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? 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
