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 // * Replace calls to 'sbyte *%malloc(uint)' and 'void %free(sbyte *)' with
10 // malloc and free instructions.
12 // Note: This code produces dead declarations, it is a good idea to run DCE
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Transforms/CleanupGCCOutput.h"
18 #include "TransformInternals.h"
19 #include "llvm/SymbolTable.h"
20 #include "llvm/DerivedTypes.h"
21 #include "llvm/iOther.h"
22 #include "llvm/iMemory.h"
23 #include "llvm/iTerminators.h"
26 static const Type *PtrArrSByte = 0; // '[sbyte]*' type
27 static const Type *PtrSByte = 0; // 'sbyte*' type
29 // ConvertCallTo - Convert a call to a varargs function with no arg types
30 // specified to a concrete nonvarargs method.
32 static void ConvertCallTo(CallInst *CI, Method *Dest) {
33 const MethodType::ParamTypes &ParamTys =
34 Dest->getMethodType()->getParamTypes();
35 BasicBlock *BB = CI->getParent();
37 // Get an iterator to where we want to insert cast instructions if the
38 // argument types don't agree.
40 BasicBlock::iterator BBI = find(BB->begin(), BB->end(), CI);
41 assert(BBI != BB->end() && "CallInst not in parent block?");
43 assert(CI->getNumOperands()-1 == ParamTys.size()&&
44 "Method calls resolved funny somehow, incompatible number of args");
46 vector<Value*> Params;
48 // Convert all of the call arguments over... inserting cast instructions if
49 // the types are not compatible.
50 for (unsigned i = 1; i < CI->getNumOperands(); ++i) {
51 Value *V = CI->getOperand(i);
53 if (V->getType() != ParamTys[i-1]) { // Must insert a cast...
54 Instruction *Cast = new CastInst(V, ParamTys[i-1]);
55 BBI = BB->getInstList().insert(BBI, Cast)+1;
62 // Replace the old call instruction with a new call instruction that calls
65 ReplaceInstWithInst(BB->getInstList(), BBI, new CallInst(Dest, Params));
69 // PatchUpMethodReferences - Go over the methods that are in the module and
70 // look for methods that have the same name. More often than not, there will
73 // void "foo"(int, int)
74 // because of the way things are declared in C. If this is the case, patch
77 bool CleanupGCCOutput::PatchUpMethodReferences(Module *M) {
78 SymbolTable *ST = M->getSymbolTable();
79 if (!ST) return false;
81 map<string, vector<Method*> > Methods;
83 // Loop over the entries in the symbol table. If an entry is a method pointer,
84 // then add it to the Methods map. We do a two pass algorithm here to avoid
85 // problems with iterators getting invalidated if we did a one pass scheme.
87 for (SymbolTable::iterator I = ST->begin(), E = ST->end(); I != E; ++I)
88 if (const PointerType *PT = dyn_cast<PointerType>(I->first))
89 if (const MethodType *MT = dyn_cast<MethodType>(PT->getValueType())) {
90 SymbolTable::VarMap &Plane = I->second;
91 for (SymbolTable::type_iterator PI = Plane.begin(), PE = Plane.end();
93 const string &Name = PI->first;
94 Method *M = cast<Method>(PI->second);
95 Methods[Name].push_back(M);
101 // Now we have a list of all methods with a particular name. If there is more
102 // than one entry in a list, merge the methods together.
104 for (map<string, vector<Method*> >::iterator I = Methods.begin(),
105 E = Methods.end(); I != E; ++I) {
106 vector<Method*> &Methods = I->second;
107 Method *Implementation = 0; // Find the implementation
108 Method *Concrete = 0;
109 for (unsigned i = 0; i < Methods.size(); ) {
110 if (!Methods[i]->isExternal()) { // Found an implementation
111 assert(Implementation == 0 && "Multiple definitions of the same"
112 " method. Case not handled yet!");
113 Implementation = Methods[i];
115 // Ignore methods that are never used so they don't cause spurious
116 // warnings... here we will actually DCE the function so that it isn't
119 if (Methods[i]->use_size() == 0) {
120 M->getMethodList().remove(Methods[i]);
122 Methods.erase(Methods.begin()+i);
128 if (Methods[i] && (!Methods[i]->getMethodType()->isVarArg() ||
129 Methods[i]->getMethodType()->getParamTypes().size())) {
130 if (Concrete) { // Found two different methods types. Can't choose
134 Concrete = Methods[i];
139 if (Methods.size() > 1) { // Found a multiply defined method.
