Language: Generator JIT lowering (yield opcodes)

[PurHur]

Category

language · php-src-strict

Problem

Generators work on VM (lib/VM/GeneratorState.php, TYPE_YIELD / TYPE_YIELD_FROM) but JIT aborts with LogicException: Generators (yield) are VM-only (issue #167) in lib/JIT.php (~5574). bin/jit.php falls back to VM; there is no LLVM lowering for suspend/resume.

Blocks JIT-native compliance for generator-heavy code and self-host paths that compile lib/ with yield.

php-src reference

• php/php-src Zend/zend_generators.c — generator object, zend_generator_resume(), send/throw/getReturn
• php/php-src Zend/zend_execute.c — ZEND_YIELD / ZEND_YIELD_FROM opcode handlers
• php/php-src Zend/zend_compile.c — generator function flag

Repro (failure today)

<?php
function gen(): Generator {
    yield 1;
    yield 2;
}
foreach (gen() as $v) {
    echo $v;
}

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/jit.php -r "
function gen() { yield 1; yield 2; }
foreach (gen() as \$v) { echo \$v; }
"'
php bin/jit.php repro.php 2>&1 | head -5

Runtime	Expected	Actual
Zend + OPcache JIT	12	12
bin/jit.php	12 without VM fallback	LogicException or VM-only deferral ❌

Scope (this repo)

Layer	Path	Work
JIT	lib/JIT.php	Remove VM-only guard; emit suspend/resume control flow
Context	lib/JIT/Context.php	Generator frame/stack slots
VM reference	lib/VM/GeneratorState.php	Mirror semantics (do not duplicate in C)
Tests	test/compliance/cases/language/generator_jit.phpt
AOT	out of scope	#3115 / #167

PHP-in-PHP: LLVM lowering in lib/JIT/; no new runtime/*.c.

Done when

• bin/jit.php repro prints 12 without VM fallback
• yield from on arrays at minimum (full parity tracked in Language: generators (yield / yield from) — Generator object + send/throw/getReturn parity #4489)
• ./script/ci-local.sh --filter generator_jit green (LLVM phase when JIT group enabled)
• docs/capabilities.md JIT column yes for generators via script/capability-matrix.php

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && ./vendor/bin/phpunit --filter generator_jit test/compliance/JITTest.php'

Strictness

php-src-strict for user-visible generator iteration; #4599 tracks foreach-by-ref phase 2.

Related

• Language: Generators (yield and yield from) #167 · Language: Generator JIT lowering (yield opcodes) #3074 · Language: generators (yield / yield from) — Generator object + send/throw/getReturn parity #4489 (Generator object parity) · Language: Generator foreach by-reference — JIT/AOT (phase 2 of #3074, Zend/zend_generators.c) #4599 (foreach by-ref JIT) · Language: Generator AOT lowering (yield / suspend resume) #3115 (AOT) · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: worker-lane-c-automation — starting this run

[PurHur]

WIP shipped: PR adds GeneratorHelper MCJIT resume lowering + script-scope requiresVmLowering. LLVM verify green; MCJIT execute segfaults in harness (pre-existing). See PR for details.