Pacify GCC's -Wreturn-type

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156189 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 5ceade2..711321c 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -2175,6 +2175,7 @@
     case TLSModel::LocalExec:
       return LowerToTLSExecModels(GA, DAG, model);
   }
+  llvm_unreachable("bogus TLS model");
 }
 
 SDValue ARMTargetLowering::LowerGlobalAddressELF(SDValue Op,