https://bugs.freedesktop.org/show_bug.cgi?id=97338
--- Comment #3 from Nicolai Hähnle nhaehnle@gmail.com --- Created attachment 126172 --> https://bugs.freedesktop.org/attachment.cgi?id=126172&action=edit Problematic fragment shader
Okay, so here's a bit more detail of what is happening: the attached fragment shader (shader object 31) samples a 2D vector from PSampler2 (texture object 3153) and does some computations on it involving inversesqrt, under the assumption that the dot product of the vector is <= 1. This is false: looking at level 0 of texture 3153 reveals e.g. a unorm value (142, 255) at texel 155,263.
The likely cause here is that this is a port from D3D, which specifies that rsq should take the absolute value of its argument, to GLSL, which says that inversesqrt is undefined for values <= 0.