ext/bcmath: If size of BC_VECTOR array is within 64 bytes, stack area is now used

[SakiTakamachi]

Benchmark

Multiplication

Codes

1 (Has no effect since this code using the fast path):

for ($i = 0; $i < 5000000; $i++) {
    bcmul('1.2345678', '2.1234567', 7);
}

2 (Affected by this change):

for ($i = 0; $i < 3000000; $i++) {
    bcmul('1234567890123456', '9234567890123456', 0);
}

3 (Does not use stack):

for ($i = 0; $i < 6000; $i++) {
    bcmul(str_repeat('1234567890', 300), str_repeat('9876543210', 300), 0);
}

Results

Example 1 is not affected by this change, so there is no speed change. A positive effect can be seen in example 2, where the requested size is very close to 64 bytes.
I thought that Example 3, which does not use a stack, would be slower due to the increased number of branches, but there was almost no change and the impact seems to be negligible.

1:

Benchmark 1: /php-dev/sapi/cli/php /mount/bc/mul/1.php
  Time (mean ± σ):     695.0 ms ±   6.9 ms    [User: 682.4 ms, System: 6.1 ms]
  Range (min … max):   688.5 ms … 711.6 ms    10 runs
 
Benchmark 2: /master/sapi/cli/php /mount/bc/mul/1.php
  Time (mean ± σ):     699.3 ms ±   2.6 ms    [User: 687.8 ms, System: 6.0 ms]
  Range (min … max):   696.2 ms … 703.6 ms    10 runs
 
Summary
  '/php-dev/sapi/cli/php /mount/bc/mul/1.php' ran
    1.01 ± 0.01 times faster than '/master/sapi/cli/php /mount/bc/mul/1.php'

2:

Benchmark 1: /php-dev/sapi/cli/php /mount/bc/mul/2.php
  Time (mean ± σ):     450.6 ms ±   7.1 ms    [User: 439.3 ms, System: 6.1 ms]
  Range (min … max):   444.1 ms … 465.7 ms    10 runs
 
Benchmark 2: /master/sapi/cli/php /mount/bc/mul/2.php
  Time (mean ± σ):     484.3 ms ±   4.6 ms    [User: 474.6 ms, System: 4.5 ms]
  Range (min … max):   476.6 ms … 490.4 ms    10 runs
 
Summary
  '/php-dev/sapi/cli/php /mount/bc/mul/2.php' ran
    1.07 ± 0.02 times faster than '/master/sapi/cli/php /mount/bc/mul/2.php'

3:

Benchmark 1: /php-dev/sapi/cli/php /mount/bc/mul/3.php
  Time (mean ± σ):     544.1 ms ±   4.0 ms    [User: 532.7 ms, System: 6.1 ms]
  Range (min … max):   540.9 ms … 554.4 ms    10 runs
 
Benchmark 2: /master/sapi/cli/php /mount/bc/mul/3.php
  Time (mean ± σ):     546.9 ms ±   4.0 ms    [User: 534.7 ms, System: 6.5 ms]
  Range (min … max):   541.3 ms … 553.8 ms    10 runs
 
Summary
  '/php-dev/sapi/cli/php /mount/bc/mul/3.php' ran
    1.01 ± 0.01 times faster than '/master/sapi/cli/php /mount/bc/mul/3.php'

Divide

Codes

1 (Affected by this change (with fast path)):

for ($i = 0; $i < 2000000; $i++) {
    bcdiv('1.23', '2', 5);
}

2 (Affected by this change (with standard path)):

for ($i = 0; $i < 3000000; $i++) {
    bcdiv('1234567890123456', '1234567891234', 0);
}

3 (Does not use stack):

for ($i = 0; $i < 4000; $i++) {
    bcdiv(str_repeat('1234567890', 300), str_repeat('9876543210', 300), 1000);
}

Results

Examples 1 and 2 are affected by this change and show a positive effect.
Example 3, which doesn't use the stack, is also somehow faster...

1:

Benchmark 1: /php-dev/sapi/cli/php /mount/bc/div/1.php
  Time (mean ± σ):     285.9 ms ±   1.8 ms    [User: 275.4 ms, System: 5.6 ms]
  Range (min … max):   282.0 ms … 289.1 ms    10 runs
 
Benchmark 2: /master/sapi/cli/php /mount/bc/div/1.php
  Time (mean ± σ):     303.7 ms ±   2.8 ms    [User: 292.5 ms, System: 5.9 ms]
  Range (min … max):   300.3 ms … 308.3 ms    10 runs
 
Summary
  '/php-dev/sapi/cli/php /mount/bc/div/1.php' ran
    1.06 ± 0.01 times faster than '/master/sapi/cli/php /mount/bc/div/1.php'

2:

Benchmark 1: /php-dev/sapi/cli/php /mount/bc/div/2.php
  Time (mean ± σ):     497.4 ms ±   2.8 ms    [User: 485.8 ms, System: 6.2 ms]
  Range (min … max):   493.6 ms … 501.4 ms    10 runs
 
Benchmark 2: /master/sapi/cli/php /mount/bc/div/2.php
  Time (mean ± σ):     531.1 ms ±   8.0 ms    [User: 520.4 ms, System: 5.2 ms]
  Range (min … max):   523.3 ms … 550.8 ms    10 runs
 
Summary
  '/php-dev/sapi/cli/php /mount/bc/div/2.php' ran
    1.07 ± 0.02 times faster than '/master/sapi/cli/php /mount/bc/div/2.php'

3:

Benchmark 1: /php-dev/sapi/cli/php /mount/bc/div/3.php
  Time (mean ± σ):     383.8 ms ±   4.0 ms    [User: 372.5 ms, System: 6.1 ms]
  Range (min … max):   376.7 ms … 388.6 ms    10 runs
 
Benchmark 2: /master/sapi/cli/php /mount/bc/div/3.php
  Time (mean ± σ):     401.5 ms ±   3.0 ms    [User: 389.4 ms, System: 6.8 ms]
  Range (min … max):   397.9 ms … 407.3 ms    10 runs
 
Summary
  '/php-dev/sapi/cli/php /mount/bc/div/3.php' ran
    1.05 ± 0.01 times faster than '/master/sapi/cli/php /mount/bc/div/3.php'

[SakiTakamachi]

I pushed by mistake! I will rebase.

[SakiTakamachi]

done