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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - r600/sb: clobbers gl_Position -> gl_FragCoord"
href="https://bugs.freedesktop.org/show_bug.cgi?id=104143#c8">Comment # 8</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - r600/sb: clobbers gl_Position -> gl_FragCoord"
href="https://bugs.freedesktop.org/show_bug.cgi?id=104143">bug 104143</a>
from <span class="vcard"><a class="email" href="mailto:gw.fossdev@gmail.com" title="Gert Wollny <gw.fossdev@gmail.com>"> <span class="fn">Gert Wollny</span></a>
</span></b>
<pre>I found the problem:
if KC0[0].x == index (=0):
1 x: ADD_INT T0.x, KC0[0].x, [0xfffffffe -nan].x
2 x: MOVA_INT __.x, T0.x
Address register is now -2 and hence, in the next step R1 is unconditionally
written, and this is actually the gl_Vertex value ...
3 z: MOV R[3+AR].z, 0
w: MOV R[3+AR].w, [0x3dcccccd 0.1].x
that is here used to evaluate the gl_Posuition.
5 x: MUL_IEEE T0.x, KC0[1].w, R1.x
y: MUL_IEEE T0.y, KC0[1].z, R1.x
6 t: MULADD_IEEE T0.y, KC0[2].z, R1.y, T0.y SCL_212
...
In the un-optimized shader R[3+AR].w is only written to if (KC0[0].x >= 2), and
hence AR >= 0;
I.e. the sb optimizer is to aggressive in optimizing away the conditional
blocks.</pre>
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