https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91683
--- Comment #13 from Segher Boessenkool <segher at gcc dot gnu.org> --- 1) Yes, you'll be better of without calling gen_reg_rtx, certainly. 2) I don't see how you can make the undo scheme support this, without big cost and/or big restructuring. If we can replace this scheme by something much more local, that would be great, it is one of the biggest problems combine has (others are the sheer amount of garbage rtl it makes, and all the special cases it has accumulated over the years). 3) Do we want to prohibit calling gen_reg_rtx during combine? Why did we want it, before?
