On Wed, Sep 23, 2020 at 10:09 AM cs.ali...@gmail.com < cs.alikoyu...@gmail.com> wrote:
> Is there a paper that I can find why the compiler considers them for > ordering, why it is important for performance or anything else? > > A CPU has a limit to how many load/store instructions it can issue in a given clock cycle or in a given window of clock cycles. By reordering memory loads, you can spread them out such that they don't create conflicts against each other. This covers the part of memory ordering optimizations. As for function calls, you often have a call convention where some registers are saved by the caller and some registers are saved by the callee. Hence it can be beneficial to arrange the evaluation order in a way to avoid having to save registers. I think Go's current ABI rules are to use the stack for everything in its calling convention, but the same general rules apply: you may want to reorder the work in order to save on register pressure. It becomes especially interesting if your calling convention allows for multiple return values passed in registers. Note that https://go.googlesource.com/proposal/+/refs/changes/78/248178/1/design/40724-register-calling.md proposes a register-based calling convention for the Go compiler, which hammers through the need of flexibility in this area. -- J. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAGrdgiXN5k_d8MY1KyPK7E3i0WkjCK-wHNxi6phuAVWE2SOoOg%40mail.gmail.com.
