Convert assert(0) to llvm_unreachable

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149967 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCDwarf.cpp b/lib/MC/MCDwarf.cpp
index 65f1ad1..1b6dbdc 100644
--- a/lib/MC/MCDwarf.cpp
+++ b/lib/MC/MCDwarf.cpp
@@ -765,8 +765,7 @@
   MCContext &context = streamer.getContext();
   unsigned format = symbolEncoding & 0x0f;
   switch (format) {
-  default:
-    assert(0 && "Unknown Encoding");
+  default: llvm_unreachable("Unknown Encoding");
   case dwarf::DW_EH_PE_absptr:
   case dwarf::DW_EH_PE_signed:
     return context.getAsmInfo().getPointerSize();