[Bug 84004] New: Bizarre vertex shader results (warped geometry) unless a never executed if-branch is added.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=84004

          Priority: medium
            Bug ID: 84004
          Assignee: idr at freedesktop.org
           Summary: Bizarre vertex shader results (warped geometry) unless
                    a never executed if-branch is added.
        QA Contact: intel-3d-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: delta_luca at hotmail.com
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: git
         Component: glsl-compiler
           Product: Mesa

Created attachment 106438
  --> https://bugs.freedesktop.org/attachment.cgi?id=106438&action=edit
GLSL code for the 3 vertex shaders, work-around highlighted in each case.

WebGL, chrome + firefox on various devices (all 64bit linux + intel graphics)

Devices:

1)
Ubuntu 14.04
Intel Core i5 2500K
Mesa git a3306f02  2014-09-08 from Xorg-edgers ppa
Chrome 37 + Firefox 32

2)
Chrome book pixel
Intel Core i5 3427U
Mesa 10.3.0-devel git 1751a9b
Chrome 37

3)
Fedora 20
Intel Core i7 3612QM
Mesa 10.1.5
Chrome 37

Behaviour:

Geometry rendered with 3 particular vertex shaders ends up coming out with
seemingly completely randomn positions, with triangles stretched all over the
screen in a crazy mess.

Adding a single if branch (whose condition is always false) to the shaders
fixes behaviour.

Behaviour does not occur on windows with intel drivers, or on windows/mac/linux
with nvidia drivers. Status with ATI drivers is unknown.

Our shaders are written in CG compiled to GLSL, so apologies upfront for
atrocious GLSL code. The relevant areas are highlighted. Producing a single
reproducible can be done if required, though it would take some time, please
let me know if the GLSL code is insufficient.

Screenshot without workaround:
https://drive.google.com/file/d/0B0DebLXzXCcQYVJEQ0RQSjR6QlU
Screenshot with workaround:
https://drive.google.com/file/d/0B0DebLXzXCcQalF5WVZiWjBlY2s

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