[clang] [llvm] [BasicAA] Do not decompose past casts with different index width (PR #119365)

[Björn Pettersson via llvm-commits]

bjope wrote:

Ok. Thanks for quick feedback and clarification that regressions can be expected when having different pointer sizes (or rather different index widths).

Btw, I also think the gep with "ptr null" is probably the result of over-reducing the original program. I will need to continue analyzing our regressions, but wanted some feedback on this smaller IR snippet first.

I will also look into adding a target specific AA similar to AMDGPUAAResult and NVPTXAAResult for addspace-based AA, I think that could help out eliminating many regressions/diffs that I've seen making it easier to focus on whatever remains. So thanks a lot for those code pointers!

https://github.com/llvm/llvm-project/pull/119365