lib/Analysis/DataStructure/BottomUpClosure.cpp

//===- BottomUpClosure.cpp - Compute bottom-up interprocedural closure ----===//
// 
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// 
//===----------------------------------------------------------------------===//
//
// This file implements the BUDataStructures class, which represents the
// Bottom-Up Interprocedural closure of the data structure graph over the
// program.  This is useful for applications like pool allocation, but **not**
// applications like alias analysis.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/DataStructure/DataStructure.h"
#include "llvm/Module.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Debug.h"
#include "DSCallSiteIterator.h"
using namespace llvm;

namespace {
  Statistic<> MaxSCC("budatastructure", "Maximum SCC Size in Call Graph");
  Statistic<> NumBUInlines("budatastructures", "Number of graphs inlined");
  Statistic<> NumCallEdges("budatastructures", "Number of 'actual' call edges");
  
  RegisterAnalysis<BUDataStructures>
  X("budatastructure", "Bottom-up Data Structure Analysis");
}

using namespace DS;

// run - Calculate the bottom up data structure graphs for each function in the
// program.
//
bool BUDataStructures::runOnModule(Module &M) {
  LocalDataStructures &LocalDSA = getAnalysis<LocalDataStructures>();
  GlobalsGraph = new DSGraph(LocalDSA.getGlobalsGraph());
  GlobalsGraph->setPrintAuxCalls();

  Function *MainFunc = M.getMainFunction();
  if (MainFunc)
    calculateReachableGraphs(MainFunc);

  // Calculate the graphs for any functions that are unreachable from main...
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
    if (!I->isExternal() && !DSInfo.count(I)) {
#ifndef NDEBUG
      if (MainFunc)
        std::cerr << "*** Function unreachable from main: "
                  << I->getName() << "\n";
#endif
      calculateReachableGraphs(I);    // Calculate all graphs...
    }

  NumCallEdges += ActualCallees.size();

  // At the end of the bottom-up pass, the globals graph becomes complete.
  // FIXME: This is not the right way to do this, but it is sorta better than
  // nothing!  In particular, externally visible globals and unresolvable call
  // nodes at the end of the BU phase should make things that they point to
  // incomplete in the globals graph.
  // 
  GlobalsGraph->removeTriviallyDeadNodes();
  GlobalsGraph->maskIncompleteMarkers();
  return false;
}

void BUDataStructures::calculateReachableGraphs(Function *F) {
  std::vector<Function*> Stack;
  hash_map<Function*, unsigned> ValMap;
  unsigned NextID = 1;
  calculateGraphs(F, Stack, NextID, ValMap);
}

DSGraph &BUDataStructures::getOrCreateGraph(Function *F) {
  // Has the graph already been created?
  DSGraph *&Graph = DSInfo[F];
  if (Graph) return *Graph;

  // Copy the local version into DSInfo...
  Graph = new DSGraph(getAnalysis<LocalDataStructures>().getDSGraph(*F));

  Graph->setGlobalsGraph(GlobalsGraph);
  Graph->setPrintAuxCalls();

  // Start with a copy of the original call sites...
  Graph->getAuxFunctionCalls() = Graph->getFunctionCalls();
  return *Graph;
}

unsigned BUDataStructures::calculateGraphs(Function *F,
                                           std::vector<Function*> &Stack,
                                           unsigned &NextID, 
                                     hash_map<Function*, unsigned> &ValMap) {
  assert(!ValMap.count(F) && "Shouldn't revisit functions!");
  unsigned Min = NextID++, MyID = Min;
  ValMap[F] = Min;
  Stack.push_back(F);

  // FIXME!  This test should be generalized to be any function that we have
  // already processed, in the case when there isn't a main or there are
  // unreachable functions!
  if (F->isExternal()) {   // sprintf, fprintf, sscanf, etc...
    // No callees!
    Stack.pop_back();
    ValMap[F] = ~0;
    return Min;
  }

  DSGraph &Graph = getOrCreateGraph(F);

