php-in-php: JIT Refcount LLVM — shrink __ref__ zval refcount layer via VmValue PHP helpers (#1492)

[PurHur]

Category

php-in-php | runtime

Problem

JIT/AOT still embed a large generated LLVM module for zval refcount/typeinfo manipulation: lib/JIT/Builtin/Refcount.php (~1.7k lines, from Refcount.pre) defines __ref__ structs and helpers (__ref__init, __ref__separate, disableRefcount, …) used across Type/String_.php, SpaceshipCompareJit, and string/object builtins.

This is compiler runtime semantics that should live in PHP (lib/VM/Variable.php, ext/standard/VmString.php, shared value lifecycle) with JIT lowering calling thin ABI trampolines — not a growing hand-maintained LLVM refcount IR graph.

North star #1492: shrink C/LLVM runtime; port behavior into PHP sources this repo owns.

php-src reference

• Zend refcounting is in C (Zend/zend_types.h, zend_string.h) — reference only; port semantics to PHP VM value model, do not grow runtime/*.c.

Repro (scope probe)

wc -l lib/JIT/Builtin/Refcount.php lib/JIT/Builtin/Refcount.pre
rg '__ref__' lib/JIT/Builtin/ --count | sort -t: -k2 -nr | head

Today: widespread __ref__* LLVM types; no consolidated PHP VmRefcount helper for JIT callbacks.

Scope (this repo)

Area	Work
Audit	Map each Refcount.php symbol to VM PHP equivalent (COW, separate string, typeinfo)
PHP	New lib/VM/VmRefcount.php or extend lib/VM/Variable.php with documented lifecycle API
JIT	Replace inline LLVM refcount IR with calls to PHP-backed runtime helpers (pattern: #9515 PowInt, #9476 Spaceship)
Delete	Shrink Refcount.pre / generated Refcount.php line count in PR body
Forbidden	New permanent refcount logic in runtime/*.c

Done when

• Hot paths (string COW / refcount inc-dec on JIT string ops) call PHP VM helpers through thin LLVM bridge
• wc -l lib/JIT/Builtin/Refcount.php reduced materially (target: >30% vs baseline; cite count in PR)
• ./script/ci-fast.sh green; JIT string/compliance subset unchanged (php-src-strict)
• PR notes php-src reference paths + lines removed from LLVM layer

Verification

make bootstrap-selfhost-vm-driver-execute-probe
./script/ci-fast.sh --filter VMTest
# targeted JIT string phpt as touched

Related

• Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492 · php-in-php: JIT SpaceshipCompareJit — route <=> through CompareJitHelper PHP not ~1.2k-line LLVM (#1492) #9476 (SpaceshipCompareJit) · php-in-php: JIT StringHashCrypto — route hash()/hash_hmac() through VmHash PHP not __compiler_hash_* LLVM (#1492) #9164 (hash crypto LLVM) · lib/JIT/Builtin/Type/String_.php

[PurHur]

claim: PHP Runtime → PHP — batch (issues #9976, #9570): VmValueBoxWriteBool shrink from ValueBoxWriteBoolJit LLVM

[PurHur]

Merged #11673 — VmValueBoxWriteBool owns __value__writeBool LLVM; ValueBoxWriteBoolJit 72→21 lines. Verification: ValueBoxWriteBoolRuntimeShrinkTest (2), bootstrap-selfhost-vm-driver-execute-probe OK.