[Bug 89293] [i965] [bisected] [VMware Workstation] 514fd1c commit breaks some Piglit tests in Windows VMs

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89293

Jason Ekstrand <jason at jlekstrand.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|DUPLICATE                   |NOTOURBUG

--- Comment #4 from Jason Ekstrand <jason at jlekstrand.net> ---
The offending fragment shader in the attached apitrace has the following GLSL
source:

> #version 150
> #extension GL_ARB_shader_bit_encoding : enable
> #extension GL_ARB_texture_query_levels : enable
> vec4 O[1];
> uniform uint enableGammaDecodes;
> void shader_fn(ivec2 aL);
> out vec4 fragColor0;
> layout(pixel_center_integer) in vec4 gl_FragCoord;
> #define CONVERTOUTPUT0(v) (v)
>
> void main(){
>    shader_fn(ivec2(0));
>    fragColor0 =CONVERTOUTPUT0(O[0]);
> }
>
> void shader_fn(ivec2 aL) {
>    O[0] = vec4(1, 0, 0, 1);
> }

As you can see, this only writes to the first color attachment, not all 4.  If
you don't write to one of the color attachments, you get undefined values which
is exactly what you're getting.  The only reason why this worked before the
change was that, due to a fluke in the way the compiler was implemented, the
color from the first write was getting propagated to the other 3.  I don't know
what the code looked like before going through VMWare's shader translator so it
could be a bug there.  However, we are doing the right thing.

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