lib/Analysis/DataStructure/Steensgaard.cpp - fp2-dev/platform/external/llvm - Gitiles

 //===- Steensgaard.cpp - Context Insensitive Alias Analysis ---------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file was developed by the LLVM research group and is distributed under
 // the University of Illinois Open Source License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This pass uses the data structure graphs to implement a simple context
 // insensitive alias analysis.  It does this by computing the local analysis
 // graphs for all of the functions, then merging them together into a single big
 // graph without cloning.
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/Analysis/DataStructure/DataStructure.h"
 #include "llvm/Analysis/DataStructure/DSGraph.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/Passes.h"
 #include "llvm/Module.h"
 #include "llvm/Support/Debug.h"
 using namespace llvm;

 namespace {
   class Steens : public ModulePass, public AliasAnalysis {
     DSGraph *ResultGraph;
     DSGraph *GlobalsGraph;  // FIXME: Eliminate globals graph stuff from DNE
   public:
     Steens() : ResultGraph(0), GlobalsGraph(0) {}
     ~Steens() {
       releaseMyMemory();
       assert(ResultGraph == 0 && "releaseMemory not called?");
     }

     //------------------------------------------------
     // Implement the Pass API
     //

     // run - Build up the result graph, representing the pointer graph for the
     // program.
     //
     bool runOnModule(Module &M);

     virtual void releaseMyMemory() { delete ResultGraph; ResultGraph = 0; }

     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       AliasAnalysis::getAnalysisUsage(AU);
       AU.setPreservesAll();                    // Does not transform code...
       AU.addRequired<LocalDataStructures>();   // Uses local dsgraph
     }

     // print - Implement the Pass::print method...
     void print(std::ostream &O, const Module *M) const {
       assert(ResultGraph && "Result graph has not yet been computed!");
       ResultGraph->writeGraphToFile(O, "steensgaards");
     }

     //------------------------------------------------
     // Implement the AliasAnalysis API
     //

     // alias - This is the only method here that does anything interesting...
     AliasResult alias(const Value *V1, unsigned V1Size,
                       const Value *V2, unsigned V2Size);

   private:
     void ResolveFunctionCall(Function *F, const DSCallSite &Call,
                              DSNodeHandle &RetVal);
   };

   // Register the pass...
   RegisterOpt<Steens> X("steens-aa",
                         "Steensgaard's alias analysis (DSGraph based)");

   // Register as an implementation of AliasAnalysis
   RegisterAnalysisGroup<AliasAnalysis, Steens> Y;
 }

 ModulePass *llvm::createSteensgaardPass() { return new Steens(); }

 /// ResolveFunctionCall - Resolve the actual arguments of a call to function F
 /// with the specified call site descriptor.  This function links the arguments
 /// and the return value for the call site context-insensitively.
 ///
 void Steens::ResolveFunctionCall(Function *F, const DSCallSite &Call,
                                  DSNodeHandle &RetVal) {
   assert(ResultGraph != 0 && "Result graph not allocated!");
   DSGraph::ScalarMapTy &ValMap = ResultGraph->getScalarMap();

   // Handle the return value of the function...
   if (Call.getRetVal().getNode() && RetVal.getNode())
     RetVal.mergeWith(Call.getRetVal());

   // Loop over all pointer arguments, resolving them to their provided pointers
   unsigned PtrArgIdx = 0;
   for (Function::aiterator AI = F->abegin(), AE = F->aend();
        AI != AE && PtrArgIdx < Call.getNumPtrArgs(); ++AI) {
     DSGraph::ScalarMapTy::iterator I = ValMap.find(AI);
     if (I != ValMap.end())    // If its a pointer argument...
       I->second.mergeWith(Call.getPtrArg(PtrArgIdx++));
   }
 }


 /// run - Build up the result graph, representing the pointer graph for the
 /// program.
 ///
 bool Steens::runOnModule(Module &M) {
   InitializeAliasAnalysis(this);
   assert(ResultGraph == 0 && "Result graph already allocated!");
   LocalDataStructures &LDS = getAnalysis<LocalDataStructures>();

   // Create a new, empty, graph...
   ResultGraph = new DSGraph(getTargetData());
   GlobalsGraph = new DSGraph(getTargetData());
   ResultGraph->setGlobalsGraph(GlobalsGraph);
   ResultGraph->setPrintAuxCalls();

   // RetValMap - Keep track of the return values for all functions that return
   // valid pointers.
   //
   DSGraph::ReturnNodesTy RetValMap;

