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

lib/CodeGen/Spiller.cpp

@@ -194,4 +194,5 @@ llvm::Spiller* llvm::createSpiller(MachineFunctionPass &pass,
   case trivial: return new TrivialSpiller(pass, mf, vrm);
   case inline_: return createInlineSpiller(pass, mf, vrm);
   }
+  llvm_unreachable("Invalid spiller optimization");
 }