negated_conditions_repro.php

negated_conditions_repro.php

@ -0,0 +1,175 @@
<?php

declare(strict_types=1);

/**
 * Reproducer for commit d363881c66bf4a301bb0af9c5b8119e50f2a7494:
 * "Compile negated conditions as inverted jumps"
 *
 * Run this script on:
 * 1) a build before that commit and
 * 2) a build including that commit
 *
 * Expected: ratios for "negated / positive" move closer to 1.00x.
 */

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

$ifIters = isset($argv[1]) ? max(1, (int) $argv[1]) : 25_000_000;
$outer = isset($argv[2]) ? max(1, (int) $argv[2]) : 80_000;
$inner = isset($argv[3]) ? max(1, (int) $argv[3]) : 64;
$rounds = isset($argv[4]) ? max(1, (int) $argv[4]) : 5;

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

    $sink ^= $fn();

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

    sort($times);
    $best = $times[0];
    $avg = array_sum($times) / count($times);

    return [
        'label' => $label,
        'best' => $best,
        'avg' => $avg,
        'sink' => $sink,
    ];
}

$cases = [
    run_case('if_positive', $rounds, static function () use ($ifIters): int {
        $acc = 0;
        for ($i = 0; $i < $ifIters; $i++) {
            $x = ($i & 1) === 0;
            if ($x) {
                $acc += 1;
            } else {
                $acc += 2;
            }
        }
        return $acc;
    }),
    run_case('if_negated', $rounds, static function () use ($ifIters): int {
        $acc = 0;
        for ($i = 0; $i < $ifIters; $i++) {
            $x = ($i & 1) === 0;
            if (!$x) {
                $acc += 2;
            } else {
                $acc += 1;
            }
        }
        return $acc;
    }),
    run_case('ternary_positive', $rounds, static function () use ($ifIters): int {
        $acc = 0;
        for ($i = 0; $i < $ifIters; $i++) {
            $x = ($i & 1) === 0;
            $acc += $x ? 1 : 2;
        }
        return $acc;
    }),
    run_case('ternary_negated', $rounds, static function () use ($ifIters): int {
        $acc = 0;
        for ($i = 0; $i < $ifIters; $i++) {
            $x = ($i & 1) === 0;
            $acc += !$x ? 2 : 1;
        }
        return $acc;
    }),
    run_case('while_positive', $rounds, static function () use ($outer, $inner): int {
        $acc = 0;
        for ($o = 0; $o < $outer; $o++) {
            $j = 0;
            while ($j < $inner) {
                $acc += $j & 1;
                $j++;
            }
        }
        return $acc;
    }),
    run_case('while_negated', $rounds, static function () use ($outer, $inner): int {
        $acc = 0;
        for ($o = 0; $o < $outer; $o++) {
            $j = 0;
            while (!($j >= $inner)) {
                $acc += $j & 1;
                $j++;
            }
        }
        return $acc;
    }),
    run_case('do_while_positive', $rounds, static function () use ($outer, $inner): int {
        $acc = 0;
        for ($o = 0; $o < $outer; $o++) {
            $j = 0;
            do {
                $acc += $j & 1;
                $j++;
            } while ($j < $inner);
        }
        return $acc;
    }),
    run_case('do_while_negated', $rounds, static function () use ($outer, $inner): int {
        $acc = 0;
        for ($o = 0; $o < $outer; $o++) {
            $j = 0;
            do {
                $acc += $j & 1;
                $j++;
            } while (!($j >= $inner));
        }
        return $acc;
    }),
];

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

printf(
    "PHP %s\nifIters=%d outer=%d inner=%d rounds=%d\n\n",
    PHP_VERSION,
    $ifIters,
    $outer,
    $inner,
    $rounds
);
echo str_pad('case', 20) . str_pad('best(s)', 12) . str_pad('avg(s)', 12) . "sink\n";
echo str_repeat('-', 54) . "\n";
foreach ($cases as $row) {
    printf(
        "%-20s%-12.6f%-12.6f%d\n",
        $row['label'],
        $row['best'],
        $row['avg'],
        $row['sink']
    );
}

echo "\nnegated/positive ratios (best time, lower is better):\n";
$pairs = [
    ['if', 'if_negated', 'if_positive'],
    ['ternary', 'ternary_negated', 'ternary_positive'],
    ['while', 'while_negated', 'while_positive'],
    ['do_while', 'do_while_negated', 'do_while_positive'],
];
foreach ($pairs as [$name, $neg, $pos]) {
    $ratio = $byLabel[$neg]['best'] / $byLabel[$pos]['best'];
    printf("%-10s %.4fx\n", $name, $ratio);
}