[PATCH] D102292: [docs] Add page on opaque pointer types

Wed May 12 11:59:55 PDT 2021

aeubanks added a comment.

In D102292#2754913 <https://reviews.llvm.org/D102292#2754913>, @nlopes wrote:

> In D102292#2754879 <https://reviews.llvm.org/D102292#2754879>, @aeubanks wrote:
>
>> In D102292#2753579 <https://reviews.llvm.org/D102292#2753579>, @nlopes wrote:
>>
>>> Can you clarify if this only for data type or also for function types pls?
>>> (data and function pointer types don't have the same bit-width on all architectures)
>>
>> This should apply to all pointer types.
>> Do you have an example in LLVM of where this matters for function vs data?
>> In TargetMachine I only see the pointer size differences per address space, not function vs data. `TargetMachine::getPointerSize()`/`DataLayout::getPointerSize()`.
>
> I'm not an expert on the backend stuff. I just wanted to get it documented, while we are at it, whether LLVM supports architectures with different data/function pointer sizes or not.
> I guess the answer that you point at, is that one needs to use different address spaces if working with such architectures. I would be grateful if you could document this here as well.

I'm also not an expert on backend stuff, some clarification from somebody more knowledgeable would be great. Although documenting things like using different address spaces in those cases seems unrelated, that wouldn't change (assuming that's true) with opaque pointers, and the first section does mention that anything with address spaces is unchanged.

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