> On 24 August 2016 at 11:26, Adam Richter <adamricht...@gmail.com> wrote: > > I hope that that consideration, combined with the micro-costs to > > readability and portability of using and ELF specific and perhaps > > currently GCC specific feature might tip the balance against the > > savings of a level of function call indirection that I assume the use > > of ifunc was intended to provide. > > It doesn't actually save a level of indirection -- if you single step > through an ifunc call it goes via some ELF section. The thing it > does save is that you don't pay the cost of figuring out the right > ifunc to use on this system at startup, but only when the ifunc call > path is first used. That's useful for a big thing like glibc which > might have lots of ifuncs and not want to pay a big startup cost, > but for QEMU there's really no need given we only have one...
It does save a level of indirection after the first call AFAIK, but it shouldn't be measurable. Paolo
