re PR target/83969 (ICE in final_scan_insn, at final.c:2997 (error: could not split insn) for powerpc targets)

gcc/
	PR target/83969
	* config/rs6000/rs6000.c (rs6000_offsettable_memref_p): New prototype.
	Add strict argument and use it.
	(rs6000_split_multireg_move): Update for new strict argument.
	(mem_operand_gpr): Disallow all non-offsettable addresses.
	* config/rs6000/rs6000.md (*movdi_internal64): Use YZ constraint.

gcc/testsuite/
	PR target/83969
	* gcc.target/powerpc/pr83969.c: New test.

From-SVN: r258400