Self-host M5: MCJIT execute blocks honest bootstrap loop (track on M5 epic)

[PurHur]

Category

bootstrap | runtime

Problem

bin/jit.php -r '...' SIGSEGV during MCJIT execute (#98) blocks LLVM-assisted bootstrap experiments and erodes confidence that JIT paths can participate in self-host verification. Bootstrap probes today rely on VM/AOT; JIT crash prevents honest -r smoke on compiler sources and blocks JIT-only builtins from bootstrap iteration.

php-src reference: N/A (compiler runtime). LLVM MCJIT execute is project-owned (lib/JIT.php, bin/jit.php).

Repro

./script/docker-exec.sh -- bash -lc 'php bin/jit.php -r "echo 1;"'
# Observed: SIGSEGV / exit 139 (issue #98)

Compare VM baseline (must pass):

./script/docker-exec.sh -- bash -lc 'php bin/vm.php -r "echo 1;"'

Bootstrap impact:

• Cannot use bin/jit.php for inventory hot-loop probes (Self-host M2: BootstrapVmDriver native execute smoke (post-#2134 bin/vm.php link) #2201 VM driver probe is separate)
• JIT regression tests skipped/flaky in developer loop
• Self-host M5 cannot claim JIT parity on spine without MCJIT execute

Scope

• bin/jit.php MCJIT execute entry
• lib/JIT.php module init / symbol resolution for -r one-shot units
• test/compliance/ JIT smoke guard once execute is stable
• Document bootstrap policy: no Zend JIT fallback in self-host probes

Done when

• php bin/jit.php -r 'echo 1;' exits 0 on Docker CI image (php-compiler:22.04-dev)
• Minimal JIT compliance case added (guards re-close CI: Run JIT compliance tests in CI (fix LLVM skip in PHPUnit) #98)
• docs/bootstrap-selfhost.md notes JIT -r as available for probes (or explicit remaining limits)
• No new C runtime logic — fix in PHP JIT lowering / LLVM link only

Related

• CI: Run JIT compliance tests in CI (fix LLVM skip in PHPUnit) #98 (MCJIT SIGSEGV umbrella)
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 (M5 self-host)
• Self-host M5: MCJIT execute blocks honest bootstrap loop (track on M5 epic) #8721 track on M5 epic
• Stdlib: array_all() closure callback — MCJIT execute segfault (phase 2 #4009) #5093 (array_all MCJIT closure segfault — related LLVM execute class)
• ROADMAP 🗺️ ROADMAP: Self-host + web-capable PHP subset (living) #78

[PurHur]

claim: worker-lane-b — starting this run

[PurHur]

Verified on master (2026-06-16): php bin/jit.php -r 'echo 1;' exits 0 in Docker — MCJIT execute works. Unclaiming; continuing #8917 this run.

[PurHur]

claim: worker-lane-a — starting this run

[PurHur]

Merged via #8938

Verification (Docker):

• php bin/jit.php -r 'echo 1;' → exits 0, prints 1
• php script/jit-runtime-probe.php → jit-runtime-probe OK (file execute + inline -r)
• vendor/bin/phpunit --filter JitInlineExecuteTest → OK
• vendor/bin/phpunit --filter JitMcjitExecuteSmokeTest → OK

MCJIT execute was already green on master; this run adds regression guards and documents the bootstrap gate per done-when.