RADEON_DEBUG=noopt is not possible, the pixel shader programs are to big to be
loaded without size optimizations.
Hard limit of 512 instruction slots per pixel shader:
http://developer.amd.com/wordpress/media/2012/10/Radeon_X1x00_Programming_Guide.pdf
page 13
This limit is exceeded by far due to all the virtual texturing code, the
optimized shader barely fits.

I did try it in 9.0 and 9.1 with noopt and I did get past the segfault in
peephole_mul_omod() this way, but it did fail then because the resulting shader
program was to big.

Deactivating hyper-z has no measurable impact, and it didn't prevent the
corruption either.

Antialiasing hasn't even been enabled in the application by default, so turning
it off makes no difference at all.