Move the refcount update outside of the loop.
For the following benchmark:
```php
$r = range(0, 1000);
$v = new stdClass();
for ($i = 0; $i < 100000; $i++) {
array_fill_keys($r, $v);
}
```
On an i7-4790:
```
Benchmark 1: ./sapi/cli/php_old ../x.php
Time (mean ± σ): 507.5 ms ± 4.8 ms [User: 505.1 ms, System: 1.2 ms]
Range (min … max): 501.2 ms … 518.4 ms 10 runs
Benchmark 2: ./sapi/cli/php ../x.php
Time (mean ± σ): 479.8 ms ± 3.1 ms [User: 476.8 ms, System: 1.8 ms]
Range (min … max): 475.0 ms … 486.7 ms 10 runs
Summary
./sapi/cli/php ../x.php ran
1.06 ± 0.01 times faster than ./sapi/cli/php_old ../x.php
```
On an i7-1185G7:
```
Benchmark 1: ./sapi/cli/php x.php
Time (mean ± σ): 343.9 ms ± 3.1 ms [User: 341.1 ms, System: 2.3 ms]
Range (min … max): 337.9 ms … 347.8 ms 10 runs
Benchmark 2: ./sapi/cli/php_old x.php
Time (mean ± σ): 357.8 ms ± 2.3 ms [User: 355.7 ms, System: 1.6 ms]
Range (min … max): 355.0 ms … 362.6 ms 10 runs
Summary
./sapi/cli/php x.php ran
1.04 ± 0.01 times faster than ./sapi/cli/php_old x.php
```
7b6b233ce8