Re: [PATCH]: Make PRE handle globals

["Daniel Berlin" <dberlin at dberlin dot org>]

I have reverted the non-SCCVN parts of this patch.
I do not have time to track this miscompile down right now.

I am also not particularly enthused that it required duplicating decls
to get right.  I will probably redo this a different way as part of a
larger rework of some parts of PRE.

(Though if someone wants to track it down beforehand, feel free!).



On 7/6/07, Daniel Berlin <dberlin@dberlin.org> wrote:
> One of the longstanding deficiencies of GVNPRE (and FRE) was it's
> inability to optimize away duplicate loads from globals, as well as
> hoist them.
>
> The attached fixes this.  SCCVN knows how to value number globals
> properly, which takes care of FRE.
>
> PRE needed a little more work.  In order to be able to store different
> values on a global at different times, we "unshare" the global locally
> when creating it's value expression (this does not affect the original
> IR), and have a pointer map for value handles for decl's.
>
> Bootstrapped and regtested on i686-darwin
>
> Committed to mainline
>
> 2007-07-06  Daniel Berlin  <dberlin@dberlin.org>
>
>         * tree-ssa-sccvn.c (expr_has_constants): Handle tcc_declaration.
>         (try_to_simplify): Ditto.
>         (visit_use): Ditto.
>         * tree-vn.c (set_value_handle): Use decl_vh_map for decl value
>         handles.
>         * tree-flow-inline.h (get_value_handle): Ditto.
>         * tree-ssa-pre.c (decl_vh_map): New.
>         (decl_node_pool): New.
>         (can_value_number_operation): Support DECL_P.
>         (can_PRE_operation): Ditto.
>         (create_expression_by_pieces): Ditto.
>         (find_existing_value_expr): Modify to differnetiate between
>         addressing and top level.
>         (create_value_handle_for_expr): Handle DECL's.
>         (poolify_tree): Ditto.
>         (make_values_for_phi): Don't insert into PHI_GEN during FRE.
>         (make_values_for_stmt): Handle DECL's properly.
>         (init_pre): Reorg to not init useless things during FRE.
>         (fini_pre): Ditto.
>         * tree-flow.h: Include pointer-set.h.
>         (decl_vh_map): Declare.
>         * Makefile.in (TREE_FLOW_H): Add pointer-set.h