Update size of inst correctly with segment override.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57414 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86CodeEmitter.cpp b/lib/Target/X86/X86CodeEmitter.cpp
index ab57e3d..e08688b 100644
--- a/lib/Target/X86/X86CodeEmitter.cpp
+++ b/lib/Target/X86/X86CodeEmitter.cpp
@@ -420,6 +420,8 @@
   case X86II::GS:
     MCE.emitByte(0x65);
     break;
+  default: assert(0 && "Invalid segment!");
+  case 0: break;  // No segment override!
   }
 
   // Emit the repeat opcode prefix as needed.