1 //===- CleanupGCCOutput.cpp - Cleanup GCC Output --------------------------===//
3 // This pass is used to cleanup the output of GCC. GCC's output is
4 // unneccessarily gross for a couple of reasons. This pass does the following
5 // things to try to clean it up:
7 // * Eliminate names for GCC types that we know can't be needed by the user.
8 // * Eliminate names for types that are unused in the entire translation unit
9 // * Fix various problems that we might have in PHI nodes and casts
10 // * Link uses of 'void %foo(...)' to 'void %foo(sometypes)'
12 // Note: This code produces dead declarations, it is a good idea to run DCE
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Transforms/CleanupGCCOutput.h"
18 #include "llvm/Analysis/FindUsedTypes.h"
19 #include "TransformInternals.h"
20 #include "llvm/Module.h"
21 #include "llvm/SymbolTable.h"
22 #include "llvm/DerivedTypes.h"
23 #include "llvm/iPHINode.h"
24 #include "llvm/iMemory.h"
25 #include "llvm/iTerminators.h"
26 #include "llvm/iOther.h"
27 #include "llvm/Support/CFG.h"
28 #include "llvm/Pass.h"
35 static const Type *PtrSByte = 0; // 'sbyte*' type
38 struct CleanupGCCOutput : public FunctionPass {
39 const char *getPassName() const { return "Cleanup GCC Output"; }
41 // doPassInitialization - For this pass, it removes global symbol table
42 // entries for primitive types. These are never used for linking in GCC and
43 // they make the output uglier to look at, so we nuke them.
45 // Also, initialize instance variables.
47 bool doInitialization(Module *M);
49 // runOnFunction - This method simplifies the specified function hopefully.
51 bool runOnFunction(Function *F);
53 // doPassFinalization - Strip out type names that are unused by the program
54 bool doFinalization(Module *M);
56 // getAnalysisUsage - This function needs FindUsedTypes to do its job...
58 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
59 AU.addRequired(FindUsedTypes::ID);
64 Pass *createCleanupGCCOutputPass() {
65 return new CleanupGCCOutput();
70 // ShouldNukSymtabEntry - Return true if this module level symbol table entry
71 // should be eliminated.
73 static inline bool ShouldNukeSymtabEntry(const std::pair<string, Value*> &E) {
74 // Nuke all names for primitive types!
75 if (cast<Type>(E.second)->isPrimitiveType()) return true;
77 // Nuke all pointers to primitive types as well...
78 if (const PointerType *PT = dyn_cast<PointerType>(E.second))
79 if (PT->getElementType()->isPrimitiveType()) return true;
81 // The only types that could contain .'s in the program are things generated
82 // by GCC itself, including "complex.float" and friends. Nuke them too.
83 if (E.first.find('.') != string::npos) return true;
88 // doInitialization - For this pass, it removes global symbol table
89 // entries for primitive types. These are never used for linking in GCC and
90 // they make the output uglier to look at, so we nuke them.
92 bool CleanupGCCOutput::doInitialization(Module *M) {
96 PtrSByte = PointerType::get(Type::SByteTy);
98 if (M->hasSymbolTable()) {
99 SymbolTable *ST = M->getSymbolTable();
101 // Check the symbol table for superfluous type entries...
103 // Grab the 'type' plane of the module symbol...
104 SymbolTable::iterator STI = ST->find(Type::TypeTy);
105 if (STI != ST->end()) {
106 // Loop over all entries in the type plane...
107 SymbolTable::VarMap &Plane = STI->second;
108 for (SymbolTable::VarMap::iterator PI = Plane.begin(); PI != Plane.end();)
109 if (ShouldNukeSymtabEntry(*PI)) { // Should we remove this entry?
110 #if MAP_IS_NOT_BRAINDEAD
111 PI = Plane.erase(PI); // STD C++ Map should support this!
113 Plane.erase(PI); // Alas, GCC 2.95.3 doesn't *SIGH*
127 // FixCastsAndPHIs - The LLVM GCC has a tendancy to intermix Cast instructions
128 // in with the PHI nodes. These cast instructions are potentially there for two
129 // different reasons:
131 // 1. The cast could be for an early PHI, and be accidentally inserted before
132 // another PHI node. In this case, the PHI node should be moved to the end
133 // of the PHI nodes in the basic block. We know that it is this case if
134 // the source for the cast is a PHI node in this basic block.
136 // 2. If not #1, the cast must be a source argument for one of the PHI nodes
137 // in the current basic block. If this is the case, the cast should be
138 // lifted into the basic block for the appropriate predecessor.
