Optimize ZEND_COUNT opcodes on arrays in the jit

[TysonAndre]

Avoid the overhead of a call and checking types
when the argument is definitely an array.
Avoid the overhead of gc when __destruct won't get called.

This seemed cheap enough to check for in the jit.

EDIT: Because of https://wiki.php.net/rfc/restrict_globals_usage
we can be sure in the ZEND_COUNT handler that the array count does not have to
be recomputed in php 8.1.

The below example took 0.854 seconds before the optimization,
and 0.564 seconds after the optimization, giving the same result

<?php
/** @jit */
function bench_count(int $n): int {
    $total = 0;
    $arr = [];
    for ($i = 0; $i < $n; $i++) {
        $arr[] = $i;
        $total += count($arr);
    }
    return $total;
}

function main() {
    $n = 1000;
    $iterations = 50000;
    $start = microtime(true);
    $result = 0;
    for ($i = 0; $i < $iterations; $i++) {
        $result += bench_count($n);
    }
    $elapsed = microtime(true) - $start;

    printf("Total for n=%d, iterations=%d = %d, elapsed=%.3f\n", $n, $iterations, $result, $elapsed);
}
main();

Before

mov $0x7feb8cf8a858, %r15
mov $ZEND_COUNT_SPEC_CV_UNUSED_HANDLER, %rax
call *%rax

After (much faster without a function call)

mov 0x70(%r14), %rdi - Copy the count from the `zend_array*` pointer
mov %rdi, (%rax)     - Store the count in the destination's value
mov $0x4, 0x8(%rax)  - Store IS_LONG(4) in the destination's type

[TysonAndre]

I updated this now that https://wiki.php.net/rfc/restrict_globals_usage has passed (related to 2279388 )

[nikic]

You also need to add it to zend_jit_trace.c for it to be meaningfully useful.

[TysonAndre]

Implemented in zend_jit_trace.c based on the handler for ZEND_STRLEN

[nikic]

I believe the common practice here is to determine this using zend_may_throw (passed in).

[TysonAndre]

I need to re-add this, I was running into issues because nNumOfElements was 32-bit when working on the tracing jit

[TysonAndre]

Done, could use another look

[nikic]

Maybe use FREE_OP?

[TysonAndre]

Done

[TysonAndre]

@nikic @dstogov - This is ready for another look

[dstogov]

Everything should be fine. Merge this.