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. _______________________________________________ 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"
