produce better OPcodes in strict IF or-conditions

[staabm]

Description

could php-src be smarter about IF or-conditions which only contain strict-comparisions to make it produce the same opcodes as in a strict in-array call?

see https://3v4l.org/QQQMr/vld

indentified in phpstan/phpstan-src#2618 (comment)

[morrisonlevi]

I'm not sure about the optimizer, but just wanted to point out that if we're going to do this, we may as well make it a lookup table instead of a linear search: https://3v4l.org/V5PeZ/vld

function f1(string $name): bool {
    if (in_array($name, ['__construct', '__destruct', '__unset', '__wakeup', '__clone'], true)) {
        return true;
    }

    return false;
}

function f2(string $name): bool {
    if ($name === '__construct'
        || $name === '__destruct'
        || $name === '__unset'
        || $name === '__wakeup'
        || $name === '__clone'
    ) {
      return true;
    }

    return false;
}

function f3(string $name): bool {
    return isset([
        '__construct' => true,
        '__destruct' => true,
        '__unset' => true,
        '__wakeup' => true,
        '__clone' => true,
    ][$name]);
}

Of these, f3 should perform the best. Disclaimer: I never ran this code ^_^

[iluuu1994]

match already has support for jump tables with strict equality, so I'm not sure we need another variant. https://3v4l.org/vbrLB/vld ifs are intended for complex expressions and/or varying subjects where I a jump table isn't possible. Switch also uses jump tables, but needs a fallback chain with loose comparison.

[zonuexe]

I'm not sure about the optimizer, but just wanted to point out that if we're going to do this, we may as well make it a lookup table instead of a linear search:

When searching a constant array, already in PHP 7.2 the in_array() function is compiled into an instruction that looks up from a hash table rather than a linear search.

[staabm]

Sounds like we already have plenty alternatives.

Thanks for the input. Closing.