php-in-php: gc_collect_cycles() JIT — delete phpc_gc.c (~368 lines), sweep in lib/VM/CycleCollector.php

[PurHur]

Category

php-in-php | runtime | stdlib

Problem

VM gc_collect_cycles() uses PHP (lib/VM/CycleCollector.php, ext/standard/gc_collect_cycles.php) but JIT/AOT link lib/AOT/runtime/phpc_gc.c (~368 lines) duplicating Tarjan sweep, weakref clearing, and object graph walks in C. #3160 tracks JIT parity; this issue tracks deleting the C TU once native lowering calls the PHP collector.

php-src reference

• php/php-src Zend/zend_gc.c — gc_collect_cycles(), zend_gc_collect_cycles()
• php/php-src ext/standard/basic_functions.c — PHP_FUNCTION(gc_collect_cycles)

Repro (failure today)

C runtime still linked:

./script/docker-exec.sh -- bash -lc 'grep phpc_gc lib/AOT/Linker.php; wc -l lib/AOT/runtime/phpc_gc.c'

VM vs JIT count mismatch on cyclic graph — save as test/repro-maintainer/parity_gc_collect_cycles_jit.php:

<?php
class Node { public ?Node $next = null; }
$a = new Node();
$b = new Node();
$a->next = $b;
$b->next = $a;
unset($a, $b);
echo gc_collect_cycles(), "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php test/repro-maintainer/parity_gc_collect_cycles_jit.php
php bin/jit.php test/repro-maintainer/parity_gc_collect_cycles_jit.php 2>&1 | head -5
'

Runtime	Expected (Zend)	This compiler
VM	positive int (cycles collected)	✅ PHP collector
JIT	same count as VM	❌ C overlay or stub

Scope (this repo)

Area	Files
VM (source of truth)	lib/VM/CycleCollector.php
JIT	lib/JIT/Builtin/GcCollectCyclesRuntime.php — call PHP collector, not C
Delete	lib/AOT/runtime/phpc_gc.c
Tests	test/compliance/cases/stdlib/gc_collect_cycles_cyclic.phpt

Done when

• JIT gc_collect_cycles() returns same count as VM on cyclic object repro above
• phpc_gc.c dropped from lib/AOT/Linker.php link set
• PR notes ~368 lines removed from runtime/
• Closes overlap with Stdlib JIT: gc_collect_cycles() LLVM lowering (phase 2 of #3113) #3160 (reference in PR when C deleted)

Related

• Stdlib JIT: gc_collect_cycles() LLVM lowering (phase 2 of #3113) #3160 — JIT lowering tracker
• Runtime: gc_collect_cycles() — run cyclic GC (Zend GC parity) #3113 — VM collector (closed)
• php-in-php: WeakReference/WeakMap — delete phpc_weakref.c (~156 lines), GC weak refs in lib/VM #5303 WeakReference php-in-php (weakref clearing during sweep)
• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 self-host

[PurHur]

claim: PHP Runtime → PHP — starting this run.

[PurHur]

Unclaiming — phpc_gc.c still provides object registry/shutdown/destructor infrastructure beyond gc_collect_cycles(); full deletion needs a multi-step migration. Switching to #5364+#5373 (C already removed; bridge facades remaining).

[PurHur]

claim: PHP Runtime → PHP — starting this run (migrate gc_collect_cycles JIT/AOT off phpc_gc.c to PHP CycleCollector path).

[PurHur]

Unclaiming #5315 this run: phpc_gc.c (~362 lines) implements native object graph Tarjan sweep + destructor/shutdown/weakref hooks tightly coupled to Object_.php JIT layout — full deletion requires LLVM-lowering the entire collector (similar scope to #7078 json_decode, ~2k lines PHP IR). Handoff: next run should port phpc_gc_collect_cycles_impl + register/unregister/destruct paths into GcCollectCyclesRuntime.php LLVM implement(), then drop bitcode link.

[PurHur]

claim: PHP Runtime → PHP — starting this run (#5315: port phpc_gc.c (~361 lines) to GcCollectCyclesRuntime.php LLVM, drop from Linker).

[PurHur]

Merged via PR #7554.

C removed: lib/AOT/runtime/phpc_gc.c (361 lines). GC registry + gc_collect_cycles() sweep now live in lib/JIT/Builtin/GcCollectCyclesRuntime.php LLVM IR.

Verification:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit test/unit/JIT/GcCollectCyclesRuntimeStandaloneTest.php test/unit/JIT/WeakRefRegistryRuntimeStandaloneTest.php'

OK (4 tests, 41 assertions)