I looked up the Polly reference concerning discussion of BLIS missing optimized implementations, and GCC and clang apparently failing on BLIS-type loops. (It mentioned examples of people not using the relevant libraries in national labs, not that I'd defend that.) It might also have been other types of kernel that don't exist for ARM or POWER, say. Surely it would be good to have an effective general-purpose tool (compiler) that could replace labourious hand-optimization or building special-purpose tools.