[SystemZ] Split out comparison elimination into a separate pass

Perhaps predictably, doing comparison elimination on the fly during
SystemZLongBranch turned out to be a bad idea.  The next patches make
use of LOAD AND TEST and BRANCH ON COUNT, both of which require
changes to earlier instructions.

No functionality change intended.

llvm-svn: 187718
diff --git a/llvm/lib/Target/SystemZ/SystemZ.h b/llvm/lib/Target/SystemZ/SystemZ.h
index 4c1e81a0..eccc2aa 100644
--- a/llvm/lib/Target/SystemZ/SystemZ.h
+++ b/llvm/lib/Target/SystemZ/SystemZ.h
@@ -85,6 +85,7 @@
 
   FunctionPass *createSystemZISelDag(SystemZTargetMachine &TM,
                                      CodeGenOpt::Level OptLevel);
+  FunctionPass *createSystemZElimComparePass(SystemZTargetMachine &TM);
   FunctionPass *createSystemZLongBranchPass(SystemZTargetMachine &TM);
 } // end namespace llvm;
 #endif