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+//===- EdgeProfiling.cpp - Insert counters for 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.
+//
+// Note that this implementation is very naive. We insert a counter for *every*
+// edge in the program, instead of using control flow information to prune the
+// number of counters inserted.
+//
+//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "insert-edge-profiling"
+#include "ProfilingUtils.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Instrumentation.h"
+#include "llvm/ADT/Statistic.h"
+#include <set>
+using namespace llvm;
+
+STATISTIC(NumEdgesInserted, "The # of edges inserted.");
+
+namespace {
+ class EdgeProfiler : public ModulePass {
+ bool runOnModule(Module &M);
+ public:
+ static char ID; // Pass identification, replacement for typeid
+ EdgeProfiler() : ModulePass(&ID) {}
+
+ virtual const char *getPassName() const {
+ return "Edge Profiler";
+ }
+ };
+}
+
+char EdgeProfiler::ID = 0;
+static RegisterPass<EdgeProfiler>
+X("insert-edge-profiling", "Insert instrumentation for edge profiling");
+
+ModulePass *llvm::createEdgeProfilerPass() { return new EdgeProfiler(); }
+
+bool EdgeProfiler::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!
+ }
+
+ std::set<BasicBlock*> BlocksToInstrument;
+ 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!
+ BlocksToInstrument.insert(BB);
+ NumEdges += BB->getTerminator()->getNumSuccessors();
+ }
+ }
+
+ const Type *ATy = ArrayType::get(Type::getInt32Ty(M.getContext()), NumEdges);
+ GlobalVariable *Counters =
+ new GlobalVariable(M, ATy, false, GlobalValue::InternalLinkage,
+ Constant::getNullValue(ATy), "EdgeProfCounters");
+ NumEdgesInserted = NumEdges;
+
+ // Instrument all of the edges...
+ unsigned i = 0;
+ for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+ if (F->isDeclaration()) continue;
+ // Create counter for (0,entry) edge.
+ IncrementCounterInBlock(&F->getEntryBlock(), i++, Counters);
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+ if (BlocksToInstrument.count(BB)) { // Don't instrument inserted blocks
+ // Okay, we have to add a counter of each outgoing edge. If the
+ // outgoing edge is not critical don't split it, just insert the counter
+ // in the source or destination of the edge.
+ TerminatorInst *TI = BB->getTerminator();
+ for (unsigned s = 0, e = TI->getNumSuccessors(); s != e; ++s) {
+ // If the edge is critical, split it.
+ SplitCriticalEdge(TI, s, this);
+
+ // 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
+ IncrementCounterInBlock(BB, i++, Counters);
+ } else {
+ // Insert counter at the start of the block
+ IncrementCounterInBlock(TI->getSuccessor(s), i++, Counters);
+ }
+ }
+ }
+ }
+
+ // Add the initialization call to main.
+ InsertProfilingInitCall(Main, "llvm_start_edge_profiling", Counters);
+ return true;
+}
+
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