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Re: SIMPLE and fat pointers
- From: Diego Novillo <dnovillo at redhat dot com>
- To: Steven Bosscher <s dot bosscher at student dot tudelft dot nl>
- Cc: gcc at gcc dot gnu dot org, Paul Brook <paul at nowt dot org>
- Date: Fri, 5 Jul 2002 17:28:17 -0400
- Subject: Re: SIMPLE and fat pointers
- Organization: Red Hat Canada
- References: <1025819366.1932.37.camel@steven>
On Thu, 04 Jul 2002, Steven Bosscher wrote:
> G95 uses "fat pointers" because F95 needs array descriptors, so we use
> the PLACEHOLDER_EXPR and WITH_RECORD_EXPR tree codes. G95 is the second
> front end I know of that uses these nodes to implement unconstrained
> array types (the other is GNAT). G95 tries to translate its AST to
> SIMPLE, and we use the C tree expander to generate RTL.
>
> The C expander seems to have no problems with PLACEHOLDER_EXPR and
> WITH_RECORD_EXPR nodes. But in the SIMPLE grammar there's no such thing
> as an unconstrained array; SIMPLE doesn't really need these nodes.
>
I was almost tempted to ask you to simplify these types into
regular ARRAY types, but that would change type information for
G95's unconstrained arrays. Something which is likely to cause
problems.
> So I'm not sure these nodes will be supported in SIMPLE. But if the
> long-term goal is to make all front ends generate SIMPLE (and from what
> I understand, it is), then support for these nodes is important for all
> languages that support unconstrained arrays.
>
Do you have a grammar in mind for supporting these types in
SIMPLE?
Diego.