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	git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4029 91177308-0d34-0410-b5e6-96231b3b80d8
		
			
				
	
	
		
			414 lines
		
	
	
		
			14 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
			
		
		
	
	
			414 lines
		
	
	
		
			14 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
//===- Local.cpp - Compute a local data structure graph for a function ----===//
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//
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// Compute the local version of the data structure graph for a function.  The
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// external interface to this file is the DSGraph constructor.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/DSGraph.h"
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#include "llvm/Analysis/DataStructure.h"
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#include "llvm/iMemory.h"
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#include "llvm/iTerminators.h"
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#include "llvm/iPHINode.h"
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#include "llvm/iOther.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/Support/InstVisitor.h"
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#include "llvm/Target/TargetData.h"
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#include "Support/Statistic.h"
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// FIXME: This should eventually be a FunctionPass that is automatically
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// aggregated into a Pass.
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//
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#include "llvm/Module.h"
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using std::map;
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using std::vector;
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static RegisterAnalysis<LocalDataStructures>
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X("datastructure", "Local Data Structure Analysis");
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using namespace DataStructureAnalysis;
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namespace DataStructureAnalysis {
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  // FIXME: Do something smarter with target data!
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  TargetData TD("temp-td");
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  unsigned PointerSize(TD.getPointerSize());
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  // isPointerType - Return true if this type is big enough to hold a pointer.
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  bool isPointerType(const Type *Ty) {
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    if (isa<PointerType>(Ty))
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      return true;
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    else if (Ty->isPrimitiveType() && Ty->isInteger())
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      return Ty->getPrimitiveSize() >= PointerSize;
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    return false;
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  }
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}
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namespace {
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  //===--------------------------------------------------------------------===//
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  //  GraphBuilder Class
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  //===--------------------------------------------------------------------===//
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  //
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  /// This class is the builder class that constructs the local data structure
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  /// graph by performing a single pass over the function in question.
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  ///
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  class GraphBuilder : InstVisitor<GraphBuilder> {
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    DSGraph &G;
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    vector<DSNode*> &Nodes;
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    DSNodeHandle &RetNode;               // Node that gets returned...
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    map<Value*, DSNodeHandle> &ValueMap;
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    vector<vector<DSNodeHandle> > &FunctionCalls;
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  public:
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    GraphBuilder(DSGraph &g, vector<DSNode*> &nodes, DSNodeHandle &retNode,
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                 map<Value*, DSNodeHandle> &vm,
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                 vector<vector<DSNodeHandle> > &fc)
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      : G(g), Nodes(nodes), RetNode(retNode), ValueMap(vm), FunctionCalls(fc) {
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      // Create scalar nodes for all pointer arguments...
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      for (Function::aiterator I = G.getFunction().abegin(),
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             E = G.getFunction().aend(); I != E; ++I)
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        if (isPointerType(I->getType()))
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          getValueDest(*I);
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      visit(G.getFunction());  // Single pass over the function
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      // Not inlining, only eliminate trivially dead nodes.
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      G.removeTriviallyDeadNodes();
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    }
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  private:
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    // Visitor functions, used to handle each instruction type we encounter...
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    friend class InstVisitor<GraphBuilder>;
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    void visitMallocInst(MallocInst &MI) { handleAlloc(MI, DSNode::NewNode); }
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    void visitAllocaInst(AllocaInst &AI) { handleAlloc(AI, DSNode::AllocaNode);}
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    void handleAlloc(AllocationInst &AI, DSNode::NodeTy NT);
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    void visitPHINode(PHINode &PN);
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    void visitGetElementPtrInst(GetElementPtrInst &GEP);
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    void visitReturnInst(ReturnInst &RI);
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    void visitLoadInst(LoadInst &LI);
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    void visitStoreInst(StoreInst &SI);
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    void visitCallInst(CallInst &CI);
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    void visitSetCondInst(SetCondInst &SCI) {}  // SetEQ & friends are ignored
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    void visitFreeInst(FreeInst &FI) {}         // Ignore free instructions
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    void visitCastInst(CastInst &CI);
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    void visitInstruction(Instruction &I) {}
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  private:
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    // Helper functions used to implement the visitation functions...
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    /// createNode - Create a new DSNode, ensuring that it is properly added to
