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llvm-mirror/lib/Transforms/Instrumentation/ProfilePaths/ProfilePaths.cpp
Chris Lattner 12573def64 * Changes to compile successfully with GCC 3.0
* Eliminated memory leak in processGraph
* Pass vectors by const reference to moveDummyCode instead of by copy

llvm-svn: 1808
2002-02-26 19:40:28 +00:00

163 lines
5.4 KiB
C++

//===-- ProfilePaths.cpp - interface to insert instrumentation ---*- C++ -*--=//
//
// This inserts intrumentation for counting
// execution of paths though a given method
// Its implemented as a "Method" Pass, and called using opt
//
// This pass is implemented by using algorithms similar to
// 1."Efficient Path Profiling": Ball, T. and Larus, J. R.,
// Proceedings of Micro-29, Dec 1996, Paris, France.
// 2."Efficiently Counting Program events with support for on-line
// "queries": Ball T., ACM Transactions on Programming Languages
// and systems, Sep 1994.
//
// The algorithms work on a Graph constructed over the nodes
// made from Basic Blocks: The transformations then take place on
// the constucted graph (implementation in Graph.cpp and GraphAuxillary.cpp)
// and finally, appropriate instrumentation is placed over suitable edges.
// (code inserted through EdgeCode.cpp).
//
// The algorithm inserts code such that every acyclic path in the CFG
// of a method is identified through a unique number. the code insertion
// is optimal in the sense that its inserted over a minimal set of edges. Also,
// the algorithm makes sure than initialization, path increment and counter
// update can be collapsed into minmimum number of edges.
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Instrumentation/ProfilePaths.h"
#include "llvm/Transforms/UnifyMethodExitNodes.h"
#include "llvm/Support/CFG.h"
#include "llvm/Method.h"
#include "llvm/BasicBlock.h"
#include "llvm/ConstantVals.h"
#include "llvm/DerivedTypes.h"
#include "llvm/iMemory.h"
#include "Graph.h"
using std::vector;
static Node *findBB(std::set<Node *> &st, BasicBlock *BB){
for(std::set<Node *>::iterator si=st.begin(); si!=st.end(); ++si){
if(((*si)->getElement())==BB){
return *si;
}
}
return NULL;
}
//Per method pass for inserting counters and trigger code
bool ProfilePaths::runOnMethod(Method *M){
//Transform the cfg s.t. we have just one exit node
BasicBlock *ExitNode =
getAnalysis<UnifyMethodExitNodes>().getExitNode();
//iterating over BBs and making graph
std::set<Node *> nodes;
std::set<Edge> edges;
Node *tmp;
Node *exitNode, *startNode;
//The nodes must be uniquesly identified:
//That is, no two nodes must hav same BB*
//First enter just nodes: later enter edges
for (Method::iterator BB = M->begin(), BE=M->end(); BB != BE; ++BB){
Node *nd=new Node(*BB);
nodes.insert(nd);
if(*BB==ExitNode)
exitNode=nd;
if(*BB==M->front())
startNode=nd;
}
//now do it againto insert edges
for (Method::iterator BB = M->begin(), BE=M->end(); BB != BE; ++BB){
Node *nd=findBB(nodes, *BB);
assert(nd && "No node for this edge!");
for(BasicBlock::succ_iterator s=succ_begin(*BB), se=succ_end(*BB);
s!=se; ++s){
Node *nd2=findBB(nodes,*s);
assert(nd2 && "No node for this edge!");
Edge ed(nd,nd2,0);
edges.insert(ed);
}
}
Graph g(nodes,edges, startNode, exitNode);
#ifdef DEBUG_PATH_PROFILES
printGraph(g);
#endif
BasicBlock *fr=M->front();
//If only one BB, don't instrument
if (M->getBasicBlocks().size() == 1) {
//The graph is made acyclic: this is done
//by removing back edges for now, and adding them later on
vector<Edge> be;
g.getBackEdges(be);
#ifdef DEBUG_PATH_PROFILES
cerr<<"Backedges:"<<be.size()<<endl;
#endif
//Now we need to reflect the effect of back edges
//This is done by adding dummy edges
//If a->b is a back edge
//Then we add 2 back edges for it:
//1. from root->b (in vector stDummy)
//and 2. from a->exit (in vector exDummy)
vector<Edge> stDummy;
vector<Edge> exDummy;
addDummyEdges(stDummy, exDummy, g, be);
//Now, every edge in the graph is assigned a weight
//This weight later adds on to assign path
//numbers to different paths in the graph
// All paths for now are acyclic,
//since no back edges in the graph now
//numPaths is the number of acyclic paths in the graph
int numPaths=valueAssignmentToEdges(g);
//create instruction allocation r and count
//r is the variable that'll act like an accumulator
//all along the path, we just add edge values to r
//and at the end, r reflects the path number
//count is an array: count[x] would store
//the number of executions of path numbered x
Instruction *rVar=new
AllocaInst(PointerType::get(Type::IntTy),
ConstantUInt::get(Type::UIntTy,1),"R");
Instruction *countVar=new
AllocaInst(PointerType::get(Type::IntTy),
ConstantUInt::get(Type::UIntTy, numPaths), "Count");
//insert initialization code in first (entry) BB
//this includes initializing r and count
insertInTopBB(M->getEntryNode(),numPaths, rVar, countVar);
//now process the graph: get path numbers,
//get increments along different paths,
//and assign "increments" and "updates" (to r and count)
//"optimally". Finally, insert llvm code along various edges
processGraph(g, rVar, countVar, be, stDummy, exDummy);
}
return true; // Always modifies method
}
//Before this pass, make sure that there is only one
//entry and only one exit node for the method in the CFG of the method
void ProfilePaths::getAnalysisUsageInfo(Pass::AnalysisSet &Requires,
Pass::AnalysisSet &Destroyed,
Pass::AnalysisSet &Provided) {
Requires.push_back(UnifyMethodExitNodes::ID);
}