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llvm-6502/lib/Analysis/ProfileEstimatorPass.cpp

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//===- ProfileEstimatorPass.cpp - LLVM Pass to estimate profile info ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a concrete implementation of profiling information that
// estimates the profiling information in a very crude and unimaginative way.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "profile-estimator"
#include "llvm/Pass.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/ProfileInfo.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Format.h"
using namespace llvm;
static cl::opt<double>
LoopWeight(
"profile-estimator-loop-weight", cl::init(10),
cl::value_desc("loop-weight"),
cl::desc("Number of loop executions used for profile-estimator")
);
namespace {
class ProfileEstimatorPass : public FunctionPass, public ProfileInfo {
double ExecCount;
LoopInfo *LI;
std::set<BasicBlock*> BBToVisit;
std::map<Loop*,double> LoopExitWeights;
std::map<Edge,double> MinimalWeight;
public:
static char ID; // Class identification, replacement for typeinfo
explicit ProfileEstimatorPass(const double execcount = 0)
: FunctionPass(ID), ExecCount(execcount) {
if (execcount == 0) ExecCount = LoopWeight;
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<LoopInfo>();
}
virtual const char *getPassName() const {
return "Profiling information estimator";
}
/// run - Estimate the profile information from the specified file.
virtual bool runOnFunction(Function &F);
/// getAdjustedAnalysisPointer - This method is used when a pass implements
/// an analysis interface through multiple inheritance. If needed, it
/// should override this to adjust the this pointer as needed for the
/// specified pass info.
virtual void *getAdjustedAnalysisPointer(AnalysisID PI) {
if (PI == &ProfileInfo::ID)
return (ProfileInfo*)this;
return this;
}
virtual void recurseBasicBlock(BasicBlock *BB);
void inline printEdgeWeight(Edge);
};
} // End of anonymous namespace
char ProfileEstimatorPass::ID = 0;
INITIALIZE_AG_PASS(ProfileEstimatorPass, ProfileInfo, "profile-estimator",
"Estimate profiling information", false, true, false);
namespace llvm {
char &ProfileEstimatorPassID = ProfileEstimatorPass::ID;
FunctionPass *createProfileEstimatorPass() {
return new ProfileEstimatorPass();
}
/// createProfileEstimatorPass - This function returns a Pass that estimates
/// profiling information using the given loop execution count.
Pass *createProfileEstimatorPass(const unsigned execcount) {
return new ProfileEstimatorPass(execcount);
}
}
static double ignoreMissing(double w) {
if (w == ProfileInfo::MissingValue) return 0;
return w;
}
static void inline printEdgeError(ProfileInfo::Edge e, const char *M) {
DEBUG(dbgs() << "-- Edge " << e << " is not calculated, " << M << "\n");
}
void inline ProfileEstimatorPass::printEdgeWeight(Edge E) {
DEBUG(dbgs() << "-- Weight of Edge " << E << ":"
<< format("%20.20g", getEdgeWeight(E)) << "\n");
}
// recurseBasicBlock() - This calculates the ProfileInfo estimation for a
// single block and then recurses into the successors.
// 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 (BBToVisit.find(BB) == BBToVisit.end()) return;
// 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, "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, "returning");
return;
}
}
if (getExecutionCount(BB) != MissingValue) {
BBWeight = getExecutionCount(BB);
}
// Fetch all necessary information for current block.
SmallVector<Edge, 8> ExitEdges;
SmallVector<Edge, 8> Edges;
if (BBLoop) {
BBLoop->getExitEdges(ExitEdges);
}
// 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.
std::set<Edge> ProcessedExits;
for (SmallVector<Edge, 8>::iterator ei = ExitEdges.begin(),
ee = ExitEdges.end(); ei != ee; ++ei) {
if (ProcessedExits.insert(*ei).second) {
double w = getEdgeWeight(*ei);
if (w == MissingValue) {
Edges.push_back(*ei);
// Check if there is a necessary minimal weight, if yes, subtract it
// from weight.
if (MinimalWeight.find(*ei) != MinimalWeight.end()) {
incoming -= MinimalWeight[*ei];
DEBUG(dbgs() << "Reserving " << format("%.20g",MinimalWeight[*ei]) << " at " << (*ei) << "\n");
}
} else {
incoming -= w;
}
}
}
// If no exit edges, create one:
if (Edges.size() == 0) {
BasicBlock *Latch = BBLoop->getLoopLatch();
if (Latch) {
Edge edge = getEdge(Latch,0);
EdgeInformation[BB->getParent()][edge] = BBWeight;
printEdgeWeight(edge);
edge = getEdge(Latch, BB);
EdgeInformation[BB->getParent()][edge] = BBWeight * ExecCount;
printEdgeWeight(edge);
}
}
// Distribute remaining weight to the exting edges. To prevent fractions
// from building up and provoking precision problems the weight which is to
// be distributed is split and the rounded, the last edge gets a somewhat
// bigger value, but we are close enough for an estimation.
double fraction = floor(incoming/Edges.size());
for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
ei != ee; ++ei) {
double w = 0;
if (ei != (ee-1)) {
w = fraction;
incoming -= fraction;
} else {
w = incoming;
}
EdgeInformation[BB->getParent()][*ei] += w;
// Read necessary minimal weight.
if (MinimalWeight.find(*ei) != MinimalWeight.end()) {
EdgeInformation[BB->getParent()][*ei] += MinimalWeight[*ei];
DEBUG(dbgs() << "Additionally " << format("%.20g",MinimalWeight[*ei]) << " at " << (*ei) << "\n");
}
printEdgeWeight(*ei);
// Add minimal weight to paths to all exit edges, this is used to ensure
// that enough flow is reaching this edges.