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    /// the graph.
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    ///
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    DSNode *createNode(DSNode::NodeTy NodeType, const Type *Ty);
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    /// getValueNode - Return a DSNode that corresponds the the specified LLVM
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    /// value.  This either returns the already existing node, or creates a new
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    /// one and adds it to the graph, if none exists.
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    ///
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    DSNodeHandle getValueNode(Value &V);
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    /// getValueDest - Return the DSNode that the actual value points to.  This
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    /// is basically the same thing as: getLink(getValueNode(V), 0)
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    ///
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    DSNodeHandle &getValueDest(Value &V);
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    /// getGlobalNode - Just like getValueNode, except the global node itself is
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    /// returned, not a scalar node pointing to a global.
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    ///
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    DSNodeHandle &getGlobalNode(GlobalValue &V);
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    /// getLink - This method is used to return the specified link in the
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    /// specified node if one exists.  If a link does not already exist (it's
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    /// null), then we create a new node, link it, then return it.  We must
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    /// specify the type of the Node field we are accessing so that we know what
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    /// type should be linked to if we need to create a new node.
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    ///
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    DSNodeHandle &getLink(const DSNodeHandle &Node, unsigned Link,
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                          const Type *FieldTy);
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  };
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}
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//===----------------------------------------------------------------------===//
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// DSGraph constructor - Simply use the GraphBuilder to construct the local
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// graph.
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DSGraph::DSGraph(Function &F) : Func(&F) {
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  // Use the graph builder to construct the local version of the graph
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  GraphBuilder B(*this, Nodes, RetNode, ValueMap, FunctionCalls);
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  markIncompleteNodes();
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}
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//===----------------------------------------------------------------------===//
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// Helper method implementations...
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//
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// createNode - Create a new DSNode, ensuring that it is properly added to the
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// graph.
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//
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DSNode *GraphBuilder::createNode(DSNode::NodeTy NodeType, const Type *Ty) {
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  DSNode *N = new DSNode(NodeType, Ty);
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  Nodes.push_back(N);
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  return N;
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}
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// getGlobalNode - Just like getValueNode, except the global node itself is
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// returned, not a scalar node pointing to a global.
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//
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DSNodeHandle &GraphBuilder::getGlobalNode(GlobalValue &V) {
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  DSNodeHandle &NH = ValueMap[&V];
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  if (NH.getNode()) return NH;       // Already have a node?  Just return it...
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  // Create a new global node for this global variable...
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  DSNode *G = createNode(DSNode::GlobalNode, V.getType()->getElementType());
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  G->addGlobal(&V);
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  // If this node has outgoing edges, make sure to recycle the same node for
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  // each use.  For functions and other global variables, this is unneccesary,
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  // so avoid excessive merging by cloning these nodes on demand.
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  //
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  NH.setNode(G);
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  return NH;
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}
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// getValueNode - Return a DSNode that corresponds the the specified LLVM value.
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// This either returns the already existing node, or creates a new one and adds
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// it to the graph, if none exists.
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//
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DSNodeHandle GraphBuilder::getValueNode(Value &V) {
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  assert(isPointerType(V.getType()) && "Should only use pointer scalars!");
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  // Do not share the pointer value to globals... this would cause way too much
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  // false merging.
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  //
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  DSNodeHandle &NH = ValueMap[&V];
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  if (!isa<GlobalValue>(V) && NH.getNode())
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    return NH;     // Already have a node?  Just return it...
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  // Otherwise we need to create a new scalar node...
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  DSNode *N = createNode(DSNode::ScalarNode, V.getType());
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  // If this is a global value, create the global pointed to.
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  if (GlobalValue *GV = dyn_cast<GlobalValue>(&V)) {
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    N->addEdgeTo(0, getGlobalNode(*GV));
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    return DSNodeHandle(N, 0);
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  } else {
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    NH.setOffset(0);
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    NH.setNode(N);
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  }
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  return NH;
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}
