S/390: PR79904: Disallow reg + sym_ref literal pool addresses.

S/390: PR79904: Disallow reg + sym_ref literal pool addresses.

We accept reg + sym_ref as valid address if sym_ref is a literal pool
reference knowing that it will be rewritten as r13 + reg + offset.
However, annotate_constant_pool_refs was never able to handle that.

With the patch only single sym_refs are accepted.

Regression tested on s390x.

2017-03-24  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	PR target/79904
	* config/s390/s390.c (s390_decompose_address): Reject reg +
	sym_ref literal pool references.

gcc/testsuite/ChangeLog:

2017-03-24  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* gcc.dg/ubsan/pr79904-2.c: New test.

From-SVN: r246443