php-in-php: JIT IteratorHelper — route foreach iterator protocol through VmIterator PHP not ~725-line LLVM (#1492)

[PurHur]

Category

php-in-php · refs #1492

Problem

lib/JIT/IteratorHelper.php (~725 lines) implements foreach iterator protocol, by-ref foreach guards, object-key traversal, and hashtable index slots directly in LLVM. VM already walks arrays/objects/generators in PHP (lib/VM.php opcode handlers + iterator state).

Duplicate logic causes foreach drift (by-ref on iterators, IteratorAggregate, generator re-entry) between VM and JIT.

php-src reference

• php/php-src Zend/zend_execute.c — ZEND_FE_FETCH_*, iterator ops
• php/php-src Zend/zend_iterators.c — zend_iterator_*

Repro

test/repro/foreach_jit_vm_agree.php:

<?php
declare(strict_types=1);

class Agg implements IteratorAggregate {
    public function getIterator(): Generator {
        yield 'k' => 'v';
    }
}

$out = [];
foreach (new Agg() as $k => $v) {
    $out[] = "$k=$v";
}
echo implode(',', $out), "\n";

$g = (function (): Generator { yield 1; yield 2; })();
$sum = 0;
foreach ($g as $n) { $sum += $n; }
echo "sum=$sum\n";

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

Expected both: k=v and sum=3. JIT mismatch = bug.

Scope (PHP-in-PHP first)

Path	Work
New/existing lib/VM/IteratorSupport.php	Shared FE_FETCH semantics for VM + JIT callback
lib/JIT/IteratorHelper.php	Trampoline to compiled PHP helper; delete per-opcode LLVM
lib/JIT/IteratorProtocolHelper.php	Fold into PHP path where duplicated
Tests	test/compliance/cases/language/foreach_jit_vm_agree.phpt

Done when

• Repro identical VM vs JIT
• By-ref foreach on Iterator throws before body (Language: property hook foreach by-reference on get-only hook — must Error before loop body (re-#6435, Zend/zend_property_hooks.c) #9761 pattern) via shared PHP guard
• IteratorHelper.php ≤ ~100 lines (glue only)
• ./script/ci-fast.sh --filter ForeachJit green

Verification

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

Related

• Language: property hook foreach by-reference on get-only hook — must Error before loop body (re-#6435, Zend/zend_property_hooks.c) #9761 foreach by-ref + hooks · php-in-php: JIT IncludeHelper — route include/require LLVM through VmInclude PHP not ~1k-line monolith (#1492) #10063 IncludeHelper migration (parallel) · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: PHP Runtime → PHP — batch (issues #10080 IteratorHelper, #9972 JitValueCompare slice)

[PurHur]

Merged via #11652.

LLVM shrink: IteratorHelper.php 725→54 lines (trampoline); SSOT moved to lib/VM/VmIteratorForeach.php (744 lines).

Verification:

• IteratorHelperRuntimeShrinkTest OK (2/2)
• spine sync + bootstrap-selfhost-vm-driver-execute-probe OK
• bootstrap-inventory --check OK

[PurHur]

claim: PHP Runtime → PHP — continuing unmerged branch agent/issue-10080-iterator-helper-php, rebasing onto master.

[PurHur]

Merged via #17990 — IteratorHelper is now a 54-line trampoline; foreach hashtable/object-key LLVM lives in lib/VM/VmIteratorForeach.php.

Verification (all green):

• IteratorHelperRuntimeShrinkTest (2 tests)
• test/repro/foreach_jit_vm_agree.php on VM + JIT
• check-selfhost-spine-coverage-sync.php OK
• bootstrap-inventory.php --check OK
• make north-star5-verify-fast OK