Comment by chc4

IMO You should just stick some programs in Ghidra/Godbolt and see what they emit, especially for small individual snippets whenever you think "I want to do X, what's the best way of doing it". There really isn't much difference between "baby's first assembly" program, where you just have movs and like five other common instructions, and the kind of assembly an optimizing compiler emits: it's a matter of recognizing that some operations can be merged into a more specialized one or the addressing mode of another, or you can use a setcc with a results flag from something you already computed, or what have you. The good code that LLVM and JITs emit for the most part aren't due to much better instruction selection but due to much better optimization passes, which learning more about assembly doesn't help with: it's about transforming code in general at a high level, which you would do at the compiler IR step before touching assembly at all.