AlexVlx wrote: > I am personally not opposed to the DL solution, but I guess it's a big change > that feels too much for me to approve. I'm also worried the "flat" concept is > a special case of something more generic and we should instead define that. > E.g.,
In reply to your question above re whether this is a DL or a Target property, I don't have a strong opinion there (it appears @shiltian and @arsenm might). I do believe that this is a necessary bit of query-able information, especially from a Clang, for correctness reasons (more on that below). > * Does flat imply all AS can cast to it? If so, what happens if that is not > true anymore in the future. If it's not implied, how do we query what's > allowed and what is not? To make this generically useful, it probably should, but I don't think the current words imply it. > * Is there a value in not defining 0 as flat? It's what we basically assume > everywhere already, isn't it? Ah, this is part of the challenge - we do indeed assume that 0 is flat, but Targets aren't bound by LangRef to use 0 to denote flat (and some, like SPIR / SPIR-V) do not, but rather problematically use 0 to denote Private, which is extremely constrained. This leads to problematic IR, due to the assumption you mentioned. An example I ran into the other day is [`emitCalloc`](https://github.com/llvm/llvm-project/blob/5dc15ddf575978e0115b1a6edacb59f056792a80/llvm/lib/Transforms/Utils/BuildLibCalls.cpp#L1989) - note it just uses the default pointer type for its return, which is problematic unless 0 is flat(-ish). It is, of course, fixable via other means, but it's just an example of where we rely on 0 just working. Perhaps another solution(?) here would be to tweak LangRef to be binding in that it spells out that iff a particular Target has a Flat AS, that will be reflected in LLVM as AS0? https://github.com/llvm/llvm-project/pull/108786 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
