* combine.c (set_nonzero_bits_and_sign_copies): Don't call
	nonzero_bits if not needed.
	(nonzero_bits) [XOR]: Likewise.
	(nonzero_bits) [REG]: Use reg_last_set_nonzero_bits even if
	reg_last_set_mode and mode are both MODE_INT, but not equal.
	(record_value_for_reg): Compute reg_last_set_nonzero_bits
	in nonzero_bits_mode for MODE_INT modes.

From-SVN: r51551