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"
 #include <iostream>
 using namespace llvm;

 namespace {
   class Steens : public ModulePass, public AliasAnalysis {
     DSGraph *ResultGraph;

     EquivalenceClasses<GlobalValue*> GlobalECs;  // Always empty
   public:
     Steens() : ResultGraph(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
     //

     AliasResult alias(const Value *V1, unsigned V1Size,
                       const Value *V2, unsigned V2Size);

     ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);

   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::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
        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(GlobalECs, getTargetData());
   ResultGraph->spliceFrom(LDS.getGlobalsGraph());

   // Loop over the rest of the module, merging graphs for non-external functions
   // into this graph.
   //
   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
     if (!I->isExternal())
       ResultGraph->spliceFrom(LDS.getDSGraph(*I));

   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<Function*> CallTargets;
     if (CurCall.isDirectCall())
       CallTargets.push_back(CurCall.getCalleeFunc());
     else
       CurCall.getCalleeNode()->addFullFunctionList(CallTargets);

     for (unsigned c = 0; c != CallTargets.size(); ) {
       // If we can eliminate this function call, do so!
       Function *F = CallTargets[c];
       if (!F->isExternal()) {
         ResolveFunctionCall(F, CurCall, ResultGraph->getReturnNodes()[F]);
         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
     }
   }

   // Remove our knowledge of what the return values of the functions are, except
   // for functions that are externally visible from this module (e.g. main).  We
   // keep these functions so that their arguments are marked incomplete.
   for (DSGraph::ReturnNodesTy::iterator I =
          ResultGraph->getReturnNodes().begin(),
          E = ResultGraph->getReturnNodes().end(); I != E; )
     if (I->first->hasInternalLinkage())
       ResultGraph->getReturnNodes().erase(I++);
     else
       ++I;

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

   // 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;
 }

 AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
                                          const Value *V2, unsigned V2Size) {
   assert(ResultGraph && "Result graph has not been computed yet!");

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

   DSGraph::ScalarMapTy::iterator I = GSM.find(const_cast<Value*>(V1));
   DSGraph::ScalarMapTy::iterator J = GSM.find(const_cast<Value*>(V2));
   if (I != GSM.end() && !I->second.isNull() &&
       J != GSM.end() && !J->second.isNull()) {
     DSNodeHandle &V1H = I->second;
     DSNodeHandle &V2H = J->second;

     // If at least one of the nodes is complete, we can say something about
     // this.  If one is complete and the other isn't, then they are obviously
     // different nodes.  If they are both complete, we can't say anything
     // useful.
     if (I->second.getNode()->isComplete() ||
         J->second.getNode()->isComplete()) {
       // If the two pointers point to different data structure graph nodes, they
       // cannot alias!
       if (V1H.getNode() != V2H.getNode())
         return NoAlias;

       // See if they point to different offsets...  if so, we may be able to
       // determine that they do not alias...
       unsigned O1 = I->second.getOffset(), O2 = J->second.getOffset();
       if (O1 != O2) {
         if (O2 < O1) {    // Ensure that O1 <= O2
           std::swap(V1, V2);
           std::swap(O1, O2);
           std::swap(V1Size, V2Size);
         }

         if (O1+V1Size <= O2)
           return NoAlias;
       }
     }
   }

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

 AliasAnalysis::ModRefResult
 Steens::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
   AliasAnalysis::ModRefResult Result = ModRef;

   // Find the node in question.
   DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();
   DSGraph::ScalarMapTy::iterator I = GSM.find(P);

   if (I != GSM.end() && !I->second.isNull()) {
     DSNode *N = I->second.getNode();
     if (N->isComplete()) {
       // If this is a direct call to an external function, and if the pointer
       // points to a complete node, the external function cannot modify or read
       // the value (we know it's not passed out of the program!).
       if (Function *F = CS.getCalledFunction())
         if (F->isExternal())
           return NoModRef;

       // Otherwise, if the node is complete, but it is only M or R, return this.
       // This can be useful for globals that should be marked const but are not.
       if (!N->isModified())
         Result = (ModRefResult)(Result & ~Mod);
       if (!N->isRead())
         Result = (ModRefResult)(Result & ~Ref);
     }
   }

   return (ModRefResult)(Result & AliasAnalysis::getModRefInfo(CS, P, Size));
 }
	//===- 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"
	#include <iostream>
	using namespace llvm;

	namespace {
	class Steens : public ModulePass, public AliasAnalysis {
	DSGraph *ResultGraph;

