Re: [PATCH v9 0/2] MR821: Replace obsolete RtlUniform tests that no longer work (currently skipped) since Windows Vista; update RtlUniform impl.

[Huw Davies (＠huw)]

Huw Davies (@huw) commented about dlls/ntdll/rtl.c:
> -    result = *seed * 0xffffffed + 0x7fffffc3;
> -    if (result == 0xffffffff || result == 0x7ffffffe) {
> -	result = (result + 2) & MAXLONG;
> -    } else if (result == 0x7fffffff) {
> -	result = 0;
> -    } else if ((result & 0x80000000) == 0) {
> -	result = result + (~result & 1);
> -    } else {
> -	result = (result + (result & 1)) & MAXLONG;
> -    } /* if */
> +    /* The algorithm below is equivalent to the following expression:
> +     *
> +     * result = ((ULONGLONG)*seed * 0x7fffffed + 0x7fffffc3) % 0x7fffffff;
> +     * return (*seed = result);
> +     */
> +
> The optimization below doesn't seem to be worth it.  On x86_64 I couldn't measure a difference between the algorithm above and the optimization below.  On i386, while the optimization was about 10% faster, the algorithm above matched native's performance, so there seems little point in adding the complexity.

If you really need the optimization, you could potentially introduce it in a later MR.

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https://gitlab.winehq.org/wine/wine/-/merge_requests/821#note_24059