[llvm-dev] Skip redundant checks in AliasSet::aliasesUnknownInst

[Roman Gareev via llvm-dev]

Thank you for the idea! Could you please explain it? If I’m not
mistaken, you advise to insert the unknown insts of an every AS from
AliasSetTracker::add(const AliasSetTracker &AST) into a smallptrset
and consequently append it to merged alias sets from
AliasSetTracker::findAliasSetForUnknownInst. I think that Philip
proposed something similar to your approach in
https://llvm.org/bugs/show_bug.cgi?id=23077.

2016-01-24 22:44 GMT+05:00 Daniel Berlin <dberlin at dberlin.org>:
> It sounds like UnknownInsts should really be a SmallSet, SmallPtrSet, or
> DenseSet (if you can't do the others).
>
> Otherwise, even with your patch, we are still wasting time traversing and
> copying and .... the unknown instructions.
>
> If that doesn't work, I suspect the way you get dupes is through mergeSetIn,
> so you also could probably just change:
>
> 00061   } else if (ASHadUnknownInsts) {
> 00062     UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(),
> AS.UnknownInsts.end());
> 00063     AS.UnknownInsts.clear();
> 00064   }
>
>
>
> You could insert the current unknown insts into a smallptrset, and then only
> append them to UnknownInsts if they aren't in the set.
>
> This should remove your dupes.
>
>
>
> On Sun, Jan 24, 2016 at 5:28 AM, Roman Gareev via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>>
>> Dear llvm contributors,
>>
>> Could you please advise me how to skip
>> checks, which are performed in AliasSet::aliasesUnknownInst, of
>> unknown instructions from different alias sets of an alias set tracker
>> that is a parameter of ‘AliasSetTracker::add(const AliasSetTracker
>> &AST)’?
>>
>> If this wasn’t available at the moment and someone could review me, I
>> would try to implement it. A temporary patch can be found attached
>> (for example, ViewedInst can become a second parameter of
>> AliasSetTracker::addUnknown ). It
>> passes the LLVM regression tests and helps to reduce the runtime of
>> 'opt -basicaa -licm out.opt.ll’ from 130ms to 67ms and the runtime of
>> 'opt -basicaa -licm out.opt2.ll’ from 117ms to 62ms (out.opt.ll and
>> out.opt2.ll can be found on the following link
>> https://llvm.org/bugs/show_bug.cgi?id=23077).
>>
>> Thank you for the attention!
>>
>> --
>>                                     Cheers, Roman Gareev.
>>
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>>
>



-- 
                                    Cheers, Roman Gareev.