Add baseline x64 Linux builds for CPUs without AVX by robobun · Pull Request #137 · oven-sh/WebKit

robobun · 2026-01-14T18:46:02Z

Summary

Adds baseline builds (-march=nehalem) for x86_64 Linux to support CPUs that have SSE4.2 but lack AVX instructions
Fixes "Illegal instruction" crash when running baseline Bun builds on CPUs without AVX support

Changes

Dockerfile: Apply MARCH_FLAG to both ICU and WebKit compiler flags
release.sh: Pass MARCH_FLAG build argument to Docker buildx
build-reusable.yml:
- Add baseline matrix entries with cpu: nehalem and MARCH_FLAG: "-march=nehalem"
- Update release job to download and publish baseline artifacts

New Artifacts

bun-webkit-linux-amd64-baseline (non-LTO)
bun-webkit-linux-amd64-baseline-lto (LTO)

Related Issue

This is required to fix oven-sh/bun#26071 - baseline Bun builds crash with "Illegal instruction" on CPUs without AVX because the prebuilt WebKit is compiled with -march=haswell (AVX2) while baseline Bun is compiled with -march=nehalem (SSE4.2).

Test plan

CI builds successfully for new baseline variants
Resulting artifacts can be used by Bun's SetupWebKit.cmake for baseline builds
Bun baseline build runs on CPUs without AVX (e.g., Xeon E5-2697A v4)

🤖 Generated with Claude Code

This adds baseline builds (`-march=nehalem`) for x86_64 Linux to support CPUs that have SSE4.2 but lack AVX instructions. Changes: - Add MARCH_FLAG build argument to Dockerfile for custom -march flags - Update release.sh to pass MARCH_FLAG to Docker buildx - Add baseline matrix entries in build-reusable.yml: - bun-webkit-linux-amd64-baseline (non-LTO) - bun-webkit-linux-amd64-baseline-lto (LTO) - Update release job to download and publish baseline artifacts This fixes the "Illegal instruction" crash when running baseline Bun builds on CPUs without AVX support (oven-sh/bun#26071). Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

This adds baseline musl builds (`-march=nehalem`) for x86_64 Alpine Linux to support CPUs that have SSE4.2 but lack AVX instructions. Changes: - Add MARCH_FLAG support to Dockerfile.musl (ICU and WebKit builds) - Update musl-release.sh to pass MARCH_FLAG to Docker buildx - Add baseline musl matrix entries in build-reusable.yml: - bun-webkit-linux-amd64-musl-baseline (non-LTO) - bun-webkit-linux-amd64-musl-baseline-lto (LTO) - Update release job to download and publish baseline musl artifacts Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

robobun · 2026-01-14T18:48:51Z

/build

coderabbitai · 2026-01-14T18:54:39Z

Walkthrough

Adds CPU baseline build variants targeting nehalem-era processors without AVX support to the build matrix. Introduces architecture-specific compilation flag (MARCH_FLAG) throughout build pipeline, enabling support for older CPUs and addressing compatibility with systems lacking AVX instructions.

Changes

Cohort / File(s)	Summary
Workflow Build Matrix `\.github/workflows/build-reusable\.yml`	Adds baseline and baseline-lto variants for Linux amd64 and musl architectures targeting nehalem CPU. Propagates MARCH_FLAG environment variable to Docker builds via release scripts. Updates artifact download and release artifact handling to include new baseline build outputs.
Build Scripts `release\.sh`, `musl-release\.sh`	Introduces MARCH_FLAG environment variable with default empty value and propagates it as build argument to Docker buildx command invocations.
Dockerfiles `Dockerfile`, `Dockerfile\.musl`	Appends MARCH_FLAG to CFLAGS and CXXFLAGS in both ICU and WebKit build stages to apply architecture-specific compiler optimizations.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding baseline x64 Linux builds for CPUs without AVX support.
Description check	✅ Passed	The PR description provides a comprehensive summary, changes, artifacts, related issue, and test plan, though it deviates from the repository's template format which requires Bugzilla issue format.
Linked Issues check	✅ Passed	The PR directly addresses the coding requirements from linked issue `#26071` by implementing baseline builds with -march=nehalem to support CPUs lacking AVX, which fixes the Illegal instruction crash.
Out of Scope Changes check	✅ Passed	All code changes are scoped to implementing baseline build support: Dockerfiles apply MARCH_FLAG to compilation, release scripts propagate the flag, and build workflow adds baseline matrix entries and artifact handling.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

📜 Recent review details

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Disabled knowledge base sources:

Linear integration is disabled by default for public repositories

You can enable these sources in your CodeRabbit configuration.

