On Mon, Jul 13, 2020 at 6:41 AM Erick Ochoa <erick.oc...@theobroma-systems.com> wrote: > > Hi, > > I just wanted to answer myself. > It seems that there are two thresholds that need to be met if a function > is to be specialized within a particular context: > > 1. --param=hot-bb-count-ws-permille=. This option controls the hotness > threshold of basic blocks and is needed for function specialization > during LTO. If a callsite is not in a hot basic block, it seems that the > callsite will not be specialized for a particular parameter. > 2. --param=ipa-cp-eval-threshold=. This option controls a heuristic that > lets constant propagation happen if a function is a good candidate for > cloning. This parameter is used for both: function specialization within > a particular context and for all contexts. > > On 10/07/2020 13:19, Erick Ochoa wrote: > > Forgot to mention that these functions take a function pointer as a > > parameter and as a result, the specialized functions are able to replace > > the indirect function call with a direct function call. > > > > On 10/07/2020 13:17, Erick Ochoa wrote: > >> Hello, > >> > >> I'm working on an optimization and I encountered this interesting > >> behaviour. There are a couple of functions that are specialized when > >> the program is not compiled with PGO (-fprofile-generate and > >> -fprofile-use) > >> > >> However, when the program is compiled with PGO the compiler does not > >> specialize the function calls. > >> > >> I printing the program just after materializing all clones. > >> > >> I am running this version of GCC: > >> Author: GCC Administrator <gccad...@gcc.gnu.org> > >> Date: Fri Jul 10 00:16:28 2020 +0000 > >> > >> Daily bump. > >> > >> I can imagine that the profiling information was used to determine > >> that specializing these functions is a bad tradeoff between binary > >> size and speed. But I do not know this for sure. How can I find out > >> why these functions were not specialized? (I.e. is there a threshold > >> that wasn't met, and if so, where is it located and what's its value?) > >>
Have you tried the new option-fprofile-partial-training ? -fprofile-partial-training can now be used to inform the compiler that code paths not covered by the training run should not be optimized for size. I tested by myself this week and it literally do not optimize at all the functions not touched by the training Regards Victor Rodriguez > >> Thanks!
