needless deep recursion in gt-c-decl.h

[Per Bothner]

Geoff Keating wrote:
> Even if this particular case turns out to be impossible, it would be
> very hard to make an argument that there's always another reference to
> the DECL_RTL; and even if there actually always was another reference,
> you'd have to ask yourself whether the (tiny) speed increase is worth
> the extra complexity and the maintenance headache.

If the DECL_RTL is what causes the recursion to blow up, as I got
the impresson from your message, and it prevents the simple
iterate-on-TREE_CHAIN solution from working, then it could well be
worth it.  In fact, if it allows iterating on TREE_CHAIN, instead of the
more complicated and general solution, it would be a simplification.

> The patch I finally committed solves this problem in a more general
> way.

Yes, but by slowing down marking by 5%, when compile-time speed is a
major concern.
-- 
	--Per Bothner
per@bothner.com   http://www.bothner.com/per/