Comment # 7 on bug 25297 from Benjamin Bellec

I didn't test with the softrender, but this bug is now fixed since:

commit: 1337da51152db7fa1a71ac86b61b51a42d29d595
summary: r600g: implement edge flags
author: Marek Olšák
date: 2014-03-04 11:26:16 (GMT)

r600g now render the square like your screenshot. Tested on AMD CYPRESS.