GLSL fun: I tried to keep nested scopes down but still only load the data when needed, and got rewarded with ~50 VGPRs being zeroed and then discarded again (image 1, longer). Caved and added another scope (with the load inside), and got something _somewhat_ more reasonable (image 2, shorter). Still not clear to me if local structs in GLSL are supposed to be zero-initialized or not; my spec-reading skill are insufficient.
