chipStar : Making HIP/CUDA applications cross-vendor portable by building on open standards

We describe chipStar , an open source software stack that enables building unmodified CUDA and HIP programs into binaries that rely solely on open cross-vendor compute standards OpenCL and SPIR-V. The relevant technical aspects of chipStar and the feature mismatches between the CUDA/HIP APIs and OpenCL are discussed along with a set of standard extension proposals to bridge the essential gaps in the future. The key benefit of the software stack is its portability, which is demonstrated by providing performance evaluations on a diversity of less common CPU/GPU platforms including RISC-V/PowerVR and ARM Mali. A comparison against the original AMD HIP platform provides a geometric mean of 0.75, a reasonable price to pay for the enhanced portability. chipStar is now considered mature enough for wider testing and even production use, which is demonstrated by successful porting and competitive performance of GAMESS-GPU-HF, a complex HPC application.