path: root/lib/Transforms/IPO/FunctionResolution.cpp

//===- FunctionResolution.cpp - Resolve declarations to implementations ---===//
//
// Loop over the functions that are in the module and look for functions that
// have the same name.  More often than not, there will be things like:
//
//    declare void %foo(...)
//    void %foo(int, int) { ... }
//
// because of the way things are declared in C.  If this is the case, patch
// things up.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/IPO.h"
#include "llvm/Module.h"
#include "llvm/SymbolTable.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Pass.h"
#include "llvm/iOther.h"
#include "llvm/Constants.h"
#include "llvm/Assembly/Writer.h"  // FIXME: remove when varargs implemented
#include "Support/Statistic.h"
#include <algorithm>

namespace {
  Statistic<>NumResolved("funcresolve", "Number of varargs functions resolved");
  Statistic<> NumGlobals("funcresolve", "Number of global variables resolved");

  struct FunctionResolvingPass : public Pass {
    bool run(Module &M);
  };
  RegisterOpt<FunctionResolvingPass> X("funcresolve", "Resolve Functions");
}

Pass *createFunctionResolvingPass() {
  return new FunctionResolvingPass();
}

// ConvertCallTo - Convert a call to a varargs function with no arg types
// specified to a concrete nonvarargs function.
//
static void ConvertCallTo(CallInst *CI, Function *Dest) {
  const FunctionType::ParamTypes &ParamTys =
    Dest->getFunctionType()->getParamTypes();
  BasicBlock *BB = CI->getParent();

  // Keep an iterator to where we want to insert cast instructions if the
  // argument types don't agree.
  //
  unsigned NumArgsToCopy = CI->getNumOperands()-1;
  if (NumArgsToCopy != ParamTys.size() &&
      !(NumArgsToCopy > ParamTys.size() &&
        Dest->getFunctionType()->isVarArg())) {
    std::cerr << "WARNING: Call arguments do not match expected number of"
              << " parameters.\n";
    std::cerr << "WARNING: In function '"
              << CI->getParent()->getParent()->getName() << "': call: " << *CI;
    std::cerr << "Function resolved to: ";
    WriteAsOperand(std::cerr, Dest);
    std::cerr << "\n";
    if (NumArgsToCopy > ParamTys.size())
      NumArgsToCopy = ParamTys.size();
  }

  std::vector<Value*> Params;

  // Convert all of the call arguments over... inserting cast instructions if
  // the types are not compatible.
  for (unsigned i = 1; i <= NumArgsToCopy; ++i) {
    Value *V = CI->getOperand(i);

    if (i-1 < ParamTys.size() && V->getType() != ParamTys[i-1]) {
      // Must insert a cast...
      V = new CastInst(V, ParamTys[i-1], "argcast", CI);
    }

    Params.push_back(V);
  }
  
  // If the function takes extra parameters that are not being passed in, pass
  // null values in now...
  for (unsigned i = NumArgsToCopy; i < ParamTys.size(); ++i)
    Params.push_back(Constant::getNullValue(ParamTys[i]));

  // Replace the old call instruction with a new call instruction that calls
  // the real function.
  //
  Instruction *NewCall = new CallInst(Dest, Params, "", CI);
  std::string Name = CI->getName(); CI->setName("");

  // Transfer the name over...
  if (NewCall->getType() != Type::VoidTy)
    NewCall->setName(Name);

  // Replace uses of the old instruction with the appropriate values...
  //
  if (NewCall->getType() == CI->getType()) {
    CI->replaceAllUsesWith(NewCall);
    NewCall->setName(Name);

