[llvm] [llvm] Use ABI instead of preferred alignment for const prop checks (PR #142500)

[via llvm-commits]

PiJoules wrote:

> Why is the only change in the test to the data layout string? Shouldn't there be some check that the case you've brought up is handled?

I can add another test that asserts the ABI alignment is used instead of the preferred alignment. Existing tests only specified the preferred alignment so the ABI alignment could be anything which led to different codegen (for example, some i8 constants weren't propagated since they had an ABI alignment of 4). I updated the tests just to be explicit about the ABI alignment since we were previously explicit about the preferred alignment.

https://github.com/llvm/llvm-project/pull/142500