Faster compilation speed

[David Edelsohn]

	Here's an interesting (aka depressing) data point.  My previous
cache miss statistics were for GCC -O2.  At -O0, GCC's cache miss
statistics stay the same or get up to 20% *worse*.  In comparison, the
cache statistics for IBM's compiler without optimization enabled *improve*
up to 50 for the same reload.c and insn-recog.c input files compared to
optimized.

	GCC has some sort of overhead, maybe the tree->RTL conversion as
Dan mentioned, which really hurts re-use at -O0.

David