   // Loop over the rest of the module, merging graphs for non-external functions
   // into this graph.
   //
   unsigned Count = 0;
   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
     if (!I->isExternal()) {
       DSGraph::ScalarMapTy ValMap;
       {  // Scope to free NodeMap memory ASAP
         DSGraph::NodeMapTy NodeMap;
         const DSGraph &FDSG = LDS.getDSGraph(*I);
         ResultGraph->cloneInto(FDSG, ValMap, RetValMap, NodeMap,
                                DSGraph::UpdateInlinedGlobals);
       }

       // Incorporate the inlined Function's ScalarMap into the global
       // ScalarMap...
       DSGraph::ScalarMapTy &GVM = ResultGraph->getScalarMap();
       for (DSGraph::ScalarMapTy::iterator I = ValMap.begin(),
              E = ValMap.end(); I != E; ++I)
         GVM[I->first].mergeWith(I->second);

       if ((++Count & 1) == 0)   // Prune nodes out every other time...
         ResultGraph->removeTriviallyDeadNodes();
     }

   // FIXME: Must recalculate and use the Incomplete markers!!

   // Now that we have all of the graphs inlined, we can go about eliminating
   // call nodes...
   //
   std::list<DSCallSite> &Calls = ResultGraph->getAuxFunctionCalls();
   assert(Calls.empty() && "Aux call list is already in use??");

   // Start with a copy of the original call sites.
   Calls = ResultGraph->getFunctionCalls();

   for (std::list<DSCallSite>::iterator CI = Calls.begin(), E = Calls.end();
        CI != E;) {
     DSCallSite &CurCall = *CI++;

     // Loop over the called functions, eliminating as many as possible...
     std::vector<GlobalValue*> CallTargets;
     if (CurCall.isDirectCall())
       CallTargets.push_back(CurCall.getCalleeFunc());
     else
       CallTargets = CurCall.getCalleeNode()->getGlobals();

     for (unsigned c = 0; c != CallTargets.size(); ) {
       // If we can eliminate this function call, do so!
       bool Eliminated = false;
       if (Function *F = dyn_cast<Function>(CallTargets[c]))
         if (!F->isExternal()) {
           ResolveFunctionCall(F, CurCall, RetValMap[F]);
           Eliminated = true;
         }
       if (Eliminated) {
         CallTargets[c] = CallTargets.back();
         CallTargets.pop_back();
       } else
         ++c;  // Cannot eliminate this call, skip over it...
     }

     if (CallTargets.empty()) {        // Eliminated all calls?
       std::list<DSCallSite>::iterator I = CI;
       Calls.erase(--I);               // Remove entry
     }
   }

   RetValMap.clear();

   // Update the "incomplete" markers on the nodes, ignoring unknownness due to
   // incoming arguments...
   ResultGraph->maskIncompleteMarkers();
   ResultGraph->markIncompleteNodes(DSGraph::IgnoreFormalArgs);

   // Remove any nodes that are dead after all of the merging we have done...
   // FIXME: We should be able to disable the globals graph for steens!
   ResultGraph->removeDeadNodes(DSGraph::KeepUnreachableGlobals);

   DEBUG(print(std::cerr, &M));
   return false;
 }

 // alias - This is the only method here that does anything interesting...
 AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
                                          const Value *V2, unsigned V2Size) {
   // FIXME: HANDLE Size argument!
   assert(ResultGraph && "Result graph has not been computed yet!");

   DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();

   DSGraph::ScalarMapTy::iterator I = GSM.find(const_cast<Value*>(V1));
   if (I != GSM.end() && I->second.getNode()) {
     DSNodeHandle &V1H = I->second;
     DSGraph::ScalarMapTy::iterator J=GSM.find(const_cast<Value*>(V2));
     if (J != GSM.end() && J->second.getNode()) {
       DSNodeHandle &V2H = J->second;
       // If the two pointers point to different data structure graph nodes, they
       // cannot alias!
       if (V1H.getNode() != V2H.getNode())    // FIXME: Handle incompleteness!
         return NoAlias;

       // FIXME: If the two pointers point to the same node, and the offsets are
       // different, and the LinkIndex vector doesn't alias the section, then the
       // two pointers do not alias.  We need access size information for the two
       // accesses though!
       //
     }
   }

