[Bug 108179] [ivb] gpu hang on Star Ruler 2

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108179

Danylo <danylo.piliaiev at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |danylo.piliaiev at gmail.com

--- Comment #4 from Danylo <danylo.piliaiev at gmail.com> ---
Compiling the offending shader "ringworld_procedural_ps.txt" produces warnings
about uninitialized variable "atmoSteps".

> atmoSteps = 4 - int(atmoSteps * 2.0);
As could be seen in shader it is used without being initialized.

Later it is passed to cloudMaker function where is used for the loop as
iterations count.

Accessing uninitialized variable is a valid operation but yields undefined
result, "atmoSteps" became a huge value in some of invocations thus hanging the
GPU.  

GLSL 4.4 spec says:

> Reading a variable before writing (or initializing) it is legal, however the value is undefined.

I don't know what value it should be initialized to but initializing it
resolves the hang.

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