C++ JSContext::activation方法代码示例

uint32_t
jit::Bailout(BailoutStack* sp, BaselineBailoutInfo** bailoutInfo)
{
    JSContext* cx = TlsContext.get();
    MOZ_ASSERT(bailoutInfo);

    // We don't have an exit frame.
    MOZ_ASSERT(IsInRange(FAKE_EXITFP_FOR_BAILOUT, 0, 0x1000) &&
               IsInRange(FAKE_EXITFP_FOR_BAILOUT + sizeof(CommonFrameLayout), 0, 0x1000),
               "Fake exitfp pointer should be within the first page.");

    cx->activation()->asJit()->setExitFP(FAKE_EXITFP_FOR_BAILOUT);

    JitActivationIterator jitActivations(cx);
    BailoutFrameInfo bailoutData(jitActivations, sp);
    JitFrameIterator iter(jitActivations);
    MOZ_ASSERT(!iter.ionScript()->invalidated());
    CommonFrameLayout* currentFramePtr = iter.current();

    TraceLoggerThread* logger = TraceLoggerForCurrentThread(cx);
    TraceLogTimestamp(logger, TraceLogger_Bailout);

    JitSpew(JitSpew_IonBailouts, "Took bailout! Snapshot offset: %d", iter.snapshotOffset());

    MOZ_ASSERT(IsBaselineEnabled(cx));

    *bailoutInfo = nullptr;
    uint32_t retval = BailoutIonToBaseline(cx, bailoutData.activation(), iter, false, bailoutInfo,
                                           /* excInfo = */ nullptr);
    MOZ_ASSERT(retval == BAILOUT_RETURN_OK ||
               retval == BAILOUT_RETURN_FATAL_ERROR ||
               retval == BAILOUT_RETURN_OVERRECURSED);
    MOZ_ASSERT_IF(retval == BAILOUT_RETURN_OK, *bailoutInfo != nullptr);

    if (retval != BAILOUT_RETURN_OK) {
        JSScript* script = iter.script();
        probes::ExitScript(cx, script, script->functionNonDelazifying(),
                           /* popProfilerFrame = */ false);
    }

    // This condition was wrong when we entered this bailout function, but it
    // might be true now. A GC might have reclaimed all the Jit code and
    // invalidated all frames which are currently on the stack. As we are
    // already in a bailout, we could not switch to an invalidation
    // bailout. When the code of an IonScript which is on the stack is
    // invalidated (see InvalidateActivation), we remove references to it and
    // increment the reference counter for each activation that appear on the
    // stack. As the bailed frame is one of them, we have to decrement it now.
    if (iter.ionScript()->invalidated())
        iter.ionScript()->decrementInvalidationCount(cx->runtime()->defaultFreeOp());

    // NB: Commentary on how |lastProfilingFrame| is set from bailouts.
    //
    // Once we return to jitcode, any following frames might get clobbered,
    // but the current frame will not (as it will be clobbered "in-place"
    // with a baseline frame that will share the same frame prefix).
    // However, there may be multiple baseline frames unpacked from this
    // single Ion frame, which means we will need to once again reset
    // |lastProfilingFrame| to point to the correct unpacked last frame
    // in |FinishBailoutToBaseline|.
    //
    // In the case of error, the jitcode will jump immediately to an
    // exception handler, which will unwind the frames and properly set
    // the |lastProfilingFrame| to point to the frame being resumed into
    // (see |AutoResetLastProfilerFrameOnReturnFromException|).
    //
    // In both cases, we want to temporarily set the |lastProfilingFrame|
    // to the current frame being bailed out, and then fix it up later.
    if (cx->runtime()->jitRuntime()->isProfilerInstrumentationEnabled(cx->runtime()))
        cx->jitActivation->setLastProfilingFrame(currentFramePtr);

    return retval;
}