Convert assert(0) to llvm_unreachable

llvm-svn: 149814
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
index 4db1e2f..68259e3 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
@@ -24,6 +24,7 @@
 #include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Support/Host.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/TargetRegistry.h"
 
 #define GET_REGINFO_MC_DESC