1 files changed, 3 insertions, 0 deletions
diff --git a/llvm/utils/TableGen/AsmMatcherEmitter.cpp b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
index 503d0730bbf..dc92a6c218e 100644
--- a/llvm/utils/TableGen/AsmMatcherEmitter.cpp
+++ b/llvm/utils/TableGen/AsmMatcherEmitter.cpp
@@ -1329,6 +1329,9 @@ void AsmMatcherInfo::BuildInfo() {
     Record *Rec = AllTokenAliases[i];
     ClassInfo *FromClass = getTokenClass(Rec->getValueAsString("FromToken"));
     ClassInfo *ToClass = getTokenClass(Rec->getValueAsString("ToToken"));
+    if (FromClass == ToClass)
+      throw TGError(Rec->getLoc(),
+                    "error: Destination value identical to source value.");
     FromClass->SuperClasses.push_back(ToClass);
   }