llvm/lib/Analysis/LazyCallGraph.cpp

//===- LazyCallGraph.cpp - Analysis of a Module's call graph --------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/LazyCallGraph.h"
#include "llvm/ADT/SCCIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/InstVisitor.h"

using namespace llvm;

static void findCallees(
    SmallVectorImpl<Constant *> &Worklist, SmallPtrSetImpl<Constant *> &Visited,
    SmallVectorImpl<PointerUnion<Function *, LazyCallGraph::Node *> > &Callees,
    SmallPtrSetImpl<Function *> &CalleeSet) {
  while (!Worklist.empty()) {
    Constant *C = Worklist.pop_back_val();

    if (Function *F = dyn_cast<Function>(C)) {
      // Note that we consider *any* function with a definition to be a viable
      // edge. Even if the function's definition is subject to replacement by
      // some other module (say, a weak definition) there may still be
      // optimizations which essentially speculate based on the definition and
      // a way to check that the specific definition is in fact the one being
      // used. For example, this could be done by moving the weak definition to
      // a strong (internal) definition and making the weak definition be an
      // alias. Then a test of the address of the weak function against the new
      // strong definition's address would be an effective way to determine the
      // safety of optimizing a direct call edge.
      if (!F->isDeclaration() && CalleeSet.insert(F))
          Callees.push_back(F);
      continue;
    }

    for (User::value_op_iterator OI = C->value_op_begin(),
                                 OE = C->value_op_end();
         OI != OE; ++OI)
      if (Visited.insert(cast<Constant>(*OI)))
        Worklist.push_back(cast<Constant>(*OI));
  }
}

LazyCallGraph::Node::Node(LazyCallGraph &G, Function &F) : G(G), F(F) {
  SmallVector<Constant *, 16> Worklist;
  SmallPtrSet<Constant *, 16> Visited;
  // Find all the potential callees in this function. First walk the
  // instructions and add every operand which is a constant to the worklist.
  for (Function::iterator BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI)
    for (BasicBlock::iterator II = BBI->begin(), IE = BBI->end(); II != IE;
         ++II)
      for (User::value_op_iterator OI = II->value_op_begin(),
                                   OE = II->value_op_end();
           OI != OE; ++OI)
        if (Constant *C = dyn_cast<Constant>(*OI))
          if (Visited.insert(C))
            Worklist.push_back(C);

  // We've collected all the constant (and thus potentially function or
  // function containing) operands to all of the instructions in the function.
  // Process them (recursively) collecting every function found.
  findCallees(Worklist, Visited, Callees, CalleeSet);
}

LazyCallGraph::Node::Node(LazyCallGraph &G, const Node &OtherN)
    : G(G), F(OtherN.F), CalleeSet(OtherN.CalleeSet) {
  // Loop over the other node's callees, adding the Function*s to our list
  // directly, and recursing to add the Node*s.
  Callees.reserve(OtherN.Callees.size());
  for (NodeVectorImplT::iterator OI = OtherN.Callees.begin(),
                                 OE = OtherN.Callees.end();
       OI != OE; ++OI)
    if (Function *Callee = OI->dyn_cast<Function *>())
      Callees.push_back(Callee);
    else
      Callees.push_back(G.copyInto(*OI->get<Node *>()));
}

LazyCallGraph::Node::Node(LazyCallGraph &G, Node &&OtherN)
    : G(G), F(OtherN.F), Callees(std::move(OtherN.Callees)),
      CalleeSet(std::move(OtherN.CalleeSet)) {
  // Loop over our Callees. They've been moved from another node, but we need
  // to move the Node*s to live under our bump ptr allocator.
  for (NodeVectorImplT::iterator CI = Callees.begin(), CE = Callees.end();
       CI != CE; ++CI)
    if (Node *ChildN = CI->dyn_cast<Node *>())
      *CI = G.moveInto(std::move(*ChildN));
}

LazyCallGraph::LazyCallGraph(Module &M) : M(M) {
  for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI)
    if (!FI->isDeclaration() && !FI->hasLocalLinkage())
      if (EntryNodeSet.insert(&*FI))
        EntryNodes.push_back(&*FI);

