On Wed, Feb 29, 2012 at 4:12 AM, William J. Schmidt
<wschm...@linux.vnet.ibm.com> wrote:
> This patch fixes PR52424 by pushing a missing marker onto
> const_and_copies_stack before calling dom_thread_across_edge. This bug
> has resulted in lost copy propagation opportunities in the presence of
> edge threading.
>
> Bootstrapped and tested with no regressions on powerpc64-linux-gnu. I'm
> waiting on Jiangning Liu to verify the patch fixes his performance
> concern. Provided it does, is this OK for trunk?
Ok.
> Also, this bug has apparently been there for a long time. Should we
> consider backporting the fix to 4.6 and/or 4.5?
It's even present on the 4.1 branch, so I guess it has been there forever.
Not worth backporting IMHO.
Thanks,
Richard.
> Thanks,
> Bill
>
>
> 2012-02-28 Bill Schmidt <wschm...@linux.vnet.ibm.com>
>
> PR tree-optimization/52424
> * tree-ssa-dom.c (dom_opt_leave_block): Push a marker before
> calling dom_thread_across_edge.
>
>
> Index: gcc/tree-ssa-dom.c
> ===================================================================
> --- gcc/tree-ssa-dom.c (revision 184625)
> +++ gcc/tree-ssa-dom.c (working copy)
> @@ -1779,6 +1779,9 @@ dom_opt_leave_block (struct dom_walk_data *walk_da
> && (single_succ_edge (bb)->flags & EDGE_ABNORMAL) == 0
> && potentially_threadable_block (single_succ (bb)))
> {
> + /* Push a marker on the stack, which thread_across_edge expects
> + and will remove. */
> + VEC_safe_push (tree, heap, const_and_copies_stack, NULL_TREE);
> dom_thread_across_edge (walk_data, single_succ_edge (bb));
> }
> else if ((last = last_stmt (bb))
>
>
