[PATCH] D114533: LLVM IR should allow bitcast between address spaces with the same size.

[Keno Fischer via Phabricator via llvm-commits]

loladiro added a comment.

@jrtc27 is correct. This absolutely must not apply to non-integral address spaces. It is not legal for LLVM to introduce additional ptrtoint instructions for non-integral address spaces that were not present in the original input IR. That doesn't change if the spelling of a ptrtoint/inttoptr pair is changed to bitcast. There is a bit of a larger issue here that LLVM IR isn't really rich enough to currently describe what operations are legal for the optimizer to introduce and what aren't. Every frontend/backend that uses them has their own rules that appear obvious for a particular use case, but aren't necessarily general. A similar issue applies to commuting GEPs with addrspacecasts. I'm wondering if we need something like the datalayout but for describing relationships between addrspaces and what things are legal and what are not.


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  https://reviews.llvm.org/D114533/new/

https://reviews.llvm.org/D114533