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/// getValueDest - Return the DSNode that the actual value points to.  This
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/// is basically the same thing as: getLink(getValueNode(V), 0)
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///
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DSNodeHandle &GraphBuilder::getValueDest(Value &V) {
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  return getLink(getValueNode(V), 0, V.getType());
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}
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/// getLink - This method is used to return the specified link in the
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/// specified node if one exists.  If a link does not already exist (it's
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/// null), then we create a new node, link it, then return it.  We must
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/// specify the type of the Node field we are accessing so that we know what
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/// type should be linked to if we need to create a new node.
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///
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DSNodeHandle &GraphBuilder::getLink(const DSNodeHandle &node,
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                                    unsigned LinkNo, const Type *FieldTy) {
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  DSNodeHandle &Node = const_cast<DSNodeHandle&>(node);
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  DSNodeHandle *Link = Node.getLink(LinkNo);
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  if (Link) return *Link;
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  // If the link hasn't been created yet, make and return a new shadow node of
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  // the appropriate type for FieldTy...
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  //
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  // If we are indexing with a typed pointer, then the thing we are pointing
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  // to is of the pointed type.  If we are pointing to it with an integer
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  // (because of cast to an integer), we represent it with a void type.
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  //
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  const Type *ReqTy;
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  if (const PointerType *Ptr = dyn_cast<PointerType>(FieldTy))
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    ReqTy = Ptr->getElementType();
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  else
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    ReqTy = Type::VoidTy;
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  DSNode *N = createNode(DSNode::ShadowNode, ReqTy);
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  Node.setLink(LinkNo, N);
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  return *Node.getLink(LinkNo);
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}
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//===----------------------------------------------------------------------===//
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// Specific instruction type handler implementations...
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//
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/// Alloca & Malloc instruction implementation - Simply create a new memory
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/// object, pointing the scalar to it.
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///
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void GraphBuilder::handleAlloc(AllocationInst &AI, DSNode::NodeTy NodeType) {
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  DSNode *New = createNode(NodeType, AI.getAllocatedType());
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  // Make the scalar point to the new node...
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  getValueNode(AI).addEdgeTo(New);
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}
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// PHINode - Make the scalar for the PHI node point to all of the things the
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// incoming values point to... which effectively causes them to be merged.
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//
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void GraphBuilder::visitPHINode(PHINode &PN) {
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  if (!isPointerType(PN.getType())) return; // Only pointer PHIs
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  DSNodeHandle &ScalarDest = getValueDest(PN);
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  for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
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    if (!isa<ConstantPointerNull>(PN.getIncomingValue(i)))
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      ScalarDest.mergeWith(getValueDest(*PN.getIncomingValue(i)));
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}
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void GraphBuilder::visitGetElementPtrInst(GetElementPtrInst &GEP) {
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  DSNodeHandle Value = getValueDest(*GEP.getOperand(0));
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  unsigned Offset = 0;
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  const Type *CurTy = GEP.getOperand(0)->getType();
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  for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i)
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    if (GEP.getOperand(i)->getType() == Type::LongTy) {
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      // Get the type indexing into...
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      const SequentialType *STy = cast<SequentialType>(CurTy);
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      CurTy = STy->getElementType();
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      if (ConstantSInt *CS = dyn_cast<ConstantSInt>(GEP.getOperand(i))) {
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        if (isa<PointerType>(STy))
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          std::cerr << "Pointer indexing not handled yet!\n";
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        else 
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          Offset += CS->getValue()*TD.getTypeSize(CurTy);
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      } else {
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        // Variable index into a node.  We must merge all of the elements of the
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        // sequential type here.
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        if (isa<PointerType>(STy))
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          std::cerr << "Pointer indexing not handled yet!\n";
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        else {
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          const ArrayType *ATy = cast<ArrayType>(STy);
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          unsigned ElSize = TD.getTypeSize(CurTy);
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          DSNode *N = Value.getNode();
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          assert(N && "Value must have a node!");
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          unsigned RawOffset = Offset+Value.getOffset();
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          // Loop over all of the elements of the array, merging them into the
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          // zero'th element.
