Add workflow and scripts to build LLVM prebuilts#3
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cc @LegNeato |
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Sweet, I've been meaning to do this. Thanks! I was thinking of switching it from committing into the repo, which is pretty big, and switching to pulling from GitHub releases. What do you think? |
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absolutely. I will help drive that. I'm getting my butt kicked (as expected) with "compile LLVM on windows" but i'll power through and figure it out. will ping you when it's ready! thanks for the support. |
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Introduces the build pipeline that produces the prebuilt LLVM tarballs
consumed by rustc_codegen_nvvm's build.rs, and switches distribution
from in-repo binaries to GitHub release assets.
Workflow (.github/workflows/build-llvm.yml)
* workflow_dispatch with two inputs: llvm_version (e.g. 7.1.0 or
19.1.7) and release (default true).
* Matrix builds on ubuntu-22.04 (glibc 2.35 floor matching the
rust-cuda container baseline) and windows-2022, each producing
<triple>.tar.xz uploaded as a run artifact.
* Final `release` job needs both matrix legs, downloads the artifacts,
and either creates or --clobber-uploads to a release tagged
llvm-<version>. Re-running a build for the same version is therefore
idempotent. Uncheck the release input for a build-only run.
Build scripts
* scripts/build-llvm-linux.sh — fetches the upstream tarball, configures
cmake with X86;NVPTX targets, dylib link, assertions off, examples
/tests/benchmarks off, then ninja install. Handles the 7.x vs 8+
layout split (llvm-X.Y.Z.src vs llvm-project-X.Y.Z.src monorepo).
* scripts/build-llvm-windows.ps1 — same shape, with a few Windows
specifics worth flagging:
- Calls Git for Windows' GNU tar by full path. The default tar.exe
on PATH is Microsoft's bsdtar, which hangs indefinitely on
.tar.xz (actions/runner-images#282).
- For LLVM 8+ extracts only llvm/, cmake/, and third-party/ from
the monorepo. clang/test/Driver/Inputs contains out-of-order
symlinks that msys-tar cannot create on Windows
(CreateSymbolicLink requires the target's FILE/DIR type, which
msys resolves via stat — it fails when the target hasn't been
extracted yet).
- LLVM 7 is built with clang-cl from the runner's preinstalled
LLVM toolchain because MSVC v143 rejects 7.x sources without
patches.
* scripts/package-prebuilt.sh — repackages the install tree into the
layout build.rs expects (bin/llvm-config[.exe], bin/llvm-as[.exe],
include/llvm{,-c}, lib/*), strips lib/cmake and lib/pkgconfig (build
.rs goes through llvm-config, and pkgconfig contains absolute
build-host paths), and tars to .tar.xz.
Distribution
* Tarballs no longer live in the repo. The previous prebuilt/ tree
(~300 MB working-tree, ~30 MB on disk via xz) is removed; assets are
pulled from the release at
github.com/<owner>/<repo>/releases/download/llvm-<version>/<triple>.tar.xz
* .gitignore prevents the build/install/source dirs and stray *.tar.xz
from being committed back in.
* README rewritten around the release-based flow.
Note: removing prebuilt/ from HEAD shrinks future commits but the
binaries remain in earlier history (dd512c5, e6b86c6, b432cd4, a90da8c,
596215d). A follow-up filter-repo + force-push would be needed to
actually shrink fresh clones.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Contributor
Author
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@LegNeato went to damn war with this thing!!!! https://github.com/brandonros/rustc_codegen_nvvm-llvm/releases/tag/llvm-7.1.0 windows + linux, should be ready to merge. i'll go to https://github.com/Rust-GPU/rust-cuda and wire up the prebuild for llvm-19 now once we merge this and then trigger the releases on the official Rust-GPU org |
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Yay! |
LegNeato
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Apr 30, 2026
Add workflow and scripts to build LLVM prebuilts
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