On Thu, Oct 13, 2011 at 05:02:58PM -0400, Arnaud Lacombe wrote: > Hi, > > On Thu, Oct 13, 2011 at 4:47 PM, YongHyeon PYUN <pyu...@gmail.com> wrote: > > On Thu, Oct 13, 2011 at 12:59:35AM -0700, per...@pluto.rain.com wrote: > >> YongHyeon PYUN <pyu...@gmail.com> wrote: > >> > On Wed, Oct 12, 2011 at 10:07:02AM -0400, Karim wrote: > >> > > ... why are we ORing the same call twice isn't the same thing > >> > > as calling it once: > >> > > > >> > > bmsr = PHY_READ(sc, E1000_SR) | PHY_READ(sc, E1000_SR); > >> > > >> > The E1000_SR_LINK_STATUS bit is latched low so it should be read > >> > twice. > >> > >> It might not be a bad idea to check the generated code to be sure > >> that the read _is_ being done twice. ?An optimizer might well come > >> to the same conclusion as Karim, and discard the "redundant" second > >> instance (unless there's a "volatile" declaration somewhere in the > >> expansion of PHY_READ, to explicitly indicate that it has side > >> effects). > > > > Last time I checked it, compiler generated correct code. > > Tried again on amd64 and I can still see the code is there. > > > What about other architecture (especially i386) ? which optimization
Don't use i386 so I don't know. > level did you use ? which compiler version ? CURRENT, default optimization(O2). > > About the last question, I know for sure that there has been change in > FreeBSD's gcc between 7-STABLE, and FreeBSD -CURRENT. > > I agree with perryh@ than such hardware requirement _requires_ being > explicit in the code, ie proper `volatile' marking. > I'm not saying adding more safe belt is bad idea. If you have a patch please submit it. I don't like touching every PHY drivers. > - Arnaud > _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
