[Bug target/78857] S390: Do not use load-and-test floating-point instruction to compare against 0.0 as SNaN is converted to QNaN.

["krebbel at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78857

--- Comment #1 from Andreas Krebbel <krebbel at gcc dot gnu.org> ---
Author: krebbel
Date: Mon Mar 20 09:33:11 2017
New Revision: 246274

URL: https://gcc.gnu.org/viewcvs?rev=246274&root=gcc&view=rev
Log:
S/390: PR78857: Don't use load and test if result is live.

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.


Added:
    trunk/gcc/testsuite/gcc.target/s390/load-and-test-fp-1.c
    trunk/gcc/testsuite/gcc.target/s390/load-and-test-fp-2.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/s390/s390.md
    trunk/gcc/testsuite/ChangeLog