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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80711 91177308-0d34-0410-b5e6-96231b3b80d8
251 lines
8.0 KiB
C++
251 lines
8.0 KiB
C++
//===- ProfileEstimatorPass.cpp - LLVM Pass to estimate profile info ------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements a concrete implementation of profiling information that
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// estimates the profiling information in a very crude and unimaginative way.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "profile-estimator"
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#include "llvm/Pass.h"
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#include "llvm/Analysis/Passes.h"
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#include "llvm/Analysis/ProfileInfo.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/Format.h"
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using namespace llvm;
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static cl::opt<double>
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LoopWeight(
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"profile-estimator-loop-weight", cl::init(10),
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cl::value_desc("loop-weight"),
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cl::desc("Number of loop executions used for profile-estimator")
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);
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namespace {
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class VISIBILITY_HIDDEN ProfileEstimatorPass :
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public FunctionPass, public ProfileInfo {
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double ExecCount;
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LoopInfo *LI;
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std::set<BasicBlock*> BBisVisited;
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std::map<Loop*,double> LoopExitWeights;
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public:
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static char ID; // Class identification, replacement for typeinfo
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explicit ProfileEstimatorPass(const double execcount = 0)
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: FunctionPass(&ID), ExecCount(execcount) {
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if (execcount == 0) ExecCount = LoopWeight;
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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AU.addRequired<LoopInfo>();
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}
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virtual const char *getPassName() const {
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return "Profiling information estimator";
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}
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/// run - Estimate the profile information from the specified file.
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virtual bool runOnFunction(Function &F);
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virtual void recurseBasicBlock(BasicBlock *BB);
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void inline printEdgeWeight(Edge);
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};
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} // End of anonymous namespace
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char ProfileEstimatorPass::ID = 0;
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static RegisterPass<ProfileEstimatorPass>
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X("profile-estimator", "Estimate profiling information", false, true);
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static RegisterAnalysisGroup<ProfileInfo> Y(X);
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namespace llvm {
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const PassInfo *ProfileEstimatorPassID = &X;
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FunctionPass *createProfileEstimatorPass() {
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return new ProfileEstimatorPass();
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}
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/// createProfileEstimatorPass - This function returns a Pass that estimates
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/// profiling information using the given loop execution count.
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Pass *createProfileEstimatorPass(const unsigned execcount) {
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return new ProfileEstimatorPass(execcount);
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}
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}
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static double ignoreMissing(double w) {
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if (w == ProfileInfo::MissingValue) return 0;
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return w;
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}
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static void inline printEdgeError(BasicBlock *V1, BasicBlock *V2) {
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DEBUG(errs() << "-- Edge (" <<(V1)->getName() << "," << (V2)->getName() \
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<< ") is not calculated, returning\n");
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}
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void inline ProfileEstimatorPass::printEdgeWeight(Edge E) {
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DEBUG(errs() << "-- Weight of Edge " << E << ":"
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<< format("%g", getEdgeWeight(E)) << "\n");
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}
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// recurseBasicBlock() - This calculates the ProfileInfo estimation for a
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// single block and then recurses into the successors.
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void ProfileEstimatorPass::recurseBasicBlock(BasicBlock *BB) {
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// Break the recursion if this BasicBlock was already visited.
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if (BBisVisited.find(BB) != BBisVisited.end()) return;
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// Check if incoming edges are calculated already, if BB is header allow
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// backedges that are uncalculated for now.
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bool BBisHeader = LI->isLoopHeader(BB);
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Loop* BBLoop = LI->getLoopFor(BB);
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double BBWeight = 0;
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std::set<BasicBlock*> ProcessedPreds;
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for ( pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
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bbi != bbe; ++bbi ) {
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if (ProcessedPreds.insert(*bbi).second) {
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Edge edge = getEdge(*bbi,BB);
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BBWeight += ignoreMissing(getEdgeWeight(edge));
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}
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if (BBisHeader && BBLoop == LI->getLoopFor(*bbi)) {
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printEdgeError(*bbi,BB);
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continue;
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}
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if (BBisVisited.find(*bbi) == BBisVisited.end()) {
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printEdgeError(*bbi,BB);
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return;
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}
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}
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if (getExecutionCount(BB) != MissingValue) {
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BBWeight = getExecutionCount(BB);
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}
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// Fetch all necessary information for current block.
