// explaining why.
//
//go:nosplit
func debugCallCheck(pc uintptr) string {
	// No user calls from the system stack.
	if getg() != getg().m.curg {
		return debugCallSystemStack
	}
	if sp := getcallersp(); !(getg().stack.lo < sp && sp <= getg().stack.hi) {
		// Fast syscalls (nanotime) and racecall switch to the
		// g0 stack without switching g. We can't safely make
		// a call in this state. (We can't even safely

func uint64tofloat64(uint64) float64
func uint64tofloat32(uint64) float32
func uint32tofloat64(uint32) float64

func complex128div(num complex128, den complex128) (quo complex128)

func getcallerpc() uintptr
func getcallersp() uintptr

// race detection
func racefuncenter(uintptr)
func racefuncexit()
func raceread(uintptr)
func racewrite(uintptr)
func racereadrange(addr, size uintptr)

		prof.stack[1] = abi.FuncPCABIInternal(_LostContendedRuntimeLock) + sys.PCQuantum
		prof.stack[2] = 0
		return
	}

	var nstk int
	gp := getg()
	sp := getcallersp()
	pc := getcallerpc()
	systemstack(func() {
		var u unwinder
		u.initAt(pc, sp, 0, gp, unwindSilentErrors|unwindJumpStack)
		nstk = 1 + tracebackPCs(&u, skip, prof.stack[1:])
	})
	if nstk < len(prof.stack) {

(IsNonNil p) => (I64Eqz (I64Eqz p))
(IsInBounds ...) => (I64LtU ...)
(IsSliceInBounds ...) => (I64LeU ...)
(NilCheck ...) => (LoweredNilCheck ...)
(GetClosurePtr ...) => (LoweredGetClosurePtr ...)
(GetCallerPC ...) => (LoweredGetCallerPC ...)
(GetCallerSP ...) => (LoweredGetCallerSP ...)
(Addr {sym} base) => (LoweredAddr {sym} [0] base)
(LocalAddr <t> {sym} base mem) && t.Elem().HasPointers() => (LoweredAddr {sym} (SPanchored base mem))

	{"int64tofloat32", funcTag, 138},
	{"uint64tofloat64", funcTag, 139},
	{"uint64tofloat32", funcTag, 140},
	{"uint32tofloat64", funcTag, 141},
	{"complex128div", funcTag, 142},
	{"getcallerpc", funcTag, 143},
	{"getcallersp", funcTag, 143},
	{"racefuncenter", funcTag, 31},
	{"racefuncexit", funcTag, 9},
	{"raceread", funcTag, 31},
	{"racewrite", funcTag, 31},
	{"racereadrange", funcTag, 144},

	traceback1(pc, sp, lr, gp, 0)
}

// tracebacktrap is like traceback but expects that the PC and SP were obtained
// from a trap, not from gp->sched or gp->syscallpc/gp->syscallsp or getcallerpc/getcallersp.
// Because they are from a trap instead of from a saved pair,
// the initial PC must not be rewound to the previous instruction.
// (All the saved pairs record a PC that is a return address, so we

	{name: "GetClosurePtr"},                       // get closure pointer from dedicated register
	{name: "GetCallerPC"},                         // for getcallerpc intrinsic
	{name: "GetCallerSP", argLength: 1},           // for getcallersp intrinsic. arg0=mem.

	// Indexing operations

			panic("nil lockedm on locked goroutine")
		}
	}
	return gp.m.lockedExt, gp.m.lockedInt
}

//go:noinline
func TracebackSystemstack(stk []uintptr, i int) int {
	if i == 0 {
		pc, sp := getcallerpc(), getcallersp()
		var u unwinder
		u.initAt(pc, sp, 0, getg(), unwindJumpStack) // Don't ignore errors, for testing
		return tracebackPCs(&u, 0, stk)
	}
	n := 0
	systemstack(func() {

			// Otherwise, before making a VDSO call we save the g to the
			// bottom of the signal stack. Fetch from there.
			// TODO: in efence mode, stack is sysAlloc'd, so this wouldn't
			// work.
			sp := getcallersp()
			s := spanOf(sp)
			if s != nil && s.state.get() == mSpanManual && s.base() < sp && sp < s.limit {
				gp := *(**g)(unsafe.Pointer(s.base()))
				return gp
			}
			return nil
		}
	}

//go:nosplit
//go:linkname entersyscall
func entersyscall() {
	// N.B. getcallerfp cannot be written directly as argument in the call
	// to reentersyscall because it forces spilling the other arguments to
	// the stack. This results in exceeding the nosplit stack requirements
	// on some platforms.
	fp := getcallerfp()
	reentersyscall(getcallerpc(), getcallersp(), fp)
}

func entersyscall_sysmon() {
	lock(&sched.lock)