1 files changed, 219 insertions, 0 deletions
diff --git a/lib/Transforms/Instrumentation/OptimalEdgeProfiling.cpp b/lib/Transforms/Instrumentation/OptimalEdgeProfiling.cpp
new file mode 100644
index 0000000..b2e6747
--- /dev/null
+++ b/lib/Transforms/Instrumentation/OptimalEdgeProfiling.cpp
@@ -0,0 +1,219 @@
+//===- OptimalEdgeProfiling.cpp - Insert counters for opt. edge profiling -===//
+//
+//                      The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass instruments the specified program with counters for edge profiling.
+// Edge profiling can give a reasonable approximation of the hot paths through a
+// program, and is used for a wide variety of program transformations.
+//
+//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "insert-optimal-edge-profiling"
+#include "ProfilingUtils.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/ProfileInfo.h"
+#include "llvm/Analysis/ProfileInfoLoader.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Instrumentation.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "MaximumSpanningTree.h"
+#include <set>
+using namespace llvm;
+
+STATISTIC(NumEdgesInserted, "The # of edges inserted.");
+
+namespace {
+  class VISIBILITY_HIDDEN OptimalEdgeProfiler : public ModulePass {
+    bool runOnModule(Module &M);
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    OptimalEdgeProfiler() : ModulePass(&ID) {}
+
+    void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequiredID(ProfileEstimatorPassID);
+      AU.addRequired<ProfileInfo>();
+    }
+
+    virtual const char *getPassName() const {
+      return "Optimal Edge Profiler";
+    }
+  };
+}
+
+char OptimalEdgeProfiler::ID = 0;
+static RegisterPass<OptimalEdgeProfiler>
+X("insert-optimal-edge-profiling", 
+  "Insert optimal instrumentation for edge profiling");
+
+ModulePass *llvm::createOptimalEdgeProfilerPass() {
+  return new OptimalEdgeProfiler();
+}
+
+inline static void printEdgeCounter(ProfileInfo::Edge e,
+                                    BasicBlock* b,
+                                    unsigned i) {
+  DEBUG(errs() << "--Edge Counter for " << (e) << " in " \
+               << ((b)?(b)->getNameStr():"0") << " (# " << (i) << ")\n");
+}
+
+bool OptimalEdgeProfiler::runOnModule(Module &M) {
+  Function *Main = M.getFunction("main");
+  if (Main == 0) {
+    errs() << "WARNING: cannot insert edge profiling into a module"
+           << " with no main function!\n";
+    return false;  // No main, no instrumentation!
+  }
+
+  // NumEdges counts all the edges that may be instrumented. Later on its
+  // decided which edges to actually instrument, to achieve optimal profiling.
+  // For the entry block a virtual edge (0,entry) is reserved, for each block
+  // with no successors an edge (BB,0) is reserved. These edges are necessary
+  // to calculate a truly optimal maximum spanning tree and thus an optimal
+  // instrumentation.
+  unsigned NumEdges = 0;
+
+  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+    if (F->isDeclaration()) continue;
+    // Reserve space for (0,entry) edge.
+    ++NumEdges;
+    for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
+      // Keep track of which blocks need to be instrumented.  We don't want to
+      // instrument blocks that are added as the result of breaking critical
+      // edges!
+      if (BB->getTerminator()->getNumSuccessors() == 0) {
+        // Reserve space for (BB,0) edge.
+        ++NumEdges;
+      } else {
+        NumEdges += BB->getTerminator()->getNumSuccessors();
+      }
+    }
+  }
+
+  // In the profiling output a counter for each edge is reserved, but only few
+  // are used. This is done to be able to read back in the profile without
+  // calulating the maximum spanning tree again, instead each edge counter that
+  // is not used is initialised with -1 to signal that this edge counter has to
+  // be calculated from other edge counters on reading the profile info back
+  // in.
+
+  const Type *Int32 = Type::getInt32Ty(M.getContext());
+  const ArrayType *ATy = ArrayType::get(Int32, NumEdges);
+  GlobalVariable *Counters =
+    new GlobalVariable(M, ATy, false, GlobalValue::InternalLinkage,
+                       Constant::getNullValue(ATy), "OptEdgeProfCounters");
+  NumEdgesInserted = 0;
+
+  std::vector<Constant*> Initializer(NumEdges);
+  Constant* Zero = ConstantInt::get(Int32, 0);
+  Constant* Uncounted = ConstantInt::get(Int32, ProfileInfoLoader::Uncounted);
+
+  // Instrument all of the edges not in MST...
