First order optimization is always overall program architecture, then hotspots, then fixing architectural issues in the code (e.g. getting rid of misspeculated

First order optimization is always overall program architecture, then hotspots, then fixing architectural issues in the code (e.g. getting rid of misspeculated branches, reducing instructions etc), and then optimizing the code the compiler is generating. And at no point does it require to know the internals of the optimization passes as to how it generates the code. As for the compiler’s role in C, it’s equivalent to javac - it’s taking your source and creating machine code, except the machine code isn’t an abstract bytecode but the exact machine instructions intended to run on the CPU. The issues with C and C++ are around memory safety. Practice has repeatedly shown that the defect rate with these languages is high enough that it results in lots of easily exploitable vulnerabilities. That’s a bit more serious than a personal preference. That’s why there’s pushes to shift the professional industry itself to stop using C and C++ in favor of Rust or even Go.