s390: arch15: Load indexed address

s390: arch15: Load indexed address

Add instructions lxa and llxa.

gcc/ChangeLog:

	* config/s390/s390.md (*lxa<LXAMODE>_index): Add.
	(*lxa<LXAMODE>_displacement_index): Add.
	(*lxa<LXAMODE>_index_base): Add.
	(*lxa<LXAMODE>_displacement_index_base): Add.
	(*lxab_displacement_index_base): Add.
	(*llxa<LXAMODE>_displacement_index): Add.
	(*llxa<LXAMODE>_index_base): Add.
	(*llxa<LXAMODE>_displacement_index_base): Add.
	(*llxab_displacement_index_base): Add.

gcc/testsuite/ChangeLog:

	* gcc.target/s390/llxa-1.c: New test.
	* gcc.target/s390/llxa-2.c: New test.
	* gcc.target/s390/llxa-3.c: New test.
	* gcc.target/s390/lxa-1.c: New test.
	* gcc.target/s390/lxa-2.c: New test.
	* gcc.target/s390/lxa-3.c: New test.
	* gcc.target/s390/lxa-4.c: New test.