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From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <55B61562.2030808@redhat.com>
Date: Mon, 27 Jul 2015 13:26:26 +0200
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Subject: Re: [Qemu-devel] [PATCH v2 for-2.5 05/12] tcg/optimize: track
 const/copy status separately
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To: Aurelien Jarno <aurelien@aurel32.net>, qemu-devel@nongnu.org
Cc: Richard Henderson <rth@twiddle.net>



On 27/07/2015 12:56, Aurelien Jarno wrote:
>          temps[dst].next_copy =3D temps[src].next_copy;
>          temps[dst].prev_copy =3D src;
>          temps[temps[dst].next_copy].prev_copy =3D dst;
>          temps[src].next_copy =3D dst;

This is:

    dst->next =3D src->next;
    dst->prev =3D src;
    dst->next->prev =3D dst;
    src->next =3D dst;

which seems weird.  I think it should be one of

    /* splice src after dst */
    dst->next->prev =3D src->prev;
    src->prev->next =3D dst->next;
    dst->next =3D src;
    src->prev =3D dst;

or

    /* splice src before dst */
    last =3D src->prev;
    dst->prev->next =3D src;
    src->prev =3D dst->prev;
    last->next =3D dst;
    dst->prev =3D last;

(written as pointer manipulations for clarity).

Maybe I'm missing the obvious, but if it's a problem it's better to fix
it before the links are used more pervasively.

Paolo