  // The edges out of the current node are the call site targets...
  for (DSCallSiteIterator I = DSCallSiteIterator::begin_aux(Graph),
         E = DSCallSiteIterator::end_aux(Graph); I != E; ++I) {
    Function *Callee = *I;
    unsigned M;
    // Have we visited the destination function yet?
    hash_map<Function*, unsigned>::iterator It = ValMap.find(Callee);
    if (It == ValMap.end())  // No, visit it now.
      M = calculateGraphs(Callee, Stack, NextID, ValMap);
    else                    // Yes, get it's number.
      M = It->second;
    if (M < Min) Min = M;
  }

  assert(ValMap[F] == MyID && "SCC construction assumption wrong!");
  if (Min != MyID)
    return Min;         // This is part of a larger SCC!

  // If this is a new SCC, process it now.
  if (Stack.back() == F) {           // Special case the single "SCC" case here.
    DEBUG(std::cerr << "Visiting single node SCC #: " << MyID << " fn: "
                    << F->getName() << "\n");
    Stack.pop_back();
    DSGraph &G = getDSGraph(*F);
    DEBUG(std::cerr << "  [BU] Calculating graph for: " << F->getName()<< "\n");
    calculateGraph(G);
    DEBUG(std::cerr << "  [BU] Done inlining: " << F->getName() << " ["
                    << G.getGraphSize() << "+" << G.getAuxFunctionCalls().size()
                    << "]\n");

    if (MaxSCC < 1) MaxSCC = 1;

    // Should we revisit the graph?
    if (DSCallSiteIterator::begin_aux(G) != DSCallSiteIterator::end_aux(G)) {
      ValMap.erase(F);
      return calculateGraphs(F, Stack, NextID, ValMap);
    } else {
      ValMap[F] = ~0U;
    }
    return MyID;

  } else {
    // SCCFunctions - Keep track of the functions in the current SCC
    //
    hash_set<DSGraph*> SCCGraphs;

    Function *NF;
    std::vector<Function*>::iterator FirstInSCC = Stack.end();
    DSGraph *SCCGraph = 0;
    do {
      NF = *--FirstInSCC;
      ValMap[NF] = ~0U;

      // Figure out which graph is the largest one, in order to speed things up
      // a bit in situations where functions in the SCC have widely different
      // graph sizes.
      DSGraph &NFGraph = getDSGraph(*NF);
      SCCGraphs.insert(&NFGraph);
      // FIXME: If we used a better way of cloning graphs (ie, just splice all
      // of the nodes into the new graph), this would be completely unneeded!
      if (!SCCGraph || SCCGraph->getGraphSize() < NFGraph.getGraphSize())
        SCCGraph = &NFGraph;
    } while (NF != F);

    std::cerr << "Calculating graph for SCC #: " << MyID << " of size: "
              << SCCGraphs.size() << "\n";

    // Compute the Max SCC Size...
    if (MaxSCC < SCCGraphs.size())
      MaxSCC = SCCGraphs.size();

    // First thing first, collapse all of the DSGraphs into a single graph for
    // the entire SCC.  We computed the largest graph, so clone all of the other
    // (smaller) graphs into it.  Discard all of the old graphs.
    //
    for (hash_set<DSGraph*>::iterator I = SCCGraphs.begin(),
           E = SCCGraphs.end(); I != E; ++I) {
      DSGraph &G = **I;
      if (&G != SCCGraph) {
        {
          DSGraph::NodeMapTy NodeMap;
          SCCGraph->cloneInto(G, SCCGraph->getScalarMap(),
                              SCCGraph->getReturnNodes(), NodeMap);
        }
        // Update the DSInfo map and delete the old graph...
        for (DSGraph::ReturnNodesTy::iterator I = G.getReturnNodes().begin(),
               E = G.getReturnNodes().end(); I != E; ++I)
          DSInfo[I->first] = SCCGraph;
        delete &G;
      }
    }

    // Clean up the graph before we start inlining a bunch again...
    SCCGraph->removeDeadNodes(DSGraph::KeepUnreachableGlobals);

    // Now that we have one big happy family, resolve all of the call sites in
    // the graph...
    calculateGraph(*SCCGraph);
    DEBUG(std::cerr << "  [BU] Done inlining SCC  [" << SCCGraph->getGraphSize()
                    << "+" << SCCGraph->getAuxFunctionCalls().size() << "]\n");

    std::cerr << "DONE with SCC #: " << MyID << "\n";

    // We never have to revisit "SCC" processed functions...
    
