Hi, On Fri, Nov 19 2021, Jan Hubicka wrote: >> > Hi, >> > >> > On Fri, Nov 12 2021, Martin Jambor wrote: >> > > Hi, >> > > >> > > using -fno-semantic-interposition has been reported by various people >> > > to bring about considerable speed up at the cost of strict compliance >> > > to the ELF symbol interposition rules See for example >> > > https://fedoraproject.org/wiki/Changes/PythonNoSemanticInterpositionSpeedup >> > > >> > > As such I believe it should be implied by our -Ofast optimization >> > > level, not only so that benchmarks that can benefit run faster, but >> > > also so that people looking at -Ofast documentation for options that >> > > could speed their programs find it. >> > > >> > > I have verified that with the following patch IPA-CP sees >> > > flag_semantic_interposition set to zero at Ofast and that info and pdf >> > > manual builds fine with the documentation change. I am bootstrapping >> > > and testing it now in order to comply with submission criteria but I >> > > don't think an Ofast change gets much tested. >> > > >> > > Assuming it passes, is the patch OK? (If it is, I will also add a note >> > > about it in the "Caveats" section in gcc-12/changes.html of wwwdocs >> > > after I commit the patch.) >> > > >> > >> > Unfortunately, I was wrong, there are testcases which use the optimize >> > attribute to switch a function to Ofast and those ICE because >> > -fsemantic-interposition is not an optimization flag and only >> > optimization flags can change in an optimize attribute (AFAIK, I only >> > had a quick glance at the results). >> > >> > I am not sure what is the right way to tackle this, whether to set the >> > flag at Ofast in some nonstandard way or make the flag an optimization >> > flag - probably affecting function definitions, having it affect >> > call-sites seems too fine-grained. I will try to discuss this on IRC on >> > Monday (and hope such change is still doable early stage3). >> > >> > Sorry for posting this a bit prematurely, >> >> Hi, >> >> This patch turns flag_semantic_interposition to optimization option so >> it can be enabled with per-function granuality. This is done by adding >> the flag among visibility flags into the symbol table. This fixes the >> behaviour on the testcase I added to testsuite. >> >> There are bugs where get_availability misbehaves on partitioned program. >> We can also use the new flag to fix those, but I will do that >> incrementally. >> >> The -Ofast change should be safe now. > > Also forgot to say it explicitly, the patch is OK, so please commit it. >
Thanks a lot for the enabling patch. I have committed mine after re-testing. Martin
