.invalidate();
            localFe->data.invalidate();
            localFe->isNumber = backing->isNumber;
            return;
        }

        /*
         * If control flow lands here, then there was a bytecode sequence like
         *
         *  ENTERBLOCK 2
         *  GETLOCAL 1
         *  SETLOCAL 0
         *
         * The problem is slot N can't be backed by M if M could be popped
         * before N. We want a guarantee that when we pop M, even if it was
         * copied, it has no outstanding copies.
         * 
         * Because of |let| expressions, it's kind of hard to really know
         * whether a region on the stack will be popped all at once. Bleh!
         *
         * This should be rare except in browser code (and maybe even then),
         * but even so there's a quick workaround. We take all copies of the
         * backing fe, and redirect them to be copies of the destination.
         */
        FrameEntry *tos = tosFe();
        for (uint32 i = backing->trackerIndex() + 1; i < tracker.nentries; i++) {
            FrameEntry *fe = tracker[i];
//.........这里部分代码省略.........

void
FrameState::sync(Assembler &masm, Uses uses) const
{
    /*
     * Keep track of free registers using a bitmask. If we have to drop into
     * syncFancy(), then this mask will help avoid eviction.
     */
    Registers avail(freeRegs);
    Registers temp(Registers::TempRegs);

    FrameEntry *tos = tosFe();
    FrameEntry *bottom = tos - uses.nuses;

    if (inTryBlock)
        bottom = NULL;

    for (uint32 i = tracker.nentries - 1; i < tracker.nentries; i--) {
        FrameEntry *fe = tracker[i];
        if (fe >= tos)
            continue;

        Address address = addressOf(fe);

        if (!fe->isCopy()) {
            /* Keep track of registers that can be clobbered. */
            if (fe->data.inRegister())
                avail.putReg(fe->data.reg());
            if (fe->type.inRegister())
                avail.putReg(fe->type.reg());

            /* Sync. */
            if (!fe->data.synced() && (fe->data.inRegister() || fe >= bottom)) {
                syncData(fe, address, masm);
                if (fe->isConstant())
                    continue;
            }
            if (!fe->type.synced() && (fe->type.inRegister() || fe >= bottom))
                syncType(fe, addressOf(fe), masm);
        } else if (fe >= bottom) {
            FrameEntry *backing = fe->copyOf();
            JS_ASSERT(backing != fe);
            JS_ASSERT(!backing->isConstant() && !fe->isConstant());

            /*
             * If the copy is backed by something not in a register, fall back
             * to a slower sync algorithm.
             */
            if ((!fe->type.synced() && !backing->type.inRegister()) ||
                (!fe->data.synced() && !backing->data.inRegister())) {
                syncFancy(masm, avail, i, bottom);
                return;
            }

            if (!fe->type.synced()) {
                /* :TODO: we can do better, the type is learned for all copies. */
                if (fe->isTypeKnown()) {
                    //JS_ASSERT(fe->getTypeTag() == backing->getTypeTag());
                    masm.storeTypeTag(ImmType(fe->getKnownType()), address);
                } else {
                    masm.storeTypeTag(backing->type.reg(), address);
                }
            }

            if (!fe->data.synced())
                masm.storePayload(backing->data.reg(), address);
        }
    }
}

void
FrameState::allocForBinary(FrameEntry *lhs, FrameEntry *rhs, JSOp op, BinaryAlloc &alloc,
                           bool needsResult)
{
    FrameEntry *backingLeft = lhs;
    FrameEntry *backingRight = rhs;

    if (backingLeft->isCopy())
        backingLeft = backingLeft->copyOf();
    if (backingRight->isCopy())
        backingRight = backingRight->copyOf();

    /*
     * For each remat piece of both FEs, if a register is assigned, get it now
     * and pin it. This is safe - constants and known types will be avoided.
     */
    if (AllocHelper(backingLeft->type, alloc.lhsType))
        pinReg(alloc.lhsType.reg());
    if (AllocHelper(backingLeft->data, alloc.lhsData))
        pinReg(alloc.lhsData.reg());
    if (AllocHelper(backingRight->type, alloc.rhsType))
        pinReg(alloc.rhsType.reg());
    if (AllocHelper(backingRight->data, alloc.rhsData))
        pinReg(alloc.rhsData.reg());

    /* For each type without a register, give it a register if needed. */
    if (!alloc.lhsType.isSet() && backingLeft->type.inMemory()) {
        alloc.lhsType = tempRegForType(lhs);
        pinReg(alloc.lhsType.reg());
    }
    if (!alloc.rhsType.isSet() && backingRight->type.inMemory()) {
        alloc.rhsType = tempRegForType(rhs);
        pinReg(alloc.rhsType.reg());
    }

    bool commu;
    switch (op) {
      case JSOP_EQ:
      case JSOP_GT:
      case JSOP_GE:
      case JSOP_LT:
      case JSOP_LE:
        /* fall through */
      case JSOP_ADD:
      case JSOP_MUL:
      case JSOP_SUB:
        commu = true;
        break;

      case JSOP_DIV:
        commu = false;
        break;

      default:
        JS_NOT_REACHED("unknown op");
        return;
    }

    /*
     * Data is a little more complicated. If the op is MUL, not all CPUs
     * have multiplication on immediates, so a register is needed. Also,
     * if the op is not commutative, the LHS _must_ be in a register.
     */
    JS_ASSERT_IF(lhs->isConstant(), !rhs->isConstant());
    JS_ASSERT_IF(rhs->isConstant(), !lhs->isConstant());

    if (!alloc.lhsData.isSet()) {
        if (backingLeft->data.inMemory()) {
            alloc.lhsData = tempRegForData(lhs);
            pinReg(alloc.lhsData.reg());
        } else if (op == JSOP_MUL || !commu) {
            JS_ASSERT(lhs->isConstant());
            alloc.lhsData = allocReg();
            alloc.extraFree = alloc.lhsData;
            masm.move(Imm32(lhs->getValue().toInt32()), alloc.lhsData.reg());
        }
    }
    if (!alloc.rhsData.isSet()) {
        if (backingRight->data.inMemory()) {
            alloc.rhsData = tempRegForData(rhs);
            pinReg(alloc.rhsData.reg());
        } else if (op == JSOP_MUL) {
            JS_ASSERT(rhs->isConstant());
            alloc.rhsData = allocReg();
            alloc.extraFree = alloc.rhsData;
            masm.move(Imm32(rhs->getValue().toInt32()), alloc.rhsData.reg());
        }
    }

    alloc.lhsNeedsRemat = false;
    alloc.rhsNeedsRemat = false;

    if (!needsResult)
        goto skip;

    /*
     * Now a result register is needed. It must contain a mutable copy of the
     * LHS. For commutative operations, we can opt to use the RHS instead. At
     * this point, if for some reason either must be in a register, that has
     * already been guaranteed at this point.
//.........这里部分代码省略.........