	EquivalenceClasses<GlobalValue*> GlobalECs; // Always empty
	public:
	Steens() : ResultGraph(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
	//

	AliasResult alias(const Value *V1, unsigned V1Size,
	const Value *V2, unsigned V2Size);

	ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);

	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::arg_iterator AI = F->arg_begin(), AE = F->arg_end();
	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(GlobalECs, getTargetData());
	ResultGraph->spliceFrom(LDS.getGlobalsGraph());

	// Loop over the rest of the module, merging graphs for non-external functions
	// into this graph.
	//
	for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
	if (!I->isExternal())
	ResultGraph->spliceFrom(LDS.getDSGraph(*I));

	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<Function*> CallTargets;
	if (CurCall.isDirectCall())
	CallTargets.push_back(CurCall.getCalleeFunc());
	else
	CurCall.getCalleeNode()->addFullFunctionList(CallTargets);

	for (unsigned c = 0; c != CallTargets.size(); ) {
	// If we can eliminate this function call, do so!
	Function *F = CallTargets[c];
	if (!F->isExternal()) {
	ResolveFunctionCall(F, CurCall, ResultGraph->getReturnNodes()[F]);
	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
	}
	}

	// Remove our knowledge of what the return values of the functions are, except
	// for functions that are externally visible from this module (e.g. main). We
	// keep these functions so that their arguments are marked incomplete.
	for (DSGraph::ReturnNodesTy::iterator I =
	ResultGraph->getReturnNodes().begin(),
	E = ResultGraph->getReturnNodes().end(); I != E; )
	if (I->first->hasInternalLinkage())
	ResultGraph->getReturnNodes().erase(I++);
	else
	++I;

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

	// 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;
	}

	AliasAnalysis::AliasResult Steens::alias(const Value *V1, unsigned V1Size,
	const Value *V2, unsigned V2Size) {
	assert(ResultGraph && "Result graph has not been computed yet!");

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

	DSGraph::ScalarMapTy::iterator I = GSM.find(const_cast<Value*>(V1));
	DSGraph::ScalarMapTy::iterator J = GSM.find(const_cast<Value*>(V2));
	if (I != GSM.end() && !I->second.isNull() &&
	J != GSM.end() && !J->second.isNull()) {
	DSNodeHandle &V1H = I->second;
	DSNodeHandle &V2H = J->second;

	// If at least one of the nodes is complete, we can say something about
	// this. If one is complete and the other isn't, then they are obviously
	// different nodes. If they are both complete, we can't say anything
	// useful.
	if (I->second.getNode()->isComplete() \|\|
	J->second.getNode()->isComplete()) {
	// If the two pointers point to different data structure graph nodes, they
	// cannot alias!
	if (V1H.getNode() != V2H.getNode())
	return NoAlias;

	// See if they point to different offsets... if so, we may be able to
	// determine that they do not alias...
	unsigned O1 = I->second.getOffset(), O2 = J->second.getOffset();
	if (O1 != O2) {
	if (O2 < O1) { // Ensure that O1 <= O2
	std::swap(V1, V2);
	std::swap(O1, O2);
	std::swap(V1Size, V2Size);
	}

	if (O1+V1Size <= O2)
	return NoAlias;
	}
	}
	}

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

	AliasAnalysis::ModRefResult
	Steens::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
	AliasAnalysis::ModRefResult Result = ModRef;

	// Find the node in question.
	DSGraph::ScalarMapTy &GSM = ResultGraph->getScalarMap();
	DSGraph::ScalarMapTy::iterator I = GSM.find(P);

	if (I != GSM.end() && !I->second.isNull()) {
	DSNode *N = I->second.getNode();
	if (N->isComplete()) {
	// If this is a direct call to an external function, and if the pointer
	// points to a complete node, the external function cannot modify or read
	// the value (we know it's not passed out of the program!).
	if (Function *F = CS.getCalledFunction())
	if (F->isExternal())
	return NoModRef;

	// Otherwise, if the node is complete, but it is only M or R, return this.
	// This can be useful for globals that should be marked const but are not.
	if (!N->isModified())
	Result = (ModRefResult)(Result & ~Mod);
	if (!N->isRead())
	Result = (ModRefResult)(Result & ~Ref);
	}
	}

	return (ModRefResult)(Result & AliasAnalysis::getModRefInfo(CS, P, Size));
	}