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            <b><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - [i965] Downward causes GPU hangs and misrendering on Haswell"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=104297#c41">Comment # 41</a>
              on <a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - [i965] Downward causes GPU hangs and misrendering on Haswell"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=104297">bug 104297</a>
              from <span class="vcard"><a class="email" href="mailto:kenneth@whitecape.org" title="Kenneth Graunke <kenneth@whitecape.org>"> <span class="fn">Kenneth Graunke</span></a>
</span></b>
        <pre>Check out the resulting assembly:

mov(8)          g22<1>UD        0x00000000UD                    { align1 WE_all
1Q compacted };
mov(1)          g22.5<1>UD      0x0000ff00UD                    { align1 WE_all
1N };
mov(2)          g22<1>UD        g0<0,1,0>UD                     { align1 WE_all
1N };
mov(2)          g22.3<1>UD      g15<4,1,0>UD                    { align1 WE_all
1N };
mov(8)          g125<1>UD       g0<4>UD                         { align16
WE_all 1Q };
mov(1)          g126<1>UD       0x00000000UD                    { align1 WE_all
1N compacted };
mov(1)          g126.4<1>UD     0x00000001UD                    { align1 WE_all
1N compacted };
mov(8)          g127<1>D        g22<4>D                         { align16 1Q };
send(8)         null<1>UW       g125<0>.xF      0x060a80fd
                            data MsgDesc: ( DC OWORD dual block write, 253, 0)
mlen 3 rlen 0 { align16 1Q };

g22 is a message header produced by a series of WE_all instructions.  It's then
copied to g127 without WE_all set, which will only copy some of the channels. 
It's then partially spilled and later partially reloaded.   Guessing that's
your bug.  I'll leave it to you.</pre>
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