[LLVMdev] Contributing the Apple ARM64 compiler backend

[Eric Christopher]

On Fri, Mar 28, 2014 at 12:35 PM, James Grosbach <grosbach at apple.com> wrote:
> All,
>
> Attached below are the patches that make up the Apple ARM64 compiler backend (in addition to compiler_rt, libc++ and lldb support), and we'd like to start the process of integrating them into mainline LLVM.  We and ARM have discussed a general approach to integrating them into mainline and look forward to working through this with the community at large.
>
> First a bit of context to help jump-start the discussion. The ARM64 backend is a complete production quality implementation for ARM's 64-bit architecture, AArch64. It supports both iOS and Linux as target platforms. In the source tree, the backend co-exists with the AArch64 backend without conflicts.
>
> As a first step, we'd like to add this as a peer of the AArch64 backend.  While having two AArch64 backends in the tree long term doesn't make sense, this approach worked well when the Sparc backends were merged and for AMDIL. This will allow us to work quickly towards merging the ports to create a backend that is truly the best of both. The public AArch64 backend has attracted an excellent core group of contributors all of whom have done great work and we are very much looking forward to collaborating with them and the rest of the community to make this happen.
>
> Getting to that idillic end-state of one AArch64 backend in the tree which encompasses the best of both is going to take a fair bit of work and a lot of discussion amongst the interested parties. To get there, I think a rough roadmap like the following makes sense:
>
> 1. Import the ARM64 backend into the public tree so it's easily accessible for everyone to investigate.

For the record I've reviewed the lib/Basic stuff (non-neon,
non-mangling) code for arm64 for clang and that's OK to commit.

-eric