php-in-php: JIT FiberHelper — route Fiber suspend/resume through VmFiber PHP not ~587-line LLVM (#1492)

[PurHur]

Category

php-in-php · php-src-strict runtime · refs #1492

Problem

Fiber MCJIT lowering is a ~587-line monolith in lib/JIT/FiberHelper.php (resume-ip switch functions, suspend static sites, stack limits). VM fiber semantics already live in PHP: lib/VM/FiberSupport.php, lib/VM/FiberState.php, lib/VM/Builtin/Fiber*.php mirroring php/php-src Zend/zend_fibers.c.

Maintaining fiber edge cases twice (VM vs LLVM) blocks #3130 / #4019 parity and self-host compile of compiler sources using Fiber.

php-src reference

• php/php-src Zend/zend_fibers.c — suspend/resume/throw/getReturn
• php/php-src ext/reflection/php_reflection.c — ReflectionFiber (Stdlib: ReflectionFiber — introspection for Fiber objects (ext/reflection/php_reflection.c) #4609)

Repro

test/repro/fiber_jit_vm_agree.php:

<?php
declare(strict_types=1);

$fiber = new Fiber(function (): int {
    Fiber::suspend('step1');
    return 42;
});
var_export($fiber->start());
echo "\n";
var_export($fiber->resume());
echo "\n";
var_export($fiber->getReturn());
echo "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php test/repro/fiber_jit_vm_agree.php
php bin/jit.php test/repro/fiber_jit_vm_agree.php'

Step	Expected (Zend)
start()	'step1'
resume()	42
getReturn()	42

Any JIT divergence from VM output is in scope for this migration.

Scope (PHP-in-PHP first)

Path	Work
lib/VM/FiberSupport.php	Canonical suspend/resume/throw state machine
lib/JIT/FiberHelper.php	Replace resume-ip LLVM switch with calls into compiled FiberSupport helpers
lib/JIT/Call/Fiber*.php	Trampoline to PHP lowering
Tests	test/compliance/cases/language/fiber_jit_vm_agree.phpt

No: no new runtime/*.c — fiber stack guard may stay as thin ABI only (#4019).

Done when

• Repro matches on VM + JIT
• FiberHelper.php shrinks to registration + trampoline (target ≤ ~150 lines)
• Suspend from nested call / property-hook fiber signal (Language: property hooks — get-only virtual properties without set hook (zend_property_hooks.c) #4687) still defers to VM PHP path
• ./script/ci-fast.sh --filter FiberJit green

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter Fiber'

Related

• Language: Fiber — PHP 8.1 green threads (Zend fibers parity) #3130 / Language: Fiber JIT/AOT — native suspend/resume (phase 2 of #3130) #4019 Fiber baseline · Stdlib: ReflectionFiber — introspection for Fiber objects (ext/reflection/php_reflection.c) #4609 ReflectionFiber · php-in-php: JIT ExceptionHandlerJitRuntime + TryCatchHelper — route try/catch through VmException PHP not ~1.5k-line LLVM (#1492) #9663 try/catch in fibers · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: cursor-agent-lane-c — batch (issues #10079)

[PurHur]

Merged via #11488.

Verification: FiberHelper 587→112 lines; VmFiberValue PHP guards for assignValueField type dispatch; FiberHelperLlvm holds resume-ip LLVM. Repro test/repro/fiber_jit_vm_agree.php matches Zend + VM + JIT ('step1'\nNULL\n42). Unit tests + bootstrap VM driver probe green.