[llvm] [InstCombine] Add fold combining adjacent extracted bit fields to restore optimization for separate truncations (PR #219598)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

cc @maubri

> Failed to cherry-pick: [3493720](https://github.com/llvm/llvm-project/commit/3493720eca95cf844a8d7e58fdd12e0e5644e7d0)
> 
> https://github.com/llvm/llvm-project/actions/runs/35132324807
> 
> Please manually backport the fix and push it to your github fork. Once this is done, please create a [pull request](https://github.com/llvm/llvm-project/compare)



https://github.com/llvm/llvm-project/pull/219598