On 10/30/2011 09:20 AM, Tom de Vries wrote:
> Richard,
>
> I have a fix for PR50878.
Sorry, with patch this time.
Thanks,
- Tom
>
> A simplified form of the problem from the test-case of the PR is shown in this
> cfg. Block 12 has as direct dominator block 5.
>
> 5
> / \
> / \
> * *
> 6 7
> | |
> | |
> * *
> 8 9
> \ /
> \ /
> *
> 12
>
> tail_merge_optimize finds that blocks 6 and 7 are duplicates. After replacing
> block 7 by block 6, the cfg looks like this:
>
> 5
> |
> |
> *
> 6
> / \
> / \
> * *
> 8 9
> \ /
> \ /
> *
> 12
>
> The new direct dominator of block 12 is block 6, but the current algorithm
> only
> recalculates dominator info for blocks 6, 8 and 9.
>
> The patch fixes this by additionally recalculating the dominator info for
> blocks
> immediately dominated by bb2 (block 6 in the example), if bb2 has a single
> predecessor after replacement.
>
> Bootstapped and reg-tested on x86_64 and i686. Build and reg-tested on MIPS
> and ARM.
>
> Ok for trunk?
>
> Thanks,
> - Tom
>
> 2011-10-30 Tom de Vries <t...@codesourcery.com>
>
> PR tree-optimization/50878
> * tree-ssa-tail-merge.c (replace_block_by): Recalculate dominator info
> for blocks immediately dominated by bb2, if bb2 has a single predecessor
> after replacement.
Index: gcc/tree-ssa-tail-merge.c
===================================================================
--- gcc/tree-ssa-tail-merge.c (revision 180562)
+++ gcc/tree-ssa-tail-merge.c (working copy)
@@ -1604,7 +1604,10 @@ replace_block_by (basic_block bb1, basic
same_succ_flush_bb (bb1);
delete_basic_block (bb1);
- fix_dom_bb = VEC_alloc (basic_block, heap, 2);
+ if (single_pred_p (bb2))
+ fix_dom_bb = get_dominated_by (CDI_DOMINATORS, single_pred (bb2));
+ else
+ fix_dom_bb = VEC_alloc (basic_block, heap, 2);
VEC_safe_push (basic_block, heap, fix_dom_bb, bb2);
FOR_EACH_EDGE (e, ei, bb2->succs)
VEC_safe_push (basic_block, heap, fix_dom_bb, e->dest);
