I'm only aware of Brandis’s thesis who did optimizations on a subset of Oberon for the PPC architecture. There was also a JIT compiler, but not particularly optimized. OP2 was the prevalent compiler and continued to be extended and used for AOS, and it wasn't optimizing. To really assess whether a given language can achieve higher performance than other languages due to its special design features, we should actually implement it on the same optimizing infrastructure as the other languages (e.g. LLVM) so that both implementations have the same chance to get out the maximum possible benefit. Otherwise there are always alternative explanations for performance differences.