// instead on the g0 stack.
		throw("cannot trace user goroutine on its own stack")
	}

	if pc0 == ^uintptr(0) && sp0 == ^uintptr(0) { // Signal to fetch saved values from gp.
		if gp.syscallsp != 0 {
			pc0 = gp.syscallpc
			sp0 = gp.syscallsp
			if usesLR {
				lr0 = 0
			}
		} else {
			pc0 = gp.sched.pc
			sp0 = gp.sched.sp
			if usesLR {
				lr0 = gp.sched.lr
			}
		}
	}

		throw("can't scan our own stack")
	}

	// scannedSize is the amount of work we'll be reporting.
	//
	// It is less than the allocated size (which is hi-lo).
	var sp uintptr
	if gp.syscallsp != 0 {
		sp = gp.syscallsp // If in a system call this is the stack pointer (gp.sched.sp can be 0 in this case on Windows).
	} else {
		sp = gp.sched.sp
	}
	scannedSize := gp.stack.hi - sp