case unknownVal:
		return 0, false
	default:
		panic(fmt.Sprintf("%v not an Int", x))
	}
}

// Uint64Val returns the Go uint64 value of x and whether the result is exact;
// x must be an [Int] or an [Unknown]. If the result is not exact, its value is undefined.
// If x is [Unknown], the result is (0, false).
func Uint64Val(x Value) (uint64, bool) {
	switch x := x.(type) {
	case int64Val:

	bits := int32(8 * n.Type().Size())

	if ir.IsSmallIntConst(n) {
		v := ir.Int64Val(n)
		return 0 <= v && v < max
	}

	switch n.Op() {
	case ir.OAND, ir.OANDNOT:
		n := n.(*ir.BinaryExpr)
		v := int64(-1)
		switch {
		case ir.IsSmallIntConst(n.X):
			v = ir.Int64Val(n.X)
		case ir.IsSmallIntConst(n.Y):
			v = ir.Int64Val(n.Y)
			if n.Op() == ir.OANDNOT {
				v = ^v
				if !sign {

	{"22\n", &int8Val, int8(22)},
	{"23\n", &int16Val, int16(23)},
	{"24\n", &int32Val, int32(24)},
	{"25\n", &int64Val, int64(25)},
	{"127\n", &int8Val, int8(127)},
	{"-21\n", &intVal, -21},
	{"-22\n", &int8Val, int8(-22)},
	{"-23\n", &int16Val, int16(-23)},
	{"-24\n", &int32Val, int32(-24)},
	{"-25\n", &int64Val, int64(-25)},
	{"-128\n", &int8Val, int8(-128)},
	{"+21\n", &intVal, +21},
	{"+22\n", &int8Val, int8(+22)},

	n.Cap = DefaultLit(Expr(n.Cap), types.Types[types.TINT])

	if ir.IsConst(n.Len, constant.Int) && ir.Int64Val(n.Len) < 0 {
		base.Fatalf("len for OSLICEHEADER must be non-negative")
	}

	if ir.IsConst(n.Cap, constant.Int) && ir.Int64Val(n.Cap) < 0 {
		base.Fatalf("cap for OSLICEHEADER must be non-negative")
	}

		return
	}

	if x.mode != constant_ {
		return x.typ, -1
	}

	if x.val.Kind() == constant.Unknown {
		return
	}

	v, ok := constant.Int64Val(x.val)
	assert(ok)
	if max >= 0 && v >= max {
		check.errorf(&x, InvalidIndex, invalidArg+"index %s out of bounds [0:%d]", x.val.String(), max)
		return
	}

	// 0 <= v [ && v < max ]
	return x.typ, v

		return
	}

	if x.mode != constant_ {
		return x.typ, -1
	}

	if x.val.Kind() == constant.Unknown {
		return
	}

	v, ok := constant.Int64Val(x.val)
	assert(ok)
	if max >= 0 && v >= max {
		check.errorf(&x, InvalidIndex, invalidArg+"index %s out of bounds [0:%d]", x.val.String(), max)
		return
	}

	// 0 <= v [ && v < max ]
	return x.typ, v

	return op
}

func tracecmpArg(n ir.Node, t *types.Type, init *ir.Nodes) ir.Node {
	// Ugly hack to avoid "constant -1 overflows uintptr" errors, etc.
	if n.Op() == ir.OLITERAL && n.Type().IsSigned() && ir.Int64Val(n) < 0 {
		n = copyExpr(n, n.Type(), init)
	}

	return typecheck.Conv(n, t)

		}
		return -1
	}

	if isUntyped(x.typ) || isInteger(x.typ) {
		if val := constant.ToInt(x.val); val.Kind() == constant.Int {
			if representableConst(val, check, Typ[Int], nil) {
				if n, ok := constant.Int64Val(val); ok && n >= 0 {
					return n
				}
			}
		}
	}

	var msg string
	if isInteger(x.typ) {
		msg = "invalid array length %s"
	} else {
		msg = "array length %s must be integer"
	}

		}
		return -1
	}

	if isUntyped(x.typ) || isInteger(x.typ) {
		if val := constant.ToInt(x.val); val.Kind() == constant.Int {
			if representableConst(val, check, Typ[Int], nil) {
				if n, ok := constant.Int64Val(val); ok && n >= 0 {
					return n
				}
			}
		}
	}

	var msg string
	if isInteger(x.typ) {
		msg = "invalid array length %s"
	} else {
		msg = "array length %s must be integer"
	}

	// and string values, so only create Go values for these
	// types.
	switch val.Kind() {
	case constant.Int:
		if x, ok := constant.Int64Val(val); ok {
			return x
		}
		if x, ok := constant.Uint64Val(val); ok {
			return x
		}
	case constant.Float:
		if x, ok := constant.Float64Val(val); ok {
			return x
		}
	case constant.String:
		return constant.StringVal(val)