Adding unreachable code leads to image being rendered incorrectly

[0152la]

[Shaders, screenshots, error log, reproduction steps, etc.] [ZIP]

Recipient:

Variant:

Similar to #7, albeit different observable effect and machine.

[0152la]

AMD Report Form ("n/a" means not filled):

Graphics Card Model:
Radeon R7 Series

Graphics Card Part Number:
n/a

AMD Radeon Software Driver Version:
Other

Driver History:
Fresh System Install

Operating System:
Other

Type of Issue:
Other

Crossfire Configuration:
No

Using Mantle:
No

Other Games/Applications:
OpenGL

Describe the Issue and Steps to replicate:
OS: Ubuntu 16.04 64-bit
Driver: http://support.amd.com/en-us/kb-articles/Pages/AMD-Radeon-GPU-PRO-Linux-Beta-Driver%E2%80%93Release-Notes.aspx

We used a custom-written OpenGL launcher (pre-compiled binaries available for download at [1]). [2] contains a fragment shader which yields the expected image ("original.frag") and a fragment shader which produces the incorrect output ("variant.frag"). Note that the difference between the two shaders is very similar to a bug observed on Windows 10, on a R9 Fury device (already reported via this form and available at [3]).

Command-line usage:
	$ ./get-image variant.frag --persist

[1] https://github.com/mc-imperial/get-image/releases/tag/v-f2328689086208e5ab6978b93cca325253dcd69a
[2] https://github.com/mc-imperial/shader-compiler-bugs/issues/11
[3] https://github.com/mc-imperial/shader-compiler-bugs/issues/7

CPU Details:
AMD A10-7850K Radeon R7, 12 Compute Cores 4C+8G

Display Devices and Connections used:
BenQ BL2400 on DVI

Motherboard or System Make & Model:
n/a

Motherboard BIOS version:
n/a

System Memory Type & Amount:
14GB

Power Supply Wattage:
n/a