  } else if (NewCall->getType() == Type::VoidTy) {
    // Resolved function does not return a value but the prototype does.  This
    // often occurs because undefined functions default to returning integers.
    // Just replace uses of the call (which are broken anyway) with dummy
    // values.
    CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
  } else if (CI->getType() == Type::VoidTy) {
    // If we are gaining a new return value, we don't have to do anything
    // special here, because it will automatically be ignored.
  } else {
    // Insert a cast instruction to convert the return value of the function
    // into it's new type.  Of course we only need to do this if the return
    // value of the function is actually USED.
    //
    if (!CI->use_empty()) {
      // Insert the new cast instruction...
      CastInst *NewCast = new CastInst(NewCall, CI->getType(), Name, CI);
      CI->replaceAllUsesWith(NewCast);
    }
  }

  // The old instruction is no longer needed, destroy it!
  BB->getInstList().erase(CI);
}


static bool ResolveFunctions(Module &M, std::vector<GlobalValue*> &Globals,
                             Function *Concrete) {
  bool Changed = false;
  for (unsigned i = 0; i != Globals.size(); ++i)
    if (Globals[i] != Concrete) {
      Function *Old = cast<Function>(Globals[i]);
      const FunctionType *OldMT = Old->getFunctionType();
      const FunctionType *ConcreteMT = Concrete->getFunctionType();
      
      if (OldMT->getParamTypes().size() > ConcreteMT->getParamTypes().size() &&
          !ConcreteMT->isVarArg())
        if (!Old->use_empty()) {
          std::cerr << "WARNING: Linking function '" << Old->getName()
                    << "' is causing arguments to be dropped.\n";
          std::cerr << "WARNING: Prototype: ";
          WriteAsOperand(std::cerr, Old);
          std::cerr << " resolved to ";
          WriteAsOperand(std::cerr, Concrete);
          std::cerr << "\n";
        }
      
      // Check to make sure that if there are specified types, that they
      // match...
      //
      unsigned NumArguments = std::min(OldMT->getParamTypes().size(),
                                       ConcreteMT->getParamTypes().size());

      if (!Old->use_empty() && !Concrete->use_empty())
        for (unsigned i = 0; i < NumArguments; ++i)
          if (OldMT->getParamTypes()[i] != ConcreteMT->getParamTypes()[i]) {
            std::cerr << "WARNING: Function [" << Old->getName()
                      << "]: Parameter types conflict for: '" << OldMT
                      << "' and '" << ConcreteMT << "'\n";
            return Changed;
          }
      
      // Attempt to convert all of the uses of the old function to the concrete
      // form of the function.  If there is a use of the fn that we don't
      // understand here we punt to avoid making a bad transformation.
      //
      // At this point, we know that the return values are the same for our two
      // functions and that the Old function has no varargs fns specified.  In
      // otherwords it's just <retty> (...)
      //
      for (unsigned i = 0; i < Old->use_size(); ) {
        User *U = *(Old->use_begin()+i);
        if (CastInst *CI = dyn_cast<CastInst>(U)) {
          // Convert casts directly
          assert(CI->getOperand(0) == Old);
          CI->setOperand(0, Concrete);
          Changed = true;
          ++NumResolved;
        } else if (CallInst *CI = dyn_cast<CallInst>(U)) {
          // Can only fix up calls TO the argument, not args passed in.
          if (CI->getCalledValue() == Old) {
            ConvertCallTo(CI, Concrete);
            Changed = true;
            ++NumResolved;
          } else {
            ++i;
          }
        } else {
          ++i;
        }
      }

      // If there are any more uses that we could not resolve, force them to use
      // a casted pointer now.
      if (!Old->use_empty()) {
        NumResolved += Old->use_size();
        Constant *NewCPR = ConstantPointerRef::get(Concrete);
        Old->replaceAllUsesWith(ConstantExpr::getCast(NewCPR, Old->getType()));
        Changed = true;
      }

      // Since there are no uses of Old anymore, remove it from the module.
      M.getFunctionList().erase(Old);
    }
  return Changed;
}


static bool ResolveGlobalVariables(Module &M,
                                   std::vector<GlobalValue*> &Globals,
                                   GlobalVariable *Concrete) {
  bool