Re: [Qemu-devel] Bug in helper_pcmpestrm and helper_pcmpistrm

[Blue Swirl]

On Thu, Sep 29, 2011 at 8:12 AM, Frank Mehnert <address@hidden> wrote:
> Hi,
>
> the two functions helper_pcmpestrm() and helper_pcmpistrm() in
> target-i386/ops_sse.h contain obviously typos. I think that at
> all 4 marked places should increment the index 'i', not decrement
> it during the loop:
>
>
> void glue(helper_pcmpestrm, SUFFIX) (Reg *d, Reg *s, uint32_t ctrl)
> {
>    int i;
>    unsigned int res = pcmpxstrx(d, s, ctrl,
>                    pcmp_elen(R_EDX, ctrl),
>                    pcmp_elen(R_EAX, ctrl));
>
>    if ((ctrl >> 6) & 1) {
>        if (ctrl & 1)
>            for (i = 0; i <= 8; i--, res >>= 1)
>            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>                d->W(i) = (res & 1) ? ~0 : 0;

I think this line will also fill the entire memory with 0xff and 0x00.

Please make a patch, http://wiki.qemu.org/Contribute/SubmitAPatch
should tell how (seems to be down ATM).

>        else
>            for (i = 0; i <= 16; i--, res >>= 1)
>            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>                d->B(i) = (res & 1) ? ~0 : 0;
>    } else {
>        d->Q(1) = 0;
>        d->Q(0) = res;
>    }
> }
>
>
> void glue(helper_pcmpistrm, SUFFIX) (Reg *d, Reg *s, uint32_t ctrl)
> {
>    int i;
>    unsigned int res = pcmpxstrx(d, s, ctrl,
>                    pcmp_ilen(s, ctrl),
>                    pcmp_ilen(d, ctrl));
>
>    if ((ctrl >> 6) & 1) {
>        if (ctrl & 1)
>            for (i = 0; i <= 8; i--, res >>= 1)
>            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>                d->W(i) = (res & 1) ? ~0 : 0;
>        else
>            for (i = 0; i <= 16; i--, res >>= 1)
>            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>                d->B(i) = (res & 1) ? ~0 : 0;
>    } else {
>        d->Q(1) = 0;
>        d->Q(0) = res;
>    }
> }
>
>
> Kind regards,
>
> Frank
> --
> Dr.-Ing. Frank Mehnert
> Senior Manager Software Development Desktop Virtualization, VirtualBox
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