On Thu, Sep 10, 2020 at 05:50:40PM -0500, Qing Zhao wrote: > >>>> Shrink-wrapped stuff. Quite important for performance. Not something > >>>> you can throw away.
^^^ !!! ^^^ > > Start looking at handle_simple_exit()? targetm.gen_simple_return()… > > Yes, I have been looking at this since this morning. > You are right, we also need to insert zeroing sequence before this > simple_return which the current patch missed. Please run the performance loss numbers again after you have something more realistic :-( > I am currently try to resolve this issue with the following idea: > > In the routine “thread_prologue_and_epilogue_insns”, After both > “make_epilogue_seq” and “try_shrink_wrapping” finished, > > Scan every exit block to see whether the last insn is a ANY_RETURN_P(insn), > If YES, generate the zero sequence before this RETURN insn. > > Then we should take care all the exit path that returns. > > Do you see any issue from this idea? You need to let the backend decide what to do, for this as well as for all other cases. I do not know how often I will have to repeat that. There also is separate shrink-wrapping, which you haven't touched on at all yet. Joy. Segher
