llvm/lib/Transforms/IPO/FunctionResolution.cpp

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//===- 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/CleanupGCCOutput.h"
#include "llvm/Module.h"
#include "llvm/SymbolTable.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Pass.h"
#include "llvm/iOther.h"
#include "llvm/Constant.h"
#include "Support/StatisticReporter.h"
#include <iostream>
#include <algorithm>
using std::vector;
using std::string;
using std::cerr;
namespace {
Statistic<>NumResolved("funcresolve\t- Number of varargs functions resolved");
struct FunctionResolvingPass : public Pass {
bool run(Module &M);
};
RegisterPass<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.
//
BasicBlock::iterator BBI = CI;
assert(CI->getNumOperands()-1 == ParamTys.size() &&
"Function calls resolved funny somehow, incompatible number of args");
vector<Value*> Params;
// Convert all of the call arguments over... inserting cast instructions if
// the types are not compatible.
for (unsigned i = 1; i < CI->getNumOperands(); ++i) {
Value *V = CI->getOperand(i);
if (V->getType() != ParamTys[i-1]) { // Must insert a cast...
Instruction *Cast = new CastInst(V, ParamTys[i-1]);
BBI = ++BB->getInstList().insert(BBI, Cast);
V = Cast;
}
Params.push_back(V);
}
Instruction *NewCall = new CallInst(Dest, Params);
// Replace the old call instruction with a new call instruction that calls
// the real function.
//
BBI = ++BB->getInstList().insert(BBI, NewCall);
// Remove the old call instruction from the program...
BB->getInstList().remove(BBI);
// Replace uses of the old instruction with the appropriate values...
//
if (NewCall->getType() == CI->getType()) {
CI->replaceAllUsesWith(NewCall);
NewCall->setName(CI->getName());
} 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.
} else {
assert(0 && "This should have been checked before!");
abort();
}
// The old instruction is no longer needed, destroy it!
delete CI;
}
bool FunctionResolvingPass::run(Module &M) {
SymbolTable *ST = M.getSymbolTable();
if (!ST) return false;
std::map<string, vector<Function*> > Functions;
// Loop over the entries in the symbol table. If an entry is a func pointer,
// then add it to the Functions map. We do a two pass algorithm here to avoid
// problems with iterators getting invalidated if we did a one pass scheme.
//
for (SymbolTable::iterator I = ST->begin(), E = ST->end(); I != E; ++I)
if (const PointerType *PT = dyn_cast<PointerType>(I->first))
if (isa<FunctionType>(PT->getElementType())) {
SymbolTable::VarMap &Plane = I->second;
for (SymbolTable::type_iterator PI = Plane.begin(), PE = Plane.end();
PI != PE; ++PI) {
Function *F = cast<Function>(PI->second);
assert(PI->first == F->getName() &&
"Function name and symbol table do not agree!");
if (F->hasExternalLinkage()) // Only resolve decls to external fns
Functions[PI->first].push_back(F);
}
}
bool Changed = false;
// Now we have a list of all functions with a particular name. If there is
// more than one entry in a list, merge the functions together.
//
for (std::map<string, vector<Function*> >::iterator I = Functions.begin(),
E = Functions.end(); I != E; ++I) {
vector<Function*> &Functions = I->second;
Function *Implementation = 0; // Find the implementation
Function *Concrete = 0;
for (unsigned i = 0; i < Functions.size(); ) {
if (!Functions[i]->isExternal()) { // Found an implementation
if (Implementation != 0)
assert(Implementation == 0 && "Multiple definitions of the same"
" function. Case not handled yet!");
Implementation = Functions[i];
} else {
// Ignore functions that are never used so they don't cause spurious
// warnings... here we will actually DCE the function so that it isn't
// used later.
//
if (Functions[i]->use_empty()) {
M.getFunctionList().erase(Functions[i]);
Functions.erase(Functions.begin()+i);
Changed = true;
++NumResolved;
continue;
}
}
if (Functions[i] && (!Functions[i]->getFunctionType()->isVarArg())) {
if (Concrete) { // Found two different functions types. Can't choose
Concrete = 0;
break;
}
Concrete = Functions[i];
}
++i;
}
if (Functions.size() > 1) { // Found a multiply defined function...
// We should find exactly one non-vararg function definition, which is
// probably the implementation. Change all of the function definitions
// and uses to use it instead.
//
if (!Concrete) {
cerr << "Warning: Found functions types that are not compatible:\n";
for (unsigned i = 0; i < Functions.size(); ++i) {
cerr << "\t" << Functions[i]->getType()->getDescription() << " %"
<< Functions[i]->getName() << "\n";
}
cerr << " No linkage of functions named '" << Functions[0]->getName()
<< "' performed!\n";
} else {
for (unsigned i = 0; i < Functions.size(); ++i)
if (Functions[i] != Concrete) {
Function *Old = Functions[i];
const FunctionType *OldMT = Old->getFunctionType();
const FunctionType *ConcreteMT = Concrete->getFunctionType();
bool Broken = false;
assert((Old->getReturnType() == Concrete->getReturnType() ||
Concrete->getReturnType() == Type::VoidTy ||
Old->getReturnType() == Type::VoidTy) &&
"Differing return types not handled yet!");
assert(OldMT->getParamTypes().size() <=
ConcreteMT->getParamTypes().size() &&
"Concrete type must have more specified parameters!");
// Check to make sure that if there are specified types, that they
// match...
//
for (unsigned i = 0; i < OldMT->getParamTypes().size(); ++i)
if (OldMT->getParamTypes()[i] != ConcreteMT->getParamTypes()[i]) {
cerr << "Parameter types conflict for" << OldMT
<< " and " << ConcreteMT;
Broken = true;
}
if (Broken) break; // Can't process this one!
// 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 {
cerr << "Couldn't cleanup this function call, must be an"
<< " argument or something!" << CI;
++i;
}
} else {
cerr << "Cannot convert use of function: " << U << "\n";
++i;
}
}
}
}
}
}
return Changed;
}