+  unsigned i = 0;
+  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+    if (F->isDeclaration()) continue;
+    DEBUG(errs()<<"Working on "<<F->getNameStr()<<"\n");
+
+    // Calculate a Maximum Spanning Tree with the edge weights determined by
+    // ProfileEstimator. ProfileEstimator also assign weights to the virtual
+    // edges (0,entry) and (BB,0) (for blocks with no successors) and this
+    // edges also participate in the maximum spanning tree calculation. 
+    // The third parameter of MaximumSpanningTree() has the effect that not the
+    // actual MST is returned but the edges _not_ in the MST.
+
+    ProfileInfo::EdgeWeights ECs = 
+      getAnalysisID<ProfileInfo>(ProfileEstimatorPassID, *F).getEdgeWeights(F);
+    std::vector<ProfileInfo::EdgeWeight> EdgeVector(ECs.begin(), ECs.end());
+    MaximumSpanningTree<BasicBlock> MST (EdgeVector);
+    std::stable_sort(MST.begin(),MST.end());
+
+    // Check if (0,entry) not in the MST. If not, instrument edge
+    // (IncrementCounterInBlock()) and set the counter initially to zero, if
+    // the edge is in the MST the counter is initialised to -1.
+
+    BasicBlock *entry = &(F->getEntryBlock());
+    ProfileInfo::Edge edge = ProfileInfo::getEdge(0,entry);
+    if (!std::binary_search(MST.begin(), MST.end(), edge)) {
+      printEdgeCounter(edge,entry,i);
+      IncrementCounterInBlock(entry, i, Counters); NumEdgesInserted++;
+      Initializer[i++] = (Zero);
+    } else{
+      Initializer[i++] = (Uncounted);
+    }
+
+    // InsertedBlocks contains all blocks that were inserted for splitting an
+    // edge, this blocks do not have to be instrumented.
+    DenseSet<BasicBlock*> InsertedBlocks;
+    for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
+      // Check if block was not inserted and thus does not have to be
+      // instrumented.
+      if (InsertedBlocks.count(BB)) continue;
+
+      // Okay, we have to add a counter of each outgoing edge not in MST. If
+      // the outgoing edge is not critical don't split it, just insert the
+      // counter in the source or destination of the edge. Also, if the block
+      // has no successors, the virtual edge (BB,0) is processed.
+      TerminatorInst *TI = BB->getTerminator();
+      if (TI->getNumSuccessors() == 0) {
+        ProfileInfo::Edge edge = ProfileInfo::getEdge(BB,0);
+        if (!std::binary_search(MST.begin(), MST.end(), edge)) {
+          printEdgeCounter(edge,BB,i);
+          IncrementCounterInBlock(BB, i, Counters); NumEdgesInserted++;
+          Initializer[i++] = (Zero);
+        } else{
+          Initializer[i++] = (Uncounted);
+        }
+      }
+      for (unsigned s = 0, e = TI->getNumSuccessors(); s != e; ++s) {
+        BasicBlock *Succ = TI->getSuccessor(s);
+        ProfileInfo::Edge edge = ProfileInfo::getEdge(BB,Succ);
+        if (!std::binary_search(MST.begin(), MST.end(), edge)) {
+
+          // If the edge is critical, split it.
+          bool wasInserted = SplitCriticalEdge(TI, s, this);
+          Succ = TI->getSuccessor(s);
+          if (wasInserted)
+            InsertedBlocks.insert(Succ);
+
+          // Okay, we are guaranteed that the edge is no longer critical.  If
+          // we only have a single successor, insert the counter in this block,
+          // otherwise insert it in the successor block.
+          if (TI->getNumSuccessors() == 1) {
+            // Insert counter at the start of the block
+            printEdgeCounter(edge,BB,i);
+            IncrementCounterInBlock(BB, i, Counters); NumEdgesInserted++;
+          } else {
+            // Insert counter at the start of the block
+            printEdgeCounter(edge,Succ,i);
+            IncrementCounterInBlock(Succ, i, Counters); NumEdgesInserted++;
+          }
+          Initializer[i++] = (Zero);
+        } else {
+          Initializer[i++] = (Uncounted);
+        }
+      }
+    }
+  }
+
+  // Check if the number of edges counted at first was the number of edges we
+  // considered for instrumentation.
+  assert(i==NumEdges && "the number of edges in counting array is wrong");
+
+  // Assing the now completely defined initialiser to the array.
+  Constant *init = ConstantArray::get(ATy, Initializer);
+  Counters->setInitializer(init);
+
+  // Add the initialization call to main.
+  InsertProfilingInitCall(Main, "llvm_start_opt_edge_profiling", Counters);
+  return true;
+}
+