//===- Steensgaard.cpp - Context Insensitive Data Structure Analysis ------===//
//
//                     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 pass computes a context-insensitive data analysis graph.  It does this
// by computing the local analysis graphs for all of the functions, then merging
// them together into a single big graph without cloning.
//
//===----------------------------------------------------------------------===//

#include "rdsa/DataStructure.h"
#include "rdsa/DSGraph.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Module.h"
#include "llvm/Support/Debug.h"
#include <ostream>

using namespace llvm;

SteensgaardDataStructures::~SteensgaardDataStructures() { }

void
SteensgaardDataStructures::releaseMemory() {
  delete ResultGraph; ResultGraph = 0;
  DataStructures::releaseMemory();
}

// print - Implement the Pass::print method...
void
SteensgaardDataStructures::print(OStream O, const Module *M) const {
  if (O.stream()) print(*O.stream(), M);
}

void
SteensgaardDataStructures::print(std::ostream &O, const Module *M) const {
  assert(ResultGraph && "Result graph has not yet been computed!");
  ResultGraph->writeGraphToFile(O, "steensgaards");
}

/// run - Build up the result graph, representing the pointer graph for the
/// program.
///
bool
SteensgaardDataStructures::runOnModule(Module &M) {
  DS = &getAnalysis<StdLibDataStructures>();
  init(&getAnalysis<DataLayout>());
  return runOnModuleInternal(M);
}

bool
SteensgaardDataStructures::runOnModuleInternal(Module &M) {
  assert(ResultGraph == 0 && "Result graph already allocated!");
  
  // Get a copy for the globals graph.
  DSGraph * GG = DS->getGlobalsGraph();
  GlobalsGraph = new DSGraph(GG, GG->getGlobalECs(), 0, 0);

  // Create a new, empty, graph...
  ResultGraph = new DSGraph(GG->getGlobalECs(), getDataLayout(), GlobalsGraph);
  
  // Loop over the rest of the module, merging graphs for non-external functions
  // into this graph.
  //
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
    if (!I->isDeclaration()) {
      ResultGraph->spliceFrom(DS->getDSGraph(I));
    }
  }

  ResultGraph->removeTriviallyDeadNodes();

  // FIXME: Must recalculate and use the Incomplete markers!!

  // Now that we have all of the graphs inlined, we can go about eliminating
  // call nodes...
  //

  // Start with a copy of the original call sites.
  std::list<DSCallSite> & Calls = ResultGraph->getFunctionCalls();

  for (std::list<DSCallSite>::iterator CI = Calls.begin(), E = Calls.end();
       CI != E;) {
    DSCallSite &CurCall = *CI++;

    // Loop over the called functions, eliminating as many as possible...
    std::vector<const Function*> CallTargets;
    if (CurCall.isDirectCall())
      CallTargets.push_back(CurCall.getCalleeFunc());
    else
      CurCall.getCalleeNode()->addFullFunctionList(CallTargets);

    for (unsigned c = 0; c != CallTargets.size(); ) {
      // If we can eliminate this function call, do so!
      const Function *F = CallTargets[c];
      if (!F->isDeclaration()) {
        ResolveFunctionCall(F, CurCall, ResultGraph->getReturnNodes()[F]);
        CallTargets[c] = CallTargets.back();
        CallTargets.pop_back();
      } else
        ++c;  // Cannot eliminate this call, skip over it...
    }

    if (CallTargets.empty()) {        // Eliminated all calls?
      std::list<DSCallSite>::iterator I = CI;
      Calls.erase(--I);               // Remove entry
    }
  }

  // Remove our knowledge of what the return values of the functions are, except
  // for functions that are externally visible from this module (e.g. main).  We
  // keep these functions so that their arguments are marked incomplete.
  for (DSGraph::ReturnNodesTy::iterator I =
         ResultGraph->getReturnNodes().begin(),
         E = ResultGraph->getReturnNodes().end(); I != E; )
    if (I->first->hasInternalLinkage())
      ResultGraph->getReturnNodes().erase(I++);
    else
      ++I;

  // Update the "incomplete" markers on the nodes, ignoring unknownness due to
  // incoming arguments...
  ResultGraph->maskIncompleteMarkers();

  ResultGraph->markIncompleteNodes(DSGraph::MarkFormalArgs | DSGraph::IgnoreGlobals);

  // Remove any nodes that are dead after all of the merging we have done...

  ResultGraph->removeDeadNodes(DSGraph::KeepUnreachableGlobals);

  GlobalsGraph->removeTriviallyDeadNodes(true);
  GlobalsGraph->maskIncompleteMarkers();

  // Mark external globals incomplete.
  GlobalsGraph->markIncompleteNodes(DSGraph::IgnoreGlobals);

  formGlobalECs();

  // Clone the global nodes into this graph.
  ReachabilityCloner RC(ResultGraph, GlobalsGraph,
      DSGraph::DontCloneCallNodes |
      DSGraph::DontCloneAuxCallNodes);
  for (DSScalarMap::global_iterator I = GlobalsGraph->getScalarMap().global_begin(),
      E = GlobalsGraph->getScalarMap().global_end(); I != E; ++I)
    if (isa<GlobalVariable>(*I))
      RC.getClonedNH(GlobalsGraph->getNodeForValue(*I));
   

  print(DOUT, &M);
  return false;
}

/// ResolveFunctionCall - Resolve the actual arguments of a call to function F
/// with the specified call site descriptor.  This function links the arguments
/// and the return value for the call site context-insensitively.
///
void
SteensgaardDataStructures::ResolveFunctionCall(const Function *F, 
                                                const DSCallSite &Call,
                                                DSNodeHandle &RetVal) {

  assert(ResultGraph != 0 && "Result graph not allocated!");
  DSGraph::ScalarMapTy &ValMap = ResultGraph->getScalarMap();

  // Handle the return value of the function...
  if (Call.getRetVal().getNode() && RetVal.getNode())
    RetVal.mergeWith(Call.getRetVal());

  // Loop over all pointer arguments, resolving them to their provided pointers
  unsigned PtrArgIdx = 0;
  for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
       AI != AE && PtrArgIdx < Call.getNumPtrArgs(); ++AI) {
    DSGraph::ScalarMapTy::iterator I = ValMap.find(AI);
    if (I != ValMap.end())    // If its a pointer argument...
      I->second.mergeWith(Call.getPtrArg(PtrArgIdx++));
  }
}

char SteensgaardDataStructures::ID = 0;

// Register the pass...
static RegisterPass<SteensgaardDataStructures> X
("dsa-steens",
 "Context-insensitive Data Structure Analysis");