re PR target/59401 ([SH] GBR addressing mode optimization produces wrong code)

re PR target/59401 ([SH] GBR addressing mode optimization produces wrong code)

gcc/
	PR target/59401
	* config/sh/sh-protos (sh_find_equiv_gbr_addr): Use rtx_insn* instead
	of rtx.
	* config/sh/sh.c (sh_find_equiv_gbr_addr): Use def chains instead of
	insn walking.
	(sh_find_equiv_gbr_addr): Do nothing if input mem is already a GBR
	address.  Use def chains to handle GBR clobbering call insns.

gcc/testsuite/
	PR target/59401
	PR target/54760
	* gcc.target/pr54760-5.c: New.
	* gcc.target/pr54760-6.c: New.
	* gcc.target/sh/pr59401-1.c: New.

From-SVN: r216128