Hi Segher, > Thank you for telling the maintainer of combine the basics of what all of this > does! I hadn't noticed any of that before.
You're welcome. I've also been maintaining combine for some time now: https://gcc.gnu.org/legacy-ml/gcc/2003-10/msg00455.html > They can be, as clearly documented (and obvious from the code), but you can > not ever have that in the RTL stream, which is needed for your patch to do > anything. That's the misunderstanding; neither this nor the previous SUBREG patch, affect/change what is in the RTL stream, no COMPARE nodes are every changed or modified, only eliminated by the propagation/fusion in combine (or CSE). We have --enable-checking=rtl to guarantee that the documented invariants always hold in the RTL stream. Cheers, Roger
