bootstrapping with profiling feedback?

[Jeff Garzik]

Has anyone done any work towards inserting a -fprofile-arcs step into 
"make bootstrap"?  A search of gcc and gcc-patches list archives didn't 
reveal anything immediately...

I'm assuming an implementation would look something like:

build stage1 using platform compiler
build stage2 using stage1 and -fprofile-arcs
build stage3 using stage2 and -fbranch-probabilities
build stage4 using stage3 and -fbranch-probabilities
compare stage 3 and 4 .o files

Maybe this could be called "make profilestrap"?  ;-)