Created attachment 140294 [details] [review]
Fix crashes

color_interp_vgpr_index was declared as a generic char value.  Because signed
values are used in this variable, the result was not safe across architectures
and crashed on ppc64[el] and arm systems.

The atttached patch declares color_interp_vgpr_index as a signed type, and has
been verified to work with alien-arena, glxgears, and Flightgear, all of which
were crashing before the patch.