// same mechanism for async preemption.
	if ep.context.ip() == abi.FuncPCABI0(sigresume) {
		// sigresume has already been set up by a previous exception.
		return ret
	}
	prepareContextForSigResume(ep.context)
	ep.context.set_sp(gp.m.g0.sched.sp)
	ep.context.set_ip(abi.FuncPCABI0(sigresume))
	return ret
}

// Called by sigtramp from Windows VEH handler.