  We discuss the efficient implementation of a high-performance second-order
collocation-type finite-element scheme for solving the compressible Euler
equations of gas dynamics on unstructured meshes. The solver is based on the
convex limiting technique introduced by Guermond et al. (SIAM J. Sci. Comput.
40, A3211-A3239, 2018). As such it is invariant-domain preserving, i.e., the
solver maintains important physical invariants and is guaranteed to be stable
without the use of ad-hoc tuning parameters. This stability comes at the
expense of a significantly more involved algorithmic structure that renders
conventional high-performance discretizations challenging. We develop an
algorithmic design that allows SIMD vectorization of the compute kernel,
identify the main ingredients for a good node-level performance, and report
excellent weak and strong scaling of a hybrid thread/MPI parallelization.