📥 Commits

Reviewing files that changed from the base of the PR and between 9808f0c and 8ea8666.

📒 Files selected for processing (5)

.github/workflows/build-reusable.yml
Dockerfile
Dockerfile.musl
musl-release.sh
release.sh

🔇 Additional comments (11)

Dockerfile (3)

1-1: MARCH_FLAG ARG declaration and propagation looks correct.

The MARCH_FLAG is properly declared at the top level with an empty default, re-declared in the base stage to inherit the build argument, and set as an environment variable for use in build steps.

Also applies to: 15-15, 186-186

170-171: ICU build flag integration is correct.

The $MARCH_FLAG is properly appended to both CFLAGS and CXXFLAGS for the ICU build, ensuring the architecture-specific flags are applied consistently.

190-191: WebKit build flag integration is correct.

The $MARCH_FLAG is properly integrated into the WebKit build step, maintaining consistency with the ICU build approach.

Dockerfile.musl (1)

1-1: MARCH_FLAG integration in musl Dockerfile is consistent and correct.

The MARCH_FLAG is properly declared, re-declared in each build stage (base, build_icu, build_webkit), and applied to both ICU and WebKit builds in a manner consistent with the main Dockerfile.

Also applies to: 10-10, 26-26, 38-38, 49-50, 62-62, 81-82

musl-release.sh (1)

10-10: MARCH_FLAG propagation in musl-release.sh is correct.

The script follows the established pattern for LTO_FLAG, with proper default handling and build argument propagation to Docker.

Also applies to: 47-47

release.sh (1)

10-10: MARCH_FLAG propagation in release.sh is correct.

The implementation is consistent with musl-release.sh and follows the established pattern for build argument propagation.

Also applies to: 59-59

.github/workflows/build-reusable.yml (5)

185-201: Baseline matrix entries for Linux glibc are well-structured.

The new baseline variants correctly specify cpu: nehalem and MARCH_FLAG: "-march=nehalem" for Release builds, with both LTO and non-LTO configurations. This appropriately targets x86_64 CPUs with SSE4.2 but without AVX support.

339-353: Baseline matrix entries for Linux musl are consistent.

The musl baseline variants follow the same pattern as glibc, using MinSizeRel build type which is consistent with other musl configurations in the matrix.

234-237: MARCH_FLAG propagation in Linux job is correct.

The MARCH_FLAG is properly set in the environment and passed to release.sh. The CPU fallback to 'native' ensures backward compatibility for non-baseline builds.

369-373: MARCH_FLAG propagation in Linux musl job is consistent with glibc job.

The implementation mirrors the Linux glibc job, maintaining consistency across the workflow.

506-521: Release job correctly handles all baseline artifacts.

The download, rename, and release steps properly handle all four baseline variants (glibc baseline, glibc baseline-lto, musl baseline, musl baseline-lto) with consistent naming.

Also applies to: 550-553, 581-582, 594-595

_{✏️ Tip: You can disable this entire section by setting review_details to false in your review settings.}

Warning

Review ran into problems

🔥 Problems

Git: Failed to clone repository. Please run the @coderabbitai full review command to re-trigger a full review. If the issue persists, set path_filters to include or exclude specific files.

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

robobun · 2026-01-14T18:59:21Z

/build-preview

robobun · 2026-01-14T18:59:32Z

/build-preview

github-actions · 2026-01-14T18:59:32Z

🔄 Preview build started

Release tag: autobuild-preview-pr-137-8ea86667
Workflow: View progress

github-actions · 2026-01-14T18:59:42Z

⚠️ Preview build was cancelled

This may have been caused by a newer build being triggered for the same PR.

github-actions · 2026-01-14T18:59:53Z

🔄 Preview build started

Release tag: autobuild-preview-pr-137-8ea86667
Workflow: View progress

github-actions · 2026-01-14T19:40:12Z

✅ Preview build completed

Release: autobuild-preview-pr-137-8ea86667

When ENABLE_BASELINE=ON is set for x86_64 builds, append `-baseline` to the WebKit download URL suffix. Without this, baseline Bun links against a WebKit library compiled with AVX/AVX2 instructions, causing SIGILL crashes on CPUs without AVX support. The baseline suffix is placed after the musl suffix and before the debug/lto/asan suffixes to match the naming convention used by the WebKit CI (oven-sh/WebKit#137). Closes #27090 Co-Authored-By: Claude <noreply@anthropic.com>

