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//===-- InstLoops.cpp -----------------------------------------------------===//
//
// 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 is the first-level instrumentation pass for the Reoptimizer. It
// instrument the back-edges of loops by inserting a basic block
// containing a call to llvm_first_trigger (the first-level trigger function),
// and inserts an initialization call to the main() function.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/CFG.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Type.h"
#include "llvm/Support/Debug.h"
#include "../ProfilingUtils.h"
namespace llvm {
//this is used to color vertices
//during DFS
enum Color{
WHITE,
GREY,
BLACK
};
namespace {
typedef std::map<BasicBlock *, BasicBlock *> BBMap;
struct InstLoops : public FunctionPass {
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorSet>();
}
private:
Function *inCountMth;
DominatorSet *DS;
void getBackEdgesVisit(BasicBlock *u,
std::map<BasicBlock *, Color > &color,
std::map<BasicBlock *, int > &d,
int &time, BBMap &be);
void removeRedundant(BBMap &be);
void findAndInstrumentBackEdges(Function &F);
public:
bool doInitialization(Module &M);
bool runOnFunction(Function &F);
};
RegisterOpt<InstLoops> X("instloops", "Instrument backedges for profiling");
}
//helper function to get back edges: it is called by
//the "getBackEdges" function below
void InstLoops::getBackEdgesVisit(BasicBlock *u,
std::map<BasicBlock *, Color > &color,
std::map<BasicBlock *, int > &d,
int &time, BBMap &be) {
color[u]=GREY;
time++;
d[u]=time;
for(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 InstLoops::removeRedundant(BBMap &be) {
std::vector<BasicBlock *> toDelete;
for(std::map<BasicBlock *, BasicBlock *>::iterator MI = be.begin(),
ME = be.end(); MI != ME; ++MI)
for(BBMap::iterator MMI = be.begin(), MME = be.end(); MMI != MME; ++MMI)
if(DS->properlyDominates(MI->first, MMI->first))
toDelete.push_back(MMI->first);
// Remove all the back-edges we found from be.
for(std::vector<BasicBlock *>::iterator VI = toDelete.begin(),
VE = toDelete.end(); VI != VE; ++VI)
be.erase(*VI);
}
//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 InstLoops::findAndInstrumentBackEdges(Function &F){
std::map<BasicBlock *, Color > color;
std::map<BasicBlock *, int> d;
BBMap be;
int time=0;
getBackEdgesVisit(F.begin(), color, d, time, be);
removeRedundant(be);
for(std::map<BasicBlock *, BasicBlock *>::iterator MI = be.begin(),
ME = be.end(); MI != ME; ++MI){
BasicBlock *u = MI->first;
BasicBlock *BB = MI->second;
// We have a back-edge from BB --> u.
DEBUG (std::cerr << "Instrumenting back-edge from " << BB->getName ()
<< "-->" << u->getName () << "\n");
// Split the back-edge, inserting a new basic block on it, and modify the
// source BB's terminator accordingly.
BasicBlock *newBB = new BasicBlock("backEdgeInst", u->getParent());
BranchInst *ti = cast<BranchInst>(u->getTerminator());
unsigned char index = ((ti->getSuccessor(0) == BB) ? 0 : 1);
assert(ti->getNumSuccessors() > index && "Not enough successors!");
ti->setSuccessor(index, newBB);
BasicBlock::InstListType < = newBB->getInstList();
lt.push_back(new CallInst(inCountMth));
new BranchInst(BB, newBB);
// Now, set the sources of Phi nodes corresponding to the back-edge
// in BB to come from the instrumentation block instead.
for(BasicBlock::iterator BB2Inst = BB->begin(), BBend = BB->end();
BB2Inst != BBend; ++BB2Inst) {
if (PHINode *phiInst = dyn_cast<PHINode>(BB2Inst)) {
int bbIndex = phiInst->getBasicBlockIndex(u);
if (bbIndex>=0)
phiInst->setIncomingBlock(bbIndex, newBB);
}
}
}
}
bool InstLoops::doInitialization (Module &M) {
inCountMth = M.getOrInsertFunction("llvm_first_trigger", Type::VoidTy, 0);
return true; // Module was modified.
}
/// runOnFunction - Entry point for FunctionPass that inserts calls to
/// trigger function.
///
bool InstLoops::runOnFunction(Function &F){
if (F.isExternal ())
return false;
DS = &getAnalysis<DominatorSet> ();
// Add a call to reoptimizerInitialize() to beginning of function named main.
if (F.getName() == "main")
InsertProfilingInitCall (&F, "reoptimizerInitialize");
findAndInstrumentBackEdges(F);
return true; // Function was modified.
}
} // End llvm namespace
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