gcc also supports OpenMP 4.x and OpenACC, both of which are used extensively in the HPC world to support automated parallelization and offloading to accelerator

gcc also supports OpenMP 4.x and OpenACC, both of which are used extensively in the HPC world to support automated parallelization and offloading to accelerators like GPUs. clang only recently added support for OpenMP 3.1, and my understanding is that there are no plans for OpenACC support.