C++ JSRuntime::ionRuntime方法代码示例

IonBailoutIterator::IonBailoutIterator(const JitActivationIterator &activations,
                                       BailoutStack *bailout)
  : IonFrameIterator(activations),
    machine_(bailout->machine())
{
    uint8_t *sp = bailout->parentStackPointer();
    uint8_t *fp = sp + bailout->frameSize();

    current_ = fp;
    type_ = IonFrame_OptimizedJS;
    topFrameSize_ = current_ - sp;
    topIonScript_ = script()->ionScript();

    if (bailout->frameClass() == FrameSizeClass::None()) {
        snapshotOffset_ = bailout->snapshotOffset();
        return;
    }

    // Compute the snapshot offset from the bailout ID.
    JitActivation *activation = activations.activation()->asJit();
    JSRuntime *rt = activation->compartment()->runtimeFromMainThread();
    IonCode *code = rt->ionRuntime()->getBailoutTable(bailout->frameClass());
    uintptr_t tableOffset = bailout->tableOffset();
    uintptr_t tableStart = reinterpret_cast<uintptr_t>(code->raw());

    JS_ASSERT(tableOffset >= tableStart &&
              tableOffset < tableStart + code->instructionsSize());
    JS_ASSERT((tableOffset - tableStart) % BAILOUT_TABLE_ENTRY_SIZE == 0);

    uint32_t bailoutId = ((tableOffset - tableStart) / BAILOUT_TABLE_ENTRY_SIZE) - 1;
    JS_ASSERT(bailoutId < BAILOUT_TABLE_SIZE);

    snapshotOffset_ = topIonScript_->bailoutToSnapshot(bailoutId);
}

static bool
HandleException(PEXCEPTION_POINTERS exception)
{
    EXCEPTION_RECORD *record = exception->ExceptionRecord;
    CONTEXT *context = exception->ContextRecord;

    if (record->ExceptionCode != EXCEPTION_ACCESS_VIOLATION)
        return false;

    uint8_t **ppc = ContextToPC(context);
    uint8_t *pc = *ppc;
    JS_ASSERT(pc == record->ExceptionAddress);

    if (record->NumberParameters < 2)
        return false;

    void *faultingAddress = (void*)record->ExceptionInformation[1];

    JSRuntime *rt = RuntimeForCurrentThread();

    // Don't allow recursive handling of signals, see AutoSetHandlingSignal.
    if (!rt || rt->handlingSignal)
        return false;
    AutoSetHandlingSignal handling(rt);

    if (rt->ionRuntime() && rt->ionRuntime()->handleAccessViolation(rt, faultingAddress))
        return true;

    AsmJSActivation *activation = InnermostAsmJSActivation();
    if (!activation)
        return false;

    const AsmJSModule &module = activation->module();
    if (!module.containsPC(pc))
        return false;

    // If we faulted trying to execute code in 'module', this must be an
    // operation callback (see TriggerOperationCallbackForAsmJSCode). Redirect
    // execution to a trampoline which will call js_HandleExecutionInterrupt.
    // The trampoline will jump to activation->resumePC if execution isn't
    // interrupted.
    if (module.containsPC(faultingAddress)) {
        activation->setResumePC(pc);
        *ppc = module.operationCallbackExit();
        DWORD oldProtect;
        if (!VirtualProtect(module.functionCode(), module.functionBytes(), PAGE_EXECUTE, &oldProtect))
            MOZ_CRASH();
        return true;
    }

# if defined(JS_CPU_X64)
    // These checks aren't necessary, but, since we can, check anyway to make
    // sure we aren't covering up a real bug.
    if (!module.maybeHeap() ||
            faultingAddress < module.maybeHeap() ||
            faultingAddress >= module.maybeHeap() + AsmJSBufferProtectedSize)
    {
        return false;
    }

    const AsmJSHeapAccess *heapAccess = LookupHeapAccess(module, pc);
    if (!heapAccess)
        return false;

    // Also not necessary, but, since we can, do.
    if (heapAccess->isLoad() != !record->ExceptionInformation[0])
        return false;

    // We now know that this is an out-of-bounds access made by an asm.js
    // load/store that we should handle. If this is a load, assign the
    // JS-defined result value to the destination register (ToInt32(undefined)
    // or ToNumber(undefined), determined by the type of the destination
    // register) and set the PC to the next op. Upon return from the handler,
    // execution will resume at this next PC.
    if (heapAccess->isLoad())
        SetRegisterToCoercedUndefined(context, heapAccess->isFloat32Load(), heapAccess->loadedReg());
    *ppc += heapAccess->opLength();
    return true;
# else
    return false;
# endif
}