I happened to google WHIRL today (the intermediate language
used by the SGI compilers), and found that is the basis of the
Open64 compiler.

A specification of WHIRL is available at
www-unix.mcs.anl.gov/OpenAD/open64A.pdf

Does anyone happen to know anything about the status of
Open64 compilers for IRIX? (Now if only there were open-licensed
header files...)