Here is another patch that fixes the first of my examples. (let* ((x (random)) (y x)) (eq? x y)) now folds to (begin (random) #t). It turned out to be much smaller than the previous approach. Is it all right if I push this?
I'm not sure how to make the other one work yet, but I will think about it. I will send a separate email about the CPS stuff. Noah On Fri, Feb 17, 2012 at 3:13 AM, Andy Wingo <wi...@pobox.com> wrote: > Hi Noah, > > On Fri 17 Feb 2012 03:22, Noah Lavine <noah.b.lav...@gmail.com> writes: > >>>> (let* ((x (random)) >>>> (y (list x)) >>>> (z (car y)) >>>> (eq? x z)) >>> >> To make sure I understand, in the x-y-z example, psyntax would produce >> different gensyms for x and z, but peval could merge them later on, >> right? > > When processing `z' for value, it should reduce to `x'. The strategy is > to do computation at compile time -- if at compile time, `z' can reduce > to `x', peval will do it. But there is no global "give me all the > things that are equal to x" procedure. > >> In that case, peval would maintain the invariant "if two values must >> always be the same, they have the same gensym". Correct? > > More like the other way around! If one identifier partially evaluates > to another, then they will have the same gensym, and therefore are the > same identifier. > >>> This is related to range analysis. But, it's also something that's >>> easier to do with an explicit notion of control flow (i.e. a CPS IR). >> >> Yes, I think you're right. I would be very interested in working on a >> CPS IR, but I remember you had a blog post a couple months ago where >> you said you weren't sure if CPS or ANF was better for Guile. What do >> you think about intermediate representations now? > > I have no idea :-) I am a little hesitant to move to either one right > now, because our stack machine penalizes named temporaries, and with CPS > (or ANF -- which is closer to what we have, but without the advantage of > treating control flow on a first-class level) you would get a lot more > named temporaries. But my uncertainty is also because I don't know what > it would make the compiler look like. Would it simplify things or would > it add complication? I don't know. > > But, writing a pass to turn tree-il into some CPS language would be a > really interesting step in any case. If you wanted to work on that, I'm > sure it would be instructive to us all. > > My humble thoughts :) > > Cheers, > > Andy > -- > http://wingolog.org/
0001-Optimize-Equality-Primitives.patch
Description: Binary data