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SmallVector<Edge, 8> ExitEdges;
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SmallVector<Edge, 8> Edges;
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if (BBLoop) {
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BBLoop->getExitEdges(ExitEdges);
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}
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// If block is an loop header, first subtract all weights from edges that
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// exit this loop, then distribute remaining weight on to the edges exiting
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// this loop. Finally the weight of the block is increased, to simulate
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// several executions of this loop.
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if (BBisHeader) {
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double incoming = BBWeight;
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// Subtract the flow leaving the loop.
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for (SmallVector<Edge, 8>::iterator ei = ExitEdges.begin(),
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ee = ExitEdges.end(); ei != ee; ++ei) {
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double w = getEdgeWeight(*ei);
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if (w == MissingValue) {
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Edges.push_back(*ei);
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} else {
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incoming -= w;
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}
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}
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// Distribute remaining weight onto the exit edges.
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for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
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ei != ee; ++ei) {
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EdgeInformation[BB->getParent()][*ei] += incoming/Edges.size();
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printEdgeWeight(*ei);
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}
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// Increase flow into the loop.
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BBWeight *= (ExecCount+1);
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}
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// Remove from current flow of block all the successor edges that already
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// have some flow on them.
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Edges.clear();
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std::set<BasicBlock*> ProcessedSuccs;
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// Otherwise consider weight of outgoing edges and store them for
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// distribution of remaining weight. In case the block has no successors
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// create a (BB,0) edge.
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succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
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if (bbi == bbe) {
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Edge edge = getEdge(BB,0);
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EdgeInformation[BB->getParent()][edge] = BBWeight;
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printEdgeWeight(edge);
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}
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for ( ; bbi != bbe; ++bbi ) {
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if (ProcessedSuccs.insert(*bbi).second) {
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Edge edge = getEdge(BB,*bbi);
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double w = getEdgeWeight(edge);
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if (w != MissingValue) {
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BBWeight -= getEdgeWeight(edge);
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} else {
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Edges.push_back(edge);
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}
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}
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}
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// Distribute remaining flow onto the outgoing edges.
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for (SmallVector<Edge, 8>::iterator ei = Edges.begin(), ee = Edges.end();
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ei != ee; ++ei) {
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EdgeInformation[BB->getParent()][*ei] += BBWeight/Edges.size();
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printEdgeWeight(*ei);
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}
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// Mark this Block visited and recurse into successors.
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BBisVisited.insert(BB);
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for ( succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
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bbi != bbe;
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++bbi ) {
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recurseBasicBlock(*bbi);
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}
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}
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bool ProfileEstimatorPass::runOnFunction(Function &F) {
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if (F.isDeclaration()) return false;
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LI = &getAnalysis<LoopInfo>();
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FunctionInformation.erase(&F);
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BlockInformation[&F].clear();
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EdgeInformation[&F].clear();
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BBisVisited.clear();
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DEBUG(errs() << "Working on function " << F.getNameStr() << "\n");
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// Since the entry block is the first one and has no predecessors, the edge
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// (0,entry) is inserted with the starting weight of 1.
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BasicBlock *entry = &F.getEntryBlock();
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BlockInformation[&F][entry] = 1;
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Edge edge = getEdge(0,entry);
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EdgeInformation[&F][edge] = 1; printEdgeWeight(edge);
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recurseBasicBlock(entry);
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// In case something went wrong, clear all results, not profiling info is
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// available.
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if (BBisVisited.size() != F.size()) {
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DEBUG(errs() << "-- could not estimate profile, using default profile\n");
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FunctionInformation.erase(&F);
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BlockInformation[&F].clear();
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for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) {
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for (pred_iterator bbi = pred_begin(BB), bbe = pred_end(BB);
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bbi != bbe; ++bbi) {
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Edge e = getEdge(*bbi,BB);
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EdgeInformation[&F][e] = 1;
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printEdgeWeight(e);
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}
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for (succ_iterator bbi = succ_begin(BB), bbe = succ_end(BB);
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bbi != bbe; ++bbi) {
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Edge e = getEdge(BB,*bbi);
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EdgeInformation[&F][e] = 1;
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printEdgeWeight(e);
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}
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}
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}
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return false;
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}
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