On Wed, Oct 16, 2002 at 02:20:42PM +0200, Maciej W. Rozycki wrote:
> It also introduces an indirect call (jump?) overhead. Anyway, you don't
> need to sacrifice anything. We may simply assume the universally
> compatible way is the R3k one (be it sysmips() or whatever, if it gets
> replaced). Then there is the branch-likely way, which requires
> branch-likely support (thus excludes R3k-class processors). Then there is
> the ll/sc way, which requires ll/sc (thus excludes R3k-class processors
> and ones that lack the ll/sc instructions). And you select the minimum
> set of features required at the build time.
sysmips is history with current glibc since the Linux kernel emulates
LL/SC for CPUs that don't have it. This emulation is actually faster than
sysmips. (You'd think it's slower because it's one syscall vs. two
emulated instructions. But with LL/SC glibc can use test-and-set
which enables a more efficient linux-threads mutex implementation.)
AFAIK, current Linux distributions based on glibc-2.2.5 were built for
R3K be default and thus used sysmips even on platforms which have
> > But all that is of interest only, if VR41XX-like platforms
> > would use a glibc from a binary distribution like RedHat or
> > Debian (I use Debian for development, but have a custom
> > compiled glibc for production use).
> I wouldn't care of distributions -- if one really needs optimized
> binaries it may make them be build somehow (either by doing the task
> oneself or by convincing someone else).
OK, that simplifies the issue. I will prepare a patches for
Linux and glibc.