On 8/1/2018 10:03 PM, Stephen Hemminger wrote: > On Wed, 1 Aug 2018 18:03:04 +0000 > Yongseok Koh <ys...@mellanox.com> wrote: > >>> On Jul 31, 2018, at 11:07 AM, Stephen Hemminger >>> <step...@networkplumber.org> wrote: >>> >>> On Tue, 31 Jul 2018 18:48:40 +0200 >>> Adrien Mazarguil <adrien.mazarg...@6wind.com> wrote: >>> >>>> On Tue, Jul 31, 2018 at 09:30:54AM -0700, Stephen Hemminger wrote: >>>>> Declaring variables as register in C is a leftover from an earlier >>>>> era (like cassette tape decks in cars). >>>> >>>> I don't agree here. It's a hint for compilers and developers that the >>>> address of such variables won't be needed (and cannot be taken) to enable >>>> whatever optimizations are possible knowing this. >>>> >>>> Somewhat like inline functions, it's not a forced optimization, just a >>>> useful hint that shouldn't hurt if used wisely. >>>> >>>> Besides, cassette decks are not dead yet :) >>> >>> If you look at the code, that is not how register is being used (ie. don't >>> take >>> address of this). It seems like an attempt at optimization. >> >> I know compilers are smart enough and the occurrences in mlx4/5 were made >> from >> my old fashioned habit. But, I don't see any urgency to push this patch in RC >> stage even though I'm 99% sure that it is harmless. And in general I don't >> even >> understand why we can't live with that if it isn't harmful (or a violation) >> but >> informative. I mean no badness but at least one goodness :-) >> >> Thanks, >> Yongseok >> > > Sure, this is intended for next release not rc stage. > Just trying to clean up code base where I see it.
I agree with Yongseok, at worst they show the intention of the developer, I don't see motivation to remove them unless they are doing something wrong, which seems not the reason of this patch. And although I found some information that says "register" ignored completely for gcc, I can see it differs when optimization disabled. I am not saying practically it differs, since we enable optimization expect from debugging, most probably there is no practical difference between having the keyword or not, but what I am trying to say is it not completely ignored either.
