// asyncPreempt call.
var asyncPreemptStack = ^uintptr(0)

func init() {
	f := findfunc(abi.FuncPCABI0(asyncPreempt))
	total := funcMaxSPDelta(f)
	f = findfunc(abi.FuncPCABIInternal(asyncPreempt2))
	total += funcMaxSPDelta(f)
	// Add some overhead for return PCs, etc.
	asyncPreemptStack = uintptr(total) + 8*goarch.PtrSize
	if asyncPreemptStack > stackNosplit {

		print("invalid spdelta ", funcname(f), " ", hex(f.entry()), " ", hex(targetpc), " ", hex(f.pcsp), " ", x, "\n")
		throw("bad spdelta")
	}
	return x
}

// funcMaxSPDelta returns the maximum spdelta at any point in f.
func funcMaxSPDelta(f funcInfo) int32 {
	datap := f.datap
	p := datap.pctab[f.pcsp:]
	pc := f.entry()
	val := int32(-1)
	most := int32(0)
	for {
		var ok bool

	// (This is just an optimization - the caller of morestack will
	// recheck the bounds on return.)
	if f := findfunc(gp.sched.pc); f.valid() {
		max := uintptr(funcMaxSPDelta(f))
		needed := max + stackGuard
		used := gp.stack.hi - gp.sched.sp
		for newsize-used < needed {
			newsize *= 2
		}
	}

	if stackguard0 == stackForceMove {