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

1 files changed, 236 insertions, 0 deletions

diff --git a/lib/Analysis/ProfileEstimatorPass.cpp b/lib/Analysis/ProfileEstimatorPass.cpp
new file mode 100644
index 0000000..0efb5ac
--- /dev/null
+++ b/lib/Analysis/ProfileEstimatorPass.cpp
@@ -0,0 +1,236 @@
+//===- 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;
+}