Language: throw expressions — JIT lowering (phase 2 of #3802)

[PurHur]

Category

language

Problem

#3802 delivered VM + compile lowering for throw in expression context (?:, ??, short-circuit). docs/capabilities-syntax.md still marks JIT = no for throw expressions.

bin/jit.php / self-host native emit must compile throw-expression CFG (TYPE_THROW from expression slots, no duplicate TYPE_NEW) or fall back with a documented gate.

Related open: #4041 (AOT phase 2) — coordinate so JIT and AOT share the same throw-expression merge rules.

php-src reference

• php/php-src Zend/zend_compile.c — zend_compile_throw in expression context
• php/php-src Zend/zend_ast.c — ZEND_AST_THROW as zend_ast_kind)

Repro

<?php
try {
    echo (false ? 1 : throw new LogicException('x'));
} catch (LogicException $e) {
    echo $e->getMessage(), "\n";
}

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/vm.php repro.php
php bin/jit.php repro.php 2>&1 | head -20
'

Driver	Expected
VM	x
JIT	x (no VM fallback / no compile abort)

Scope (this repo)

Layer	Files
Compiler	lib/Compiler.php — compileThrowExpression, fresh slots for ?: / ?? (already VM)
JIT	lib/JIT.php, lib/JIT/TypeReconstructor.php — Expr_Throw / TYPE_THROW lowering
Policy	lib/JIT/SelfHostBuiltinPolicy.php — remove throw-expression from MCJIT skip list if present
Tests	test/compliance/cases/language/throw_expression.phpt (extend JIT execute), test/fixtures/aot/compile-only/throw_expression.php
Matrix	script/capability-syntax-lib.php — set jit => true when green

Done when

• Repro prints x under bin/jit.php without VM-only fallback
• throw on RHS of && / || and nested ?? covered by compliance PHPT
• docs/capabilities-syntax.md throw_expression row: JIT yes
• ./script/ci-fast.sh --filter throw_expression green (VM + JIT groups)

Links

• Language: throw expressions (PHP 8.0) — parse and lowering in expression context #3802 (VM throw expressions) · Language: throw expressions — AOT lowering (phase 2 of #3802) #4041 (AOT phase 2) · Language: throw expression in assignment — $x = throw new Exception() (Zend zend_compile.c parity) #3521 (assignment throw, closed)
• North star: Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: worker-lane-a — starting this run

[PurHur]

Merged via #7324

Verification:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php bin/jit.php -r "try { echo (false ? 1 : throw new LogicException(\"x\")); } catch (LogicException \$e) { echo \$e->getMessage(); }"'
# x

php vendor/bin/phpunit --filter throw_expression
# OK (6 tests, 6 assertions)

Script-scope try/catch/throw no longer forces VM fallback in bin/jit.php; Type::never() overlay ensures throw-expression compile succeeds after Expr_Throw type reconstruction.