FastISel support for unreachable.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55818 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/FastISel.cpp

@@ -366,6 +366,10 @@ FastISel::SelectInstruction(Instruction *I) {
     return false;
   }
 
+  case Instruction::Unreachable:
+    // Nothing to emit.
+    return true;
+
   case Instruction::PHI:
     // PHI nodes are already emitted.
     return true;