Apple, LLVM Developers Figure Out Their 64-Bit ARM Approach
Written by Michael Larabel in Compiler on 14 April 2014 at 09:33 PM EDT. 2 Comments
Two weeks ago Apple open-sourced their 64-bit ARM back-end to LLVM. Following last week's EuroLLVM meeting, they have decided that the community's existing open-source 64-bit ARM back-end will likely be merged into Apple's now-public back-end.

At the "EuroLLVM" meeting last week in Edinburgh, Scotland, developers met to figure out the approach of ARM 64-bit support within LLVM/Clang now that Apple has open-sourced their code-base while various other organizations and community developers have focused on their own 64-bit ARM back-end. Both sides have agreed that the code-bases are to be merged, but the main plan was figuring out the most reasonable approach for combining the two code-bases.

Last week's meeting reaffirmed that the ARM64 back-end is the merge target. The "ARM64" back-end is Apple's back-end while the "AArch64" back-end is the existing 64-bit ARM code. Developers will be working to merge the extra functionality of the existing back-end into the newly open-sourced back-end as soon as possible to avoid code fragmentation and problems. This merging of the two 64-bit ARM back-ends might not happen before the LLVM 3.5 release this summer, but when it does the ARM64 (Apple) back-end will be renamed to AArch64 for ARM's correct naming scheme.

When the two code-bases are complete, no significant regressions can be found from code correctness to features to stability and performance. For those wishing to learn more about the ongoing 64-bit ARM LLVM work can be discovered via this mailing list thread.

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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter or contacted via

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