Hi,
On Tue, Feb 02, 2010 at 09:45:32AM +0200, Pauli Nieminen wrote:
> I bisected the rendering problem to commit adding xmm0 zeroing code to
> transform functions.
Unfortunately, xmm0 happens to be undefined at least sometimes, for
example on one SDL + OpenGL game I tried. It made the game crash in a
reproductible manner (all the time).
Please refer to my original comment for details about why I believe my
change is correct. If it so happens that the upper qword of %xmm0 does
sometimes contain fog factor, then it probably is because of luck rather
than a voluntary thing, because you cannot rely on %xmm0 keeping its
value between two calls to the GL driver.
As a result, reverting my patch is *not* the proper way to fix the bug
you are encountering. Properly loading %xmm0 with the value you want to
see in there is the correct solution.
> 4c31632817a0bde28ad6c9ee8032d838ce4b7bfb is first bad commit
> commit 4c31632817a0bde28ad6c9ee8032d838ce4b7bfb
> Author: Arthur HUILLET <arthur.huil...@free.fr>
> Date: Tue Jun 30 12:46:27 2009 +0200
>
> mesa: fix transform_points_3d_no_rot using undefined values in %xmm0
>
> Signed-off-by: Arthur HUILLET <arthur.huil...@free.fr>
>
> I don't have good enough image of what is going as whole but my guess
> is that xmm0 is not undefined but it is defined to be fog factor.
> Reverting the commit fixed prgos/tests/fog rendering with sse swrast
> for me. I didn't run regression test to see if it causes some others
> bugs. But if xmm0 is undefined sometimes in transform functions the
> fix should be done earlier in path where fog information is coming in.
>
> I proposal reverting the commit to fix the fog/EXT_fogcoord in sse
> swrast, But Someone with good image of how the code functions should
> check it.
>
> PS. https://bugs.freedesktop.org/show_bug.cgi?id=23494
>
--
Greetings,
A.H.
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