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250 lines
8.0 KiB
C++
250 lines
8.0 KiB
C++
//===-- ProfilePaths.cpp - interface to insert instrumentation --*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This inserts instrumentation for counting execution of paths though a given
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// function Its implemented as a "Function" Pass, and called using opt
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//
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// This pass is implemented by using algorithms similar to
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// 1."Efficient Path Profiling": Ball, T. and Larus, J. R.,
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// Proceedings of Micro-29, Dec 1996, Paris, France.
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// 2."Efficiently Counting Program events with support for on-line
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// "queries": Ball T., ACM Transactions on Programming Languages
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// and systems, Sep 1994.
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//
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// The algorithms work on a Graph constructed over the nodes made from Basic
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// Blocks: The transformations then take place on the constructed graph
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// (implementation in Graph.cpp and GraphAuxiliary.cpp) and finally, appropriate
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// instrumentation is placed over suitable edges. (code inserted through
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// EdgeCode.cpp).
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//
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// The algorithm inserts code such that every acyclic path in the CFG of a
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// function is identified through a unique number. the code insertion is optimal
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// in the sense that its inserted over a minimal set of edges. Also, the
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// algorithm makes sure than initialization, path increment and counter update
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// can be collapsed into minimum number of edges.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/Module.h"
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#include "Graph.h"
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#include <fstream>
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#include <cstdio>
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namespace llvm {
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struct ProfilePaths : public FunctionPass {
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bool runOnFunction(Function &F);
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// Before this pass, make sure that there is only one
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// entry and only one exit node for the function in the CFG of the function
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//
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void ProfilePaths::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<UnifyFunctionExitNodes>();
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}
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};
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static RegisterOpt<ProfilePaths> X("paths", "Profile Paths");
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static Node *findBB(std::vector<Node *> &st, BasicBlock *BB){
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for(std::vector<Node *>::iterator si=st.begin(); si!=st.end(); ++si){
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if(((*si)->getElement())==BB){
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return *si;
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}
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}
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return NULL;
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}
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//Per function pass for inserting counters and trigger code
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bool ProfilePaths::runOnFunction(Function &F){
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static int mn = -1;
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static int CountCounter = 1;
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if(F.isExternal()) {
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return false;
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}
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//increment counter for instrumented functions. mn is now function#
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mn++;
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// Transform the cfg s.t. we have just one exit node
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BasicBlock *ExitNode =
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getAnalysis<UnifyFunctionExitNodes>().getReturnBlock();
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//iterating over BBs and making graph
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std::vector<Node *> nodes;
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std::vector<Edge> edges;
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Node *tmp;
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Node *exitNode = 0, *startNode = 0;
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// The nodes must be uniquely identified:
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// That is, no two nodes must hav same BB*
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for (Function::iterator BB = F.begin(), BE = F.end(); BB != BE; ++BB) {
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Node *nd=new Node(BB);
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nodes.push_back(nd);
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if(&*BB == ExitNode)
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exitNode=nd;
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if(BB==F.begin())
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startNode=nd;
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}
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// now do it again to insert edges
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for (Function::iterator BB = F.begin(), BE = F.end(); BB != BE; ++BB){
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Node *nd=findBB(nodes, BB);
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assert(nd && "No node for this edge!");
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for(succ_iterator s=succ_begin(BB), se=succ_end(BB); s!=se; ++s){
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Node *nd2=findBB(nodes,*s);
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assert(nd2 && "No node for this edge!");
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Edge ed(nd,nd2,0);
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edges.push_back(ed);
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}
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}
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Graph g(nodes,edges, startNode, exitNode);
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#ifdef DEBUG_PATH_PROFILES
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std::cerr<<"Original graph\n";
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printGraph(g);
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#endif
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BasicBlock *fr = &F.front();
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// The graph is made acyclic: this is done
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// by removing back edges for now, and adding them later on
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std::vector<Edge> be;
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std::map<Node *, int> nodePriority; //it ranks nodes in depth first order traversal
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g.getBackEdges(be, nodePriority);
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#ifdef DEBUG_PATH_PROFILES
