[patch] Remove unused code from dse.c.

[Jeff Law]

On 03/29/2013 12:12 PM, Steven Bosscher wrote:
> On Fri, Mar 29, 2013 at 6:29 PM, Jeff Law <law@redhat.com> wrote:
>> On 03/29/2013 11:24 AM, Lawrence Crowl wrote:
>>
>>>> At what point did we stop setting clear_alias_sets?  Was that
>>>> intentional or not?
>>>
>>>
>>> I do not know the answer to either question.
>>
>> That's what needs to be determined before I'll approve.  It means digging a
>> bit.
>>
>>
>>
>>> My view is that we have already lost the feature.  The code
>>> that populates the set is gone.  The remaining code has probably
>>> suffered bitrot because it is not being tested.  Trying to recreate
>>> the population will probably result in inconsistencies anyway,
>>> necessitating a rewrite of the remaining code.  So, the remaining
>>> code has little value, and might have negative value.
>>
>> But that doesn't mean dropping the code is the right thing to do.  The right
>> thing to do is see if the feature was dropped on purpose.  If so, then we
>> remove this dead code.  If not, then we fix the real problem, namely the
>> code was accidentally disabled (and add suitable tests to the suite to catch
>> this kind of problem in the future).
>
> It's left over cleanups from code removed last year:
> http://gcc.gnu.org/ml/gcc-patches/2012-03/msg01862.html
More correctly, it's been dead since an Oct 2008 patch from Richard 
Henderson which introduced set_mem_attrs_for_spill which effectively 
provides the alias analysis code with the information it needs to 
disambiguate stack slots from everything else without the callback.

Lawrence, that's the critical bit of information you failed to provide.

Patch approved, please install.

Thanks,
Jeff