Faster validation logic in bc_str2num()

[ndossche]

Using SIMD to accelerate the validation.

Using the benchmark from #14076.

After:

1.3504369258881
1.6206321716309
1.6845638751984

Before:

1.4750170707703
1.9039781093597
1.9632289409637

[SakiTakamachi]

LGTM, Your tricks always amaze me!

One suggestion: what about implementing this in zend instead of BCMath?

For example, ctype_digit checks if a string is a digit in exactly the same way as the existing BCMath does.

[Girgias]

I am not going to claim I understand the SSE intrinsic code, but I'm trusting this is fine.

[ndossche]

One suggestion: what about implementing this in zend instead of BCMath?

For example, ctype_digit checks if a string is a digit in exactly the same way as the existing BCMath does.

Maybe, although isdigit takes into account the locale and I'm not sure if all locales have the same digit range.

[Girgias]

Seems like isdigit is not affected by the locale according to the note: https://devdocs.io/c/string/byte/isdigit

[ndossche]

Interesting, in that case someone may feel free to move it somewhere more generally such that it can be reused.