RDNA 4's Dynamic VGPR Allocation: A Ray Tracing Bottleneck Breaker
AMD's RDNA 4 architecture introduces a novel dynamic VGPR (vector general-purpose register) allocation mode to address the trade-off between register count and occupancy in ray tracing. Traditional GPUs face limitations in ray tracing where fixed register allocation per thread restricts thread parallelism in stages with high register demands. RDNA 4's dynamic allocation allows threads to adjust register counts at runtime, increasing occupancy without enlarging the register file, thus reducing latency and boosting ray tracing performance. While this mode can lead to deadlocks, AMD mitigates this with a deadlock avoidance mode. This isn't a universal solution, limited to wave32 compute shaders, but significantly advances AMD's ray tracing capabilities.