Compiler: VM/JIT comparison and equality for mixed types (routing guards)

[PurHur]

Problem

lib/VM/Variable.php throws for many equality pairs:

Equals comparison between {type} and {type} not implemented

Routers and guards frequently compare strings to literals, or mixed int/string from $_GET:

if ($_GET['page'] === 'admin') { ... }
if ($route == 1) { ... }

JIT may lack lowering for === / == on some type pairs even when VM works. Blocks #210 route tables and #270 JSON guard patterns.

Goal

Complete comparison operators (==, ===, !=, <, >, <=, >=) for web-common type pairs: string/string, string/int, int/int, bool/bool, null checks.

Implementation hints

Audit first

rg "not implemented" lib/VM/Variable.php
rg "TYPE_IS_EQUAL|TYPE_IS_IDENTICAL" lib/JIT.php lib/Compiler.php

Variable::equals() (~line 368) and compareOp() (~441) — extend switch arms before adding JIT.

VM (lib/VM/Variable.php)

• string === string: byte-wise compare (Zend uses binary-safe; match PHP for ASCII routes)
• string == int: PHP coercion rules — add PHPT table in test/real/cases/compare_mixed.phpt
• null === null: already partial; ensure $_GET['missing'] undefined key behavior aligns with Runtime: Undefined array/superglobal key — Zend notice parity #273 before strict compares

JIT (lib/JIT.php)

• Search assignop / compare lowering for Op\Expr\BinaryOp\Equal / Identical
• Reuse string compare helpers from existing concat/strlen JIT paths
• Order: === string/string first (routing), then loose == for query params

AOT

• Same LLVM paths as JIT once opcode coverage lands

Tasks

• Audit Variable::equals and compareOp uncovered pairs; list in PR
• Add VM implementations (document coercion in PHPT headers)
• JIT: icmp + strcmp helpers in compare lowering
• PHPT: strict vs loose equality table + $_GET['id'] === '1'
• Link from Reference app: examples/003-MiniWebApp (router, templates, forms) #67 / Web: MiniWebApp routing pattern (front controller + path dispatch) #210 router tests when Language: while, do-while, and for loops (CFG → VM → JIT) #192/Language: Implement foreach (CFG → VM → JIT) #53 exist

Acceptance criteria

docker run --rm -v "$(pwd):/compiler" -w /compiler php-compiler:22.04-dev \
  ./phpc run -r 'var_export("1" === "1");'

if ($route === 'home') and if ($_GET['id'] === '1') work in VM, JIT, and AOT.

Key files

• lib/VM/Variable.php — equals(), compareOp(), _compareOp()
• lib/JIT.php — binary compare opcodes
• lib/Compiler.php — expr lowering for Equal / Identical

Dependencies

• Runtime: Undefined array/superglobal key — Zend notice parity #273 undefined superglobal key semantics (affects === with missing keys)
• Language: Null coalescing operator (??) in compiler pipeline #99 ?? (orthogonal; use together in apps)

Verification (local only)

./script/ci-local.sh --filter compare

Related

• JIT: Implement switch/case opcodes (TYPE_CASE) — VM works, JIT stubbed #96 switch/case (uses compare internally)
• Compiler: VM/JIT comparison and equality for mixed types (routing guards) #90 blocks Web: MiniWebApp routing pattern (front controller + path dispatch) #210, Examples: 004-ApiJson — minimal JSON API endpoint (lint-first) #270