[llvm] [InstCombine] Add combines/simplifications for `llvm.ptrmask` (PR #67166)

[Nikita Popov via llvm-commits]

nikic wrote:

We should update LangRef and require that the integer arg has the size of the pointer index type (with current GEP semantics implying a 1-extend to pointer type width), implement a Verifier check for that, and add an assert in SDAG lowering that the index type size is the pointer size -- I don't believe we currently have any in-tree SDAG support for pointers with narrow index types, so this is just a breadcrumb for out-of-tree targets to implement a 1-extend at that point.

I was planning to do this, but never found the time.


https://github.com/llvm/llvm-project/pull/67166