GH-136895: Update JIT builds to use LLVM 20 #140329
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With LLVM 20, individual files are greater than the 100MiB single file limit for items checked into git. Therefore, this PR pulls down binaries from GitHub releases, as `.tar.xz` files to additionally maximize compression ratio. Currently this is somewhat of a first draft, as there are things like hash checking needed to be done.
This reverts commit e6450de.
savannahostrowski
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a team,
brandtbucher and
diegorusso
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savannahostrowski
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AA-Turner,
ezio-melotti and
hugovk
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diegorusso
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Oct 19, 2025
zware
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Oct 20, 2025
diegorusso
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Oct 21, 2025
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Alright, this took me longer than expected for two reasons:
Bumping to LLVM 20 required some changes to the infrastructure we use to grab LLVM as a dependency on Windows. As of 20, LLVM now contains files that exceed GitHub's allowable size, so checking these directly into
cpython-bin-deps' tree was not an option. Instead, this PR adds the ability to pull from release artifacts (see https://github.com/python/cpython-bin-deps/releases/tag/llvm-20.1.8.0). This also makes the process of bumping LLVM for Windows a little less hairy. Thank you, @emmatyping, for much of this code, and thank you, @zware, for publishing the release artifact for me 🙏 !For macOS x86_64 debug builds, external symbol references generated by LLVM 20 can exceed the ±2GB PC-relative addressing range that
patch_32rrequires. This manifested as assertion failures in free-threading tests (see https://github.com/savannahostrowski/cpython/actions/runs/18438327725/job/52537027963?pr=10 as an example). After going down a rabbit hole, I believe the correct fix here is to implement x86_64 trampolines (similar to our existing aarch64 implementation) to handle out-of-range symbols...and so I've done that. AFAICT, trampolines are only needed on macOS right now, as the other target platforms have different relocation mechanisms.