[LLVMdev] alias result

[Hal Finkel]

----- Original Message -----
> From: "Haopeng Liu" <hyliuhp at gmail.com>
> To: llvmdev at cs.uiuc.edu
> Sent: Monday, February 16, 2015 12:12:18 PM
> Subject: [LLVMdev] alias result
> 
> Hi all,
> 
> I am implementing a pass which needs aliasanalysis in llvm.
> 
> My pass firstly records all store or load instructions as follows:
> loc[cnt++] = AA.getLocation(si/li);
> 
> Then, get each pairwise alias result.
> AliasAnalysis::AliasResult ar = AA.alias(loc[i], loc[j]);
> switch(ar){ case 0,1,2,3;}
> 
> And the command is: opt -load mypass.so -mypass -basicaa test.bc
> 
> The store/load in test.bc:
> 
> (1): store i64* %thd, i64** %t, align 8    //int64 *t = &thd;
> (2): %1 = load i64** %t, align 8             //load t
> (3): store i64* %1, i64** %t2, align 8     //int64 *t2 = t;
> (4): %2 = load i64** %t, align 8             //load t
> (5): %3 = load i64** %t2, align 8           //load t2
> 
> It seems that all these 5 instructions should be aliased to each
> other.
> 
> But the result should that only (1,2) (1,4) (2,4) (3,5) are must
> alias.
> Others are no alias.

Where do %t and %t2 come from?

 -Hal

> 
> Who can explain these results? Any hits would be appreciated. Thank
> you.
> 
> 
> 
> 
> 
> 
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory