llvm dev - Feb 2018 - Question about using LoopAccessLegacyAnalysis

Hi LLVM community,

I am writing a custom pass for analyzing the dependence information for the
memory access within a loop. I found “LoopAccessLegacyAnalysis” class useful,
however I m not able to obtain information from that pass. Here is what I did to
get the information:

// require pass 
virtual void getAnalysisUsage(AnalysisUsage &AU) const
    {
         AU.addRequired<LoopInfoWrapperPass>();
         AU.addRequired<LoopAccessLegacyAnalysis>();
         AU.setPreservesAll();
    }

// processing
virtual bool runOnFunction(Function &F) {
         LoopInfo &li =
getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
         LoopAccessLegacyAnalysis &lala =
getAnalysis<LoopAccessLegacyAnalysis>();

         for(LoopInfo::iterator lp = li.begin(); lp != li.end(); lp++)
         {
             Loop *loop = *lp;
             const LoopAccessInfo &lai = lala.getInfo(loop);
	      
	      // need help here
	      // I can’t get any information from the LoopAccessInfo instance.
	      errs()<<lai.getNumLoads(); // return 0
	  }
}


// register
static RegisterPass<SkeletonPass> X("test", "test for using
the existing pass",
                                    “false",
                                    “false”);


I must be missing something important. Any response would be greatly
appreciated!

Thanks,
Kewen




Best regards,
Kewen

Have you check `LoopAccessLegacyAnalysis::runOnFunction` ran as you expect?
Besides, I am not sure if `LoopAccessLegacyAnalysis::runOnFunction` does
anything useful, have you check that, too?


2018-02-08 1:49 GMT+08:00 Kewen Meng via llvm-dev <llvm-dev at
lists.llvm.org>:
> Hi LLVM community,
>
> I am writing a custom pass for analyzing the dependence information for
> the memory access within a loop. I found “LoopAccessLegacyAnalysis” class
> useful, however I m not able to obtain information from that pass. Here is
> what I did to get the information:
>
> // require pass
> virtual void getAnalysisUsage(AnalysisUsage &AU) const
>     {
>          AU.addRequired<LoopInfoWrapperPass>();
>          AU.addRequired<LoopAccessLegacyAnalysis>();
>          AU.setPreservesAll();
>     }
>
> // processing
> virtual bool runOnFunction(Function &F) {
>          LoopInfo &li =
getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
>          LoopAccessLegacyAnalysis &lala = getAnalysis<
> LoopAccessLegacyAnalysis>();
>
>          for(LoopInfo::iterator lp = li.begin(); lp != li.end(); lp++)
>          {
>              Loop *loop = *lp;
>              const LoopAccessInfo &lai = lala.getInfo(loop);
>
>               // need help here
>               // I can’t get any information from the LoopAccessInfo
> instance.
>               errs()<<lai.getNumLoads(); // return 0
>           }
> }
>
>
> // register
> static RegisterPass<SkeletonPass> X("test", "test for
using the existing
> pass",
>                                     “false",
>                                     “false”);
>
>
> I must be missing something important. Any response would be greatly
> appreciated!
>
> Thanks,
> Kewen
>
>
>
>
> Best regards,
> Kewen
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>


-- 
Wei-Ren Chen (陳韋任)
Homepage: https://people.cs.nctu.edu.tw/~chenwj
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Hi Wei-Ren,


Thanks for your reply.


I use --debug-pass=Structure and it says Loop access analysis pass is executed
before my pass. The interesting part is when I use -mem2reg and -loop-rotate it
returns dependence information. I have no idea how to explain that. I would be
great if one could help me with it. Thanks in advance.


Best,

Kewen


________________________________
From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of 陳韋任 via
llvm-dev <llvm-dev at lists.llvm.org>
Sent: Thursday, February 8, 2018 7:06:30 AM
To: Kewen Meng
Cc: LLVM Developers Mailing List
Subject: Re: [llvm-dev] Question about using LoopAccessLegacyAnalysis

Have you check `LoopAccessLegacyAnalysis::runOnFunction` ran as you expect?
Besides, I am not sure if `LoopAccessLegacyAnalysis::runOnFunction` does
anything useful, have you check that, too?


2018-02-08 1:49 GMT+08:00 Kewen Meng via llvm-dev <llvm-dev at
lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>:
Hi LLVM community,

I am writing a custom pass for analyzing the dependence information for the
memory access within a loop. I found “LoopAccessLegacyAnalysis” class useful,
however I m not able to obtain information from that pass. Here is what I did to
get the information:

// require pass
virtual void getAnalysisUsage(AnalysisUsage &AU) const
    {
         AU.addRequired<LoopInfoWrapperPass>();
         AU.addRequired<LoopAccessLegacyAnalysis>();
         AU.setPreservesAll();
    }

// processing
virtual bool runOnFunction(Function &F) {
         LoopInfo &li =
getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
         LoopAccessLegacyAnalysis &lala =
getAnalysis<LoopAccessLegacyAnalysis>();

         for(LoopInfo::iterator lp = li.begin(); lp != li.end(); lp++)
         {
             Loop *loop = *lp;
             const LoopAccessInfo &lai = lala.getInfo(loop);

              // need help here
              // I can’t get any information from the LoopAccessInfo instance.
              errs()<<lai.getNumLoads(); // return 0
          }
}


// register
static RegisterPass<SkeletonPass> X("test", "test for using
the existing pass",
                                    “false",
                                    “false”);


I must be missing something important. Any response would be greatly
appreciated!

Thanks,
Kewen




Best regards,
Kewen
_______________________________________________
LLVM Developers mailing list
llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev



--
Wei-Ren Chen (陳韋任)
Homepage: https://people.cs.nctu.edu.tw/~chenwj
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