Add s390_valid_shift_count to determine the validity of a
shift-count operand.  This is used to replace increasingly
complex substitutions that should have allowed address-style
shift-count handling, an and mask as well as no-op subregs
on the operand.

gcc/ChangeLog:

2019-07-08  Robin Dapp  <rdapp@linux.ibm.com>

        * config/s390/constraints.md: Add new jsc constraint.
        * config/s390/predicates.md: New predicates.
        * config/s390/s390-protos.h (s390_valid_shift_count): New function.
        * config/s390/s390.c (s390_valid_shift_count): New function.
        (print_shift_count_operand): Use s390_valid_shift_count.
        (print_operand): Likewise.
        * config/s390/s390.md: Use new predicate.
        * config/s390/subst.md: Remove addr_style_op and masked_op substs.
        * config/s390/vector.md: Use new predicate.

2019-07-08  Robin Dapp  <rdapp@linux.ibm.com>

        * gcc.target/s390/combine-rotate-modulo.c: New test.
        * gcc.target/s390/combine-shift-rotate-add-mod.c: New test.
        * gcc.target/s390/vector/combine-shift-vec.c: New test.

From-SVN: r273236