1 //===- FunctionResolution.cpp - Resolve declarations to implementations ---===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Loop over the functions that are in the module and look for functions that
11 // have the same name. More often than not, there will be things like:
13 // declare void %foo(...)
14 // void %foo(int, int) { ... }
16 // because of the way things are declared in C. If this is the case, patch
19 //===----------------------------------------------------------------------===//
21 #include "llvm/Transforms/IPO.h"
22 #include "llvm/Module.h"
23 #include "llvm/DerivedTypes.h"
24 #include "llvm/Pass.h"
25 #include "llvm/iOther.h"
26 #include "llvm/Constants.h"
27 #include "llvm/Target/TargetData.h"
28 #include "llvm/Assembly/Writer.h"
29 #include "Support/Statistic.h"
33 Statistic<>NumResolved("funcresolve", "Number of varargs functions resolved");
34 Statistic<> NumGlobals("funcresolve", "Number of global variables resolved");
36 struct FunctionResolvingPass : public Pass {
37 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
38 AU.addRequired<TargetData>();
43 RegisterOpt<FunctionResolvingPass> X("funcresolve", "Resolve Functions");
46 Pass *createFunctionResolvingPass() {
47 return new FunctionResolvingPass();
50 static bool ResolveFunctions(Module &M, std::vector<GlobalValue*> &Globals,
53 for (unsigned i = 0; i != Globals.size(); ++i)
54 if (Globals[i] != Concrete) {
55 Function *Old = cast<Function>(Globals[i]);
56 const FunctionType *OldMT = Old->getFunctionType();
57 const FunctionType *ConcreteMT = Concrete->getFunctionType();
59 if (OldMT->getParamTypes().size() > ConcreteMT->getParamTypes().size() &&
60 !ConcreteMT->isVarArg())
61 if (!Old->use_empty()) {
62 std::cerr << "WARNING: Linking function '" << Old->getName()
63 << "' is causing arguments to be dropped.\n";
64 std::cerr << "WARNING: Prototype: ";
65 WriteAsOperand(std::cerr, Old);
66 std::cerr << " resolved to ";
67 WriteAsOperand(std::cerr, Concrete);
71 // Check to make sure that if there are specified types, that they
74 unsigned NumArguments = std::min(OldMT->getParamTypes().size(),
75 ConcreteMT->getParamTypes().size());
77 if (!Old->use_empty() && !Concrete->use_empty())
78 for (unsigned i = 0; i < NumArguments; ++i)
79 if (OldMT->getParamTypes()[i] != ConcreteMT->getParamTypes()[i])
80 if (OldMT->getParamTypes()[i]->getPrimitiveID() !=
81 ConcreteMT->getParamTypes()[i]->getPrimitiveID()) {
82 std::cerr << "WARNING: Function [" << Old->getName()
83 << "]: Parameter types conflict for: '" << OldMT
84 << "' and '" << ConcreteMT << "'\n";
88 // Attempt to convert all of the uses of the old function to the concrete
89 // form of the function. If there is a use of the fn that we don't
90 // understand here we punt to avoid making a bad transformation.
92 // At this point, we know that the return values are the same for our two
93 // functions and that the Old function has no varargs fns specified. In
94 // otherwords it's just <retty> (...)
96 if (!Old->use_empty()) { // Avoid making the CPR unless we really need it
97 Value *Replacement = Concrete;
98 if (Concrete->getType() != Old->getType())
99 Replacement = ConstantExpr::getCast(ConstantPointerRef::get(Concrete),
101 NumResolved += Old->use_size();
102 Old->replaceAllUsesWith(Replacement);
105 // Since there are no uses of Old anymore, remove it from the module.
