[llvm] [Attributor] Guard alignment query after pointer-vector stripping (PR #205389)

[via llvm-commits]

lijinpei-amd wrote:

> I get this happens because <1 x ptr> is bitcastable into ptr, which is ... anyway. I left comments.

On the necessary of each changed line,  I have structured the pr as a test commit followed by a fix commit, and locally verified the fixes are necessary.
On the exotic of the IR, there are still other attributor core dumps...... https://github.com/llvm/llvm-project/issues?q=is%3Aissue%20state%3Aopen%20author%3Ak-arrows%20Attributor


https://github.com/llvm/llvm-project/pull/205389