Even if a global register is being clobbered in a function we usually
do not save and restore it. However, we still have to do this if it is
a special register. Most of the places in the backend handle this
correctly but not the prologue/epilogue optimization.

gcc/ChangeLog:

2019-03-20  Andreas Krebbel  <krebbel@linux.ibm.com>

	PR target/89775
	* config/s390/s390.c (global_not_special_regno_p): Move to make it
	available to ...
	(s390_optimize_register_info): Use global_not_special_regno_p to
	check for global regs.

2019-03-20  Jakub Jelinek  <jakub@redhat.com>

	PR target/89775
	* gcc.target/s390/pr89775-1.c: New test.
	* gcc.target/s390/pr89775-2.c: New test.

From-SVN: r269823