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 "Support/Statistic.h"
#include <algorithm>
using std::vector;
using std::string;
using std::cerr;
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.
//
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...
V = new CastInst(V, ParamTys[i-1], "argcast", BBI);
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, "", BBI);
// Remove the old call instruction from the program...
BB->getInstList().remove(BBI);
// Transfer the name over...
if (NewCall->getType() != Type::VoidTy)
NewCall->setName(CI->getName());
// 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 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(),
NewCall->getName(), BBI);
CI->replaceAllUsesWith(NewCast);
}
}
// The old instruction is no longer needed, destroy it!
delete CI;
}
static bool ResolveFunctions(Module &M, 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();
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 << "'\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 {
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;
}
static bool ResolveGlobalVariables(Module &M, 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 Type *AETy =
cast<ArrayType>(Concrete->getType()->getElementType())->getElementType();
std::vector<Constant*> Args;
Args.push_back(Constant::getNullValue(Type::LongTy));
Args.push_back(Constant::getNullValue(Type::LongTy));
ConstantExpr *Replacement =
ConstantExpr::getGetElementPtr(ConstantPointerRef::get(Concrete), Args);
for (unsigned i = 0; i != Globals.size(); ++i)
if (Globals[i] != Concrete) {
GlobalVariable *Old = cast<GlobalVariable>(Globals[i]);
if (Old->getType()->getElementType() != AETy) {
std::cerr << "WARNING: Two global variables exist with the same name "
<< "that cannot be resolved!\n";
return false;
}
// In this case, Old is a pointer to T, Concrete is a pointer to array of
// T. Because of this, replace all uses of Old with a constantexpr
// getelementptr that returns the address of the first element of the
// array.
//
Old->replaceAllUsesWith(Replacement);
// 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,
vector<GlobalValue*> &Globals) {
assert(!Globals.empty() && "Globals list shouldn't be empty here!");
bool isFunction = isa<Function>(Globals[0]); // Is this group all functions?
bool Changed = false;
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;
}
++i;
} else {
// For global variables, we have to merge C definitions int A[][4] with
// int[6][4]
GlobalVariable *GV = cast<GlobalVariable>(Globals[i]);
if (Concrete == 0) {
if (isa<ArrayType>(GV->getType()->getElementType()))
Concrete = GV;
} else { // Must have different types... one is an array of the other?
const ArrayType *AT =
dyn_cast<ArrayType>(GV->getType()->getElementType());
// If GV is an array of Concrete, then GV is the array.
if (AT && AT->getElementType() == Concrete->getType()->getElementType())
Concrete = GV;
else {
// Concrete must be an array type, check to see if the element type of
// concrete is already GV.
AT = cast<ArrayType>(Concrete->getType()->getElementType());
if (AT->getElementType() != GV->getType()->getElementType())
Concrete = 0; // Don't know how to handle it!
}
}
++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) {
cerr << "WARNING: Found function types that are not compatible:\n";
for (unsigned i = 0; i < Globals.size(); ++i) {
cerr << "\t" << Globals[i]->getType()->getDescription() << " %"
<< Globals[i]->getName() << "\n";
}
cerr << " No linkage of globals named '" << Globals[0]->getName()
<< "' performed!\n";
return Changed;
}
if (isFunction)
return Changed | ResolveFunctions(M, Globals, cast<Function>(Concrete));
else
return Changed | ResolveGlobalVariables(M, Globals,
cast<GlobalVariable>(Concrete));
}
return Changed;
}
bool FunctionResolvingPass::run(Module &M) {
SymbolTable &ST = M.getSymbolTable();
std::map<string, 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<string, 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;
}