[IR] Fix string overlap issue in Value::setNameImpl

Author: w-gc

llvm/lib/IR/Value.cpp

@@ -356,6 +356,16 @@ void Value::setNameImpl(const Twine &NewName) {
   if (getSymTab(this, ST))
     return;  // Cannot set a name on this value (e.g. constant).
 
+  // Copy NewName forcely if the memory overlaps.
+  if (!NameRef.empty()) {
+    StringRef OldNameRef = getName();
+    if ((OldNameRef.bytes_begin() < NameRef.bytes_end()) &&
+        (NameRef.bytes_begin() < OldNameRef.bytes_end())) {
+      NewName.toVector(NameData);
+      NameRef = StringRef(NameData.data(), NameData.size());
+    }
+  }
+
   if (!ST) { // No symbol table to update?  Just do the change.
     // NOTE: Could optimize for the case the name is shrinking to not deallocate
     // then reallocated.
@@ -374,15 +384,6 @@ void Value::setNameImpl(const Twine &NewName) {
   // NOTE: Could optimize for the case the name is shrinking to not deallocate
   // then reallocated.
   if (hasName()) {
-    if (!NameRef.empty()) {
-      StringRef OldNameRef = getName();
-      if ((OldNameRef.bytes_begin() < NameRef.bytes_end()) &&
-          (NameRef.bytes_begin() < OldNameRef.bytes_end())) {
-        NewName.toVector(NameData);
-        NameRef = StringRef(NameData.data(), NameData.size());
-      }
-    }
-
     // Remove old name.
     ST->removeValueName(getValueName());
     destroyValueName();