106 M.getFunctionList().erase(Old);
112 static bool ResolveGlobalVariables(Module &M,
113 std::vector<GlobalValue*> &Globals,
114 GlobalVariable *Concrete) {
115 bool Changed = false;
116 Constant *CCPR = ConstantPointerRef::get(Concrete);
118 for (unsigned i = 0; i != Globals.size(); ++i)
119 if (Globals[i] != Concrete) {
120 Constant *Cast = ConstantExpr::getCast(CCPR, Globals[i]->getType());
121 Globals[i]->replaceAllUsesWith(Cast);
123 // Since there are no uses of Old anymore, remove it from the module.
124 M.getGlobalList().erase(cast<GlobalVariable>(Globals[i]));
132 static bool ProcessGlobalsWithSameName(Module &M, TargetData &TD,
133 std::vector<GlobalValue*> &Globals) {
134 assert(!Globals.empty() && "Globals list shouldn't be empty here!");
136 bool isFunction = isa<Function>(Globals[0]); // Is this group all functions?
137 GlobalValue *Concrete = 0; // The most concrete implementation to resolve to
139 for (unsigned i = 0; i != Globals.size(); ) {
140 if (isa<Function>(Globals[i]) != isFunction) {
141 std::cerr << "WARNING: Found function and global variable with the "
142 << "same name: '" << Globals[i]->getName() << "'.\n";
143 return false; // Don't know how to handle this, bail out!
147 // For functions, we look to merge functions definitions of "int (...)"
148 // to 'int (int)' or 'int ()' or whatever else is not completely generic.
150 Function *F = cast<Function>(Globals[i]);
151 if (!F->isExternal()) {
152 if (Concrete && !Concrete->isExternal())
153 return false; // Found two different functions types. Can't choose!
155 Concrete = Globals[i];
156 } else if (Concrete) {
157 if (Concrete->isExternal()) // If we have multiple external symbols...x
158 if (F->getFunctionType()->getNumParams() >
159 cast<Function>(Concrete)->getFunctionType()->getNumParams())
160 Concrete = F; // We are more concrete than "Concrete"!
166 GlobalVariable *GV = cast<GlobalVariable>(Globals[i]);
167 if (!GV->isExternal()) {
169 std::cerr << "WARNING: Two global variables with external linkage"
170 << " exist with the same name: '" << GV->getName()
180 if (Globals.size() > 1) { // Found a multiply defined global...
181 // If there are no external declarations, and there is at most one
182 // externally visible instance of the global, then there is nothing to do.
184 bool HasExternal = false;
185 unsigned NumInstancesWithExternalLinkage = 0;
187 for (unsigned i = 0, e = Globals.size(); i != e; ++i) {
188 if (Globals[i]->isExternal())
190 else if (!Globals[i]->hasInternalLinkage())
191 NumInstancesWithExternalLinkage++;
194 if (!HasExternal && NumInstancesWithExternalLinkage <= 1)
195 return false; // Nothing to do? Must have multiple internal definitions.
197 // There are a couple of special cases we don't want to print the warning
198 // for, check them now.
199 bool DontPrintWarning = false;
200 if (Concrete && Globals.size() == 2) {
201 GlobalValue *Other = Globals[Globals[0] == Concrete];
202 // If the non-concrete global is a function which takes (...) arguments,
203 // and the return values match, do not warn.
204 if (Function *ConcreteF = dyn_cast<Function>(Concrete))
205 if (Function *OtherF = dyn_cast<Function>(Other))
206 if (ConcreteF->getReturnType() == OtherF->getReturnType() &&
207 OtherF->getFunctionType()->isVarArg() &&
208 OtherF->getFunctionType()->getParamTypes().empty())
209 DontPrintWarning = true;
211 // Otherwise, if the non-concrete global is a global array variable with a
212 // size of 0, and the concrete global is an array with a real size, don't
213 // warn. This occurs due to declaring 'extern int A[];'.
