On Tue, Feb 26, 2019 at 08:13:32PM -0700, Jeff Law wrote: > My point is we see this stuff all the time on common platforms with > simple -O2 optimization. It deleted something like 2k dead insns on an > x86_64 bootstrap before I added goof'd up trap_p test. What I don't > have a sense of is how often removing that trivially dead code > ultimately helped cprop on x86_64. But the amount of trivially dead > code on a standard -O2 bootstrap was a huge surprise.
It is a big surprise. I wonder what causes it; I don't see it? Do you have an example maybe? Or are you talking not about the subreg thing, but just about the dead code? Most of that will be deleted a little later anyway. Maybe some more places should call delete_trivially_dead_insns (). Segher
