Convert assert(0) to llvm_unreachable in X86 Target directory.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149809 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86MCInstLower.cpp b/lib/Target/X86/X86MCInstLower.cpp
index 8955458..89e1967 100644
--- a/lib/Target/X86/X86MCInstLower.cpp
+++ b/lib/Target/X86/X86MCInstLower.cpp
@@ -416,7 +416,7 @@
   case X86::TAILJMPd64: {
     unsigned Opcode;
     switch (OutMI.getOpcode()) {
-    default: assert(0 && "Invalid opcode");
+    default: llvm_unreachable("Invalid opcode");
     case X86::TAILJMPr: Opcode = X86::JMP32r; break;
     case X86::TAILJMPd:
     case X86::TAILJMPd64: Opcode = X86::JMP_1; break;