public FunctionPass, public ProfileInfo {
double ExecCount;
LoopInfo *LI;
- std::set<BasicBlock*> BBisVisited;
+ std::set<BasicBlock*> BBToVisit;
std::map<Loop*,double> LoopExitWeights;
public:
static char ID; // Class identification, replacement for typeinfo
/// run - Estimate the profile information from the specified file.
virtual bool runOnFunction(Function &F);
- BasicBlock *recurseBasicBlock(BasicBlock *BB);
+ virtual void recurseBasicBlock(BasicBlock *BB);
void inline printEdgeWeight(Edge);
};
return w;
}
-static void inline printEdgeError(ProfileInfo::Edge e) {
- DEBUG(errs() << "-- Edge " << e << " is not calculated, returning\n");
+static void inline printEdgeError(ProfileInfo::Edge e, const char *M) {
+ DEBUG(errs() << "-- Edge " << e << " is not calculated, " << M << "\n");
}
void inline ProfileEstimatorPass::printEdgeWeight(Edge E) {
// recurseBasicBlock() - This calculates the ProfileInfo estimation for a
// single block and then recurses into the successors.
-BasicBlock* ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
+// The algorithm preserves the flow condition, meaning that the sum of the
+// weight of the incoming edges must be equal the block weight which must in
+// turn be equal to the sume of the weights of the outgoing edges.
+// Since the flow of an block is deterimined from the current state of the
+// flow, once an edge has a flow assigned this flow is never changed again,
+// otherwise it would be possible to violate the flow condition in another
+// block.
+void ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
// Break the recursion if this BasicBlock was already visited.
- if (BBisVisited.find(BB) != BBisVisited.end()) return 0;
+ if (BBToVisit.find(BB) == BBToVisit.end()) return;
- // Check if incoming edges are calculated already, if BB is header allow
- // backedges that are uncalculated for now.
+ // Read the LoopInfo for this block.
bool BBisHeader = LI->isLoopHeader(BB);
Loop* BBLoop = LI->getLoopFor(BB);
+ // To get the block weight, read all incoming edges.
double BBWeight = 0;
std::set<BasicBlock*> ProcessedPreds;
for ( pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
bbi != bbe; ++bbi ) {
+ // If this block was not considered already, add weight.
Edge edge = getEdge(*bbi,BB);
double w = getEdgeWeight(edge);
if (ProcessedPreds.insert(*bbi).second) {
BBWeight += ignoreMissing(w);
}
+ // If this block is a loop header and the predecessor is contained in this
+ // loop, thus the edge is a backedge, continue and do not check if the
+ // value is valid.
if (BBisHeader && BBLoop->contains(*bbi)) {
- printEdgeError(edge);
+ printEdgeError(edge, "but is backedge, continueing");
continue;
}
+ // If the edges value is missing (and this is no loop header, and this is
+ // no backedge) return, this block is currently non estimatable.
if (w == MissingValue) {
- printEdgeError(edge);
- return BB;
+ printEdgeError(edge, "returning");
+ return;
}
}
if (getExecutionCount(BB) != MissingValue) {
BBLoop->getExitEdges(ExitEdges);
}
- // If block is an loop header, first subtract all weights from edges that
- // exit this loop, then distribute remaining weight on to the edges exiting
- // this loop. Finally the weight of the block is increased, to simulate
- // several executions of this loop.
+ // If this is a loop header, consider the following:
+ // Exactly the flow that is entering this block, must exit this block too. So
+ // do the following:
+ // *) get all the exit edges, read the flow that is already leaving this
+ // loop, remember the edges that do not have any flow on them right now.
+ // (The edges that have already flow on them are most likely exiting edges of
+ // other loops, do not touch those flows because the previously caclulated
+ // loopheaders would not be exact anymore.)
+ // *) In case there is not a single exiting edge left, create one at the loop
+ // latch to prevent the flow from building up in the loop.
+ // *) Take the flow that is not leaving the loop already and distribute it on
+ // the remaining exiting edges.
+ // (This ensures that all flow that enters the loop also leaves it.)
+ // *) Increase the flow into the loop by increasing the weight of this block.