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std::cerr<<"BackEdges-------------\n";
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for (std::vector<Edge>::iterator VI=be.begin(); VI!=be.end(); ++VI){
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printEdge(*VI);
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cerr<<"\n";
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}
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std::cerr<<"------\n";
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#endif
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#ifdef DEBUG_PATH_PROFILES
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cerr<<"Backedges:"<<be.size()<<endl;
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#endif
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//Now we need to reflect the effect of back edges
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//This is done by adding dummy edges
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//If a->b is a back edge
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//Then we add 2 back edges for it:
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//1. from root->b (in vector stDummy)
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//and 2. from a->exit (in vector exDummy)
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std::vector<Edge> stDummy;
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std::vector<Edge> exDummy;
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addDummyEdges(stDummy, exDummy, g, be);
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#ifdef DEBUG_PATH_PROFILES
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std::cerr<<"After adding dummy edges\n";
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printGraph(g);
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#endif
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// Now, every edge in the graph is assigned a weight
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// This weight later adds on to assign path
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// numbers to different paths in the graph
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// All paths for now are acyclic,
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// since no back edges in the graph now
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// numPaths is the number of acyclic paths in the graph
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int numPaths=valueAssignmentToEdges(g, nodePriority, be);
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//if(numPaths<=1) return false;
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static GlobalVariable *threshold = NULL;
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static bool insertedThreshold = false;
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if(!insertedThreshold){
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threshold = new GlobalVariable(Type::IntTy, false,
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GlobalValue::ExternalLinkage, 0,
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"reopt_threshold");
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F.getParent()->getGlobalList().push_back(threshold);
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insertedThreshold = true;
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}
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assert(threshold && "GlobalVariable threshold not defined!");
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if(fr->getParent()->getName() == "main"){
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//initialize threshold
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// FIXME: THIS IS HORRIBLY BROKEN. FUNCTION PASSES CANNOT DO THIS, EXCEPT
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// IN THEIR INITIALIZE METHOD!!
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Function *initialize =
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F.getParent()->getOrInsertFunction("reoptimizerInitialize", Type::VoidTy,
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PointerType::get(Type::IntTy), 0);
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std::vector<Value *> trargs;
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trargs.push_back(threshold);
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new CallInst(initialize, trargs, "", fr->begin());
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}
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if(numPaths<=1 || numPaths >5000) return false;
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#ifdef DEBUG_PATH_PROFILES
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printGraph(g);
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#endif
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//create instruction allocation r and count
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//r is the variable that'll act like an accumulator
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//all along the path, we just add edge values to r
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//and at the end, r reflects the path number
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//count is an array: count[x] would store
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//the number of executions of path numbered x
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Instruction *rVar=new
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AllocaInst(Type::IntTy,
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ConstantUInt::get(Type::UIntTy,1),"R");
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//Instruction *countVar=new
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//AllocaInst(Type::IntTy,
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// ConstantUInt::get(Type::UIntTy, numPaths), "Count");
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//initialize counter array!
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std::vector<Constant*> arrayInitialize;
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for(int xi=0; xi<numPaths; xi++)
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arrayInitialize.push_back(ConstantSInt::get(Type::IntTy, 0));
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const ArrayType *ATy = ArrayType::get(Type::IntTy, numPaths);
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Constant *initializer = ConstantArray::get(ATy, arrayInitialize);
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char tempChar[20];
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sprintf(tempChar, "Count%d", CountCounter);
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CountCounter++;
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std::string countStr = tempChar;
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GlobalVariable *countVar = new GlobalVariable(ATy, false,
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GlobalValue::InternalLinkage,
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initializer, countStr,
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F.getParent());
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// insert initialization code in first (entry) BB
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// this includes initializing r and count
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insertInTopBB(&F.getEntryBlock(), numPaths, rVar, threshold);
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//now process the graph: get path numbers,
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//get increments along different paths,
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//and assign "increments" and "updates" (to r and count)
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//"optimally". Finally, insert llvm code along various edges
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processGraph(g, rVar, countVar, be, stDummy, exDummy, numPaths, mn,
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threshold);
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return true; // Always modifies function
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}
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} // End llvm namespace
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