On Fri, Dec 1, 2017 at 12:25 PM, Ugorji Nwoke <ugo...@gmail.com> wrote: > > Yes. Fundamentally, I'm asking if step #2 in your calling sequence can be > optimized. > > 1. load a function pointer from the itab > 2. call the function pointer. However, if the function pointer to is empty, > just do a NOP here and skip the function-call-dance. This should be possible > as the i-tab is created dynamically on first reference, which means that it > can know if the function is empty and put NOP indicator in the i-tab instead > of the function pointer. That's the optimization I'm asking about.
I'm sorry, I probably don't understand. You are suggesting that we change the current code, that simply calls the function pointer, to compare the function pointer to some value (zero?) and skip the call in that case? That would introduce a conditional branch to every method call, it would be larger and, on average, slower. That seems like a poor choice. Ian > On Friday, December 1, 2017 at 2:22:24 PM UTC-5, Ian Lance Taylor wrote: >> >> On Fri, Dec 1, 2017 at 10:42 AM, Ugorji Nwoke <ugo...@gmail.com> wrote: >> > >> > This is not so much about de-virtualization. It's about not making a >> > call to >> > an empty function i.e. I expect that interface calls come down to >> > 1. dereference the pointer to the i-tab, >> > 2. jump to the appropriate function in the i-tab, >> > 3. call that function. >> >> That does not seem to me to be an accurate description of the current >> implementation. Calling a method of an interface is >> 1. load a function pointer from the itab >> 2. call the function pointer >> >> >> > If that function is a no-op, is the runtime smart enough to skip that >> > function call completely (e.g. replacing the entry in the i-tab with a >> > NOP)? >> >> The itab does not contain code, it just holds function pointers. >> >> Ian > > -- > 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. > For more options, visit https://groups.google.com/d/optout. -- 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. For more options, visit https://groups.google.com/d/optout.