Linux x64 was pinned to -march=nehalem for all builds in 596e48e. This splits that: default entries get -march=haswell (matching bun's non-baseline target), new -baseline entries keep -march=nehalem. Windows had no arch pin at all. Both WebKit (clang-cl) and ICU (MSVC cl.exe via MSBuild) compiled without -march / /arch:, letting the auto-vectorizer emit AVX2/AVX-512 in ICU's hash and decimal loops with no CPUID gate. Now windows-release.ps1 takes -Baseline and threads /clang:-march= into CMake flags; build-icu.ps1 injects /arch: into the .vcxproj patches (/arch:SSE2 for baseline, /arch:AVX2 otherwise). New artifacts: bun-webkit-linux-amd64-baseline{,-lto} bun-webkit-linux-amd64-musl-baseline{,-lto} bun-webkit-windows-amd64-baseline Supersedes #137.

* Add x64 baseline WebKit builds for Linux and Windows Linux x64 was pinned to -march=nehalem for all builds in 596e48e. This splits that: default entries get -march=haswell (matching bun's non-baseline target), new -baseline entries keep -march=nehalem. Windows had no arch pin at all. Both WebKit (clang-cl) and ICU (MSVC cl.exe via MSBuild) compiled without -march / /arch:, letting the auto-vectorizer emit AVX2/AVX-512 in ICU's hash and decimal loops with no CPUID gate. Now windows-release.ps1 takes -Baseline and threads /clang:-march= into CMake flags; build-icu.ps1 injects /arch: into the .vcxproj patches (/arch:SSE2 for baseline, /arch:AVX2 otherwise). New artifacts: bun-webkit-linux-amd64-baseline{,-lto} bun-webkit-linux-amd64-musl-baseline{,-lto} bun-webkit-windows-amd64-baseline Supersedes #137. * mac-release: pin clang++ to clang++-21 The C compiler was pinned (clang-21) but the C++ compiler was unqualified clang++. GH Actions macOS runner image changed between Feb 24 and Mar 3 so clang++ now resolves to Apple Clang instead of homebrew LLVM 21. Apple Clang's libc++ doesn't define _LIBCPP_AVAILABILITY_HAS_HASH_MEMORY, so LibcxxHashMemoryShim.cpp compiles to an empty object (__TEXT=0). Bun then fails to link with undefined std::__1::__hash_memory.

Claude Bot and others added 2 commits January 14, 2026 18:45

robobun mentioned this pull request Jan 29, 2026

Linux ARM64: Illegal instruction crash on older CPUs (Cortex-A53, RPi4) due to LSE atomics in WebKit oven-sh/bun#26556

Closed

robobun mentioned this pull request Feb 13, 2026

fix(cmake): download baseline WebKit for x64 baseline builds oven-sh/bun#27007

Open

3 tasks

robobun mentioned this pull request Feb 17, 2026

fix(build): download baseline WebKit for x64 baseline builds oven-sh/bun#27091

Closed

3 tasks

dylan-conway mentioned this pull request Mar 4, 2026

Add x64 baseline WebKit builds for Linux and Windows #171

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Add baseline x64 Linux builds for CPUs without AVX#137

Add baseline x64 Linux builds for CPUs without AVX#137
robobun wants to merge 2 commits intomainfrom
claude/baseline-x64-builds

robobun commented Jan 14, 2026

Uh oh!

robobun commented Jan 14, 2026

Uh oh!

coderabbitai bot commented Jan 14, 2026 •

edited

Loading

Review ran into problems

Uh oh!

robobun commented Jan 14, 2026

Uh oh!

robobun commented Jan 14, 2026

Uh oh!

github-actions bot commented Jan 14, 2026

Uh oh!

github-actions bot commented Jan 14, 2026

Uh oh!

github-actions bot commented Jan 14, 2026

Uh oh!

github-actions bot commented Jan 14, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant

Conversation

robobun commented Jan 14, 2026

Summary

Changes

New Artifacts

Related Issue

Test plan

Uh oh!

robobun commented Jan 14, 2026

Uh oh!

coderabbitai bot commented Jan 14, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Walkthrough

Changes

Review ran into problems

Uh oh!

robobun commented Jan 14, 2026

Uh oh!

robobun commented Jan 14, 2026

Uh oh!

github-actions bot commented Jan 14, 2026

Uh oh!

github-actions bot commented Jan 14, 2026

Uh oh!

github-actions bot commented Jan 14, 2026

Uh oh!

github-actions bot commented Jan 14, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant

coderabbitai bot commented Jan 14, 2026 •

edited

Loading