A pass to combine multiple backedges that go to same target
llvm-svn: 7201
diff --git a/llvm/lib/Transforms/Instrumentation/ProfilePaths/CombineBranch.cpp b/llvm/lib/Transforms/Instrumentation/ProfilePaths/CombineBranch.cpp
new file mode 100644
index 0000000..f92de70
--- /dev/null
+++ b/llvm/lib/Transforms/Instrumentation/ProfilePaths/CombineBranch.cpp
@@ -0,0 +1,227 @@
+//===-- InstLoops.cpp ---------------------------------------- ---*- C++ -*--=//
+// Pass to instrument loops
+//
+// At every backedge, insert a counter for that backedge and a call function
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Reoptimizer/InstLoops.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Constants.h"
+#include "llvm/iMemory.h"
+#include "llvm/GlobalVariable.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/iOther.h"
+#include "llvm/iOperators.h"
+#include "llvm/iTerminators.h"
+#include "llvm/iPHINode.h"
+#include "llvm/Module.h"
+#include "llvm/Function.h"
+#include "llvm/Pass.h"
+
+//this is used to color vertices
+//during DFS
+
+enum Color{
+ WHITE,
+ GREY,
+ BLACK
+};
+
+namespace{
+ struct CombineBranches : public FunctionPass {
+ private:
+ //DominatorSet *DS;
+ void getBackEdgesVisit(BasicBlock *u,
+ std::map<BasicBlock *, Color > &color,
+ std::map<BasicBlock *, int > &d,
+ int &time,
+ std::map<BasicBlock *, BasicBlock *> &be);
+ void removeRedundant(std::map<BasicBlock *, BasicBlock *> &be);
+ void getBackEdges(Function &F);
+ public:
+ bool runOnFunction(Function &F);
+ };
+
+ RegisterOpt<CombineBranches> X("branch-combine", "Multiple backedges going to same target are merged");
+}
+
+// Create a new pass to merge branches
+//
+Pass *createCombineBranchesPass() {
+ return new CombineBranches();
+}
+
+
+//helper function to get back edges: it is called by
+//the "getBackEdges" function below
+void CombineBranches::getBackEdgesVisit(BasicBlock *u,
+ std::map<BasicBlock *, Color > &color,
+ std::map<BasicBlock *, int > &d,
+ int &time,
+ std::map<BasicBlock *, BasicBlock *> &be) {
+
+ color[u]=GREY;
+ time++;
+ d[u]=time;
+
+ for(BasicBlock::succ_iterator vl = succ_begin(u),
+ ve = succ_end(u); vl != ve; ++vl){
+
+ BasicBlock *BB = *vl;
+
+ if(color[BB]!=GREY && color[BB]!=BLACK){
+ getBackEdgesVisit(BB, color, d, time, be);
+ }
+
+ //now checking for d and f vals
+ else if(color[BB]==GREY){
+ //so v is ancestor of u if time of u > time of v
+ if(d[u] >= d[BB]){
+ //u->BB is a backedge
+ be[u] = BB;
+ }
+ }
+ }
+ color[u]=BLACK;//done with visiting the node and its neighbors
+}
+
+//look at all BEs, and remove all BEs that are dominated by other BE's in the
+//set
+void CombineBranches::removeRedundant(std::map<BasicBlock *, BasicBlock *> &be){
+ std::vector<BasicBlock *> toDelete;
+ std::map<BasicBlock *, int> seenBB;
+
+ for(std::map<BasicBlock *, BasicBlock *>::iterator MI = be.begin(),
+ ME = be.end(); MI != ME; ++MI){
+
+ if(seenBB[MI->second])
+ continue;
+
+ seenBB[MI->second] = 1;
+
+ std::vector<BasicBlock *> sameTarget;
+ sameTarget.clear();
+
+ for(std::map<BasicBlock *, BasicBlock *>::iterator MMI = be.begin(),
+ MME = be.end(); MMI != MME; ++MMI){
+
+ if(MMI->first == MI->first)
+ continue;
+
+ if(MMI->second == MI->second)
+ sameTarget.push_back(MMI->first);