140 static inline bool FixCastsAndPHIs(BasicBlock *BB) {
141 bool Changed = false;
143 BasicBlock::iterator InsertPos = BB->begin();
145 // Find the end of the interesting instructions...
146 while (isa<PHINode>(*InsertPos) || isa<CastInst>(*InsertPos)) ++InsertPos;
148 // Back the InsertPos up to right after the last PHI node.
149 while (InsertPos != BB->begin() && isa<CastInst>(*(InsertPos-1))) --InsertPos;
151 // No PHI nodes, quick exit.
152 if (InsertPos == BB->begin()) return false;
154 // Loop over all casts trapped between the PHI's...
155 BasicBlock::iterator I = BB->begin();
156 while (I != InsertPos) {
157 if (CastInst *CI = dyn_cast<CastInst>(*I)) { // Fix all cast instructions
158 Value *Src = CI->getOperand(0);
160 // Move the cast instruction to the current insert position...
161 --InsertPos; // New position for cast to go...
162 std::swap(*InsertPos, *I); // Cast goes down, PHI goes up
164 if (isa<PHINode>(Src) && // Handle case #1
165 cast<PHINode>(Src)->getParent() == BB) {
166 // We're done for case #1
167 } else { // Handle case #2
168 // In case #2, we have to do a few things:
169 // 1. Remove the cast from the current basic block.
170 // 2. Identify the PHI node that the cast is for.
171 // 3. Find out which predecessor the value is for.
172 // 4. Move the cast to the end of the basic block that it SHOULD be
175 // Remove the cast instruction from the basic block. The remove only
176 // invalidates iterators in the basic block that are AFTER the removed
177 // element. Because we just moved the CastInst to the InsertPos, no
178 // iterators get invalidated.
180 BB->getInstList().remove(InsertPos);
182 // Find the PHI node. Since this cast was generated specifically for a
183 // PHI node, there can only be a single PHI node using it.
185 assert(CI->use_size() == 1 && "Exactly one PHI node should use cast!");
186 PHINode *PN = cast<PHINode>(*CI->use_begin());
188 // Find out which operand of the PHI it is...
190 for (i = 0; i < PN->getNumIncomingValues(); ++i)
191 if (PN->getIncomingValue(i) == CI)
193 assert(i != PN->getNumIncomingValues() && "PHI doesn't use cast!");
195 // Get the predecessor the value is for...
196 BasicBlock *Pred = PN->getIncomingBlock(i);
198 // Reinsert the cast right before the terminator in Pred.
199 Pred->getInstList().insert(Pred->end()-1, CI);
209 // RefactorPredecessor - When we find out that a basic block is a repeated
210 // predecessor in a PHI node, we have to refactor the function until there is at
211 // most a single instance of a basic block in any predecessor list.
213 static inline void RefactorPredecessor(BasicBlock *BB, BasicBlock *Pred) {
214 Function *M = BB->getParent();
215 assert(find(pred_begin(BB), pred_end(BB), Pred) != pred_end(BB) &&
216 "Pred is not a predecessor of BB!");
218 // Create a new basic block, adding it to the end of the function.
219 BasicBlock *NewBB = new BasicBlock("", M);
221 // Add an unconditional branch to BB to the new block.
222 NewBB->getInstList().push_back(new BranchInst(BB));
224 // Get the terminator that causes a branch to BB from Pred.
225 TerminatorInst *TI = Pred->getTerminator();
227 // Find the first use of BB in the terminator...
228 User::op_iterator OI = find(TI->op_begin(), TI->op_end(), BB);
229 assert(OI != TI->op_end() && "Pred does not branch to BB!!!");
231 // Change the use of BB to point to the new stub basic block
234 // Now we need to loop through all of the PHI nodes in BB and convert their
235 // first incoming value for Pred to reference the new basic block instead.
237 for (BasicBlock::iterator I = BB->begin();
238 PHINode *PN = dyn_cast<PHINode>(*I); ++I) {
239 int BBIdx = PN->getBasicBlockIndex(Pred);
240 assert(BBIdx != -1 && "PHI node doesn't have an entry for Pred!");
242 // The value that used to look like it came from Pred now comes from NewBB
243 PN->setIncomingBlock((unsigned)BBIdx, NewBB);
248 // runOnFunction - Loop through the function and fix problems with the PHI nodes
249 // in the current function. The problem is that PHI nodes might exist with
250 // multiple entries for the same predecessor. GCC sometimes generates code that
253 // bb7: br bool %cond1004, label %bb8, label %bb8
254 // bb8: %reg119 = phi uint [ 0, %bb7 ], [ 1, %bb7 ]
256 // which is completely illegal LLVM code. To compensate for this, we insert
257 // an extra basic block, and convert the code to look like this:
259 // bb7: br bool %cond1004, label %bbX, label %bb8
261 // bb8: %reg119 = phi uint [ 0, %bbX ], [ 1, %bb7 ]
264 bool CleanupGCCOutput::runOnFunction(Function *M) {
265 bool Changed = false;
266 // Don't use iterators because invalidation gets messy...
