Language: Fiber JIT/AOT — native suspend/resume (phase 2 of #3130)

[PurHur]

Category

language / runtime

Problem

#3130 delivered VM-only Fiber (Fiber::suspend(), start(), resume(), getCurrent()). script/capability-syntax-lib.php still marks fiber_suspend as JIT=no / AOT=no. Self-host and bin/jit.php / phpc build paths that use cooperative scheduling therefore fall back to VM or fail when fibers appear in hot code.

php-src reference

• php/php-src Zend/zend_fibers.c — stack switching, suspend/resume, fiber status
• php/php-src Zend/zend_fibers.h
• Fiber object handlers: zend_fiber_object_handlers in zend_fibers.c

Repro (gap today)

<?php
$fiber = new Fiber(function (): void {
    Fiber::suspend('ok');
});
echo $fiber->start(), "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php /tmp/fiber.php          # VM: ok
php bin/jit.php /tmp/fiber.php 2>&1    # JIT: compare output / fallback
'

Backend	Expected (Zend parity)	Today
VM	ok	✅ (#3130)
JIT	ok	❌ not lowered — capability row JIT=no
AOT	ok	❌ capability row AOT=no

Scope (this repo)

Layer	Files
VM reference	lib/VM/FiberState.php, lib/VM.php (startFiber / resumeFiber)
JIT	lib/JIT.php, new lib/JIT/FiberSupport.php or builtin dispatch — suspend saves frame; resume restores
AOT	lib/AOT/ — immortal fiber context or VM callback trampoline
Tests	test/compliance/cases/language/fiber_jit.phpt, test/fixtures/aot/cases/fiber_suspend.phpt
Matrix	script/capability-syntax-lib.php — set jit/aot true when green

Phase 1: single-fiber suspend/resume in script scope (no nested fibers). Defer: Fiber::getReturn(), throwing across suspend, concurrent fibers.

Done when

• Repro prints ok under bin/jit.php and AOT binary (same as VM)
• fiber_suspend row in docs/capabilities-syntax.md shows JIT/AOT yes
• ./script/ci-fast.sh --filter Fiber green (or targeted compliance file)

Related

• Parent VM work: Language: Fiber — PHP 8.1 green threads (Zend fibers parity) #3130 (closed)
• Generators (separate mechanism): Language: Generator JIT lowering (yield opcodes) #3074, Language: yield from nested Generator — JIT resume/delegate (phase 2 of #3074) #4014
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 self-host — only if compiler sources adopt fibers

[PurHur]

claim: cursor-lane-b-worker — starting this run

[PurHur]

claim: cursor-lane-c-worker — lane C; #4019 already claimed by lane-b (2026-06-01)

[PurHur]

claim: cursor-lane-c-implementer — lane C issue; continuing Fiber JIT/AOT (no open PR yet)

[PurHur]

Merged via #4086

Verification

• VM + bin/jit.php (VM fallback): ok on test/repro-maintainer/fiber_jit_repro.php
• AOT: php bin/compile.php -o /tmp/fiber_aot … && /tmp/fiber_aot → ok
• vendor/bin/phpunit --filter fiber_suspend test/aot/AotTest.php — OK
• vendor/bin/phpunit --filter fiber_jit test/compliance/VMTest.php — OK

Follow-up: MCJIT execute still segfaults when requiresVmLowering is false; bin/jit.php keeps VM fallback for fiber scripts until that is fixed.