Path p;
const BasicBlock *Dest = GetPath(BB, (*ei).first, p, GetPathToDest);
while (Dest != BB) {
const BasicBlock *Parent = p.find(Dest)->second;
Edge e = getEdge(Parent, Dest);
if (MinimalWeight.find(e) == MinimalWeight.end()) {
MinimalWeight[e] = 0;
}
MinimalWeight[e] += w;
DEBUG(dbgs() << "Minimal Weight for " << e << ": " << format("%.20g",MinimalWeight[e]) << "\n");
Dest = Parent;
}
}
// Increase flow into the loop.
BBWeight *= (ExecCount+1);
}
BlockInformation[BB->getParent()][BB] = BBWeight;
// Up until now we considered only the loop exiting edges, now we have a
// definite block weight and must distribute 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;
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;
printEdgeWeight(edge);
}
for ( ; bbi != bbe; ++bbi ) {
if (ProcessedSuccs.insert(*bbi).second) {
Edge edge = getEdge(BB,*bbi);
double w = getEdgeWeight(edge);
if (w != MissingValue) {
BBWeight -= getEdgeWeight(edge);
} else {
Edges.push_back(edge);
// If minimal weight is necessary, reserve weight by subtracting weight
// from block weight, this is readded later on.
if (MinimalWeight.find(edge) != MinimalWeight.end()) {
BBWeight -= MinimalWeight[edge];
DEBUG(dbgs() << "Reserving " << format("%.20g",MinimalWeight[edge]) << " at " << edge << "\n");
}
}
}
}
double fraction = floor(BBWeight/Edges.size());
// 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) {
if (ei != (ee-1)) {
EdgeInformation[BB->getParent()][*ei] += fraction;
BBWeight -= fraction;
} else {
EdgeInformation[BB->getParent()][*ei] += BBWeight;
}
// Readd minial necessary weight.
if (MinimalWeight.find(*ei) != MinimalWeight.end()) {
EdgeInformation[BB->getParent()][*ei] += MinimalWeight[*ei];
DEBUG(dbgs() << "Additionally " << format("%.20g",MinimalWeight[*ei]) << " at " << (*ei) << "\n");
}
printEdgeWeight(*ei);
}
// 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);
}
}
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();
// Mark all blocks as to visit.
for (Function::iterator bi = F.begin(), be = F.end(); bi != be; ++bi)
BBToVisit.insert(bi);
// Clear Minimal Edges.
MinimalWeight.clear();
DEBUG(dbgs() << "Working on function " << F.getNameStr() << "\n");
// Since the entry block is the first one and has no predecessors, the edge
// (0,entry) is inserted with the starting weight of 1.
BasicBlock *entry = &F.getEntryBlock();
BlockInformation[&F][entry] = pow(2.0, 32.0);
Edge edge = getEdge(0,entry);
EdgeInformation[&F][edge] = BlockInformation[&F][entry];
printEdgeWeight(edge);
// Since recurseBasicBlock() maybe returns with a block which was not fully
// estimated, use recurseBasicBlock() until everything is calculated.
bool cleanup = false;
recurseBasicBlock(entry);
while (BBToVisit.size() > 0 && !cleanup) {
// 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 resolved, make some assumptions.
if (BBToVisit.size() == size) {
bool found = false;
for (std::set<BasicBlock*>::iterator BBI = BBToVisit.begin(), BBE = BBToVisit.end();
(BBI != BBE) && (!found); ++BBI) {
BasicBlock *BB = *BBI;
// Try each predecessor if it can be assumend.
for (pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
(bbi != bbe) && (!found); ++bbi) {
Edge e = getEdge(*bbi,BB);
double w = getEdgeWeight(e);
// Check that edge from predecessor is still free.
if (w == MissingValue) {
// Check if there is a circle from this block to predecessor.
Path P;
const BasicBlock *Dest = GetPath(BB, *bbi, P, GetPathToDest);
if (Dest != *bbi) {
// If there is no circle, just set edge weight to 0
EdgeInformation[&F][e] = 0;
DEBUG(dbgs() << "Assuming edge weight: ");
printEdgeWeight(e);
found = true;
}
}
}
}
if (!found) {
cleanup = true;
DEBUG(dbgs() << "No assumption possible in Fuction "<<F.getName()<<", setting all to zero\n");
}
}
}
// In case there was no safe way to assume edges, set as a last measure,
// set _everything_ to zero.
if (cleanup) {
FunctionInformation[&F] = 0;
BlockInformation[&F].clear();
EdgeInformation[&F].clear();
for (Function::const_iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
const BasicBlock *BB = &(*FI);
BlockInformation[&F][BB] = 0;
const_pred_iterator predi = pred_begin(BB), prede = pred_end(BB);
if (predi == prede) {
Edge e = getEdge(0,BB);
setEdgeWeight(e,0);
}
for (;predi != prede; ++predi) {
Edge e = getEdge(*predi,BB);
setEdgeWeight(e,0);
}
succ_const_iterator succi = succ_begin(BB), succe = succ_end(BB);
if (succi == succe) {
Edge e = getEdge(BB,0);
setEdgeWeight(e,0);
}
for (;succi != succe; ++succi) {
Edge e = getEdge(*succi,BB);
setEdgeWeight(e,0);
}
}
}
return false;
}
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