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Re: bounded pointers in RTL


Richard Henderson <rth@cygnus.com> writes:

> Mostly what I'm asking is: does the transformation happen entirely
> in expand_expr and it's subroutines?

I blew the dust off my 2.7.2 version and ran it with `-da'.  No
concat3s appeared in any debug file.  The only occurrences of BSI mode
were for reg use notes, setting the return-value hard reg, and
extracting subregs from the return value hard reg.

> It sounds like most of it happens up front in expand_expr, but I
> can't tell if something persists.

All of it happens in expand_expr.

> It sounds as if a good implementation of bounded pointers is
> going to be a lot of work no matter which way it gets done.
> My feeling at this moment is that the effort of doing it via trees
> will not differ significantly from the effort of doing it via
> rtl ...

Having done a lot of work the RTL way, I was hoping to avoid doing the
same amount for trees.  Oh well, I guess that's the price of progress. 8^)

> ... and further that doing it via trees is more aligned with
> where we'd like to see the compiler progress.  

Well, on several occasions have stuck my foot in it and stated
publicly that I wanted to do things "The Right Way".  8^)

> Currently, Jason and Mark and the gods of tree structure; Mark
> is currently working on a documenting (ir.texi) the language/
> middle end interface.  I'm peripherally aware that there is 
> probably some commonization that needs to happen between Java
> and C++, and (shortly) C.
> 
> ...  What's needed is a project to force the issue.

BPs will be one such project.  I gotta get this stuff done, and we
shouldn't booger-up the code with outmoded/misguided ways of doing
things.

I'm going to think about this and work up some examples of how
to do BPs in trees then come back to the list for feedback.

Greg


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