Re: C++: Why do we nreverse CLASSTYPE_TAGS

[Mark Mitchell <mark at codesourcery dot com>]

> I do not doubt that nreverse() is cheap -- the point here isn't to win
> some possible micro-seconds.  It is about datatype structures,
> associated algorithms and operations.  The main point being that
> it makes sense to use a hash-table for serving the purpose of
> CLASSTYPE_TAGS, but then, it does not make sense to maintain a given
> order or to reverse that order.  That is the fundamental reason for my
> asking the original question. 

OK, let's think in the broader context.

There should ideally be one data structure: a list of the members
declared in the class, with, if there are lots of members, a hash table
to index those things.

You need both the list and the dictionary; you want to be able to do
things like iterate through the list of FIELD_DECLs in order, and also
to find them quickly.

I don't think CLASSTYPE_TAGS should need to exist at all; everything
that you can find there should also be something you can find on
TYPE_FIELDS.

So, I'd suggest (1) eliminate CLASSTYPE_TAGS, and (2) add a hash table
for TYPE_FIELDs if there are lots of members.

-- 
Mark Mitchell
CodeSourcery, LLC
mark at codesourcery dot com