mk.conf:

USE_EGCS=1
USE_EGCS_HAIFA=1

So far i386 -current kernel, userland and X are happy with:

        for kernel:
        -O3 -mpentium    --mfancy-math-387 -fsched-interblock \ 
                         -fsched-spec -fsched-spec-load -fbranch-count-reg
        ... -mpentiumpro ...

        for userland, same but:
            -march=i686
            -march=pentium

with the caveat that the "static"s have to be excised from
lib/csu/i386_elf/crt0.c and the bootblocks have to be
recompiled with less optimization (no optimization at all
works fine).

-current on an Alpha box is happy with:

        -O3 -mcpu=21064 -mmemory-latency=main -fsched-interblock \ 
                        -fsched-spec -fsched-spec-load -fbranch-count-reg

for both the kernel and userland.

Incidentally, feeding "A>>HR" into malloc(3) seems to make my
boxes a little snappier feeling.   I have no quantitative
measurements, though, so it could just be my imagination.  -:)

(I haven't hit anything that's triggered the "A" feature
yet, except for a small script that set a resource limit too low...)

        Sean.