const math/big._M

5 uses

	math/big (current package)
		arith.go#L26: 	_M = _B - 1        // digit mask
		arith.go#L336: 	x0 := uint(_M)
		natconv.go#L34: 	for max := _M / b; p <= max; {
		natdiv.go#L664: 		qhat := Word(_M)
		prime.go#L66: 		r := x.abs.modW((primesA * primesB) & _M)