S/390: Fix symbol ref alignment

S/390: Fix symbol ref alignment

This patch fixes the treatment of symbol ref alignments for
arrays and structs in S390. Until now, the NOT_NATURALLY_ALIGNED flag
was not correctly set for array elements and structs larger than 8
bytes. Therefore, load relative instructions that require a specific
alignment would not always be generated. This patch uses separate flags
for 2-, 4-, and 8-byte alignment to fix the problem.

gcc/testsuite/ChangeLog:

2015-11-23  Robin Dapp  <rdapp@linux.vnet.ibm.com>

        * gcc.target/s390/load-relative-check.c: New test to check
        generation of load relative instructions.

gcc/ChangeLog:

2015-11-23  Robin Dapp  <rdapp@linux.vnet.ibm.com>

        * config/s390/s390.h: Add new symref flags, _NOTALIGN2 etc.
        * config/s390/s390.c (s390_check_symref_alignment): Use new
        symref flags, early abort on wrong alignment
        (s390_secondary_reload): Use new symref flags.
        (s390_encode_section_info): Likewise.
        * config/s390/predicates.md: Likewise.

From-SVN: r230735