+
+ }
+
+ //so more than one branch to same target
+ if(sameTarget.size()){
+
+ sameTarget.push_back(MI->first);
+
+ BasicBlock *newBB = new BasicBlock("newCommon", MI->first->getParent());
+ BranchInst *newBranch = new BranchInst(MI->second);
+
+ newBB->getInstList().push_back(newBranch);
+
+ std::map<PHINode *, std::vector<unsigned int> > phiMap;
+
+
+ for(std::vector<BasicBlock *>::iterator VBI = sameTarget.begin(),
+ VBE = sameTarget.end(); VBI != VBE; ++VBI){
+
+ //std::cerr<<(*VBI)->getName()<<"\n";
+
+ BranchInst *ti = cast<BranchInst>((*VBI)->getTerminator());
+ unsigned char index = 1;
+ if(ti->getSuccessor(0) == MI->second){
+ index = 0;
+ }
+
+ ti->setSuccessor(index, newBB);
+
+ for(BasicBlock::iterator BB2Inst = MI->second->begin(),
+ BBend = MI->second->end(); BB2Inst != BBend; ++BB2Inst){
+
+ if (PHINode *phiInst = dyn_cast<PHINode>(BB2Inst)){
+ int bbIndex;
+ bbIndex = phiInst->getBasicBlockIndex(*VBI);
+ if(bbIndex>=0){
+ phiMap[phiInst].push_back(bbIndex);
+ //phiInst->setIncomingBlock(bbIndex, newBB);
+ }
+ }
+ }
+ }
+
+ for(std::map<PHINode *, std::vector<unsigned int> >::iterator
+ PI = phiMap.begin(), PE = phiMap.end(); PI != PE; ++PI){
+
+ PHINode *phiNode = new PHINode(PI->first->getType(), "phi", newBranch);
+ for(std::vector<unsigned int>::iterator II = PI->second.begin(),
+ IE = PI->second.end(); II != IE; ++II){
+ phiNode->addIncoming(PI->first->getIncomingValue(*II),
+ PI->first->getIncomingBlock(*II));
+ }
+
+ std::vector<BasicBlock *> tempBB;
+ for(std::vector<unsigned int>::iterator II = PI->second.begin(),
+ IE = PI->second.end(); II != IE; ++II){
+ tempBB.push_back(PI->first->getIncomingBlock(*II));
+ }
+
+ for(std::vector<BasicBlock *>::iterator II = tempBB.begin(),
+ IE = tempBB.end(); II != IE; ++II){
+ PI->first->removeIncomingValue(*II);
+ }
+
+ PI->first->addIncoming(phiNode, newBB);
+ }
+ //std::cerr<<"%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\n";
+ //std::cerr<<MI->second;
+ //std::cerr<<"-----------------------------------\n";
+ //std::cerr<<newBB;
+ //std::cerr<<"END%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%\n";
+
+ }
+ }
+}
+
+//getting the backedges in a graph
+//Its a variation of DFS to get the backedges in the graph
+//We get back edges by associating a time
+//and a color with each vertex.
+//The time of a vertex is the time when it was first visited
+//The color of a vertex is initially WHITE,
+//Changes to GREY when it is first visited,
+//and changes to BLACK when ALL its neighbors
+//have been visited
+//So we have a back edge when we meet a successor of
+//a node with smaller time, and GREY color
+void CombineBranches::getBackEdges(Function &F){
+ std::map<BasicBlock *, Color > color;
+ std::map<BasicBlock *, int> d;
+ std::map<BasicBlock *, BasicBlock *> be;
+ int time=0;
+ getBackEdgesVisit(F.begin(), color, d, time, be);
+
+ removeRedundant(be);
+}
+
+//Per function pass for inserting counters and call function
+bool CombineBranches::runOnFunction(Function &F){
+
+ if(F.isExternal()) {
+ return false;
+ }
+
+ //if(F.getName() == "main"){
+ // F.setName("llvm_gprof_main");
+ //}
+
+ //std::cerr<<F;
+ //std::cerr<<"///////////////////////////////////////////////\n";
+ getBackEdges(F);
+
+ return true;
+}