return_type_check_elision_repro.php

return_type_check_elision_repro.php

<?php

declare(strict_types=1);

/*
 * Reproducer for commit 95d3ed1af81930f06b8e72b0bf414e52b1353a31:
 * "Elide provably-passing return type checks at compile time"
 *
 * Run this script on a build before and after that commit, ideally with:
 *   ./sapi/cli/php -n -dopcache.enable_cli=0 return_type_check_elision_repro.php
 *
 * The "direct" cases should get faster after the commit because
 * ZEND_VERIFY_RETURN_TYPE is not emitted for provably safe returns.
 */

if (PHP_SAPI !== 'cli') {
    fwrite(STDERR, "Run from CLI.\n");
    exit(1);
}

final class GetterBench
{
    private int $x = 7;

    public function direct(): int
    {
        return $this->x;
    }

    public function control(): int
    {
        $tmp = $this->x;
        return $tmp;
    }
}

function cmp_direct(int $a, int $b): bool
{
    return $a < $b;
}

function cmp_control(int $a, int $b): bool
{
    $tmp = $a < $b;
    return $tmp;
}

function run_getter_direct(int $iterations): int
{
    $obj = new GetterBench();
    $sum = 0;

    for ($i = 0; $i < $iterations; $i++) {
        $sum += $obj->direct(); $sum += $obj->direct(); $sum += $obj->direct(); $sum += $obj->direct();
        $sum += $obj->direct(); $sum += $obj->direct(); $sum += $obj->direct(); $sum += $obj->direct();
    }

    return $sum;
}

function run_getter_control(int $iterations): int
{
    $obj = new GetterBench();
    $sum = 0;

    for ($i = 0; $i < $iterations; $i++) {
        $sum += $obj->control(); $sum += $obj->control(); $sum += $obj->control(); $sum += $obj->control();
        $sum += $obj->control(); $sum += $obj->control(); $sum += $obj->control(); $sum += $obj->control();
    }

    return $sum;
}

function run_cmp_direct(int $iterations): int
{
    $sum = 0;
    $end = $iterations + 3;

    for ($i = 0; $i < $iterations; $i++) {
        $sum += cmp_direct($i, $end) ? 1 : 0; $sum += cmp_direct($i + 1, $end) ? 1 : 0;
        $sum += cmp_direct($i + 2, $end) ? 1 : 0; $sum += cmp_direct($i + 3, $end) ? 1 : 0;
        $sum += cmp_direct($i + 4, $end) ? 1 : 0; $sum += cmp_direct($i + 5, $end) ? 1 : 0;
        $sum += cmp_direct($i + 6, $end) ? 1 : 0; $sum += cmp_direct($i + 7, $end) ? 1 : 0;
    }

    return $sum;
}

function run_cmp_control(int $iterations): int
{
    $sum = 0;
    $end = $iterations + 3;

    for ($i = 0; $i < $iterations; $i++) {
        $sum += cmp_control($i, $end) ? 1 : 0; $sum += cmp_control($i + 1, $end) ? 1 : 0;
        $sum += cmp_control($i + 2, $end) ? 1 : 0; $sum += cmp_control($i + 3, $end) ? 1 : 0;
        $sum += cmp_control($i + 4, $end) ? 1 : 0; $sum += cmp_control($i + 5, $end) ? 1 : 0;
        $sum += cmp_control($i + 6, $end) ? 1 : 0; $sum += cmp_control($i + 7, $end) ? 1 : 0;
    }

    return $sum;
}

function run_case(string $label, int $iterations, int $rounds, callable $fn): array
{
    $times = [];
    $sink = 0;

    for ($w = 0; $w < 2; $w++) {
        $sink ^= $fn($iterations);
    }

    for ($r = 0; $r < $rounds; $r++) {
        $start = hrtime(true);
        $sink ^= $fn($iterations);
        $times[] = (hrtime(true) - $start) / 1e9;
    }

    sort($times);

    return [
        'label' => $label,
        'best' => $times[0],
        'avg' => array_sum($times) / count($times),
        'sink' => $sink,
    ];
}

$iterations = isset($argv[1]) ? max(1, (int) $argv[1]) : 5_000_000;
$rounds = isset($argv[2]) ? max(1, (int) $argv[2]) : 7;

gc_disable();

$cases = [
    run_case('getter-direct', $iterations, $rounds, 'run_getter_direct'),
    run_case('getter-control', $iterations, $rounds, 'run_getter_control'),
    run_case('cmp-direct', $iterations, $rounds, 'run_cmp_direct'),
    run_case('cmp-control', $iterations, $rounds, 'run_cmp_control'),
];

$byLabel = [];
foreach ($cases as $row) {
    $byLabel[$row['label']] = $row;
}

printf(
    "PHP %s\niterations=%d rounds=%d calls_per_round=%d\n\n",
    PHP_VERSION,
    $iterations,
    $rounds,
    $iterations * 8
);

echo str_pad('case', 16) . str_pad('best(s)', 12) . str_pad('avg(s)', 12) . "sink\n";
echo str_repeat('-', 50) . "\n";
foreach ($cases as $row) {
    printf(
        "%-16s%-12.6f%-12.6f%d\n",
        $row['label'],
        $row['best'],
        $row['avg'],
        $row['sink']
    );
}

echo "\nDirect/control ratio inside each pair (best time, lower is better):\n";
printf(
    "%-16s %.4fx\n",
    'getter',
    $byLabel['getter-direct']['best'] / $byLabel['getter-control']['best']
);
printf(
    "%-16s %.4fx\n",
    'cmp',
    $byLabel['cmp-direct']['best'] / $byLabel['cmp-control']['best']
);