C++ JumpList::empty方法代码示例

//.........这里部分代码省略.........
    allocator.lock(static_cast<GPRReg>(stubInfo.patch.baseTagGPR));
#endif
    allocator.lock(valueRegs);
    allocator.lock(scratchGPR);

    GPRReg paramBaseGPR = InvalidGPRReg;
    GPRReg paramGlobalObjectGPR = InvalidGPRReg;
    JSValueRegs paramValueRegs = valueRegs;
    GPRReg remainingScratchGPR = InvalidGPRReg;

    // valueRegs and baseForGetGPR may be the same. For example, in Baseline JIT, we pass the same regT0 for baseGPR and valueRegs.
    // In FTL, there is no constraint that the baseForGetGPR interferes with the result. To make implementation simple in
    // Snippet, Snippet assumes that result registers always early interfere with input registers, in this case,
    // baseForGetGPR. So we move baseForGetGPR to the other register if baseForGetGPR == valueRegs.
    if (baseForGetGPR != valueRegs.payloadGPR()) {
        paramBaseGPR = baseForGetGPR;
        if (!snippet->requireGlobalObject)
            remainingScratchGPR = scratchGPR;
        else
            paramGlobalObjectGPR = scratchGPR;
    } else {
        jit.move(valueRegs.payloadGPR(), scratchGPR);
        paramBaseGPR = scratchGPR;
        if (snippet->requireGlobalObject)
            paramGlobalObjectGPR = allocator.allocateScratchGPR();
    }

    JSGlobalObject* globalObjectForDOMJIT = structure()->globalObject();

    regs.append(paramValueRegs);
    regs.append(paramBaseGPR);
    if (snippet->requireGlobalObject) {
        ASSERT(paramGlobalObjectGPR != InvalidGPRReg);
        regs.append(SnippetParams::Value(paramGlobalObjectGPR, globalObjectForDOMJIT));
    }

    if (snippet->numGPScratchRegisters) {
        unsigned i = 0;
        if (remainingScratchGPR != InvalidGPRReg) {
            gpScratch.append(remainingScratchGPR);
            ++i;
        }
        for (; i < snippet->numGPScratchRegisters; ++i)
            gpScratch.append(allocator.allocateScratchGPR());
    }

    for (unsigned i = 0; i < snippet->numFPScratchRegisters; ++i)
        fpScratch.append(allocator.allocateScratchFPR());

    // Let's store the reused registers to the stack. After that, we can use allocated scratch registers.
    ScratchRegisterAllocator::PreservedState preservedState =
    allocator.preserveReusedRegistersByPushing(jit, ScratchRegisterAllocator::ExtraStackSpace::SpaceForCCall);

    if (verbose) {
        dataLog("baseGPR = ", baseGPR, "\n");
        dataLog("valueRegs = ", valueRegs, "\n");
        dataLog("scratchGPR = ", scratchGPR, "\n");
        dataLog("paramBaseGPR = ", paramBaseGPR, "\n");
        if (paramGlobalObjectGPR != InvalidGPRReg)
            dataLog("paramGlobalObjectGPR = ", paramGlobalObjectGPR, "\n");
        dataLog("paramValueRegs = ", paramValueRegs, "\n");
        for (unsigned i = 0; i < snippet->numGPScratchRegisters; ++i)
            dataLog("gpScratch[", i, "] = ", gpScratch[i], "\n");
    }

    if (snippet->requireGlobalObject)
        jit.move(CCallHelpers::TrustedImmPtr(globalObjectForDOMJIT), paramGlobalObjectGPR);

    // We just spill the registers used in Snippet here. For not spilled registers here explicitly,
    // they must be in the used register set passed by the callers (Baseline, DFG, and FTL) if they need to be kept.
    // Some registers can be locked, but not in the used register set. For example, the caller could make baseGPR
    // same to valueRegs, and not include it in the used registers since it will be changed.
    RegisterSet registersToSpillForCCall;
    for (auto& value : regs) {
        SnippetReg reg = value.reg();
        if (reg.isJSValueRegs())
            registersToSpillForCCall.set(reg.jsValueRegs());
        else if (reg.isGPR())
            registersToSpillForCCall.set(reg.gpr());
        else
            registersToSpillForCCall.set(reg.fpr());
    }
    for (GPRReg reg : gpScratch)
        registersToSpillForCCall.set(reg);
    for (FPRReg reg : fpScratch)
        registersToSpillForCCall.set(reg);
    registersToSpillForCCall.exclude(RegisterSet::registersToNotSaveForCCall());

    AccessCaseSnippetParams params(state.m_vm, WTFMove(regs), WTFMove(gpScratch), WTFMove(fpScratch));
    snippet->generator()->run(jit, params);
    allocator.restoreReusedRegistersByPopping(jit, preservedState);
    state.succeed();

    CCallHelpers::JumpList exceptions = params.emitSlowPathCalls(state, registersToSpillForCCall, jit);
    if (!exceptions.empty()) {
        exceptions.link(&jit);
        allocator.restoreReusedRegistersByPopping(jit, preservedState);
        state.emitExplicitExceptionHandler();
    }
}