[LLVMdev] [PATCH][RFC] NVPTX Backend

Justin Holewinski jholewinski at nvidia.com
Wed Apr 25 07:09:47 PDT 2012


From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Joshua Cranmer
Sent: Tuesday, April 24, 2012 9:54 PM
To: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] [PATCH][RFC] NVPTX Backend

On 4/24/2012 1:50 PM, Justin Holewinski wrote:
Hi LLVMers,

We at NVIDIA would like to contribute back to the LLVM open-source community by up-streaming the NVPTX back-end for LLVM.  This back-end is based on the sources used by NVIDIA, and currently provides significantly more functionality than the current PTX back-end.  Some functionality is currently disabled due to dependencies on LLVM core changes that we are also in the process of up-streaming, but the back-end is very usable in its current state and would benefit all current and future users of the LLVM PTX back-end.

I've ended up having to make some local modifications to the PTX backend that I was preparing to post patches for, although, if it's going away, I guess I shouldn't bother. :-)


If the patches are still applicable, then by all means! :)


Leafing through the patch briefly, though, I don't think I see any support for the LLVM rem instruction, nor do I see any support for the llvm exp2/log2 intrinsics... am I missing something, or are these operations (still) unsupported in the NVPTX backend? On the plus side, it's nice to see that at least two or three of the small fixes are already fixed.

Integer srem/urem are supported (see NVPTXInstrInfo.td), frem is not.  At the moment, we only support intrinsics listed in the LLVM language reference, but the PTX versions of ex2/lg2 are exposed through the llvm.nvvm.{ex2,lg2}.approx.{f,d,ftz.f} intrinsics (see include/llvm/IntrinsicsNVVM.td).





--

Joshua Cranmer

News submodule owner

DXR coauthor

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