Compile-Time Generation of Custom-Precision Floating-Point IP using HLS Tools

High-Level Synthesis (HLS) tools usually treat floating-point operators as black-box IP cores, and then schedule them as primitives when synthesising code to circuits. This approach relies on a library of IP blocks for chosen floating-point formats, which are pre-characterised to determine latency and area properties needed at compilation time. Two weaknesses of this approach are that it limits the number of floating-point formats - typically to half, single, and double - and that it requires conservative per-cycle scheduling of operators. Modern HLS tools have sophisticated intra-cycle scheduling of integer primitives, as well as C++ front-ends that can execute substantial algorithms at compile-time. This has enabled the creation of platform-independent C++ floating-point libraries which generate custom-precision operators at compile-time, while providing similar or better results as vendor-supplied IP blocks. However, certain problems and questions related to compilation performance and verification remain, so it is not yet clear how widely applicable this technique is.