+ // There is at least one incoming backedge that will bring us this flow later
+ // on. (So that the flow condition in this node is valid again.)
if (BBisHeader) {
double incoming = BBWeight;
// Subtract the flow leaving the loop.
printEdgeWeight(edge);
}
}
-
// Distribute remaining weight onto the exit edges.
for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
ei != ee; ++ei) {
BBWeight *= (ExecCount+1);
}
- // Remove from current flow of block all the successor edges that already
- // have some flow on them.
+ BlockInformation[BB->getParent()][BB] = BBWeight;
+ // Up until now we considered only the loop exiting edges, now we have a
+ // definite block weight and must ditribute this onto the outgoing edges.
+ // Since there may be already flow attached to some of the edges, read this
+ // flow first and remember the edges that have still now flow attached.
Edges.clear();
std::set<BasicBlock*> ProcessedSuccs;
- // Otherwise consider weight of outgoing edges and store them for
- // distribution of remaining weight. In case the block has no successors
- // create a (BB,0) edge.
succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
+ // Also check for (BB,0) edges that may already contain some flow. (But only
+ // in case there are no successors.)
if (bbi == bbe) {
Edge edge = getEdge(BB,0);
EdgeInformation[BB->getParent()][edge] = BBWeight;
}
}
- // Distribute remaining flow onto the outgoing edges.
+ // Finally we know what flow is still not leaving the block, distribute this
+ // flow onto the empty edges.
for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
ei != ee; ++ei) {
EdgeInformation[BB->getParent()][*ei] += BBWeight/Edges.size();
printEdgeWeight(*ei);
}
- // Mark this Block visited and recurse into successors.
- BBisVisited.insert(BB);
- BasicBlock *Uncalculated = 0;
- for ( succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
- bbi != bbe; ++bbi ) {
- BasicBlock* ret = recurseBasicBlock(*bbi);
- if (!Uncalculated)
- Uncalculated = ret;
+ // This block is visited, mark this before the recursion.
+ BBToVisit.erase(BB);
+
+ // Recurse into successors.
+ for (succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
+ bbi != bbe; ++bbi) {
+ recurseBasicBlock(*bbi);
}
- if (BBisVisited.find(Uncalculated) != BBisVisited.end())
- return 0;
- return Uncalculated;
}
bool ProfileEstimatorPass::runOnFunction(Function &F) {
if (F.isDeclaration()) return false;
+ // Fetch LoopInfo and clear ProfileInfo for this function.
LI = &getAnalysis<LoopInfo>();
FunctionInformation.erase(&F);
BlockInformation[&F].clear();
EdgeInformation[&F].clear();
- BBisVisited.clear();
+
+ // Mark all blocks as to visit.
+ for (Function::iterator bi = F.begin(), be = F.end(); bi != be; ++bi)
+ BBToVisit.insert(bi);
DEBUG(errs() << "Working on function " << F.getNameStr() << "\n");
// (0,entry) is inserted with the starting weight of 1.
BasicBlock *entry = &F.getEntryBlock();
BlockInformation[&F][entry] = 1;
-
Edge edge = getEdge(0,entry);
- EdgeInformation[&F][edge] = 1; printEdgeWeight(edge);
- BasicBlock *BB = entry;
- while (BB) {
- BB = recurseBasicBlock(BB);
- if (BB) {
+ EdgeInformation[&F][edge] = 1;
+ printEdgeWeight(edge);
+
+ // Since recurseBasicBlock() maybe returns with a block which was not fully
+ // estimated, use recurseBasicBlock() until everything is calculated.
+ recurseBasicBlock(entry);
+ while (BBToVisit.size() > 0) {
+ // Remember number of open blocks, this is later used to check if progress
+ // was made.
+ unsigned size = BBToVisit.size();
+
+ // Try to calculate all blocks in turn.
+ for (std::set<BasicBlock*>::iterator bi = BBToVisit.begin(),
+ be = BBToVisit.end(); bi != be; ++bi) {
+ recurseBasicBlock(*bi);
+ // If at least one block was finished, break because iterator may be
+ // invalid.
