C++ SnapshotIterator::slots方法代码示例

void
InlineFrameIterator::dump() const
{
    if (more())
        fprintf(stderr, " JS frame (inlined)\n");
    else
        fprintf(stderr, " JS frame\n");

    bool isFunction = false;
    if (isFunctionFrame()) {
        isFunction = true;
        fprintf(stderr, "  callee fun: ");
#ifdef DEBUG
        js_DumpObject(callee());
#else
        fprintf(stderr, "?\n");
#endif
    } else {
        fprintf(stderr, "  global frame, no callee\n");
    }

    fprintf(stderr, "  file %s line %u\n",
            script()->filename, (unsigned) script()->lineno);

    fprintf(stderr, "  script = %p, pc = %p\n", (void*) script(), pc());
    fprintf(stderr, "  current op: %s\n", js_CodeName[*pc()]);

    if (!more()) {
        numActualArgs();
    }

    SnapshotIterator si = snapshotIterator();
    fprintf(stderr, "  slots: %u\n", si.slots() - 1);
    for (unsigned i = 0; i < si.slots() - 1; i++) {
        if (isFunction) {
            if (i == 0)
                fprintf(stderr, "  scope chain: ");
            else if (i == 1)
                fprintf(stderr, "  this: ");
            else if (i - 2 < callee()->nargs)
                fprintf(stderr, "  formal (arg %d): ", i - 2);
            else {
                if (i - 2 == callee()->nargs && numActualArgs() > callee()->nargs) {
                    DumpOp d(callee()->nargs);
                    forEachCanonicalActualArg(d, d.i_, numActualArgs());
                }

                fprintf(stderr, "  slot %d: ", i - 2 - callee()->nargs);
            }
        } else
            fprintf(stderr, "  slot %u: ", i);
#ifdef DEBUG
        js_DumpValue(si.maybeRead());
#else
        fprintf(stderr, "?\n");
#endif
    }

    fputc('\n', stderr);
}

void
StackFrame::initFromBailout(JSContext *cx, SnapshotIterator &iter)
{
    AutoAssertNoGC nogc;
    uint32 exprStackSlots = iter.slots() - script()->nfixed;

#ifdef TRACK_SNAPSHOTS
    iter.spewBailingFrom();
#endif
    IonSpew(IonSpew_Bailouts, " expr stack slots %u, is function frame %u",
            exprStackSlots, isFunctionFrame());

    if (iter.bailoutKind() == Bailout_ArgumentCheck) {
        // Temporary hack -- skip the (unused) scopeChain, because it could be
        // bogus (we can fail before the scope chain slot is set). Strip the
        // hasScopeChain flag and we'll check this later to run prologue().
        iter.skip();
        flags_ &= ~StackFrame::HAS_SCOPECHAIN;
    } else {
        Value v = iter.read();
        if (v.isObject()) {
            scopeChain_ = &v.toObject();
            flags_ |= StackFrame::HAS_SCOPECHAIN;
            if (isFunctionFrame() && fun()->isHeavyweight())
                flags_ |= StackFrame::HAS_CALL_OBJ;
        } else {
            JS_ASSERT(v.isUndefined());
        }
    }

    // Assume that all new stack frames have had their entry flag set if
    // profiling has been turned on. This will be corrected if necessary
    // elsewhere.
    if (cx->runtime->spsProfiler.enabled())
        setPushedSPSFrame();

    if (isFunctionFrame()) {
        Value thisv = iter.read();
        formals()[-1] = thisv;

        // The new |this| must have already been constructed prior to an Ion
        // constructor running.
        if (isConstructing())
            JS_ASSERT(!thisv.isPrimitive());

        JS_ASSERT(iter.slots() >= CountArgSlots(fun()));
        IonSpew(IonSpew_Bailouts, " frame slots %u, nargs %u, nfixed %u",
                iter.slots(), fun()->nargs, script()->nfixed);

        for (uint32 i = 0; i < fun()->nargs; i++) {
            Value arg = iter.read();
            formals()[i] = arg;
        }
    }
    exprStackSlots -= CountArgSlots(maybeFun());

    for (uint32 i = 0; i < script()->nfixed; i++) {
        Value slot = iter.read();
        slots()[i] = slot;
    }

    IonSpew(IonSpew_Bailouts, " pushing %u expression stack slots", exprStackSlots);
    FrameRegs &regs = cx->regs();
    for (uint32 i = 0; i < exprStackSlots; i++) {
        Value v;

        // If coming from an invalidation bailout, and this is the topmost
        // value, and a value override has been specified, don't read from the
        // iterator. Otherwise, we risk using a garbage value.
        if (!iter.moreFrames() && i == exprStackSlots - 1 && cx->runtime->hasIonReturnOverride())
            v = iter.skip();
        else
            v = iter.read();

        *regs.sp++ = v;
    }
    unsigned pcOff = iter.pcOffset();
    regs.pc = script()->code + pcOff;

    if (iter.resumeAfter())
        regs.pc = GetNextPc(regs.pc);

    IonSpew(IonSpew_Bailouts, " new PC is offset %u within script %p (line %d)",
            pcOff, (void *)script(), PCToLineNumber(script(), regs.pc));
    JS_ASSERT(exprStackSlots == js_ReconstructStackDepth(cx, script(), regs.pc));
}