   // If we cannot determine alias properties based on our graph, fall back on
   // some other AA implementation.
   //
   return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
 }
	//===- Steensgaard.cpp - Context Insensitive Alias Analysis ---------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file was developed by the LLVM research group and is distributed under
	// the University of Illinois Open Source License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This pass uses the data structure graphs to implement a simple context
	// insensitive alias analysis. It does this by computing the local analysis
	// graphs for all of the functions, then merging them together into a single big
	// graph without cloning.
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/Analysis/DataStructure/DataStructure.h"
	#include "llvm/Analysis/DataStructure/DSGraph.h"
	#include "llvm/Analysis/AliasAnalysis.h"
	#include "llvm/Analysis/Passes.h"
	#include "llvm/Module.h"
	#include "llvm/Support/Debug.h"
	using namespace llvm;

	namespace {
	class Steens : public ModulePass, public AliasAnalysis {
	DSGraph *ResultGraph;
	DSGraph *GlobalsGraph; // FIXME: Eliminate globals graph stuff from DNE
	public:
	Steens() : ResultGraph(0), GlobalsGraph(0) {}
	~Steens() {
	releaseMyMemory();
	assert(ResultGraph == 0 && "releaseMemory not called?");
	}

	//------------------------------------------------
	// Implement the Pass API
	//

	// run - Build up the result graph, representing the pointer graph for the
	// program.
	//
	bool runOnModule(Module &M);

	virtual void releaseMyMemory() { delete ResultGraph; ResultGraph = 0; }

	virtual void getAnalysisUsage(AnalysisUsage &AU) const {
	AliasAnalysis::getAnalysisUsage(AU);
	AU.setPreservesAll(); // Does not transform code...
	AU.addRequired<LocalDataStructures>(); // Uses local dsgraph
	}

	// print - Implement the Pass::print method...
	void print(std::ostream &O, const Module *M) const {
	assert(ResultGraph && "Result graph has not yet been computed!");
	ResultGraph->writeGraphToFile(O, "steensgaards");
	}

	//------------------------------------------------
	// Implement the AliasAnalysis API
	//

	// alias - This is the only method here that does anything interesting...
	AliasResult alias(const Value *V1, unsigned V1Size,
	const Value *V2, unsigned V2Size);

	private:
	void ResolveFunctionCall(Function *F, const DSCallSite &Call,
	DSNodeHandle &RetVal);
	};

	// Register the pass...
	RegisterOpt<Steens> X("steens-aa",
	"Steensgaard's alias analysis (DSGraph based)");

	// Register as an implementation of AliasAnalysis
	RegisterAnalysisGroup<AliasAnalysis, Steens> Y;
	}

	ModulePass *llvm::createSteensgaardPass() { return new Steens(); }

	/// ResolveFunctionCall - Resolve the actual arguments of a call to function F
	/// with the specified call site descriptor. This function links the arguments
	/// and the return value for the call site context-insensitively.
	///
	void Steens::ResolveFunctionCall(Function *F, const DSCallSite &Call,
	DSNodeHandle &RetVal) {
	assert(ResultGraph != 0 && "Result graph not allocated!");
	DSGraph::ScalarMapTy &ValMap = ResultGraph->getScalarMap();

	// Handle the return value of the function...
	if (Call.getRetVal().getNode() && RetVal.getNode())
	RetVal.mergeWith(Call.getRetVal());

	// Loop over all pointer arguments, resolving them to their provided pointers
	unsigned PtrArgIdx = 0;
	for (Function::aiterator AI = F->abegin(), AE = F->aend();
	AI != AE && PtrArgIdx < Call.getNumPtrArgs(); ++AI) {
	DSGraph::ScalarMapTy::iterator I = ValMap.find(AI);
	if (I != ValMap.end()) // If its a pointer argument...
	I->second.mergeWith(Call.getPtrArg(PtrArgIdx++));
	}
	}


	/// run - Build up the result graph, representing the pointer graph for the
	/// program.
	///
	bool Steens::runOnModule(Module &M) {
	InitializeAliasAnalysis(this);
	assert(ResultGraph == 0 && "Result graph already allocated!");
	LocalDataStructures &LDS = getAnalysis<LocalDataStructures>();

	// Create a new, empty, graph...
	ResultGraph = new DSGraph(getTargetData());
	GlobalsGraph = new DSGraph(getTargetData());
	ResultGraph->setGlobalsGraph(GlobalsGraph);
	ResultGraph->setPrintAuxCalls();

	// RetValMap - Keep track of the return values for all functions that return
	// valid pointers.
	//
	DSGraph::ReturnNodesTy RetValMap;