267 for (unsigned MI = 0; MI < M->size(); ++MI) {
268 BasicBlock *BB = M->getBasicBlocks()[MI];
270 Changed |= FixCastsAndPHIs(BB);
272 if (isa<PHINode>(BB->front())) {
273 const vector<BasicBlock*> Preds(pred_begin(BB), pred_end(BB));
275 // Handle the problem. Sort the list of predecessors so that it is easy
276 // to decide whether or not duplicate predecessors exist.
277 vector<BasicBlock*> SortedPreds(Preds);
278 sort(SortedPreds.begin(), SortedPreds.end());
280 // Loop over the predecessors, looking for adjacent BB's that are equal.
281 BasicBlock *LastOne = 0;
282 for (unsigned i = 0; i < Preds.size(); ++i) {
283 if (SortedPreds[i] == LastOne) { // Found a duplicate.
284 RefactorPredecessor(BB, SortedPreds[i]);
287 LastOne = SortedPreds[i];
294 bool CleanupGCCOutput::doFinalization(Module *M) {
295 bool Changed = false;
297 if (M->hasSymbolTable()) {
298 SymbolTable *ST = M->getSymbolTable();
299 const std::set<const Type *> &UsedTypes =
300 getAnalysis<FindUsedTypes>().getTypes();
302 // Check the symbol table for superfluous type entries that aren't used in
305 // Grab the 'type' plane of the module symbol...
306 SymbolTable::iterator STI = ST->find(Type::TypeTy);
307 if (STI != ST->end()) {
308 // Loop over all entries in the type plane...
309 SymbolTable::VarMap &Plane = STI->second;
310 for (SymbolTable::VarMap::iterator PI = Plane.begin(); PI != Plane.end();)
311 if (!UsedTypes.count(cast<Type>(PI->second))) {
312 #if MAP_IS_NOT_BRAINDEAD
313 PI = Plane.erase(PI); // STD C++ Map should support this!
315 Plane.erase(PI); // Alas, GCC 2.95.3 doesn't *SIGH*
316 PI = Plane.begin(); // N^2 algorithms are fun. :(
328 //===----------------------------------------------------------------------===//
330 // FunctionResolvingPass - Go over the functions that are in the module and
331 // look for functions that have the same name. More often than not, there will
334 // void "foo"(int, int)
335 // because of the way things are declared in C. If this is the case, patch
338 //===----------------------------------------------------------------------===//
341 struct FunctionResolvingPass : public Pass {
342 const char *getPassName() const { return "Resolve Functions"; }
348 // ConvertCallTo - Convert a call to a varargs function with no arg types
349 // specified to a concrete nonvarargs function.
351 static void ConvertCallTo(CallInst *CI, Function *Dest) {
352 const FunctionType::ParamTypes &ParamTys =
353 Dest->getFunctionType()->getParamTypes();
354 BasicBlock *BB = CI->getParent();
356 // Get an iterator to where we want to insert cast instructions if the
357 // argument types don't agree.
359 BasicBlock::iterator BBI = find(BB->begin(), BB->end(), CI);
360 assert(BBI != BB->end() && "CallInst not in parent block?");
362 assert(CI->getNumOperands()-1 == ParamTys.size()&&
363 "Function calls resolved funny somehow, incompatible number of args");
365 vector<Value*> Params;
367 // Convert all of the call arguments over... inserting cast instructions if
368 // the types are not compatible.
369 for (unsigned i = 1; i < CI->getNumOperands(); ++i) {
370 Value *V = CI->getOperand(i);
372 if (V->getType() != ParamTys[i-1]) { // Must insert a cast...
373 Instruction *Cast = new CastInst(V, ParamTys[i-1]);
374 BBI = BB->getInstList().insert(BBI, Cast)+1;
381 // Replace the old call instruction with a new call instruction that calls
382 // the real function.
