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/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);
}
// 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 {
std::cerr << "Couldn't cleanup this function call, must be an"
<< " argument or something!" << CI;
++i;
}
} else {
std::cerr << "Cannot convert use of function: " << U << "\n";
++i;
}
}
}
return Changed;
}
static bool ResolveGlobalVariables(Module &M,
std::vector<GlobalValue*> &Globals,
GlobalVariable *Concrete) {
bool Changed = false;
assert(isa<ArrayType>(Concrete->getType()->getElementType()) &&
"Concrete version should be an array type!");
// Get the type of the things that may be resolved to us...
const ArrayType *CATy =cast<ArrayType>(Concrete->getType()->getElementType());
const Type *AETy = CATy->getElementType();
Constant *CCPR = ConstantPointerRef::get(Concrete);
for (unsigned i = 0; i != Globals.size(); ++i)
if (Globals[i] != Concrete) {
GlobalVariable *Old = cast<GlobalVariable>(Globals[i]);
const ArrayType *OATy = cast<ArrayType>(Old->getType()->getElementType());
if (OATy->getElementType() != AETy || OATy->getNumElements() != 0) {
std::cerr << "WARNING: Two global variables exist with the same name "
<< "that cannot be resolved!\n";
return false;
}
Old->replaceAllUsesWith(ConstantExpr::getCast(CCPR, Old->getType()));
// Since there are no uses of Old anymore, remove it from the module.
M.getGlobalList().erase(Old);
++NumGlobals;
Changed = true;
}
return Changed;
}
static bool ProcessGlobalsWithSameName(Module &M,
std::vector<GlobalValue*> &Globals) {
assert(!Globals.empty() && "Globals list shouldn't be empty here!");
bool isFunction = isa<Function>(Globals[0]); // Is this group all functions?
GlobalValue *Concrete = 0; // The most concrete implementation to resolve to
assert((isFunction ^ isa<GlobalVariable>(Globals[0])) &&
"Should either be function or gvar!");
for (unsigned i = 0; i != Globals.size(); ) {
if (isa<Function>(Globals[i]) != isFunction) {
std::cerr << "WARNING: Found function and global variable with the "
<< "same name: '" << Globals[i]->getName() << "'.\n";
return false; // Don't know how to handle this, bail out!
}
if (isFunction) {
// For functions, we look to merge functions definitions of "int (...)"
// to 'int (int)' or 'int ()' or whatever else is not completely generic.
//
Function *F = cast<Function>(Globals[i]);
if (!F->isExternal()) {
if (Concrete && !Concrete->isExternal())
return false; // Found two different functions types. Can't choose!
Concrete = Globals[i];
} else if (Concrete) {
if (Concrete->isExternal()) // If we have multiple external symbols...x
if (F->getFunctionType()->getNumParams() >
cast<Function>(Concrete)->getFunctionType()->getNumParams())
Concrete = F; // We are more concrete than "Concrete"!
} else {
Concrete = F;
}
} else {
// For global variables, we have to merge C definitions int A[][4] with
// int[6][4]. A[][4] is represented as A[0][4] by the CFE.
GlobalVariable *GV = cast<GlobalVariable>(Globals[i]);
if (!isa<ArrayType>(GV->getType()->getElementType())) {
Concrete = 0;
break; // Non array's cannot be compatible with other types.
} else if (Concrete == 0) {
Concrete = GV;
} else {
// Must have different types... allow merging A[0][4] w/ A[6][4] if
// A[0][4] is external.
const ArrayType *NAT = cast<ArrayType>(GV->getType()->getElementType());
const ArrayType *CAT =
cast<ArrayType>(Concrete->getType()->getElementType());
if (NAT->getElementType() != CAT->getElementType()) {
Concrete = 0; // Non-compatible types
break;
} else if (NAT->getNumElements() == 0 && GV->isExternal()) {
// Concrete remains the same
} else if (CAT->getNumElements() == 0 && Concrete->isExternal()) {
Concrete = GV; // Concrete becomes GV
} else {
Concrete = 0; // Cannot merge these types...
break;
}
}
}
++i;
}
if (Globals.size() > 1) { // Found a multiply defined global...
// We should find exactly one concrete function definition, which is
// probably the implementation. Change all of the function definitions and
// uses to use it instead.
//
if (!Concrete) {
std::cerr << "WARNING: Found global types that are not compatible:\n";
for (unsigned i = 0; i < Globals.size(); ++i) {
std::cerr << "\t" << Globals[i]->getType()->getDescription() << " %"
<< Globals[i]->getName() << "\n";
}
std::cerr << " No linkage of globals named '" << Globals[0]->getName()
<< "' performed!\n";
return false;
}
if (isFunction)
return ResolveFunctions(M, Globals, cast<Function>(Concrete));
else
return ResolveGlobalVariables(M, Globals,
cast<GlobalVariable>(Concrete));
}
return false;
}
bool FunctionResolvingPass::run(Module &M) {
SymbolTable &ST = M.getSymbolTable();
std::map<std::string, std::vector<GlobalValue*> > Globals;
// 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)) {
SymbolTable::VarMap &Plane = I->second;
for (SymbolTable::type_iterator PI = Plane.begin(), PE = Plane.end();
PI != PE; ++PI) {
GlobalValue *GV = cast<GlobalValue>(PI->second);
assert(PI->first == GV->getName() &&
"Global name and symbol table do not agree!");
if (GV->hasExternalLinkage()) // Only resolve decls to external fns
Globals[PI->first].push_back(GV);
}
}
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<std::string, std::vector<GlobalValue*> >::iterator
I = Globals.begin(), E = Globals.end(); I != E; ++I)
Changed |= ProcessGlobalsWithSameName(M, I->second);
// Now loop over all of the globals, checking to see if any are trivially
// dead. If so, remove them now.
for (Module::iterator I = M.begin(), E = M.end(); I != E; )
if (I->isExternal() && I->use_empty()) {
Function *F = I;
++I;
M.getFunctionList().erase(F);
++NumResolved;
Changed = true;
} else {
++I;
}
for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; )
if (I->isExternal() && I->use_empty()) {
GlobalVariable *GV = I;
++I;
M.getGlobalList().erase(GV);
++NumGlobals;
Changed = true;
} else {
++I;
}
return Changed;
}