+ if (BBToVisit.size() < size) break;
+ }
+
+ // If there was not a single block resovled, make some assumptions.
+ if (BBToVisit.size() == size) {
+ BasicBlock *BB = *(BBToVisit.begin());
+ // Since this BB was not calculated because of missing incoming edges,
+ // set these edges to zero.
for (pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
bbi != bbe; ++bbi) {
Edge e = getEdge(*bbi,BB);
double w = getEdgeWeight(e);
if (w == MissingValue) {
EdgeInformation[&F][e] = 0;
- errs() << "Assuming edge weight: ";
+ DEBUG(errs() << "Assuming edge weight: ");
printEdgeWeight(e);
}
}
}
}
-// compare with relative error
+// This compares A and B but considering maybe small differences.
static bool Equals(double A, double B) {
double maxRelativeError = 0.0000001;
if (A == B)
return false;
}
+// This checks if the function "exit" is reachable from an given function
+// via calls, this is necessary to check if a profile is valid despite the
+// counts not fitting exactly.
bool ProfileVerifierPass::exitReachable(const Function *F) {
if (!F) return false;
double EdgeWeight = PI->getEdgeWeight(E);
if (EdgeWeight == ProfileInfo::MissingValue) {
errs() << "Edge " << E << " in Function "
- << E.first->getParent()->getNameStr() << ": ";
+ << ProfileInfo.getFunction(E)->getNameStr() << ": ";
ASSERTMESSAGE("ASSERT:Edge has missing value");
return 0;
} else {
return;
}
+// This calculates the Information for a block and then recurses into the
+// successors.
void ProfileVerifierPass::recurseBasicBlock(const BasicBlock *BB) {
+ // Break the recursion by remembering all visited blocks.
if (BBisVisited.find(BB) != BBisVisited.end()) return;
+ // Use a data structure to store all the information, this can then be handed
+ // to debug printers.
DetailedBlockInfo DI;
DI.BB = BB;
DI.outCount = DI.inCount = DI.inWeight = DI.outWeight = 0;
+
+ // Read predecessors.
std::set<const BasicBlock*> ProcessedPreds;
pred_const_iterator bpi = pred_begin(BB), bpe = pred_end(BB);
+ // If there are none, check for (0,BB) edge.
if (bpi == bpe) {
DI.inWeight += ReadOrAssert(PI->getEdge(0,BB));
DI.inCount++;
}
}
+ // Read successors.
std::set<const BasicBlock*> ProcessedSuccs;
succ_const_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
- if (bbi == bbe) {
- double w = PI->getEdgeWeight(PI->getEdge(BB,0));
- if (w != ProfileInfo::MissingValue) {
- DI.outWeight += w;
- DI.outCount++;
- }
+ // If there is an (0,BB) edge, consider it too. (This is done not only when
+ // there are no successors, but every time; not every function contains
+ // return blocks with no successors (think loop latch as return block)).
+ double w = PI->getEdgeWeight(PI->getEdge(BB,0));
+ if (w != ProfileInfo::MissingValue) {
+ DI.outWeight += w;
+ DI.outCount++;
}
for (;bbi != bbe; ++bbi) {
if (ProcessedSuccs.insert(*bbi).second) {
}
}
+ // Read block weight.
DI.BBWeight = PI->getExecutionCount(BB);
CheckValue(DI.BBWeight == ProfileInfo::MissingValue,
"ASSERT:BasicBlock has missing value", &DI);
}
- // mark as visited and recurse into subnodes
+ // Mark this block as visited, rescurse into successors.
BBisVisited.insert(BB);
for ( succ_const_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
bbi != bbe; ++bbi ) {
bool ProfileVerifierPass::runOnFunction(Function &F) {
PI = &getAnalysis<ProfileInfo>();
- if (PI->getExecutionCount(&F) == ProfileInfo::MissingValue) {
- DEBUG(errs() << "Function " << F.getNameStr() << " has no profile\n");
- return false;
- }
-
+ // Prepare global variables.
PrintedDebugTree = false;
BBisVisited.clear();
+ // Fetch entry block and recurse into it.
const BasicBlock *entry = &F.getEntryBlock();
recurseBasicBlock(entry);
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