Manually constructing machine code (as in the example) is not the best idea - it is error-prone, difficult to debug, and prevents testing with sanitizers. I'd not do it.

Using LLVM for JIT is also not the best idea because LLVM is a complex codebase with bugs. Example: https://github.com/ClickHouse/ClickHouse/issues/50323#issuec... Although there are some marginal benefits: https://clickhouse.com/blog/clickhouse-just-in-time-compiler...