Null Reference exception when travser a flow graph

Question

foreach (Phx.Unit unit in oldModuleUnit.ChildUnits) {



   if (unit.IsFunctionUnit) { 



      Phx.FunctionUnit functionUnit = ((Phx.FunctionUnit)unit);          



      Phx.FunctionUnitState raiseToState =          Phx.FunctionUnit.LowLevelIRBeforeLayoutFunctionUnitState;   



      functionUnit = oldModuleUnit.Raise(functionUnit.FunctionSymbol, raiseToState);   



      functionUnit.BuildFlowGraph();  



      Phx.Dataflow.MemoryLivenessWalker walker = Phx.Dataflow.MemoryLivenessWalker.New(functionUnit.Lifetime); 



      walker.Traverse(Phx.Dataflow.TraversalKind.Iterative, functionUnit); //error 



    } 



}

When I execute the above code snippet, I get a null reference exeption at the line marked as "error". The error message says as follows:

Phoenix Assertion Failure: d:\enlistments\sdk_june08\src\phx\dataflow\traverser.
cpp, Line 377
  this->BlockDataArray != nullptr : Called Walker::Initialize before Traverse
  in (Data) <unnamed unit> during IR Unit Function Phases
  in (PEModule) F:\tmp1\test\test\bin\Debug\test.exe
  in (Program) <unnamed unit>
Phoenix Assertion Failure: d:\enlistments\sdk_june08\src\phx\dataflow\traverser.
cpp, Line 378
  this->Direction != Dataflow::Direction::IllegalSentinel
  in (Data) <unnamed unit> during IR Unit Function Phases
  in (PEModule) F:\tmp1\test\test\bin\Debug\test.exe
  in (Program) <unnamed unit>

Can anyone give me some suggestions on why I get such an error message?

Answer 1

The assert is trying to tell you that you left out a needed call. But it's worded a little strangely:

 this->BlockDataArray != nullptr : Called Walker::Initialize before Traverse

it should really say "you must call Walker.Initialize before you call Walker.Traverse". The fix is thus to add a call walker.Initialize(direction, functionUnit) before you call walker.Traverse. Direction for liveness should be Phx.Dataflow.Direction.Backward.

---

Architect - Microsoft Phoenix Project

Answer 2

Many thanks. I add such a call to my code. Now I have no assertion errors. However, it still does not work.
It seems that some IR units have no names. How can I build those names?

Phoenix Assertion Failure: d:\enlistments\sdk_june08\gen\rdk\phx\pdl-host\32\gen
-phx-pdl-phx.inl, Line 7155
  this->IsFunctionUnit
  in (Data) <unnamed unit> during IR Unit Function Phases
  in (PEModule) F:\tmp1\test\test\bin\Debug\test.exe
  in (Program) <unnamed unit>

Answer 3

Make sure your code is only looking at function units (you have such a test in your code sample above). There are other kinds of units, eg DataUnits, that do not contain code.

---

Architect - Microsoft Phoenix Project