S/390: Introduce relative_long attribute

In order to properly fix PR87762, we need to distinguish between
instructions which support relative addressing and instructions which
don't.  We could check whether the existing "type" attribute is equal to
"larl", but there are notable exceptions (lrl, for example), and
changing them makes scheduling worse on z10.  We could also check
whether the existing "op_type" attribute is equal to "RIL-b" or "RIL-c".
However, adding a new attribute provides more flexibility, since we
don't depend idiosyncrasies which might be introduced into PoP in the
future.

gcc/ChangeLog:

2018-11-06  Ilya Leoshkevich  <iii@linux.ibm.com>

	PR target/87762
	* config/s390/s390.md: Add relative_long attribute.

From-SVN: r265844

gcc/ChangeLog

+2018-11-06  Ilya Leoshkevich  <iii@linux.ibm.com>
+
+	PR target/87762
+	* config/s390/s390.md: Add relative_long attribute.
+
 2018-11-06  Jan Hubicka  <jh@suse.cz>
 
 	* ipa-pure-const.c (check_decl): Do not test TYPE_NEEDS_CONSTRUCTING.