[llvm-dev] NVPTX codegen for llvm.sin (and friends) (original) (raw)

Artem Belevich via llvm-dev llvm-dev at lists.llvm.org
Fri Mar 12 14:59:42 PST 2021

On Fri, Mar 12, 2021 at 2:39 PM James Y Knight <jyknight at google.com> wrote:

On Fri, Mar 12, 2021 at 1:51 PM Artem Belevich via llvm-dev <_ _llvm-dev at lists.llvm.org> wrote: Also, bitcode is platform specific. I can imagine building a bitcode file during the build but shipping one means you have to know ABI and datalayout or hope they are the same everywhere.

Agreed. We will likely need multiple variants. We will compile specifically for NVPTX or AMDGPU and we will know specific ABI and the data layout for them regardless of the host we're building on. It appears to me is the the difference vs what we have now is that we'll need to have the libm sources somewhere, the process to build them for particular GPUs (that may need to be done out of the tree as it may need CUDA/HIP SDKs) and having to incorporate such libraries into llvm distribution. OK. I'll agree that that may be a bit too much for now. It sounded before like you were saying the library should effectively _be function aliases for standard libm names, to call nv names. Isn't it utterly trivial to generate such a bitcode file as part of the toolchain build, without requiring any external SDKs?

That's true for most, but not all functions provided by libdevice. We'd still need something that's a bit more involved.

--Artem

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