GCC is not a very slow C compiler in term of compiled LOC/s (although the difference in speed between -O0 and -O3 is embarrassing). What makes compiling Unix software so slow, is the way source code is organised, headers which include headers, cpp having to generate lots of code, and all the other Unix crap.
Once I investigated why a 15MLOC project took over an hour to build. Apparently, on average, each file was processed over 2,000 times; precompiled headers helped somewhat, but even with precompiled headers, each header was still individually compiled over 200 times. I'd expect GCC compiling Plan 9 at a speed reasonably comparable to kencc. I will refrain making comments on how wise that is, however. -- Aram Hăvărneanu
