https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79185
--- Comment #6 from Vladimir Makarov <vmakarov at gcc dot gnu.org> --- (In reply to Jeffrey A. Law from comment #5) > Is the CLOBBER even necessary anymore? Wasn't its only purpose to tell > dataflow that r88 was dead because our old flow analysis couldn't? > I guess the CLOBBER was used in the very old live analysis which existed before DF-infrastructure introduction. > Doesn't the DF infrastructure get this right? If it does, then we might be > able to drop the CLOBBER entirely which might simplify the problem. No. DF infrastructure can not recognize it. One time global.c was rewritten to use live analysis done by DF and it would have had the same problem. I remember Ken Zadeck thought about implementing live analysis on subreg level but he did not finish the work. Another problem is that LRA does not use DF-infrastructure as it was too slow (I tried it first and using it made LRA at least 2 times slower than reload). So even if DF implements it we still need to do the same thing in LRA live analysis.
