Comment # 4 on bug 65968 from Andreas Ringlstetter

PS:
I will not be able to test with 9.0 or 9.1 since one of the shaders causes a
segfault while compiling in these version. This has only recently (last 1-2
months) been fixed in git.

This was caused by a faulty implementation of peephole_mul_omod() in
compiler/radeon_optimize.c, the SIGSEGV was thrown in
rc_variable_list_get_writers_one_reader due to writer_list beeing NULL.