Heuristic-Driven Resource Optimization for Decoupled Memory Channels on FPGAs

Overview & Synopsis

Determining OpenCL channel depths for Decoupled Access-Execute (DAE) architectures in High-Level Synthesis (HLS) is critical for balancing performance and hardware efficiency. Conventional static analysis tools often over-provision these memory channels to ensure performance safety, leading to significant resource stranding. This paper presents an expansion of an LLVM-based static analysis framework, originally proposed for automated DAE generation, by introducing a hardware-aware refinement layer. We identify a counter-intuitive Performance Inversion Paradox linked to baseline memory stalls, where high-stall, grid-based kernels reach peak performance at minimal channel depths and suffer up to a 61% throughput degradation when depths are increased. We propose a Heuristic Refinement Layer that optimizes OpenCL channel depths based on this correlation between baseline stalls and performance saturation. Experimental results demonstrate that our expanded framework successfully identifies the Minimal Peak Performance point across various benchmarks. By avoiding the performance traps of standard over-provisioning, we achieve a 2.52x improvement in Resource Efficiency for an illustrative HotSpot application. This approach maintains peak execution speedup while ensuring the leanest possible hardware profile, outperforming conservative tool-based static predictions.