Re: Encode UTF-8 optimizations

On 08/22/2016 02:47 PM, [email protected] wrote:
>> > And I think you misunderstand when is_utf8_char_slow() is called.  It is
>> > called only when the next byte in the input indicates that the only
>> > legal UTF-8 that might follow would be for a code point that is at least
>> > U+200000, almost twice as high as the highest legal Unicode code point.
>> > It is a Perl extension to handle such code points, unlike other
>> > languages.  But the Perl core is not optimized for them, nor will it be.
>> >   My point is that is_utf8_char_slow() will only be called in very
>> > specialized cases, and we need not make those cases have as good a
>> > performance as normal ones.
> In strict mode, there is absolutely no need to call is_utf8_char_slow(). As in strict
> mode such sequence must be always invalid (it is above last valid Unicode character)
> This is what I tried to tell.
>
> And currently is_strict_utf8_string_loc() first calls isUTF8_CHAR() (which could call
> is_utf8_char_slow()) and after that is check for UTF8_IS_SUPER().

I only have time to respond to this portion just now.

The code could be tweaked to call UTF8_IS_SUPER first, but I'm asserting 
that an optimizing compiler will see that any call to 
is_utf8_char_slow() is pointless, and will optimize it out.