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Re: [PATCH] Fix PR61221


On May 19, 2014 6:57:52 PM CEST, Jeff Law <law@redhat.com> wrote:
>On 05/19/14 06:54, Richard Biener wrote:
>>
>> In this PR we run into the issue that releasing SSA names from
>> FRE/PRE elimination corrupts the VN lattice and thus the VN lookup
>> we perform for removing redudnant stores ICEs.  The patch works
>> around the particular case by making unreachable code detection
>> in SCCVN more optimistic by ignoring backedges during reachability
>> computation and by not doing any elimination on unreachable blocks.
>>
>> I still have to think about a "proper" fix to the underlying issue
>> (propagate_value_into_stmt updating stmts on our back).
>>
>> Bootstrap and regtest running on x86_64-unknown-linux-gnu.
>>
>> Richard.
>>
>> 2014-05-19  Richard Biener  <rguenther@suse.de>
>>
>> 	PR tree-optimization/61221
>> 	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
>> 	Do nothing for unreachable blocks.
>> 	* tree-ssa-sccvn.c (cond_dom_walker::before_dom_children):
>> 	Improve unreachability detection.
>>
>> 	* gcc.dg/torture/pr61221.c: New testcase.
>Is this another case where having two lists rather than just one in the
>
>SSA_NAME manager would help?  It's something I really need to sit down 
>and just do.

No, it's unfortunately not that easy.

Richard.
>
>Jeff



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