    // Drop the stuff we don't need from the end of the stack
    Stack.erase(FirstInSCC, Stack.end());
    return MyID;
  }

  return MyID;  // == Min
}


// releaseMemory - If the pass pipeline is done with this pass, we can release
// our memory... here...
//
void BUDataStructures::releaseMemory() {
  for (hash_map<Function*, DSGraph*>::iterator I = DSInfo.begin(),
         E = DSInfo.end(); I != E; ++I) {
    I->second->getReturnNodes().erase(I->first);
    if (I->second->getReturnNodes().empty())
      delete I->second;
  }

  // Empty map so next time memory is released, data structures are not
  // re-deleted.
  DSInfo.clear();
  delete GlobalsGraph;
  GlobalsGraph = 0;
}

void BUDataStructures::calculateGraph(DSGraph &Graph) {
  // Move our call site list into TempFCs so that inline call sites go into the
  // new call site list and doesn't invalidate our iterators!
  std::list<DSCallSite> TempFCs;
  std::list<DSCallSite> &AuxCallsList = Graph.getAuxFunctionCalls();
  TempFCs.swap(AuxCallsList);

  DSGraph::ReturnNodesTy &ReturnNodes = Graph.getReturnNodes();

  // Loop over all of the resolvable call sites
  DSCallSiteIterator I = DSCallSiteIterator::begin(TempFCs);
  DSCallSiteIterator E = DSCallSiteIterator::end(TempFCs);

  // If DSCallSiteIterator skipped over any call sites, they are unresolvable:
  // move them back to the AuxCallsList.
  std::list<DSCallSite>::iterator LastCallSiteIdx = TempFCs.begin();
  while (LastCallSiteIdx != I.getCallSiteIdx())
    AuxCallsList.splice(AuxCallsList.end(), TempFCs, LastCallSiteIdx++);
    
  while (I != E) {
    // Resolve the current call...
    Function *Callee = *I;
    DSCallSite CS = I.getCallSite();

    if (Callee->isExternal()) {
      // Ignore this case, simple varargs functions we cannot stub out!
    } else if (ReturnNodes.count(Callee)) {
      // Self recursion... simply link up the formal arguments with the
      // actual arguments...
      DEBUG(std::cerr << "    Self Inlining: " << Callee->getName() << "\n");

      // Handle self recursion by resolving the arguments and return value
      Graph.mergeInGraph(CS, *Callee, Graph, 0);

    } else {
      ActualCallees.insert(std::make_pair(CS.getCallSite().getInstruction(),
                                          Callee));

      // Get the data structure graph for the called function.
      //
      DSGraph &GI = getDSGraph(*Callee);  // Graph to inline

      DEBUG(std::cerr << "    Inlining graph for " << Callee->getName()
            << "[" << GI.getGraphSize() << "+"
            << GI.getAuxFunctionCalls().size() << "] into '"
            << Graph.getFunctionNames() << "' [" << Graph.getGraphSize() << "+"
            << Graph.getAuxFunctionCalls().size() << "]\n");
      Graph.mergeInGraph(CS, *Callee, GI,
                         DSGraph::KeepModRefBits | 
                         DSGraph::StripAllocaBit | DSGraph::DontCloneCallNodes);
      ++NumBUInlines;

#if 0
      Graph.writeGraphToFile(std::cerr, "bu_" + F.getName() + "_after_" +
                             Callee->getName());
#endif
    }

    LastCallSiteIdx = I.getCallSiteIdx();
    ++I;  // Move to the next call site.

    if (I.getCallSiteIdx() != LastCallSiteIdx) {
      ++LastCallSiteIdx;   // Skip over the site we already processed.

