[llvm] [SLP] Make getSameOpcode support different instructions if they have same semantics. (PR #112181)

[Nikita Popov via llvm-commits]

nikic wrote:

Looks like this was already reverted for other reasons, so just as a FYI this also causes a significant compile-time regression: https://llvm-compile-time-tracker.com/compare.php?from=02bcaca5995de283c85acfcca61a39baac315794&to=82204154b7bd1f8c487c94c7ef00399d776b29f0&stat=instructions:u

https://github.com/llvm/llvm-project/pull/112181