llvm dev - Jan 2020 - Let CallGraphSCCPass Use Function-Level Analysis

Dear all,

I would like to use the PostDominatorTree in ArgPromotion. I did not find an
example of how to use function level analysis inside CallGraphSCCPass. I tried
to follow an example of how to use function-level pass in a module pass, but I
hit "llvm_unreachable" in PMDataManager::addLowerLevelRequiredPass.

What would be a proper way to make PostDominatorTree available in ArgPromotion?

Thanks in advance,

Mikhail
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Hello! The new pass manager provides analysis proxies from one IR unit
type to another. These are specializations of
'llvm::InnerAnalysisManagerProxy'. For example,
'llvm::FunctionAnalysisManagerModuleProxy' allows you to access
function analyses from within module passes.

In your case, it sounds like you'd want to use
'llvm::FunctionAnalysisManagerCGSCCProxy', which allows you to access
function analyses from within an CGSCC pass. Here's an example of
using it:

```
class MyCGSCCPass : public llvm::PassInfoMixin<MyCGSCCPass> {
public:
  llvm::PreservedAnalyses run(llvm::LazyCallGraph::SCC &C,
                              llvm::CGSCCAnalysisManager &AM,
                              llvm::LazyCallGraph &CG,
                              llvm::CGSCCUpdateResult &UR) {
    llvm::FunctionAnalysisManager &FAM        
AM.getResult<llvm::FunctionAnalysisManagerCGSCCProxy>(C, CG)
            .getManager();
    for (llvm::LazyCallGraph::Node &N : C) {
      llvm::Function &F = N.getFunction();
      llvm::PostDominatorTree &PDT          
FAM.getResult<llvm::PostDominatorTreeAnalysis>(F);
      PDT.print(llvm::outs());
    }
    return llvm::PreservedAnalyses::none();
  }
};
```

Here's a full example of the above:
https://gist.github.com/modocache/d5804ba567476e32cad1fd0850363532

I was just reading through this part of the codebase, so I'm a little
familiar with it now. Anyway, hope this helps!

- Brian Gesiak

On Tue, Jan 7, 2020 at 8:13 AM Mikhail Gudim via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> Dear all,
>
>
>
> I would like to use the PostDominatorTree in ArgPromotion. I did not find
an example of how to use function level analysis inside CallGraphSCCPass. I
tried to follow an example of how to use function-level pass in a module pass,
but I hit “llvm_unreachable” in PMDataManager::addLowerLevelRequiredPass.
>
>
>
> What would be a proper way to make PostDominatorTree available in
ArgPromotion?
>
>
>
> Thanks in advance,
>
>
>
> Mikhail
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Hi Mikhail,

As Brian noted, stuff like this works better in the new pass manager.

Even in the old pass manager I thought it should work though.
Did you initialize the pass, via 
 `INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)`?
Did you require it, via 
` AU.addRequired<PostDominatorTreeWrapperPass>();`?

Btw. May I ask what you are planning to do?

Cheers,
  Johannes


On 01/07, Brian Gesiak via llvm-dev wrote:
> Hello! The new pass manager provides analysis proxies from one IR unit
> type to another. These are specializations of
> 'llvm::InnerAnalysisManagerProxy'. For example,
> 'llvm::FunctionAnalysisManagerModuleProxy' allows you to access
> function analyses from within module passes.
> 
> In your case, it sounds like you'd want to use
> 'llvm::FunctionAnalysisManagerCGSCCProxy', which allows you to
access
> function analyses from within an CGSCC pass. Here's an example of
> using it:
> 
> ```
> class MyCGSCCPass : public llvm::PassInfoMixin<MyCGSCCPass> {
> public:
>   llvm::PreservedAnalyses run(llvm::LazyCallGraph::SCC &C,
>                               llvm::CGSCCAnalysisManager &AM,
>                               llvm::LazyCallGraph &CG,
>                               llvm::CGSCCUpdateResult &UR) {
>     llvm::FunctionAnalysisManager &FAM >        
AM.getResult<llvm::FunctionAnalysisManagerCGSCCProxy>(C, CG)
>             .getManager();
>     for (llvm::LazyCallGraph::Node &N : C) {
>       llvm::Function &F = N.getFunction();
>       llvm::PostDominatorTree &PDT >          
FAM.getResult<llvm::PostDominatorTreeAnalysis>(F);
>       PDT.print(llvm::outs());
>     }
>     return llvm::PreservedAnalyses::none();
>   }
> };
> ```
> 
> Here's a full example of the above:
> https://gist.github.com/modocache/d5804ba567476e32cad1fd0850363532
> 
> I was just reading through this part of the codebase, so I'm a little
> familiar with it now. Anyway, hope this helps!
> 
> - Brian Gesiak
> 
> On Tue, Jan 7, 2020 at 8:13 AM Mikhail Gudim via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> >
> > Dear all,
> >
> >
> >
> > I would like to use the PostDominatorTree in ArgPromotion. I did not
find an example of how to use function level analysis inside CallGraphSCCPass. I
tried to follow an example of how to use function-level pass in a module pass,
but I hit “llvm_unreachable” in PMDataManager::addLowerLevelRequiredPass.
> >
> >
> >
> > What would be a proper way to make PostDominatorTree available in
ArgPromotion?
> >
> >
> >
> > Thanks in advance,
> >
> >
> >
> > Mikhail
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
-- 

Johannes Doerfert
Researcher

Argonne National Laboratory
Lemont, IL 60439, USA

jdoerfert at anl.gov
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