I've configured the ompi trunk (nightly tarball 1.7a1r25927) on an SGI Altix.
I used no special arguments indicating that this is an Altix, and there does not appear to be an altix-specific file in contrib/platform.
My build fails as follows:
make: Entering directory `/mnt/home/c_phargrov/OMPI/openmpi-trunk-linux-ia64/BLD/opal/tools/wrappers'
../../../opal/.libs/libopen-pal.so: undefined reference to `opal_timer_altix_mmdev_timer_addr'
../../../opal/.libs/libopen-pal.so: undefined reference to `opal_timer_altix_freq'
collect2: ld returned 1 exit status
The configure-generated opal_config.h contains
#define MCA_timer_IMPLEMENTATION_HEADER "opal/mca/timer/altix/timer_altix.h"
Nothing appears to have been built in BUILDDIR/opal/mca/timer/altix.
However, BUILDDIR/opal/mca/timer/linux has been built.