New .md construct: define_insn_and_rewrite

New .md construct: define_insn_and_rewrite

Several SVE patterns need define_insn_and_splits that generate the
same insn_code, but with different operands.  That's probably a
niche requirement, but it's cropping up often enough on the ACLE
branch that I think it would be good to have a syntactic sugar for it.

This patch therefore adds a new construct called define_insn_and_rewrite.
It's basically a define_insn_and_split with an implicit split pattern,
obtained by copying the insn pattern and replacing match_operands with
match_dups and match_operators with match_op_dups.

2019-05-31  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* doc/md.texi: Document define_insn_and_rewrite.
	* rtl.def (DEFINE_INSN_AND_REWRITE): New rtx code.
	* gensupport.c (queue_elem): Update comment.
	(replace_operands_with_dups): New function.
	(gen_rewrite_sequence): Likewise.
	(process_rtx): Handle DEFINE_INSN_AND_REWRITE.
	* read-rtl.c (apply_subst_iterator): Likewise.
	(add_condition_to_rtx, named_rtx_p): Likewise.
	(rtx_reader::read_rtx_operand): Likewise.
	* config/aarch64/aarch64-sve.md
	(while_ult<GPI:mode><PRED_ALL:mode>_cc): Rename to...
	(*while_ult<GPI:mode><PRED_ALL:mode>_cc): ...this and use
	define_insn_and_rewrite.
	(*cond_<optab><mode>_any): Turn into define_insn_and_rewrites.
	Remove separate define_split.

From-SVN: r271815