Calling glClear on a framebuffer bound to a multisample texture doesn't seem to do anything. I think this has something to do with the fast clear implementation because if the clear is scissored or the color is changed to something that doesn't have 0.0 or 1.0 in the components then the fast color is disabled and it works.
Created attachment 100522 [details] [review]
Piglit test that demonstrates the problem
I've posted a patch for this on the mailing list:
I've pushed the commit so I guess this bug is fixed now.
I've posted the Piglit test to the mailing list as well.