llvm-6502/lib/Analysis/ProfileEstimatorPass.cpp
Daniel Dunbar 55e354ac0e Add a basic static ProfileInfo provider (ProfileEstimatorPass).
- Part of optimal static profiling patch sequence by Andreas Neustifter.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78484 91177308-0d34-0410-b5e6-96231b3b80d8
2009-08-08 18:44:18 +00:00

237 lines
7.6 KiB
C++

//===- 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"
using namespace llvm;
static cl::opt<double>
ProfileInfoExecCount(
"profile-estimator-loop-weight", cl::init(10),
cl::value_desc("loop-weight"),
cl::desc("Number of loop executions used for profile-estimator")
);
namespace {
class VISIBILITY_HIDDEN ProfileEstimatorPass :
public FunctionPass, public ProfileInfo {
double ExecCount;
LoopInfo *LI;
std::set<BasicBlock*> BBisVisited;
std::map<Loop*,double> LoopExitWeights;
public:
static char ID; // Class identification, replacement for typeinfo
explicit ProfileEstimatorPass(const double execcount = 0)
: FunctionPass(&ID), ExecCount(execcount) {
if (execcount == 0) ExecCount = ProfileInfoExecCount;
}
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);
virtual void recurseBasicBlock(BasicBlock *BB);
};
} // End of anonymous namespace
char ProfileEstimatorPass::ID = 0;
static RegisterPass<ProfileEstimatorPass>
X("profile-estimator", "Estimate profiling information", false, true);
static RegisterAnalysisGroup<ProfileInfo> Y(X);
namespace llvm {
const PassInfo *ProfileEstimatorPassID = &X;
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;
}
#define EDGE_ERROR(V1,V2) \
DEBUG(errs() << "-- Edge (" <<(V1)->getName() << "," << (V2)->getName() \
<< ") is not calculated, returning\n")
#define EDGE_WEIGHT(E) \
DEBUG(errs() << "-- Weight of Edge (" \
<< ((E).first ? (E).first->getNameStr() : "0") \
<< "," << (E).second->getName() << "):" \
<< getEdgeWeight(E) << "\n")
// recurseBasicBlock() - This calculates the ProfileInfo estimation for a
// single block and then recurses into the successors.
void ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
// break recursion if already visited
if (BBisVisited.find(BB) != BBisVisited.end()) return;
// check if uncalculated incoming edges are calculated already, if BB is
// header allow backedges
bool BBisHeader = LI->isLoopHeader(BB);
Loop* BBLoop = LI->getLoopFor(BB);
double BBWeight = 0;
std::set<BasicBlock*> ProcessedPreds;
for ( pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
bbi != bbe; ++bbi ) {
if (ProcessedPreds.insert(*bbi).second) {
Edge edge = getEdge(*bbi,BB);
BBWeight += ignoreMissing(getEdgeWeight(edge));
}
if (BBisHeader && BBLoop == LI->getLoopFor(*bbi)) {
EDGE_ERROR(*bbi,BB);
continue;
}
if (BBisVisited.find(*bbi) == BBisVisited.end()) {
EDGE_ERROR(*bbi,BB);
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 block is an loop header, first subtract all weigths 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 (BBisHeader) {
double incoming = BBWeight;
// subtract the flow leaving the loop
for (SmallVector<Edge, 8>::iterator ei = ExitEdges.begin(),
ee = ExitEdges.end(); ei != ee; ++ei) {
double w = getEdgeWeight(*ei);
if (w == MissingValue) {
Edges.push_back(*ei);
} else {
incoming -= w;
}
}
// distribute remaining weight onto the exit edges
for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
ei != ee; ++ei) {
EdgeInformation[BB->getParent()][*ei] += incoming/Edges.size();
EDGE_WEIGHT(*ei);
}
// increase flow into the loop
BBWeight *= (ExecCount+1);
}
// remove from current flow of block all the successor edges that already
// have some flow on them
Edges.clear();
std::set<BasicBlock*> ProcessedSuccs;
for ( succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
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);
}
}
}
// distribute remaining flow onto the outgoing edges
for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
ei != ee; ++ei) {
EdgeInformation[BB->getParent()][*ei] += BBWeight/Edges.size();
EDGE_WEIGHT(*ei);
}
// mark as visited and recurse into subnodes
BBisVisited.insert(BB);
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;
LI = &getAnalysis<LoopInfo>();
FunctionInformation.erase(&F);
BlockInformation[&F].clear();
EdgeInformation[&F].clear();
BBisVisited.clear();
DEBUG(errs() << "Working on function " << F.getName() << "\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] = 1;
Edge edge = getEdge(0,entry);
EdgeInformation[&F][edge] = 1; EDGE_WEIGHT(edge);
recurseBasicBlock(entry);
// in case something went wrong, clear all results, not profiling info
// available
if (BBisVisited.size() != F.size()) {
DEBUG(errs() << "-- could not estimate profile, using default profile\n");
FunctionInformation.erase(&F);
BlockInformation[&F].clear();
for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) {
for (pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
bbi != bbe; ++bbi) {
Edge e = getEdge(*bbi,BB);
EdgeInformation[&F][e] = 1; EDGE_WEIGHT(edge);
}
for (succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
bbi != bbe; ++bbi) {
Edge e = getEdge(BB,*bbi);
EdgeInformation[&F][e] = 1; EDGE_WEIGHT(edge);
}
}
}
return false;
}