diff --git a/llvm/lib/CodeGen/MIRParser/MIParser.cpp b/llvm/lib/CodeGen/MIRParser/MIParser.cpp
--- a/llvm/lib/CodeGen/MIRParser/MIParser.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MIParser.cpp
@@ -563,7 +563,7 @@
 
 void MIParser::lex(unsigned SkipChar) {
   CurrentSource = lexMIToken(
-      CurrentSource.data() + SkipChar, Token,
+      CurrentSource.slice(SkipChar, StringRef::npos), Token,
       [this](StringRef::iterator Loc, const Twine &Msg) { error(Loc, Msg); });
 }