Convert assert(0) to llvm_unreachable

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149849 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Bitcode/BitstreamWriter.h

@@ -275,7 +275,7 @@ private:
     
     // Encode the value as we are commanded.
     switch (Op.getEncoding()) {
-    default: assert(0 && "Unknown encoding!");
+    default: llvm_unreachable("Unknown encoding!");
     case BitCodeAbbrevOp::Fixed:
       if (Op.getEncodingData())
         Emit((unsigned)V, (unsigned)Op.getEncodingData());