[llvm] [LowerBufferFatPointers] Don't lose data from unaligned < word vectors (PR #132981)

[Krzysztof Drewniak via llvm-commits]

krzysz00 wrote:

> Not sure I understand how that's an alternative to this?

The shortening this patch would  have added was only needed to change the behavior of a partially out of bounds - that is, things like `load vector<8 x i8>, ptr addrspace(7) %q, align 2`, where `%p.numRecords` is 2 bytes past the end of the pointer, which - because `raw.ptr.buffer.load.v2i32` checks out-of-bounds-ness word by word, would result in some data getting masked off. 

If you're not relying on that out of bounds behavior, you don't need this underaligned load handling.

So the plan is that, if you're trying to load partially out of bounds - thus doing something that LLVM would ordinarily consider UB - that'll only get implemented for masked load

https://github.com/llvm/llvm-project/pull/132981