      // If there are call sites that get skipped over, move them to the aux
      // calls list: they are not resolvable.
      if (I != E)
        while (LastCallSiteIdx != I.getCallSiteIdx())
          AuxCallsList.splice(AuxCallsList.end(), TempFCs, LastCallSiteIdx++);
      else
        while (LastCallSiteIdx != TempFCs.end())
          AuxCallsList.splice(AuxCallsList.end(), TempFCs, LastCallSiteIdx++);
    }
  }

  TempFCs.clear();

  // Recompute the Incomplete markers
  assert(Graph.getInlinedGlobals().empty());
  Graph.maskIncompleteMarkers();
  Graph.markIncompleteNodes(DSGraph::MarkFormalArgs);

  // Delete dead nodes.  Treat globals that are unreachable but that can
  // reach live nodes as live.
  Graph.removeDeadNodes(DSGraph::KeepUnreachableGlobals);

  // When this graph is finalized, clone the globals in the graph into the
  // globals graph to make sure it has everything, from all graphs.
  DSScalarMap &MainSM = Graph.getScalarMap();
  ReachabilityCloner RC(*GlobalsGraph, Graph, DSGraph::StripAllocaBit);

  // Clone everything reachable from globals in the function graph into the
  // globals graph.
  for (DSScalarMap::global_iterator I = MainSM.global_begin(),
         E = MainSM.global_end(); I != E; ++I) 
    RC.getClonedNH(MainSM[*I]);

  //Graph.writeGraphToFile(std::cerr, "bu_" + F.getName());
}

static const Function *getFnForValue(const Value *V) {
  if (const Instruction *I = dyn_cast<Instruction>(V))
    return I->getParent()->getParent();
  else if (const Argument *A = dyn_cast<Argument>(V))
    return A->getParent();
  else if (const BasicBlock *BB = dyn_cast<BasicBlock>(V))
    return BB->getParent();
  return 0;
}

/// deleteValue/copyValue - Interfaces to update the DSGraphs in the program.
/// These correspond to the interfaces defined in the AliasAnalysis class.
void BUDataStructures::deleteValue(Value *V) {
  if (const Function *F = getFnForValue(V)) {  // Function local value?
    // If this is a function local value, just delete it from the scalar map!
    getDSGraph(*F).getScalarMap().eraseIfExists(V);
    return;
  }

  if (Function *F = dyn_cast<Function>(F)) {
    assert(getDSGraph(*F).getReturnNodes().size() == 1 &&
           "cannot handle scc's");
    delete DSInfo[F];
    DSInfo.erase(F);
    return;
  }

  assert(!isa<GlobalVariable>(V) && "Do not know how to delete GV's yet!");
}

void BUDataStructures::copyValue(Value *From, Value *To) {
  if (From == To) return;
  if (const Function *F = getFnForValue(From)) {  // Function local value?
    // If this is a function local value, just delete it from the scalar map!
    getDSGraph(*F).getScalarMap().copyScalarIfExists(From, To);
    return;
  }

  if (Function *FromF = dyn_cast<Function>(From)) {
    Function *ToF = cast<Function>(To);
    assert(!DSInfo.count(ToF) && "New Function already exists!");
    DSGraph *NG = new DSGraph(getDSGraph(*FromF));
    DSInfo[ToF] = NG;
    assert(NG->getReturnNodes().size() == 1 && "Cannot copy SCC's yet!");

    // Change the Function* is the returnnodes map to the ToF.
    DSNodeHandle Ret = NG->getReturnNodes().begin()->second;
    NG->getReturnNodes().clear();
    NG->getReturnNodes()[ToF] = Ret;
    return;
  }

  assert(!isa<GlobalVariable>(From) && "Do not know how to copy GV's yet!");
}