[Bug 89156] r300g: GL_COMPRESSED_RED_RGTC1 / ATI1N support broken

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89156

--- Comment #5 from Marek Olšák <maraeo at gmail.com> ---
(In reply to Stefan Dösinger from comment #4)
> Created attachment 113841 [details]
> Shader used to read the texture
> 
> Indeed changing the swizzle fixes the random output. I have attached the
> shader we use to sample the texture. We don't have a swizzle on the
> texture2D statement, but we do swizzle the output variable, and apparently
> the optimizer merges that.

So it's a compiler bug.

> 
> If I use the RGBA values returned by the texture sampling directly I get a
> solid color as expected. However, the value is off quite a bit: Instead of
> 0x7f I get 0x6c.
> 
> The texture data we use is this:
> 
> static const char ati1n_data[] =
> {
>     /* A 4x4 texture with the color component at 50%. */
>     0x7f, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
> };

That's expected. ATI1N operates at lower precision. I'm afraid I can't change
that.

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