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          for (unsigned i = 1, e = ATy->getNumElements(); i != e; ++i)
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            // Merge all of the byte components of this array element
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            for (unsigned j = 0; j != ElSize; ++j)
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              N->mergeIndexes(RawOffset+j, RawOffset+i*ElSize+j);
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        }
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      }
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    } else if (GEP.getOperand(i)->getType() == Type::UByteTy) {
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      unsigned FieldNo = cast<ConstantUInt>(GEP.getOperand(i))->getValue();
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      const StructType *STy = cast<StructType>(CurTy);
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      Offset += TD.getStructLayout(STy)->MemberOffsets[FieldNo];
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      CurTy = STy->getContainedType(FieldNo);
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    }
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  // Add in the offset calculated...
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  Value.setOffset(Value.getOffset()+Offset);
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  // Value is now the pointer we want to GEP to be...
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  getValueNode(GEP).addEdgeTo(Value);
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}
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void GraphBuilder::visitLoadInst(LoadInst &LI) {
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  DSNodeHandle &Ptr = getValueDest(*LI.getOperand(0));
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  if (isPointerType(LI.getType()))
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    getValueNode(LI).addEdgeTo(getLink(Ptr, 0, LI.getType()));
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}
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void GraphBuilder::visitStoreInst(StoreInst &SI) {
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  DSNodeHandle &Dest = getValueDest(*SI.getOperand(1));
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  // Avoid adding edges from null, or processing non-"pointer" stores
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  if (isPointerType(SI.getOperand(0)->getType()) &&
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      !isa<ConstantPointerNull>(SI.getOperand(0))) {
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    Dest.addEdgeTo(getValueDest(*SI.getOperand(0)));
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  }
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}
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void GraphBuilder::visitReturnInst(ReturnInst &RI) {
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  if (RI.getNumOperands() && isPointerType(RI.getOperand(0)->getType()) &&
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      !isa<ConstantPointerNull>(RI.getOperand(0))) {
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    DSNodeHandle &Value = getValueDest(*RI.getOperand(0));
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    Value.mergeWith(RetNode);
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    RetNode = Value;
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  }
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}
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void GraphBuilder::visitCallInst(CallInst &CI) {
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  // Add a new function call entry...
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  FunctionCalls.push_back(vector<DSNodeHandle>());
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  vector<DSNodeHandle> &Args = FunctionCalls.back();
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  // Set up the return value...
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  if (isPointerType(CI.getType()))
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    Args.push_back(getLink(getValueNode(CI), 0, CI.getType()));
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  else
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    Args.push_back(DSNodeHandle());
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  unsigned Start = 0;
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  // Special case for a direct call, avoid creating spurious scalar node...
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  if (GlobalValue *GV = dyn_cast<GlobalValue>(CI.getOperand(0))) {
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    Args.push_back(getGlobalNode(*GV));
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    Start = 1;
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  }
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  // Pass the arguments in...
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  for (unsigned i = Start, e = CI.getNumOperands(); i != e; ++i)
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    if (isPointerType(CI.getOperand(i)->getType()))
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      Args.push_back(getLink(getValueNode(*CI.getOperand(i)), 0,
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                             CI.getOperand(i)->getType()));
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}
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/// Handle casts...
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void GraphBuilder::visitCastInst(CastInst &CI) {
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  if (isPointerType(CI.getType()) && isPointerType(CI.getOperand(0)->getType()))
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    getValueNode(CI).addEdgeTo(getLink(getValueNode(*CI.getOperand(0)), 0,
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                                       CI.getOperand(0)->getType()));
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}
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//===----------------------------------------------------------------------===//
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// LocalDataStructures Implementation
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//===----------------------------------------------------------------------===//
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// releaseMemory - If the pass pipeline is done with this pass, we can release
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// our memory... here...
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//
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void LocalDataStructures::releaseMemory() {
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  for (std::map<const Function*, DSGraph*>::iterator I = DSInfo.begin(),
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         E = DSInfo.end(); I != E; ++I)
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    delete I->second;
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  // Empty map so next time memory is released, data structures are not
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  // re-deleted.
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  DSInfo.clear();
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}
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bool LocalDataStructures::run(Module &M) {
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  // Calculate all of the graphs...
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  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
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    if (!I->isExternal())
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      DSInfo.insert(std::make_pair(I, new DSGraph(*I)));
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  return false;
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}
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