perf: direct syscall fastpath for absolute paths in zend_virtual_cwd

[henderkes]

Absolute paths don't need to go through the per-thread cwd emulation, add a fast-path to directly hand them to libc.

since relative paths won't start with a leading slash, this adds negligible cost for them

<?php
chdir(__DIR__);

$s = microtime(true);
for ($i = 0; $i < 1000000; $i++) {
    file_exists("data.txt");
}
$rel = microtime(true) - $s;

$abs = __DIR__ . "/data.txt";
$s = microtime(true);
for ($i = 0; $i < 1000000; $i++) {
    file_exists($abs);
}
$abs_t = microtime(true) - $s;

workload	master	patch	delta
relative path	0.3521s	0.3524s	+0.09%
absolute path	0.3162s	0.2623s	−17.05%

[staabm]

should this use php_win32_ioutil_fopen on windows?

[staabm]

ohh its ifNdef ZEND_WIN32 .. nevermind

[henderkes]

yeah, I will revisit all these small findings later on Windows