Build failure due to SHA256 mismatch in KleidiAI

[Colm-in-Arm]

When building an older version of XNNPACK via TfLite 2.18.1 I encounted this build error:

04:16:26 – verifying file...
04:16:26 file='/home/workspace/LinuxDriverStackPublic/linux_driver_stack/build/kleidiai-download/kleidiai-prefix/src/kleidiai-cddf991af5de49fd34949fa39690e4e906e04074.zip'
04:16:26 – SHA256 hash of
04:16:26 /home/workspace/LinuxDriverStackPublic/linux_driver_stack/build/kleidiai-download/kleidiai-prefix/src/kleidiai-cddf991af5de49fd34949fa39690e4e906e04074.zip
04:16:26 does not match expected value
04:16:26 expected: '88233e427be6579560073267575f00f3b5fc370a31a43bbdd87a1810bd4bf1b6'
04:16:26 actual: '5d4fe6b12ab999b40b26fc2760b3f1e2d134029acd9546541e118494fe11fb03'
04:16:26 – Hash mismatch, removing...

Overview of the problem.

The current mechanism to add KleidiAI to the XNNPACK project is to use Cmake's ExternalProject_Add. If URL_HASH is specified as a parameter the SHA256 of the archive is verified before being used. GitHub does not guarantee byte-for-byte stability of Git archives as documented here.

Steps to recreate

Requires: aarch64 target environment, cmake and Ninja.

• git clone --recursive https://github.com/google/XNNPACK.git
• cd XNNPACK
• git checkout 6a834a0 (this is the SHA of XNNPACK used in TfLite 2.18.1)
• cmake -S . -B build-aarch64 -GNinja -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=cmake/aarch64.toolchain -DXNNPACK_BUILD_TESTS=OFF -DXNNPACK_BUILD_BENCHMARKS=OFF

What's going on?

As outlined in the GitHub blog they do not permanently store archives. They are cached and, when considered stale, removed. They are recreated on demand afterwards. This will likely only effect combinations of older archives.

Workaround

Modify ./cmake/DownloadKleidiAI.cmake to remove "HASH_URL" from ExternalProject_Add. This will avoid the SHA256 verification.

Longer term solution.

The KleidiAI team are investigating longer term solutions but currently don't intend to fix older releases.

[ireshetnikov24]

Experiencing same issue, but with MacOS environment.
Another workaround is to temporarily disable kleidai:
set(XNNPACK_ENABLE_KLEIDIAI OFF)

[dsharlet]

I think unfortunately we don't have a fix for this for old versions, because the SHA256s have changed.

Going forward, we should try to avoid this in the future, but I'm not sure how we should do this. I don't think removing the SHAs is an option. git_repository (vs http_archive) would avoid this problem, but I don't know if this is an option in tensorflow (due to a mirror/caching mechanism). We can do it in XNNPACK, but I don't think that will address the real problem here (in tensorflow).