On Thu, Jan 18, 2018 at 8:03 AM, Sebastian Perta <sebastian.pe...@renesas.com> wrote: > Hi, > > Thank you! > As the description says this finds equivalent functions, I would like to find > identical sequences inside > functions but at least this will provide all the up to date tools to compare > code sequences, thank you again!
There is already some identical sequence finding (code hoisting) in GCC 7 (and above), see https://gcc.gnu.org/ml/gcc-patches/2016-07/msg00360.html for the patch. Thanks, Andrew > > Best Regards, > Sebastian > > >> -----Original Message----- >> From: Martin Jambor [mailto:mjam...@suse.cz] >> Sent: 18 January 2018 15:18 >> To: Sebastian Perta <sebastian.pe...@renesas.com>; gcc- >> patc...@gcc.gnu.org >> Cc: l...@gcc.gnu.org >> Subject: Re: New code merge optimization? >> >> Hi, >> >> On Thu, Jan 18 2018, Sebastian Perta wrote: >> > Hello, >> > >> > I am interested in implementing a new pass in gcc to merge identical >> > sequences of code in GCC to be used mainly for RL78. >> > The commercial RL78 compilers have such algorithms implemented and >> they make >> > quite good use of it. >> > Opportunities arise from the limited capabilities of RL78, for other >> > targets >> > this might be a lot less useful. >> > >> > A while ago I found the following: >> > https://www.gnu.org/software/gcc/projects/cfo.html >> > And I ported all algorithms to gcc 4.9.2 and tried it on RL78 and RX and >> > this is what I found out: >> > For RX: no visible improvements with any of them >> > For RL78: some minor improvements only with -frtl-seqbastr: >> > Compiling all the C files from gcc/testsuite/gcc.c-torture/execute/*c with >> > "-Os" and "-Os -frtl-seqabstr" (using the modified gcc 4.9.2) >> > The algorithm was effective only in 60 files(out of 1643 files, that's only >> > 0.03% of the files currently present in >> > gcc/testsuite/gcc.c-torture/execute) >> > On those 60 files I got an average of 6.5% improvement with the best >> > improvement for pr58574.c (36.4%). >> > >> > What do you think: is it worthwhile porting this to the trunk or I will >> > just >> > waste my time? >> > Or should I start fresh? Maybe start from here: >> > http://llvm.org/docs/MergeFunctions.html? >> >> Martin Liška contributed identical code folding to GCC quite a few years >> ago now. Look up the -fipa-icf option. If that is not enough for you, >> starting from that seems more natural. >> >> Martin >> >> > >> > Gimple or rtl? >> > I suppose the preferred way will be to do this in gimple; however based on >> > what I did so far, it's more likely to find identical sequences in rtl >> > (for >> > RL78). >> > >> > Any thoughts? Thank you! >> > >> > Best Regards, >> > Sebastian > > > > Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, > Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered > No. 04586709.
