On Wed, May 2, 2012 at 12:03 PM, Alexander Monakov <amona...@ispras.ru> wrote: > > > On Wed, 2 May 2012, Richard Guenther wrote: > >> That's surely too coarse - you will warn about options that _will_ >> have an effect. >> There is currently no easy way to glob all affected options. > > Yeah, that's unfortunate. Do we want to have a separate flag > (CL_OPTIMIZATION_O0) to mark such options? Apropos, following is a list of > options that affect the list of produced dump files at O0. If someone knows > an option that affects compilation at O0, but is not a part of this list, > please let me know. > > -fbranch-probabilities > -fbranch-target-load-optimize > -fcombine-stack-adjustments > -fexceptions > -fhandle-exceptions > -fschedule-insns > -fsplit-wide-types > -fvar-tracking-assignments > -fvar-tracking-assignments-toggle > >> I don't think we want to warn about -O2 -ftree-pre -O0 either, nor > > Huh, I don't see why. Please explain?
Because I routinely append -O0 to an existing command-line to disable optimization. I don't want to be spammed with unconditional warnings for this (btw, I think it should be a note(), not a warning). >> about -fno-tree-pre. > > Yeah, that's an oversight in the patch, should be easy to fix. > >> Overall I would expect people to have noticed that with -O0 these options >> have >> no effect when they've gone all the way to figure out the separate >> optimization >> options, no? > > At the moment people have two easy ways to find the list of optimization > options (-fverbose-asm and --help=optimizers), but O0 issue is mentioned > once not-quite-prominently in the manual and also in the FAQ in the wiki. > In my opinion, the amount of times I've seen this issue come up warrants > some effort on making it more visible (thus, a warning). So maybe prominently say that in the output of --help=optimizers (-fverbose-asm isn't to be found easily anyway). Thus, at the end of --help-optimizers print "Note: without any -On option, excluding -O0, most options do not have any effect" Richard. > Thanks > Alexander
