refinements to definition of TREE_READONLY ?

[Richard Guenther]

On Fri, Jul 11, 2008 at 6:15 PM, Olivier Hainque <hainque@adacore.com> wrote:
> Hello,
>
> According to comments in PR/35493, when DECL_INITIAL is null on a
> TREE_READONLY decl, the middle-end may assume the value to be zero.
>
> This is not explicit from the current definitions in tree.h, we'd
> like to understand if this is actually the case and to suggest a doc
> extension to this effect.

A doc extension is ok.

> We'd also like to get to an agreement on what TREE_READONLY means on a
> decl with non static storage, if anything at all.

Good question...

> The kind of issues we're seeing is ...
>
>  Ada front-end sets TREE_RO and DECL_INITIAL on a stack decl with
>  initializer but never assigned later on,
>
>  gimplify_decl_expr turns this into an explicit assignment,
>  clears DECL_INITIAL and leaves TREE_RO set (creating an
>  unexpected assignment with TREE_RO on the lhs).

... I suggest to not clear DECL_INITIAL here.

>  later middle-end passes (e.g. tree-sra) turn this into an
>  assignment from 0 (null DECL_INITIAL).

But in the end tree-sra shouldn't try to look at DECL_INITIAL from non-static
storage.

So it looks like there are multiple issues here and a bug in tree-sra.

Richard.

> Thanks in advance for your feedback,
>
> Olivier
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