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Make ProfileEstimator even more robust on general CFGs.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81516 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andreas Neustifter 2009-09-11 08:39:33 +00:00
parent 9e6ffba26b
commit 8a58c180c2
2 changed files with 112 additions and 55 deletions
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128
lib/Analysis/ProfileEstimatorPass.cpp
View File

@ -34,7 +34,7 @@ namespace {
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
@ -55,7 +55,7 @@ namespace {
/// 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);
};
@ -86,8 +86,8 @@ static double ignoreMissing(double w) {
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) {
@ -97,32 +97,45 @@ 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) {
@ -136,10 +149,22 @@ BasicBlock* ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
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.
@ -167,7 +192,6 @@ BasicBlock* ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
printEdgeWeight(edge);
}
}
// Distribute remaining weight onto the exit edges.
for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
ei != ee; ++ei) {
@ -178,15 +202,17 @@ BasicBlock* ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
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;
@ -204,35 +230,36 @@ BasicBlock* ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
}
}
// 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");
@ -240,20 +267,39 @@ bool ProfileEstimatorPass::runOnFunction(Function &F) {
// (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);
}
}

39
lib/Analysis/ProfileVerifierPass.cpp
View File

@ -153,7 +153,7 @@ void ProfileVerifierPass::debugEntry (DetailedBlockInfo *DI) {
}
}
// 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)
@ -167,6 +167,9 @@ static bool Equals(double A, double 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;
@ -196,7 +199,7 @@ double ProfileVerifierPass::ReadOrAssert(ProfileInfo::Edge E) {
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 {
@ -215,15 +218,23 @@ void ProfileVerifierPass::CheckValue(bool Error, const char *Message,
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++;
@ -235,14 +246,16 @@ void ProfileVerifierPass::recurseBasicBlock(const BasicBlock *BB) {
}
}
// 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) {
@ -251,6 +264,7 @@ void ProfileVerifierPass::recurseBasicBlock(const BasicBlock *BB) {
}
}
// Read block weight.
DI.BBWeight = PI->getExecutionCount(BB);
CheckValue(DI.BBWeight == ProfileInfo::MissingValue,
"ASSERT:BasicBlock has missing value", &DI);
@ -303,7 +317,7 @@ void ProfileVerifierPass::recurseBasicBlock(const BasicBlock *BB) {
}
// 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 ) {
@ -314,14 +328,11 @@ void ProfileVerifierPass::recurseBasicBlock(const BasicBlock *BB) {
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);