Anastasia added inline comments.
================ Comment at: clang/lib/Basic/Targets/SPIR.h:59 + // translation). This mapping is enabled when the language mode is HIP. + 1, // cuda_device + // cuda_constant pointer can be casted to default/"flat" pointer, but in ---------------- bader wrote: > Anastasia wrote: > > linjamaki wrote: > > > bader wrote: > > > > keryell wrote: > > > > > Anastasia wrote: > > > > > > bader wrote: > > > > > > > Anastasia wrote: > > > > > > > > I am slightly confused as in the LLVM project those address > > > > > > > > spaces are for SPIR not SPIR-V though. It is however used > > > > > > > > outside of LLVM project by some tools like SPIRV-LLVM > > > > > > > > Translator as a path to SPIR-V, but it has only been done as a > > > > > > > > workaround since we had no SPIR-V support in the LLVM project > > > > > > > > yet. And if we are adding it let's do it clean to avoid/resolve > > > > > > > > any confusion. > > > > > > > > > > > > > > > > I think we need to keep both because some vendors do target/use > > > > > > > > SPIR but not SPIR-V. > > > > > > > > > > > > > > > > So if you are interested in SPIR-V and not SPIR you should > > > > > > > > probably add a new target that will make things cleaner. > > > > > > > > I think we need to keep both because some vendors do target/use > > > > > > > > SPIR but not SPIR-V. > > > > > > > > > > > > > > @Anastasia, could you elaborate more on the difference between > > > > > > > SPIR and SPIR-V? > > > > > > > I would like to understand what these terms mean in the context > > > > > > > of LLVM project. > > > > > > Their conceptual differences are just that they are two different > > > > > > intermediate formats. > > > > > > > > > > > > The important thing to highlight is that it is not impossible that > > > > > > some vendors use SPIR (without using SPIR-V) even despite the fact > > > > > > it has been discontinued by Khronos. > > > > > > > > > > > > Nobody has deprecated or discontinued SPIR in the LLVM project yet. > > > > > > Their conceptual differences are just that they are two different > > > > > > intermediate formats. > > > > > > > > > > > > The important thing to highlight is that it is not impossible that > > > > > > some vendors use SPIR (without using SPIR-V) even despite the fact > > > > > > it has been discontinued by Khronos. > > > > > > > > > > > > Nobody has deprecated or discontinued SPIR in the LLVM project yet. > > > > > > > > > > All the official Xilinx OpenCL stack is based on legacy SPIR (encoded > > > > > in LLVM 6.x IR but this is another story) and I suspect this is the > > > > > case for other companies. > > > > > So, do not deprecate or discontinue, please. :-) > > > > > The important thing to highlight is that it is not impossible that > > > > > some vendors use SPIR (without using SPIR-V) even despite the fact it > > > > > has been discontinued by Khronos. > > > > > Nobody has deprecated or discontinued SPIR in the LLVM project yet. > > > > > > > > Strictly speaking `SPIR` is not defined as an intermediate language. > > > > Khronos defines `SPIR-1.2` and `SPIR-2.0` formats which are based on > > > > LLVM 3.2 and LLVM 3.4 version (https://www.khronos.org/spir/). There is > > > > no definition of SPIR format based on current version of LLVM IR. > > > > Another note is that metadata and intrinsics emitted for OpenCL with > > > > clang-14 doesn't follow neither `SPIR-1.2` nor `SPIR-2.0`. > > > > > > > > I always think of LLVM IR as leaving thing that is subject to change by > > > > LLVM community, so tools working with LLVM IR must adjust to the > > > > particular version (e.g. release version like LLVM 13 or ToT). We apply > > > > this logic to SPIRV-LLVM-Translator tool and update it according to > > > > LLVM format changes (e.g. kernel argument information defined in > > > > Khronos spec must be named metadata whereas clang emits function > > > > metadata). > > > > > > > > > I am slightly confused as in the LLVM project those address spaces > > > > > are for SPIR not SPIR-V though. > > > > [skip] > > > > > Their conceptual differences are just that they are two different > > > > > intermediate formats. > > > > > > > > If this is the only difference, I don't think it a good idea to create > > > > another LLVM target to separate SPIR and SPIR-V. From my point of view > > > > it creates logic ambiguity and code duplication with no additional > > > > value. @Anastasia, what problems do you see if we continue treating > > > > LLVM IR with spir* target triple as LLVM IR representation of SPIR-V > > > > format? > > > The state of SPIR 1.2/2.0 in Clang seems to be that the SPIR target has > > > transformed to mean “SPIR 1.2/2.0 derivative”, but that does not still > > > make it SPIR-V, which is not based on LLVM IR. When one is targeting > > > spir* there is ambiguity on whether one is aiming to produce the > > > old-SPIR-derivative or SPIR-V. Considering that there are still > > > SPIR-derivative consumers, in my opinion we should have separate LLVM > > > targets for SPIR-V to have explicit disambiguation of intent for > > > producing the SPIR-derivative vs SPIR-V. > > @bader, if you would like to migrate SPIR into SPIR-V properly then we > > should at least rename it. I would certainly prefer triple SPIR-V to SPIR > > which eliminates the need to explain what it actually is and especially > > considering that SPIR has existed as an alternative IR format for quite a > > while. It would at least make sense tpo eliminate the confusion. > > > > However if you would like to go this route you should send a wider > > community messaging about it and then see if there are any objections. From > > my experience of previous conversations some years back there are tool > > developers using SPIR as a portable format even if it's LLVM release > > dependent however in practice it worked across the latest releases quite > > well. I would like to remind that not all vendors that support OpenCL or > > other accelerator API also support SPIR-V. There are also vendors that are > > migrating to SPIR-V but have older releases in maintenance that don't > > support SPIR-V. So my feeling is that SPIR has been and is still used as a > > portable format in tooling. > > > > Regarding an extra triple/target, I don't see a lot of code duplication if > > we use inheritance/generic programming and other C++ features that will > > allow us to share the code effectively between both. > > if you would like to migrate SPIR into SPIR-V properly then we should at > > least rename it. > > I have an impression that existing SPIR target should work for both use > cases: tools working with "SPIR 1.2/2.0 derivatives" and LLVM -> SPIR-V > translation tool(s). I'm trying to clarify why adding mapping for CUDA > address spaces works for SPIR-V, but doesn't work for "SPIR 1.2/2.0 > derivatives". > I have an impression that existing SPIR target should work for both use > cases: tools working with "SPIR 1.2/2.0 derivatives" and LLVM -> SPIR-V > translation tool(s). Ok, I have two concerns if we take this route: 1. What do we do about documentation and messaging if we use one target for both? I imagine some updates will be needed somewhere to make it clear that SPIR is SPIR-V and SPIR-V is SPIR and that they will evolve the same way if we decide to go this route... Then at least we probably need a new triple for SPIR-V? 2. What happens if we need different behavior for SPIR-V than what SPIR currently has? For example, my impression is that for SPIR-V backend some OpenCL builtins will be represented differently. Btw developers working on SPIR-V backend should probably be included into this discussion... Overall I feel adding a new target with code reuse from SPIR will probably make things clearer in a long run, but this should probably be discussed elsewhere either in https://reviews.llvm.org/D109144 or as a wider discussion perhaps via a new RFC thread about the best approach of adding SPIR-V target and the future evolution of SPIR. Then we can make sure this can reach the right audience... Then we can collect a list of requirements about different use cases that developers targets and where they are heading with those in the future and define a suitable direction. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D108621/new/ https://reviews.llvm.org/D108621 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
