message: llvm2alive: ignore MD_loop for now
  not important for correctness, only perf
diff: @@ -721,6 +721,7 @@ public:
  break;
  // non-relevant for correctness
  + case LLVMContext::MD_loop:
  case LLVMContext::MD_misexpect:
  case LLVMContext::MD_prof:
  case LLVMContext::MD_unpredictable:
  