2003-10-13 03:32:08 +00:00
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//===-- CombineBranch.cpp -------------------------------------------------===//
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//
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2003-07-18 16:08:32 +00:00
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// Pass to instrument loops
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//
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// At every backedge, insert a counter for that backedge and a call function
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2003-10-13 03:32:08 +00:00
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//
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2003-07-18 16:08:32 +00:00
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Constants.h"
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#include "llvm/iMemory.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/iOther.h"
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#include "llvm/iOperators.h"
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#include "llvm/iTerminators.h"
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#include "llvm/iPHINode.h"
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#include "llvm/Module.h"
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#include "llvm/Function.h"
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#include "llvm/Pass.h"
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//this is used to color vertices
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//during DFS
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enum Color{
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WHITE,
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GREY,
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BLACK
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};
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namespace{
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struct CombineBranches : public FunctionPass {
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private:
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//DominatorSet *DS;
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void getBackEdgesVisit(BasicBlock *u,
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std::map<BasicBlock *, Color > &color,
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std::map<BasicBlock *, int > &d,
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int &time,
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std::map<BasicBlock *, BasicBlock *> &be);
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void removeRedundant(std::map<BasicBlock *, BasicBlock *> &be);
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void getBackEdges(Function &F);
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public:
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bool runOnFunction(Function &F);
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};
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RegisterOpt<CombineBranches> X("branch-combine", "Multiple backedges going to same target are merged");
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}
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//helper function to get back edges: it is called by
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//the "getBackEdges" function below
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void CombineBranches::getBackEdgesVisit(BasicBlock *u,
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std::map<BasicBlock *, Color > &color,
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std::map<BasicBlock *, int > &d,
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int &time,
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std::map<BasicBlock *, BasicBlock *> &be) {
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color[u]=GREY;
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time++;
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d[u]=time;
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2003-09-24 22:06:25 +00:00
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for (succ_iterator vl = succ_begin(u), ve = succ_end(u); vl != ve; ++vl){
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2003-07-18 16:08:32 +00:00
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BasicBlock *BB = *vl;
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if(color[BB]!=GREY && color[BB]!=BLACK){
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getBackEdgesVisit(BB, color, d, time, be);
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}
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//now checking for d and f vals
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else if(color[BB]==GREY){
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//so v is ancestor of u if time of u > time of v
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if(d[u] >= d[BB]){
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//u->BB is a backedge
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be[u] = BB;
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}
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}
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}
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color[u]=BLACK;//done with visiting the node and its neighbors
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}
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//look at all BEs, and remove all BEs that are dominated by other BE's in the
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//set
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void CombineBranches::removeRedundant(std::map<BasicBlock *, BasicBlock *> &be){
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std::vector<BasicBlock *> toDelete;
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std::map<BasicBlock *, int> seenBB;
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for(std::map<BasicBlock *, BasicBlock *>::iterator MI = be.begin(),
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ME = be.end(); MI != ME; ++MI){
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if(seenBB[MI->second])
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continue;
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seenBB[MI->second] = 1;
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std::vector<BasicBlock *> sameTarget;
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sameTarget.clear();
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for(std::map<BasicBlock *, BasicBlock *>::iterator MMI = be.begin(),
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MME = be.end(); MMI != MME; ++MMI){
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if(MMI->first == MI->first)
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continue;
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if(MMI->second == MI->second)
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sameTarget.push_back(MMI->first);
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}
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//so more than one branch to same target
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if(sameTarget.size()){
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sameTarget.push_back(MI->first);
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BasicBlock *newBB = new BasicBlock("newCommon", MI->first->getParent());
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BranchInst *newBranch = new BranchInst(MI->second);
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newBB->getInstList().push_back(newBranch);
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std::map<PHINode *, std::vector<unsigned int> > phiMap;
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for(std::vector<BasicBlock *>::iterator VBI = sameTarget.begin(),
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VBE = sameTarget.end(); VBI != VBE; ++VBI){
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//std::cerr<<(*VBI)->getName()<<"\n";
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BranchInst *ti = cast<BranchInst>((*VBI)->getTerminator());
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unsigned char index = 1;
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if(ti->getSuccessor(0) == MI->second){
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index = 0;
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}
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ti->setSuccessor(index, newBB);
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for(BasicBlock::iterator BB2Inst = MI->second->begin(),
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BBend = MI->second->end(); BB2Inst != BBend; ++BB2Inst){
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if (PHINode *phiInst = dyn_cast<PHINode>(BB2Inst)){
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int bbIndex;
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bbIndex = phiInst->getBasicBlockIndex(*VBI);
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if(bbIndex>=0){
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phiMap[phiInst].push_back(bbIndex);
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//phiInst->setIncomingBlock(bbIndex, newBB);
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}
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}
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}
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}
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for(std::map<PHINode *, std::vector<unsigned int> >::iterator
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PI = phiMap.begin(), PE = phiMap.end(); PI != PE; ++PI){
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PHINode *phiNode = new PHINode(PI->first->getType(), "phi", newBranch);
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for(std::vector<unsigned int>::iterator II = PI->second.begin(),
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IE = PI->second.end(); II != IE; ++II){
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phiNode->addIncoming(PI->first->getIncomingValue(*II),
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PI->first->getIncomingBlock(*II));
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}
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std::vector<BasicBlock *> tempBB;
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for(std::vector<unsigned int>::iterator II = PI->second.begin(),
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IE = PI->second.end(); II != IE; ++II){
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tempBB.push_back(PI->first->getIncomingBlock(*II));
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}
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for(std::vector<BasicBlock *>::iterator II = tempBB.begin(),
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IE = tempBB.end(); II != IE; ++II){
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PI->first->removeIncomingValue(*II);
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}
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PI->first->addIncoming(phiNode, newBB);
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}
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//std::cerr<<"%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\n";
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//std::cerr<<MI->second;
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//std::cerr<<"-----------------------------------\n";
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//std::cerr<<newBB;
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//std::cerr<<"END%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\n";
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}
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}
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}
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//getting the backedges in a graph
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//Its a variation of DFS to get the backedges in the graph
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//We get back edges by associating a time
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//and a color with each vertex.
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//The time of a vertex is the time when it was first visited
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//The color of a vertex is initially WHITE,
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//Changes to GREY when it is first visited,
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//and changes to BLACK when ALL its neighbors
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//have been visited
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//So we have a back edge when we meet a successor of
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//a node with smaller time, and GREY color
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void CombineBranches::getBackEdges(Function &F){
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std::map<BasicBlock *, Color > color;
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std::map<BasicBlock *, int> d;
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std::map<BasicBlock *, BasicBlock *> be;
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int time=0;
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getBackEdgesVisit(F.begin(), color, d, time, be);
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removeRedundant(be);
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}
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//Per function pass for inserting counters and call function
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bool CombineBranches::runOnFunction(Function &F){
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if(F.isExternal()) {
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return false;
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}
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//if(F.getName() == "main"){
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// F.setName("llvm_gprof_main");
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//}
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//std::cerr<<F;
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//std::cerr<<"///////////////////////////////////////////////\n";
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getBackEdges(F);
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return true;
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}
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