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Re: [Gcl-devel] Re: subtypep issues

From: Paul F. Dietz
Subject: Re: [Gcl-devel] Re: subtypep issues
Date: Wed, 31 Aug 2005 21:08:49 -0500
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.11) Gecko/20050729

Camm Maguire wrote:

Yes, it does seem as a construct to aid in array compilation
optimization.  The point to me is that I don't see the overwhelming
benefit given the definition, though there may be some.  The big issue
in our array optimization is to be able to know the element type, rank
and sizes to calculate references quickly.  This logic does not
depend on displacement as far as I can see, nor even if a fill pointer
exists as we use the same slot for the length whether or not it is an
adjustable fill pointer.  We don't inline adjust-array, though I
suppose we could.

The benefit is that for a simple array, you can pull out the pointer
to the contents and (if you know the non-lowest order dimensions)
you can compile accesses inline as the equivalent C array access.

If the array is not simple, you must assume that it may have
its displacement status modified or its dimensions adjusted any time
you call some possibly redefinable function.

To this end, the following tests may need adjustment:


I agree those are bad, and will be removed. But...


... these are good tests, for the reason Christophe explained.


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