On Sat, Oct 14, 2017 at 10:39 AM, Eric Botcazou <ebotca...@adacore.com> wrote: >> This looks good. OK for the trunk. > > FWIW I disagree. The patch completely shuns the existing implementation of > the pass, which is based on a forward scan within basic blocks to identify the > various interesting instructions and record them, and uses full-blown def-use > and use-def chains instead, which are much more costly to compute. It's not > clear to me why the existing implementation couldn't have been extended. > > The result is that, for targets for which the pass was initially written, i.e. > targets for which most (all) arithmetic instructions clobber the flags, the > pass will be slower for absolutely no benefits, as the existing implementation > would already have caught all the interesting cases. > > So it's again a case of a generic change made for a specific target without > consideration for other, admittedly less mainstream, targets...
I agree with Eric here. Richard. > -- > Eric Botcazou
