Add 'llvm_unreachable' to passify GCC's understanding of the constraints
of several newly un-defaulted switches. This also helps optimizers
(including LLVM's) recognize that every case is covered, and we should
assume as much.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147861 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/GCMetadata.cpp b/lib/CodeGen/GCMetadata.cpp
index 45a64d2..1caf8c2 100644
--- a/lib/CodeGen/GCMetadata.cpp
+++ b/lib/CodeGen/GCMetadata.cpp
@@ -148,6 +148,7 @@
     case GC::PreCall:  return "pre-call";
     case GC::PostCall: return "post-call";
   }
+  llvm_unreachable("Invalid point kind");
 }
 
 bool Printer::runOnFunction(Function &F) {