Re: Hotspot. Dynamic compilers "better" than static one?

["Dr Richard A. O'Keefe" <ok@atlas.otago.ac.nz>]

Robert Dewar wrote:
<<Many modern compilers support profiling feedback.>>

> Actually fewer production compilers than you might imagine actually use
> this approach, though of course it has appeared in research compilers for
> a long time.

Sun's C, Pascal, and Fortran compilers for SPARC do this.
Digital's compilers for the Alpha do this.
The MIPS compilers have done this even longer.
In fact, of the machines I have or could get accounts on here,
the only ones that DON'T have 'production compilers' already
installed that use profile-driven-feedback are Macs and PCs.

What may be of more interest is that I have seen profile-driven
feedback make a difference of 0-20%, with 0% actually being quite
common, and I've had better performance using gcc -O6 (without
feedback) on an Alpha than I've had from the Dec compiler _with_
feedback.

So profile-driven feedback HAS BEEN SHIPPING FOR SEVERAL YEARS
in production compilers from MIPS, Digital, and Sun, and that's
just the ones I've used.  But it's only one technique, and not
always the most important.