On Wed, Jun 24, 2015 at 09:40:28PM -0600, Jeff Law wrote: > On 06/24/2015 05:29 PM, Segher Boessenkool wrote: > >A few define_split's in the i386 backend modify RTL in place. This does > >not work. This patch fixes all cases that do PUT_MODE on existing RTL.
> > * config/i386/i386.md (various splitters): Use copy_rtx before > > doing PUT_MODE on operands. > Are the copies really needed? If we're slamming a mode into an > ix86_comparison_operator, we should be safe since those can't be shared. > Copying is just wasteful. combine still holds pointers to the old rtx, which is what is causing the problem in the PR (it does always unshare things in the end, but it does not make copies while it's working). Either those few splitters need to do the copy (and some already do), or combine has to do the copy always, which would be more wasteful. It has always been this way as far as I see? Am I missing something? [ I see i386 also does PUT_CODE in a few more splitters, hrm. ] Segher
