The game Heroes of Newerth (also referred to as HoN) crashes in certain circumstances with the following error message in dmesg:

[ 1797.294324] [drm:radeon_cs_parser_init] *ERROR* cs IB too big: 26607
[ 1797.294327] [drm:radeon_cs_ioctl] *ERROR* Failed to initialize parser !

It's occuring during normal gameplay in situations with high graphic workload (as far as I can tell).
I was up until recently using older libs for playing HoN with the r600 driver and thus noticed this bug as a regression.
It is possible to reproduce the bug quite reliably by following these steps:

1. Start HoN
2. Create a practice game
3. Select a slot and start the game
4. Select any hero and wait for the countdown or skip the countdown by pressing ready
5. As the game starts, open the test-menu at the top left of the screen and press the “Spawn”-button right of where it reads “Creeps” multiple times (~20-30 times). There should be spawning many creeps at your base.
6. Pan the viewport to include as many creeps as possible.
7. Press the “Kill”-button right next to the “Spawn”-button.
8. 1-2 seconds later the game crashes.
9. You notice the error messages in dmesg

Bisecting issued the following bad commit:

e62e5b0922b6554431234a8a71c7aec7cff91864 is the first bad commit
commit e62e5b0922b6554431234a8a71c7aec7cff91864
Author: Andre Maasikas <amaasikas@gmail.com>
Date:   Wed Aug 11 14:30:18 2010 +0300

    r600: add support for draw_elements_base_vertex
    
    use VTX_BASE_VTX_LOC for offset, last time using INDEX_OFFSET was
    probably a wrong register for this

:040000 040000 2daa2236ba96c969c80cd62b1199d0eacb56ecce 376ee1345c8cbbb51c2b1c36cb7adafac276d5d6 M	src

I tried to the best of my ability to manually revert the commit and it proved to be the cause of the bug.
I'm running mesa-git right now with that commit manually reverted and HoN is running fine.

Note: This might be the same bug as described in this comment: https://bugs.freedesktop.org/show_bug.cgi?id=25114#c7

Let me know if there is any information missing.