llvm dev - May 2018 - CFLAndersAliasAnalysis print implementation

Hello all,

I'm having trouble getting this analysis to print out it's graph of
aliases. I am processing an example C file into llvm ir, like this:

int main(void) {
  int x=1, y=2, z=3;
  int *p;
  int **p1, **p2;
  if (x==z) { //0x100000f40
    p=&x;
    p1=&p;
    x*=2;
    *p1+=z;
  }
}

clang -S -emit-llvm example.c -o example.ll

Then, I am trying to run the Andersen alias analysis on it:

opt -analyze --cfl-anders-aa -aa example.ll

I wrote a new print function for the anders alias analysis, and the print
function parameter Module *M and the Result calculated each indicate that
there are no aliases. I'm certain I'm missing something, but I don't
know
what. To be absolutely clear, a Result is calculated of type:

  std::unique_ptr<CFLAndersAAResult> Result;

And CFLAndersAAResult contains member fields:

  DenseMap<const Function *, Optional<FunctionInfo>> Cache;

  std::forward_list<cflaa::FunctionHandle<CFLAndersAAResult>>
Handles;

The DenseMap Cache is empty, and so is Handles.

I can do -print-alias-sets, and that prints something, but I don't think
it's the result of the Andersen analysis. Because when I do commands
with --cfl-anders-aa
taken out, I still get the same alias sets.

Can anybody help me get the Andersen alias results?
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Ok, the command necessary to get past this is:

opt ./example.ll  -disable-basicaa -cfl-anders-aa -aa-eval -disable-output
-print-alias-sets

It was non-intuitive, because I thought turning on cfl-anders-aa would also
enable printing the alias sets automatically. It also helps to add this
flag: -mem2reg



On Tue, May 22, 2018 at 12:50 PM, Kenneth Adam Miller <
kennethadammiller at gmail.com> wrote:
> Hello all,
>
> I'm having trouble getting this analysis to print out it's graph of
> aliases. I am processing an example C file into llvm ir, like this:
>
> int main(void) {
>   int x=1, y=2, z=3;
>   int *p;
>   int **p1, **p2;
>   if (x==z) { //0x100000f40
>     p=&x;
>     p1=&p;
>     x*=2;
>     *p1+=z;
>   }
> }
>
> clang -S -emit-llvm example.c -o example.ll
>
> Then, I am trying to run the Andersen alias analysis on it:
>
> opt -analyze --cfl-anders-aa -aa example.ll
>
> I wrote a new print function for the anders alias analysis, and the print
> function parameter Module *M and the Result calculated each indicate that
> there are no aliases. I'm certain I'm missing something, but I
don't know
> what. To be absolutely clear, a Result is calculated of type:
>
>   std::unique_ptr<CFLAndersAAResult> Result;
>
> And CFLAndersAAResult contains member fields:
>
>   DenseMap<const Function *, Optional<FunctionInfo>> Cache;
>
>   std::forward_list<cflaa::FunctionHandle<CFLAndersAAResult>>
Handles;
>
> The DenseMap Cache is empty, and so is Handles.
>
> I can do -print-alias-sets, and that prints something, but I don't
think
> it's the result of the Andersen analysis. Because when I do commands
with --cfl-anders-aa
> taken out, I still get the same alias sets.
>
> Can anybody help me get the Andersen alias results?
>
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