Allow subgroup reductions on stable AMD GCN Vulkan drivers

[rasbid]

Summary

• refine the Vulkan subgroup enablement logic to block only known-bad AMD GCN drivers
• allow AMD proprietary drivers with working subgroup arithmetic to use the optimized reduction paths

Testing

• python - <<'PY'
  from itertools import product

def can_use_subgroups(subgroup_arithmetic, architecture, driver_id):
amd_gcn_bad_subgroup_driver = (
architecture == "AMD_GCN" and
driver_id in {"MesaRadv", "AmdOpenSource"}
)
return subgroup_arithmetic and not amd_gcn_bad_subgroup_driver

cases = [
(True, "AMD_GCN", "AmdProprietary"),
(True, "AMD_GCN", "MesaRadv"),
(True, "AMD_GCN", "AmdOpenSource"),
(True, "RDNA", "MesaRadv"),
(False, "AMD_GCN", "AmdProprietary"),
]

for subgroup_arithmetic, architecture, driver_id in cases:
print(f"subgroup_arithmetic={subgroup_arithmetic}, architecture={architecture}, driver={driver_id} -> "
f"use_subgroups={can_use_subgroups(subgroup_arithmetic, architecture, driver_id)}")
PY

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https://chatgpt.com/codex/tasks/task_e_68ebeed865e883308570b2d982b9cf60