llvm dev - Nov 2004 - [LLVMdev] Running specific passes

Hello,
in the implementation of some analysis, I need to change the program and then 
invoke Mem2Reg pass. That pass, in turn, requires other analysis, so I must 
use PassManager. Here's the code I ended up with:

        bool runOnFunction(llvm::Function& m)        
        {
            visit(m);       

            ExistingModuleProvider mp(m.getParent());
            FunctionPassManager pm(&mp);
            .....
            //m.add(createPromoteMemoryToRegister());
            pm.run(m);

There are several problems, though:

1. This looks inefficient -- the analyses necessary for Mem2Reg will be run 
again, even if they are already run by the global pass manager. But how to 
ask the global pass manager to run a pass immediately?

2. This does not work. ExistingModuleProvider takes ownership of m.getParent() 
and deletes it at the end.

3. This does not work. The Mem2Reg pass requires TargetData which does not 
seem to be available. The only reason why it requires it, is to pass to 
lib/Transforms/Utils/PromoteMemoryToRegister.cpp:isAllocaPromotable, which 
does not use that data at all.

Could anybody suggest a better solution?

- Volodya

On Fri, 26 Nov 2004, Vladimir Prus wrote:
> in the implementation of some analysis, I need to change the program and
then
> invoke Mem2Reg pass. That pass, in turn, requires other analysis, so I must
Usually you want to do this at a higher level, why not just use 'opt
-yourpass -mem2reg'?

Alternatively, if you don't want to do that, you can build mem2reg into
your pass if it works better.  To do this, your pass needs to
'addRequired' DominatorTree and DominatorFrontier, then use the
interfaces exposed through
include/llvm/Transforms/Utils/PromoteMemToReg.h.

-Chris
> use PassManager. Here's the code I ended up with:
>
>         bool runOnFunction(llvm::Function& m)
>         {
>             visit(m);
>
>             ExistingModuleProvider mp(m.getParent());
>             FunctionPassManager pm(&mp);
>             .....
>             //m.add(createPromoteMemoryToRegister());
>             pm.run(m);
>
> There are several problems, though:
>
> 1. This looks inefficient -- the analyses necessary for Mem2Reg will be run
> again, even if they are already run by the global pass manager. But how to
> ask the global pass manager to run a pass immediately?
>
> 2. This does not work. ExistingModuleProvider takes ownership of
m.getParent()
> and deletes it at the end.
>
> 3. This does not work. The Mem2Reg pass requires TargetData which does not
> seem to be available. The only reason why it requires it, is to pass to
> lib/Transforms/Utils/PromoteMemoryToRegister.cpp:isAllocaPromotable, which
> does not use that data at all.
>
> Could anybody suggest a better solution?
>
> - Volodya
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev
>
-Chris

-- 
http://llvm.org/
http://nondot.org/sabre/

On Friday 26 November 2004 19:56, Chris Lattner wrote:
> On Fri, 26 Nov 2004, Vladimir Prus wrote:
> > in the implementation of some analysis, I need to change the program
and
> > then invoke Mem2Reg pass. That pass, in turn, requires other analysis,
so
> > I must
>
> Usually you want to do this at a higher level, why not just use 'opt
> -yourpass -mem2reg'?
Because my pass must first modify the code, then run mem2reg pass and then do 
some more work. There's absolutely no way it could work without mem2reg
pass.
(That's the value analysis path I talked about earlier).
> Alternatively, if you don't want to do that, you can build mem2reg into
> your pass if it works better.  To do this, your pass needs to
> 'addRequired' DominatorTree and DominatorFrontier, then use the
> interfaces exposed through
> include/llvm/Transforms/Utils/PromoteMemToReg.h.
This still leaves the question of TargetData parameter -- which is not used by 
the PromoteMemToReg function, AFAICT. Passing *(TargetData*)0 is dirty.

- Volodya