Rework how prefixed instruction length is calculated.

Rework how prefixed instruction length is calculated.

2019-10-23  Michael Meissner  <meissner@linux.ibm.com>

	* config/rs6000/rs6000-protos.h (rs6000_adjust_insn_length): New
	declaration.
	* config/rs6000/rs6000.c (rs6000_insn_cost): Use num_insns insn
	attribute if it exists, rather than the insn size.  If we use the
	insn size, adjust the size to remove the extra size that prefixed
	instructions take.
	(rs6000_adjust_insn_length): New function.
	* config/rs6000/rs6000.h (ADJUST_INSN_LENGTH): New target hook to
	update the instruction sized if prefixed instructions are used.
	* config/rs6000/rs6000.md (prefixed_length attribute): Delete.
	(non_prefixed_length attribute): Delete.
	(num_insns attribute): New insn attribute to return the number of
	instructions.
	(max_prefixed_insns attribute): New insn attribute to return the
	maximum number of prefixed instructions in an insn.
	(length attribute): Do not adjust for prefix instructions here,
	punt to ADJUST_INSN_LENGTH.
	(mov<mode>_64bit): Set max_prefixed_insns and num_insns.
	(movtd_64bit_nodm): Set max_prefixed_insns and num_insns.
	(mov<mode>_ppc64): Set max_prefixed_insns and num_insns.
	* config/rs6000/vsx.md: (vsx_mov<mode>_64bit): Set
	max_prefixed_insns and num_insns.

From-SVN: r277352