214 if (GlobalVariable *ConcreteGV = dyn_cast<GlobalVariable>(Concrete))
215 if (GlobalVariable *OtherGV = dyn_cast<GlobalVariable>(Other))
216 if (const ArrayType *OtherAT =
217 dyn_cast<ArrayType>(OtherGV->getType()->getElementType()))
218 if (const ArrayType *ConcreteAT =
219 dyn_cast<ArrayType>(ConcreteGV->getType()->getElementType()))
220 if (OtherAT->getElementType() == ConcreteAT->getElementType() &&
221 OtherAT->getNumElements() == 0)
222 DontPrintWarning = true;
225 if (!DontPrintWarning) {
226 std::cerr << "WARNING: Found global types that are not compatible:\n";
227 for (unsigned i = 0; i < Globals.size(); ++i) {
228 std::cerr << "\t" << *Globals[i]->getType() << " %"
229 << Globals[i]->getName() << "\n";
234 Concrete = Globals[0];
235 else if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Concrete)) {
236 // Handle special case hack to change globals if it will make their types
237 // happier in the long run. The situation we do this is intentionally
238 // extremely limited.
239 if (GV->use_empty() && GV->hasInitializer() &&
240 GV->getInitializer()->isNullValue()) {
241 // Check to see if there is another (external) global with the same size
242 // and a non-empty use-list. If so, we will make IT be the real
244 unsigned TS = TD.getTypeSize(Concrete->getType()->getElementType());
245 for (unsigned i = 0, e = Globals.size(); i != e; ++i)
246 if (Globals[i] != Concrete && !Globals[i]->use_empty() &&
247 isa<GlobalVariable>(Globals[i]) &&
248 TD.getTypeSize(Globals[i]->getType()->getElementType()) == TS) {
249 // At this point we want to replace Concrete with Globals[i]. Make
250 // concrete external, and Globals[i] have an initializer.
251 GlobalVariable *NGV = cast<GlobalVariable>(Globals[i]);
252 const Type *ElTy = NGV->getType()->getElementType();
253 NGV->setInitializer(Constant::getNullValue(ElTy));
254 cast<GlobalVariable>(Concrete)->setInitializer(0);
262 return ResolveFunctions(M, Globals, cast<Function>(Concrete));
264 return ResolveGlobalVariables(M, Globals,
265 cast<GlobalVariable>(Concrete));
270 bool FunctionResolvingPass::run(Module &M) {
271 std::map<std::string, std::vector<GlobalValue*> > Globals;
273 // Loop over the globals, adding them to the Globals map. We use a two pass
274 // algorithm here to avoid problems with iterators getting invalidated if we
275 // did a one pass scheme.
277 bool Changed = false;
278 for (Module::iterator I = M.begin(), E = M.end(); I != E; ) {
280 if (F->use_empty() && F->isExternal()) {
281 M.getFunctionList().erase(F);
283 } else if (!F->hasInternalLinkage() && !F->getName().empty())
284 Globals[F->getName()].push_back(F);
287 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ) {
288 GlobalVariable *GV = I++;
289 if (GV->use_empty() && GV->isExternal()) {
290 M.getGlobalList().erase(GV);
292 } else if (!GV->hasInternalLinkage() && !GV->getName().empty())
293 Globals[GV->getName()].push_back(GV);
296 TargetData &TD = getAnalysis<TargetData>();
298 // Now we have a list of all functions with a particular name. If there is
299 // more than one entry in a list, merge the functions together.
301 for (std::map<std::string, std::vector<GlobalValue*> >::iterator
302 I = Globals.begin(), E = Globals.end(); I != E; ++I)
303 Changed |= ProcessGlobalsWithSameName(M, TD, I->second);
305 // Now loop over all of the globals, checking to see if any are trivially
306 // dead. If so, remove them now.
308 for (Module::iterator I = M.begin(), E = M.end(); I != E; )
309 if (I->isExternal() && I->use_empty()) {
312 M.getFunctionList().erase(F);
319 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; )
320 if (I->isExternal() && I->use_empty()) {
321 GlobalVariable *GV = I;
323 M.getGlobalList().erase(GV);