The FP load and test instruction should not be used for a comparison
if the target operand is being used afterwards.  It unfortunately
turns SNaNs into QNaNs.

gcc/ChangeLog:

2017-03-20  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	PR target/78857
	* config/s390/s390.md ("cmp<mode>_ccs_0"): Add a clobber of the
	target operand.  A new splitter adds the clobber statement in case
	the target operand is dead anyway.

gcc/testsuite/ChangeLog:

2017-03-20  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	PR target/78857
	* gcc.target/s390/load-and-test-fp-1.c: New test.
	* gcc.target/s390/load-and-test-fp-2.c: New test.

From-SVN: r246274