[llvm] [SLP]Improve minbitwidth analysis for trun'ed gather nodes. (PR #99072)

[Kamau Bridgeman via llvm-commits]

kamaub wrote:

I was able to show that this PRs latest commit caused a [llvm-test-suite](https://github.com/llvm/llvm-test-suite) regression on the [clang-ppc64le-rhel](https://lab.llvm.org/buildbot/#/builders/145): [build no. 623](https://lab.llvm.org/buildbot/#/builders/145/builds/623) and [clang-ppc64le-linux-test-suite](https://lab.llvm.org/buildbot/#/builders/95): [build no. 1412](https://lab.llvm.org/buildbot/#/builders/95/builds/1412) by reproducing [build no. 1412](https://lab.llvm.org/buildbot/#/builders/95/builds/1412)'s build steps on a branch and then reverting c5c1bd164fc8 and re-testing.

I'm sorry for the inconvenience but can you please resolve this error as soon as possible or revert if it will take too long to fix so we can bring the llvm-test-suite back to green status. If I can assist with reproducing the error please let me know.

https://github.com/llvm/llvm-project/pull/99072