Integer micro-benchmarks [Smalltalk Multi-Precision Numerics vis-a-vis Highly Optimized Fixed Size Integer C++ Numerics]

[Daniel Berlin]

On Wed, 25 Apr 2001, John S. Yates, Jr wrote:

> On Tue, 24 Apr 2001 19:32:32 -0400 (EDT), Daniel Berlin <dan at www.cgsoftware.com> wrote:
>
> >Errr, this is pretty basic PRE and loop hoisting.
> >
> >In other words, it's done by anyone taking a college compiler optimization
> >course.
> >--Dan
>
> Two cents from an erstwhile professional compiler-writer.
>
> Loop hoisting is indeed well known and widely practiced
> (especially if all that is being hoisted is side-effect
> free expression evaluation operations).
>
> PRE (Partial Redundancy Elimination) is much less widely
> known or implemented.  In fact I would be VERY suprised if
> MS has implemented it since on average it has relatively
> little payoff and tends to increase code size.

What?
Are you joking?
I haven't seen the source to a compiler without PRE in many years.
Most recent ones i've seen use SSA based PRE, which is even a more complex
implementation of PRE.
And claiming it has little payoff?
That's just funny.
I'll put money it's the main speed increasing code transform in most
compilers. Especially if it includes invariant code motion.
Please do a google search on "Partial redundancy compiler course"

If you really believe the above, I have a hard time believing you are any
kind of compiler professional.
--Dan