384 ReplaceInstWithInst(BB->getInstList(), BBI, new CallInst(Dest, Params));
388 bool FunctionResolvingPass::run(Module *M) {
389 SymbolTable *ST = M->getSymbolTable();
390 if (!ST) return false;
392 std::map<string, vector<Function*> > Functions;
394 // Loop over the entries in the symbol table. If an entry is a func pointer,
395 // then add it to the Functions map. We do a two pass algorithm here to avoid
396 // problems with iterators getting invalidated if we did a one pass scheme.
398 for (SymbolTable::iterator I = ST->begin(), E = ST->end(); I != E; ++I)
399 if (const PointerType *PT = dyn_cast<PointerType>(I->first))
400 if (isa<FunctionType>(PT->getElementType())) {
401 SymbolTable::VarMap &Plane = I->second;
402 for (SymbolTable::type_iterator PI = Plane.begin(), PE = Plane.end();
404 const string &Name = PI->first;
405 Functions[Name].push_back(cast<Function>(PI->second));
409 bool Changed = false;
411 // Now we have a list of all functions with a particular name. If there is
412 // more than one entry in a list, merge the functions together.
414 for (std::map<string, vector<Function*> >::iterator I = Functions.begin(),
415 E = Functions.end(); I != E; ++I) {
416 vector<Function*> &Functions = I->second;
417 Function *Implementation = 0; // Find the implementation
418 Function *Concrete = 0;
419 for (unsigned i = 0; i < Functions.size(); ) {
420 if (!Functions[i]->isExternal()) { // Found an implementation
421 assert(Implementation == 0 && "Multiple definitions of the same"
422 " function. Case not handled yet!");
423 Implementation = Functions[i];
425 // Ignore functions that are never used so they don't cause spurious
426 // warnings... here we will actually DCE the function so that it isn't
429 if (Functions[i]->use_size() == 0) {
430 M->getFunctionList().remove(Functions[i]);
432 Functions.erase(Functions.begin()+i);
438 if (Functions[i] && (!Functions[i]->getFunctionType()->isVarArg())) {
439 if (Concrete) { // Found two different functions types. Can't choose
443 Concrete = Functions[i];
448 if (Functions.size() > 1) { // Found a multiply defined function...
449 // We should find exactly one non-vararg function definition, which is
450 // probably the implementation. Change all of the function definitions
451 // and uses to use it instead.
454 cerr << "Warning: Found functions types that are not compatible:\n";
455 for (unsigned i = 0; i < Functions.size(); ++i) {
456 cerr << "\t" << Functions[i]->getType()->getDescription() << " %"
457 << Functions[i]->getName() << "\n";
459 cerr << " No linkage of functions named '" << Functions[0]->getName()
462 for (unsigned i = 0; i < Functions.size(); ++i)
463 if (Functions[i] != Concrete) {
464 Function *Old = Functions[i];
465 const FunctionType *OldMT = Old->getFunctionType();
466 const FunctionType *ConcreteMT = Concrete->getFunctionType();
469 assert(Old->getReturnType() == Concrete->getReturnType() &&
470 "Differing return types not handled yet!");
471 assert(OldMT->getParamTypes().size() <=
472 ConcreteMT->getParamTypes().size() &&
473 "Concrete type must have more specified parameters!");
475 // Check to make sure that if there are specified types, that they
478 for (unsigned i = 0; i < OldMT->getParamTypes().size(); ++i)
479 if (OldMT->getParamTypes()[i] != ConcreteMT->getParamTypes()[i]) {
480 cerr << "Parameter types conflict for" << OldMT
481 << " and " << ConcreteMT;
484 if (Broken) break; // Can't process this one!
487 // Attempt to convert all of the uses of the old function to the
488 // concrete form of the function. If there is a use of the fn
489 // that we don't understand here we punt to avoid making a bad
492 // At this point, we know that the return values are the same for
493 // our two functions and that the Old function has no varargs fns
494 // specified. In otherwords it's just <retty> (...)
496 for (unsigned i = 0; i < Old->use_size(); ) {
497 User *U = *(Old->use_begin()+i);
498 if (CastInst *CI = dyn_cast<CastInst>(U)) {
499 // Convert casts directly
500 assert(CI->getOperand(0) == Old);
501 CI->setOperand(0, Concrete);
503 } else if (CallInst *CI = dyn_cast<CallInst>(U)) {
504 // Can only fix up calls TO the argument, not args passed in.
505 if (CI->getCalledValue() == Old) {
506 ConvertCallTo(CI, Concrete);
509 cerr << "Couldn't cleanup this function call, must be an"
510 << " argument or something!" << CI;
514 cerr << "Cannot convert use of function: " << U << "\n";
526 Pass *createFunctionResolvingPass() {
527 return new FunctionResolvingPass();