diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -377,6 +377,10 @@
 }
 
 void Value::takeName(Value *V) {
+  // Without this assertion (as prescribed by original comments for this API),
+  // name deletion or down-stream assert failures may occur in other routines:
+  // e.g. at the beginning of replaceAllUsesWith() below.
+  assert(V != this && "Illegal call to this->takeName(this)!");
   ValueSymbolTable *ST = nullptr;
   // If this value has a name, drop it.
   if (hasName()) {