Please backport 604a6c409e8 to release/18.x

[jmorse]

Please cherry-pick commit 604a6c4 from PR #77774 to the LLVM 18 release branch. This is a nondeterminism fix that stems from re-use of stale pointers, that cleanly cherry-picks to the release branch. (I've no idea how to use llvmbot to make this happen automagically, sorry).

This fault seems to have been around for many years so isn't urgent, but must be reasonably annoying for anyone encountering it.

[tstellar]

/cherry-pick 604a6c4

[llvmbot]

/pull-request #80729