[llvm] [MemCpyOpt] Continue merging memset with unrelated clobber (PR #89550)

[Nikita Popov via llvm-commits]

nikic wrote:

New compile-time numbers: https://llvm-compile-time-tracker.com/compare.php?from=ba702aa067c0659d2263d2144d38666efa4a1750&to=965d72d4a9918e00a02609c40f31d00d8fe63d64&stat=instructions:u

https://github.com/llvm/llvm-project/pull/89550