[llvm] [InstCombine] Prevent i8 canonicalize for SPIR-V (PR #147527)

[Nikita Popov via llvm-commits]

nikic wrote:

> > This is something you need to handle in the SPIRV backend. This type information will cease to exist in the future.
> 
> What do you mean by `This type information will cease to exist in the future`? Is there a plan to remove the type operand from the GEP instruction?

Yes, the type operand will be removed as part of https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699.

I brought this up as a potential concern when the SPIRV target was promoted to non-experimental (https://discourse.llvm.org/t/rfc-promoting-spir-v-to-an-official-target/83614) and maintainers were confident that they will be able to accommodate this change in the SPIRV backend.

https://github.com/llvm/llvm-project/pull/147527