Segher Boessenkool <seg...@kernel.crashing.org> writes: > On Fri, Dec 13, 2019 at 12:45:47PM +0000, Richard Sandiford wrote: >> combine's to blame for the fact that we have two pseudo registers rather >> than one. See the comments about the avr-elf results in: >> >> https://gcc.gnu.org/ml/gcc-patches/2019-11/msg02150.html >> >> for more details. > > It's not combine's fault if register allocation does a bad job. And we > should *not* generate worse code in combine just because it exposes a > problem in RA (with 2-2 and make_more_copies we generate better code on > average, on all targets I tested, 50 or so). > > If having two pseudos here is not an advantage, then RA should optimise > one away. It does usually, why not here?
I didn't say it was combine's fault that RA was bad. I said it was combine's fault that we have two pseudos rather than one. Richard