  // Now add entry nodes for functions reachable via initializers to globals.
  SmallVector<Constant *, 16> Worklist;
  SmallPtrSet<Constant *, 16> Visited;
  for (Module::global_iterator GI = M.global_begin(), GE = M.global_end(); GI != GE; ++GI)
    if (GI->hasInitializer())
      if (Visited.insert(GI->getInitializer()))
        Worklist.push_back(GI->getInitializer());

  findCallees(Worklist, Visited, EntryNodes, EntryNodeSet);
}

LazyCallGraph::LazyCallGraph(const LazyCallGraph &G)
    : M(G.M), EntryNodeSet(G.EntryNodeSet) {
  EntryNodes.reserve(G.EntryNodes.size());
  for (NodeVectorImplT::const_iterator EI = G.EntryNodes.begin(),
                                       EE = G.EntryNodes.end();
       EI != EE; ++EI)
    if (Function *Callee = EI->dyn_cast<Function *>())
      EntryNodes.push_back(Callee);
    else
      EntryNodes.push_back(copyInto(*EI->get<Node *>()));
}

// FIXME: This would be crazy simpler if BumpPtrAllocator were movable without
// invalidating any of the allocated memory. We should make that be the case at
// some point and delete this.
LazyCallGraph::LazyCallGraph(LazyCallGraph &&G)
    : M(G.M), EntryNodes(std::move(G.EntryNodes)),
      EntryNodeSet(std::move(G.EntryNodeSet)) {
  // Loop over our EntryNodes. They've been moved from another graph, so we
  // need to move the Node*s to live under our bump ptr allocator. We can just
  // do this in-place.
  for (NodeVectorImplT::iterator EI = EntryNodes.begin(),
                                 EE = EntryNodes.end();
       EI != EE; ++EI)
    if (Node *EntryN = EI->dyn_cast<Node *>())
      *EI = moveInto(std::move(*EntryN));
}

LazyCallGraph::Node *LazyCallGraph::insertInto(Function &F, Node *&MappedN) {
  return new (MappedN = BPA.Allocate()) Node(*this, F);
}

LazyCallGraph::Node *LazyCallGraph::copyInto(const Node &OtherN) {
  Node *&N = NodeMap[&OtherN.F];
  if (N)
    return N;

  return new (N = BPA.Allocate()) Node(*this, OtherN);
}

LazyCallGraph::Node *LazyCallGraph::moveInto(Node &&OtherN) {
  Node *&N = NodeMap[&OtherN.F];
  if (N)
    return N;

  return new (N = BPA.Allocate()) Node(*this, std::move(OtherN));
}

char LazyCallGraphAnalysis::PassID;

LazyCallGraphPrinterPass::LazyCallGraphPrinterPass(raw_ostream &OS) : OS(OS) {}

static void printNodes(raw_ostream &OS, LazyCallGraph::Node &N,
                       SmallPtrSetImpl<LazyCallGraph::Node *> &Printed) {
  // Recurse depth first through the nodes.
  for (LazyCallGraph::iterator I = N.begin(), E = N.end(); I != E; ++I)
    if (Printed.insert(*I))
      printNodes(OS, **I, Printed);

  OS << "  Call edges in function: " << N.getFunction().getName() << "\n";
  for (LazyCallGraph::iterator I = N.begin(), E = N.end(); I != E; ++I)
    OS << "    -> " << I->getFunction().getName() << "\n";

  OS << "\n";
}

PreservedAnalyses LazyCallGraphPrinterPass::run(Module *M, ModuleAnalysisManager *AM) {
  LazyCallGraph &G = AM->getResult<LazyCallGraphAnalysis>(M);

  OS << "Printing the call graph for module: " << M->getModuleIdentifier() << "\n\n";

  SmallPtrSet<LazyCallGraph::Node *, 16> Printed;
  for (LazyCallGraph::iterator I = G.begin(), E = G.end(); I != E; ++I)
    if (Printed.insert(*I))
      printNodes(OS, **I, Printed);

  return PreservedAnalyses::all();
}