	// Loop over the rest of the module, merging graphs for non-external functions
	// into this graph.
	//
	unsigned Count = 0;
	for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
	if (!I->isExternal()) {
	DSGraph::ScalarMapTy ValMap;
	{ // Scope to free NodeMap memory ASAP
	DSGraph::NodeMapTy NodeMap;
	const DSGraph &FDSG = LDS.getDSGraph(*I);
	ResultGraph->cloneInto(FDSG, ValMap, RetValMap, NodeMap,
	DSGraph::UpdateInlinedGlobals);
	}

	// Incorporate the inlined Function's ScalarMap into the global
	// ScalarMap...
	DSGraph::ScalarMapTy &GVM = ResultGraph->getScalarMap();
	for (DSGraph::ScalarMapTy::iterator I = ValMap.begin(),
	E = ValMap.end(); I != E; ++I)
	GVM[I->first].mergeWith(I->second);

	if ((++Count & 1) == 0) // Prune nodes out every other time...
	ResultGraph->removeTriviallyDeadNodes();
	}

	// FIXME: Must recalculate and use the Incomplete markers!!

	// Now that we have all of the graphs inlined, we can go about eliminating
	// call nodes...
	//
	std::list<DSCallSite> &Calls = ResultGraph->getAuxFunctionCalls();
	assert(Calls.empty() && "Aux call list is already in use??");

	// Start with a copy of the original call sites.
	Calls = ResultGraph->getFunctionCalls();

	for (std::list<DSCallSite>::iterator CI = Calls.begin(), E = Calls.end();
	CI != E;) {
	DSCallSite &CurCall = *CI++;

	// Loop over the called functions, eliminating as many as possible...
	std::vector<GlobalValue*> CallTargets;
	if (CurCall.isDirectCall())
	CallTargets.push_back(CurCall.getCalleeFunc());
	else
	CallTargets = CurCall.getCalleeNode()->getGlobals();

	for (unsigned c = 0; c != CallTargets.size(); ) {
	// If we can eliminate this function call, do so!
	bool Eliminated = false;
	if (Function *F = dyn_cast<Function>(CallTargets[c]))
	if (!F->isExternal()) {
	ResolveFunctionCall(F, CurCall, RetValMap[F]);
	Eliminated = true;
	}
	if (Eliminated) {
	CallTargets[c] = CallTargets.back();
	CallTargets.pop_back();
	} else
	++c; // Cannot eliminate this call, skip over it...
	}

	if (CallTargets.empty()) { // Eliminated all calls?
	std::list<DSCallSite>::iterator I = CI;
	Calls.erase(--I); // Remove entry
	}
	}

	RetValMap.clear();

	// Update the "incomplete" markers on the nodes, ignoring unknownness due to
	// incoming arguments...
	ResultGraph->maskIncompleteMarkers();
	ResultGraph->markIncompleteNodes(DSGraph::IgnoreFormalArgs);

	// Remove any nodes that are dead after all of the merging we have done...
	// FIXME: We should be able to disable the globals graph for steens!
	ResultGraph->removeDeadNodes(DSGraph::KeepUnreachableGlobals);

	DEBUG(print(std::cerr, &M));
	return false;
	}

	// alias - This is the only method here that does anything interesting...
	AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
	const Value *V2, unsigned V2Size) {
	// FIXME: HANDLE Size argument!
	assert(ResultGraph && "Result graph has not been computed yet!");

	DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();

	DSGraph::ScalarMapTy::iterator I = GSM.find(const_cast<Value*>(V1));
	if (I != GSM.end() && I->second.getNode()) {
	DSNodeHandle &V1H = I->second;
	DSGraph::ScalarMapTy::iterator J=GSM.find(const_cast<Value*>(V2));
	if (J != GSM.end() && J->second.getNode()) {
	DSNodeHandle &V2H = J->second;
	// If the two pointers point to different data structure graph nodes, they
	// cannot alias!
	if (V1H.getNode() != V2H.getNode()) // FIXME: Handle incompleteness!
	return NoAlias;

	// FIXME: If the two pointers point to the same node, and the offsets are
	// different, and the LinkIndex vector doesn't alias the section, then the
	// two pointers do not alias. We need access size information for the two
	// accesses though!
	//
	}
	}

	// If we cannot determine alias properties based on our graph, fall back on
	// some other AA implementation.
	//
	return AliasAnalysis::alias(V1, V1Size, V2, V2Size);
	}