Fair. As a compiler engineer (full-time on clang/LLVM), I wouldn't make such ridiculous claim (even though the compiler is capable of nasty tricks that "normal"

Fair. As a compiler engineer (full-time on clang/LLVM), I wouldn't make such ridiculous claim (even though the compiler is capable of nasty tricks that "normal" humans wouldn't be able to pull). Someone that pretends that it is not possible to beat the compiler should start by taking something like a GEMM routine (for example from there https://github.com/flame/blis/tree/master/kernels/x86_64 https://github.com/flame/blis/tree/master/kernels/x86_64 ) and reimplement it to show how a mainstream optimizing compiler can do better using C/C++ or Fortran. A good starting point to understand the gap between hand-written optimized assembly and what you can get with C is http://apfel.mathematik.uni-ulm.de/~lehn/sghpc/gemm/index.html http://apfel.mathematik.uni-ulm.de/~lehn/sghpc/gemm/index.ht...