The read-md.c iterator callbacks previously used a void * to record the
position at which the iterator value should be installed.  This doesn't
scale easily to the SUBREG_BYTE representation used by a later patch,
so this patch replaces the void * with both an rtx and an operand
number.  The operand number is ignored for modes and codes.

2017-08-21  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* read-md.h (md_reader::record_potential_iterator_use): Replace
	pointer argument with an rtx and an index.
	* read-rtl.c (iterator_group::apply_iterator): Likewise.
	(apply_mode_iterator): Likewise.
	(apply_code_iterator): Likewise.
	(apply_int_iterator): Likewise.
	(apply_subst_iterator): Likewise.
	(record_iterator_use): Likewise.
	(record_attribute_use): Likewise.
	(md_reader::record_potential_iterator_use): Likewise.  Update calls
	to record_iterator_use and apply_iterator.
	(iterator_use): Replace ptr with x and index.
	(attribute_use): Likewise.
	(apply_attribute_uses): Update calls to apply_iterator.
	(apply_iterators): Likewise.  Update initialization of iterator_use.
	(rtx_reader::read_rtx_code): Update calls to record_iterator_use
	and record_potential_iterator_use.
	(rtx_reader::read_rtx_operand): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251219