The LEA-vs-shift thread here kind of proves the point. Compilers are insanely good at that stuff now. Where they completely fall short is data layout. I had a message parser using `std::map<int, std::string>` for field lookup and the fix was just... a flat array indexed by tag number. No compiler is ever going to suggest that. Same deal with allocation. I spent a while messing with SIMD scanning and consteval tricks chasing latency, and the single biggest win turned out to be boring. Switched from per-message heap allocs to a pre-allocated buffer with `std::span` views into the original data. ~12 allocations per message down to zero. Compiler will optimize the hell out of your allocator code, it just won't tell you to stop calling it.