[Bug middle-end/105253] __popcountdi2 calls generated in kernel code with gcc12

[crazylht at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105253

Hongtao.liu <crazylht at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |crazylht at gmail dot com

--- Comment #16 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Jakub Jelinek from comment #11)
> This is a regression (as in we don't want such a call in that case for
> performance reasons and in the past we didn't emit it).

Yes, just note it regresses 531.deepsjeng_r by 2% for -O2 -march=x86-64 since
below function.

typedef unsigned long long BITBOARD;
int PopCount (BITBOARD b) {
    int c = 0;

    while (b) {
        b &= b - 1;
        c++;
    }

    return c;
}

popcnt is supported by x86-64_v2.