[llvm] [IR] Fix string overlap issue in `Value::setNameImpl` (PR #158288)

[Nikita Popov via llvm-commits]

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@@ -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())) {
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nikic wrote:

I believe this is technically UB in the case where it doesn't overlap. One has to use std::less in this case.

https://github.com/llvm/llvm-project/pull/158288