gcc/
	* dse.c (find_shift_sequence): Reinstate "<= UNITS_PER_WORD" condition.
	* var-tracking.c (micro_operation_def): Update comment on u.loc.
	(mode_for_reg_attrs, var_lowpart): New functions.
	(add_uses): Consider recording a lowpart of LOC for MO_USE.
	(add_stores): Likewise MO_SET and MO_COPY.  If the source of a set
	or copy is known, set LOC to the SET that performs the set, instead
	of the destination.
	(find_src_status, find_src_set_src): Remove LOC parameter.
	Replace INSN with the source value.
	(compute_bb_dataflow, emit_notes_in_bb): Check for a SET u.loc when
	handling MO_SET and MO_COPY.  Update the calls to find_src_status
	and find_src_set_src.

From-SVN: r129269