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Re: [Gcl-devel] New random tester failures

From: Paul F. Dietz
Subject: Re: [Gcl-devel] New random tester failures
Date: Tue, 07 Dec 2004 18:58:29 -0600
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040803

Camm Maguire wrote:
Greetings, and thanks again as always, Paul!

I have a fix for this, as yet uncommitted.  But I realize as I chase
these down that I need very frequently to rebind arguments in a let*
using gensymmed temporaries, and this has reminded me of a
longstanding performance problem with this I'd like to fix.  In brief,
doing this destroys any type information that may exist for the
rebound variable via declaration or proclamation.

I have plan A and plan B, and would like to solicit your opinion:

A) When the compiler expands macros, or funcalls compiler macro
functions, detect whether new bindings are introduced, and if so,
recursively macroexpand the form, determine whether the binding is
changed in the body of the new let, and if not, add a declaration read
from a stack when appropriate at the head of the let.  Advantage --
centralized -- disadvantage -- could be slightly tricky.

Isn't this just a special case of the more general procedure of adding
declarations for locals that are not later assigned?  There's no need for
those locals to have been introduced by a macro.

B) Push declarations onto the environment passed to macroexpand, and
rewrite each relevant macro (mostly setf expanders and compiler
macros) to insert the declarations where appropriate.

I'm leaning toward A, but am quite open minded.

Either one sounds ok, although the first could be made more general.

Remember your aluding to an Allegro proposal by Duane Rettig (?) when
we discussed this before, but never could find this.

It's in the ACL 7.0 release notes.



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