Re: Merging stmt_ann_d into tree_statement_list_node

[Andrew MacLeod <amacleod at redhat dot com>]

On Mon, 2005-04-25 at 19:01, Kazu Hirata wrote:
> Hi Andrew,

> No, I would like to remove stmt_ann_t pointer from the stmt node, but
> not yet.  All I want to do in this project is to put
> tree_statement_list_node and stmt_ann_d next to each other in memory
> while doing necessary adjustments in the compiler.  Nothing more than
> that.
> 

does that buy us much?

> Yes, it is nice to get rid of stmt_ann_t pointer from the stmt node,
> and I want to eventually get that, but not in this project.  I think
> there are so many places that use "stmt" instead of "bsi".  They may
> either pass it to subroutines or put it in some internal data
> structures, so I would like to do that separately.  So if you like,
> the roadmap might be something like
> 
> 1. Put tree_statement_list_node and stmt_ann_d next to each other in
>    memory while doing necessary adjustments.
> 
> 2. Provide stmt_ann_from_bsi(), a function that gives you stmt_ann
>    given bsi.
> 
> 3. Let everybody use stmt_ann_from_bsi(), replace stmt_ann(), and
>    remove the stmt_ann_t pointer from the stmt node (if these are
>    possible at all).
> 
> 4. Hand off to Zdenek for his flat statement project.
> 
> I hope this message clarifies things.
> 

Then why not simply shorten this to:

1) put stmt annoation directly in the tree_statement_list_node

2) replace stmt_ann_t pointer in stmt with a pointer to its BSI, or the
tree_statement_list_node.  This makes bsi_from_stmt O(1) immediately.

3) all stmts now have access to the stmt_ann directly in the
stmt_list_node, nothing changes except get_stmt_ann() returns the
address of the stmt ann within the tree_stmt_list_node.

4) For fake stmts you will have to allocate a fake tree_stmt_list_node
which isnt linked with anything, and set the bsi pointer to that... then
you have the annotation and access to it from the stmt.

that seems like a quicker more direct approach then phasing it in
slowly, with less impact to anyone, and gives you immediate benefits. I
would think the patch to do this would be fairly small and
non-intrusive.

Andrew