[llvm] [SimplifyCFG] Avoid redundant calls in gather. (NFC) (PR #154133)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

CTMark: https://llvm-compile-time-tracker.com/compare.php?from=97d5d483ecc67d0b786a53d065b7202908cb4047&to=09c7ff6df0fc1485b358c7942610df0188e9fa71&stat=instructions:u

https://github.com/llvm/llvm-project/pull/154133