[llvm] [IR] Drop hash map for ValueHandleBase (PR #198187)

[Nikita Popov via llvm-commits]

nikic wrote:

For the record, I did a vibe-coded experiment to drop ValueMap during inlining (https://llvm-compile-time-tracker.com/compare.php?from=7e439d571e3dcf420448391eb76e58879e73ee1e&to=0359559b071dbd73ebfa41c111db71fbfb71d2b0&stat=instructions:u) but haven't found time to implement it properly yet.

For dropping other value handles, a big problem is that we're lacking a good way to validate such changes right now (https://discourse.llvm.org/t/rfc-valuedeletionlistener-context-level-value-deletion-notifications/90624/36?u=nikic).

https://github.com/llvm/llvm-project/pull/198187