* combine.c (nonzero_bits) : Allow single-ly set registers to be
	anywere in the function only if they are pseudos and set before
	being used (not live at the start of the function).
	(num_sign_bit_copies) : Same.
	(get_last_value_validate) : Same.
	(get_last_value) : Same.

From-SVN: r28871