diff --git a/llvm/utils/TableGen/GlobalISelCombinerMatchTableEmitter.cpp b/llvm/utils/TableGen/GlobalISelCombinerMatchTableEmitter.cpp
--- a/llvm/utils/TableGen/GlobalISelCombinerMatchTableEmitter.cpp
+++ b/llvm/utils/TableGen/GlobalISelCombinerMatchTableEmitter.cpp
@@ -968,6 +968,7 @@
   }
 
   const StringInit *Code = dyn_cast<StringInit>(Apply.getArg(0));
+  assert(Code && "Expected 1 StringInit argument in 'apply'");
   auto Pat = std::make_unique<CXXPattern>(*Code, makeAnonPatName("apply"),
                                           /*IsApply*/ true);
   ApplyPats[Pat->getName()] = std::move(Pat);