[RFC][PATCH] Extend store ccp

[Richard Guenther]

On Tue, 19 Jun 2007, Revital1 Eres wrote:

> 
> Hello,
> 
> Following previous review
> (http://gcc.gnu.org/ml/gcc-patches/2007-04/msg01787.html); attached is
> the patch which enhance store ccp to propagate constants from stores to
> loads when the current implementation fails due to alias uncertainty;
> 
> For example:
> 
> S[5].x = 4;
> S[5].y = 0;
> 
> x = S[5].x;
> 
> ===>
> 
> S[5].x = 4;
> S[5].y = 0;
> 
> x = 4;
> 
> This transformation extend the current implementation of the ccp propagator
> in two places:

Did you do any performance measurement to tell compile-time and
runtime effects of this patch?  (if not, I suggest cc1files for
compile-time and SPEC for runtime effects)

Richard.

> 2007-06-19  Revital Eres  <eres@il.ibm.com>
> 
>         * tree-ssa-ccp.c (visit_assignment): Call get_stmt_rhs_def_stmt
>         while performing the propagation.
>         * tree-ssa-propagate.c (do_store_ccp): New function.
>         (add_edge): New function.
>         (add_ssa_edge): Add an edge for every use by walking the virtual
>         def-use chain.
>         (get_stmt_rhs_def_stmt): New function to get
>         the defining stmt of a use by walking the virtual use-def chain.
>         (replace_vuses_in): Call get_stmt_rhs_def_stmt
>         to perform the final replacement.
>         * tree-ssa-propagate.h (get_stmt_rhs_def_stmt): Declare.
>         * tree-flow.h (offset_overlaps_with_access): Declare.
> 
> Comments are welcome.
> Thanks,
> Revital
> 
> 
> (See attached file: patch_ccp_19_6.txt)(See attached file: store_ccp-1.txt)