r600-nir: there is a subtle error in the if/else handling
The piglit spec@glsl-1.40@uniform_buffer@fs-struct-copy-complicated fails when nir_opt_peephole_select is leaving various levels of if/else branches. TGSI nosb creates a similar shader and doesn't fail.
One can workaround the issue with that specific piglit by increasing the instruction limit with nir_opt_peephole_select (Which makes sense anyway, because CF instructions are expensive), but the issue is lurking there.