php-in-php: GcCollectCyclesRuntime phase 2 — shrink collect/mark LLVM via GcCollectCyclesJitHelper PHP

[PurHur]

Category

php-in-php · runtime-shrink · php-compiler-strict (JIT/AOT collect path)

Problem

lib/JIT/Builtin/GcCollectCyclesRuntime.php is still ~1550 LOC of LLVM after registry helpers moved to GcCollectCyclesRegistryJitHelper.php (#9183). The cycle collect/mark/inbound walk and destructor invocation remain inline LLVM — the largest remaining non-Refcount runtime monolith.

C runtime phpc_gc.c is already deleted (RuntimeShrinkCloseoutTest); this issue finishes shrinking the replacement LLVM layer into compiled PHP.

php-src reference

• php/php-src Zend/zend_gc.c — gc_collect_cycles, mark/sweep
• Existing SSOT: ext/standard/GcCollectCyclesJitHelper.php, lib/VM/CycleCollector.php

PHP implementation target

• Extend ext/standard/GcCollectCyclesJitHelper.php (or sibling helper) for mark/inbound/collect phases currently in GcCollectCyclesRuntime::implement*
• Thin ABI bridges only in GcCollectCyclesRuntime.php (target <400 LOC, mirror CopyRuntime / StreamReadRuntime)
• Keep GcCollectCyclesCollectRuntime.php stats bridge unchanged

Repro / verification

./vendor/bin/phpunit test/compliance/cases/runtime/gc_collect_cycles.phpt --no-configuration 2>/dev/null || \
  php bin/vm.php test/compliance/cases/runtime/gc_collect_cycles.php
./vendor/bin/phpunit test/unit/GcCollectCyclesCollectRuntimeShrinkTest.php
make bootstrap-selfhost-vm-driver-execute-probe

Done when

• GcCollectCyclesRuntime.php net shrink ≥800 LOC; collect semantics unchanged
• Existing GC compliance + GcCollectCyclesCollectRuntimeShrinkTest green
• RuntimeShrinkCloseoutTest still passes (no C runtime reintroduced)
• VM/JIT/AOT agree on gc_collect_cycles() when JIT path in scope

Related

• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 · php-in-php: JIT GcCollectCyclesNative — route gc_collect_cycles() through Vm CycleCollector PHP not phpc_gc.c LLVM (#1492) #9183 · php-in-php: gc_collect_cycles() JIT — delete phpc_gc.c (~368 lines), sweep in lib/VM/CycleCollector.php #5315 · php-in-php: JIT Refcount LLVM — shrink __ref__ zval refcount layer via VmValue PHP helpers (#1492) #9570 (Refcount sibling)

[PurHur]

claim: PHP Runtime → PHP — starting this run

Analysis

GcCollectCyclesRuntime.php is 1553 LOC. Already split:

• Registry → GcCollectCyclesRegistryJitHelper.php (PHP, via usesPhpRegistry() embed path)
• Collect stats/bookkeeping → GcCollectCyclesCollectRuntime.php + GcCollectCyclesJitHelper.php
• Remaining LLVM: globals-backed registry (standalone AOT), phpc_gc_register/unregister, destruct invoke, shutdown sweep, mark/inbound/collect impl

First increment (recommended next run)

1. Route standalone phpc_gc_register / phpc_gc_unregister through registry helper for all load types (drop duplicate LLVM array walk ~200 LOC)
2. Move phpc_destruct_set_allow_delref / phpc_destruct_delref_allowed toggles to GcCollectCyclesJitHelper (mirror GcToggleJitHelper)

Blocker this run

Open php-in-php queue was empty; filed this issue after queue scan on #10205. Full phase 2 needs dedicated run with ./vendor/bin/phpunit test/compliance/cases/runtime/gc_collect_cycles* + make bootstrap-selfhost-vm-driver-execute-probe after each slice.

Handoff: branch agent/runtime-php-gc-collect-phase2 recommended.

[PurHur]

claim: PHP Runtime → PHP — starting this run (increment 1: universal registry PHP bridges + GcDestructAllowDelrefJitHelper)

[PurHur]

Merged increment 1 via #15866

Shipped

• Universal PHP registry bridges for register/unregister/index (embed + standalone AOT)
• GcDestructAllowDelrefJitHelper.php replaces LLVM phpc_destruct_allow_delref global
• Standalone collect routes through GcCollectCyclesJitHelper::collectCyclesEmbed (LLVM mark/inbound/sweep/visit deleted)
• GcCollectCyclesRuntime.php: 1553 → 1032 LOC (−521)

Verification (green)

• Shrink tests: GcCollectCyclesRegistryRuntimeShrinkTest, GcCollectCyclesCollectRuntimeShrinkTest, GcDestructAllowDelrefRuntimeShrinkTest, RuntimeShrinkCloseoutTest
• VM repro: two-node cycle → gc_collect_cycles() prints 2
• make bootstrap-selfhost-vm-driver-execute-probe: OK

Remaining for full phase 2 (≥800 LOC target)

• Shutdown/destruct/slot-read LLVM in GcCollectCyclesRuntime (~600 LOC) — next increment