test: add GOROOT runner baseline on main

[cpunion]

Summary

• add the GOROOT // run runner and baseline xfails on top of the latest main
• record current GOROOT failures as xfail / host_skip entries without changing compiler or runtime implementation
• add a dedicated GitHub Actions workflow that runs the GOROOT runner on Go 1.24.x / 1.25.x / 1.26.x across macOS and Ubuntu in 2 shards
• keep Go 1.25 as the required gating version; keep Go 1.24 and Go 1.26 as observational coverage for now

Scope

• current runner baseline scope is 979 selected GOROOT/test // run cases in the current runner configuration
• this is the current selected runner subset, not the whole GOROOT/test tree

Current XFail Accounting

Go	Platform	Runner Scope Baseline	xfail	host_skip	Expected Normal Pass
1.24	darwin/arm64	979	134	5	840
1.24	linux/amd64	979	133	0	846
1.25	darwin/arm64	979	165	5	809
1.25	linux/amd64	979	151	0	828
1.26	darwin/arm64	979	440	5	534
1.26	linux/amd64	979	495	0	484

Notes

• Runner Scope Baseline is the selected runner subset size used as a reporting baseline; actual discovered case counts can vary by GOVERSION / GOOS / GOARCH after build-constraint filtering
• darwin/arm64 also keeps 5 host_skip cases for known host-unsafe concurrency tests
• linux/amd64 currently uses only version-specific xfail entries
• follow-up PRs should fix compiler/runtime causes; this PR only establishes runner coverage and tracks current failures

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the testing infrastructure by introducing a GOROOT-based test runner. This new system allows for direct validation of llgo against a comprehensive suite of upstream Go tests, improving compatibility and catching regressions early. It includes mechanisms for handling platform-specific test behaviors and integrates into the continuous integration pipeline to provide ongoing feedback on llgo's performance against standard Go behavior.

Highlights

• GOROOT Runner Integration: A new GOROOT // run runner has been added to execute upstream Go tests against llgo without copying source files.
• Baseline XFails and Host Skips: Initial baseline xfails and host-unsafe skips for darwin/arm64 failures have been recorded to reflect current main branch status.
• Dedicated GitHub Actions Workflow: A new GitHub Actions workflow has been introduced to run the GOROOT runner on Go 1.25 across macOS and Ubuntu, sharded into 4 parts.

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Ignored Files

• Ignored by pattern: .github/workflows/** (1)
  • .github/workflows/goroot.yml

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[gemini-code-assist]

Code Review

This pull request introduces a new GOROOT test runner, allowing llgo to be tested against upstream Go GOROOT/test cases across various Go toolchains. It includes a shell script (dev/test_goroot.sh) to orchestrate multi-GOROOT test runs, a Go test package (test/goroot) for discovering, executing, and comparing test outputs, and platform-specific process management for robust child process handling. The review suggests improving the log timestamp parsing in runner_test.go for better readability and resilience, and using more descriptive reasons for xfail entries in xfail.yaml to enhance long-term maintainability.

[xgopilot]

Well-structured test infrastructure. The runner design (symlinked work trees, process group management, xfail/timeout config, sharding) is solid and the unit test coverage is good.

Key items to address:

1. go test default timeout — the shell script doesn't pass -timeout, so go test will kill the runner at 10 minutes (see inline comment on test_goroot.sh).
2. Version prefix matching bug — "go1.2" would incorrectly match "go1.24".
3. CI cost — 8 matrix jobs on every push to every branch is expensive; consider scoping triggers.
4. Missing Linux xfails — all entries are darwin/arm64 only; ubuntu shards may fail.

[codecov]

Codecov Report

❌ Patch coverage is 54.76190% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.69%. Comparing base (2075aa9) to head (0187bbc).
⚠️ Report is 22 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/plan9asm/translate.go	0.00%	9 Missing and 1 partial ⚠️
internal/env/env.go	62.50%	5 Missing and 1 partial ⚠️
test/goroot/proc_unix.go	66.66%	1 Missing and 1 partial ⚠️
cl/instr.go	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1750      +/-   ##
==========================================
- Coverage   93.16%   92.69%   -0.47%     
==========================================
  Files          48       49       +1     
  Lines       13349    13397      +48     
==========================================
- Hits        12437    12419      -18     
- Misses        726      781      +55     
- Partials      186      197      +11     

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