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From Yann Ylavic <ylavic....@gmail.com>
Subject Re: Better ap_casecmpstr[n]?
Date Tue, 24 Nov 2015 19:04:48 GMT
I tested this change with both Jim's and my versions, that's slower.

The better implementation I have so far is:

int ap_casecmpstr_2(const char *s1, const char *s2)
{
    size_t i;
    const unsigned char *ps1 = (const unsigned char *) s1;
    const unsigned char *ps2 = (const unsigned char *) s2;

    for (i = 0; ; ++i) {
        const int c1 = ucharmap[ps1[i]];
        const int c2 = ucharmap[ps2[i]];

        if (c1 != c2) {
            return c1 - c2;
        }
        if (!c1) {
            break;
        }
    }
    return (0);
}

which is ~15% faster than the current one (and not 50% unless I remove
the translation :)

I also tried:

    for (i = 0; ; ++i) {
        const int c1 = ps1[i];
        const int c2 = ps2[i];

        if (c1 != c2 && ucharmap[c1] != ucharmap[c2]) {
            return ucharmap[c1] - ucharmap[c2];
        }
        ...

but no.


On Tue, Nov 24, 2015 at 7:56 PM, William A Rowe Jr <wrowe@rowe-clan.net> wrote:
> For the optimization cases Graham was proposing, how does this perform on
> your test setup? Looking for both absmatches, case mismatches and proper vs
> lowercase comparisons...
>
> int ap_casecmpstr_2(const char *s1, const char *s2)
> {
>     size_t i;
>     const unsigned char *ps1 = (const unsigned char *) s1;
>     const unsigned char *ps2 = (const unsigned char *) s2;
>
>     for (i = 0; ; ++i) {
>         const int c1 = ucharmap[ps1[i]];
>         const int c2 = ucharmap[ps2[i]];
>         /* Above lookups are optimized away if first test below succeeds */
>
>         if ((ps1[i] != ps2[i]) && (c1 != c2)) {
>             return c1 - c2;
>         }
>         if (!c1) {
>             break;
>         }
>     }
>     return (0);
> }
>
>
> On Tue, Nov 24, 2015 at 12:43 PM, Yann Ylavic <ylavic.dev@gmail.com> wrote:
>>
>> On Tue, Nov 24, 2015 at 7:39 PM, Mikhail T. <mi+thun@aldan.algebra.com>
>> wrote:
>> > On 24.11.2015 13:04, Yann Ylavic wrote:
>> >
>> > int ap_casecmpstr_2(const char *s1, const char *s2)
>> > {
>> >     size_t i;
>> >     const unsigned char *ps1 = (const unsigned char *) s1;
>> >     const unsigned char *ps2 = (const unsigned char *) s2;
>> >
>> >     for (i = 0; ; ++i) {
>> >         const int c1 = ps1[i];
>> >         const int c2 = ps2[i];
>> >
>> >         if (c1 != c2) {
>> >             return c1 - c2;
>> >         }
>> >         if (!c1) {
>> >             break;
>> >         }
>> >     }
>> >     return (0);
>> > }
>> >
>> > Sorry, but would not the above declare "A" and "a" to be different?
>>
>> Yeah, forgot the translation, I went too fast :)
>
>

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