140 // We should find exactly one non-vararg method definition, which is
141 // probably the implementation. Change all of the method definitions
142 // and uses to use it instead.
145 cerr << "Warning: Found methods types that are not compatible:\n";
146 for (unsigned i = 0; i < Methods.size(); ++i) {
147 cerr << "\t" << Methods[i]->getType()->getDescription() << " %"
148 << Methods[i]->getName() << endl;
150 cerr << " No linkage of methods named '" << Methods[0]->getName()
153 for (unsigned i = 0; i < Methods.size(); ++i)
154 if (Methods[i] != Concrete) {
155 Method *Old = Methods[i];
156 assert(Old->getReturnType() == Concrete->getReturnType() &&
157 "Differing return types not handled yet!");
158 assert(Old->getMethodType()->getParamTypes().size() == 0 &&
159 "Cannot handle varargs fn's with specified element types!");
161 // Attempt to convert all of the uses of the old method to the
162 // concrete form of the method. If there is a use of the method
163 // that we don't understand here we punt to avoid making a bad
166 // At this point, we know that the return values are the same for
167 // our two functions and that the Old method has no varargs methods
168 // specified. In otherwords it's just <retty> (...)
170 for (unsigned i = 0; i < Old->use_size(); ) {
171 User *U = *(Old->use_begin()+i);
172 if (CastInst *CI = dyn_cast<CastInst>(U)) {
173 // Convert casts directly
174 assert(CI->getOperand(0) == Old);
175 CI->setOperand(0, Concrete);
177 } else if (CallInst *CI = dyn_cast<CallInst>(U)) {
178 // Can only fix up calls TO the argument, not args passed in.
179 if (CI->getCalledValue() == Old) {
180 ConvertCallTo(CI, Concrete);
183 cerr << "Couldn't cleanup this function call, must be an"
184 << " argument or something!" << CI;
188 cerr << "Cannot convert use of method: " << U << endl;
201 // ShouldNukSymtabEntry - Return true if this module level symbol table entry
202 // should be eliminated.
204 static inline bool ShouldNukeSymtabEntry(const pair<string, Value*> &E) {
205 // Nuke all names for primitive types!
206 if (cast<Type>(E.second)->isPrimitiveType()) return true;
208 // Nuke all pointers to primitive types as well...
209 if (const PointerType *PT = dyn_cast<PointerType>(E.second))
210 if (PT->getValueType()->isPrimitiveType()) return true;
212 // The only types that could contain .'s in the program are things generated
213 // by GCC itself, including "complex.float" and friends. Nuke them too.
214 if (E.first.find('.') != string::npos) return true;
219 // doPassInitialization - For this pass, it removes global symbol table
220 // entries for primitive types. These are never used for linking in GCC and
221 // they make the output uglier to look at, so we nuke them.
223 bool CleanupGCCOutput::doPassInitialization(Module *M) {
224 bool Changed = false;
226 FUT.doPassInitialization(M);
228 if (PtrArrSByte == 0) {
229 PtrArrSByte = PointerType::get(ArrayType::get(Type::SByteTy));
230 PtrSByte = PointerType::get(Type::SByteTy);
233 if (M->hasSymbolTable()) {
234 SymbolTable *ST = M->getSymbolTable();
236 // Go over the methods that are in the module and look for methods that have
237 // the same name. More often than not, there will be things like:
238 // void "foo"(...) and void "foo"(int, int) because of the way things are
239 // declared in C. If this is the case, patch things up.
241 Changed |= PatchUpMethodReferences(M);
244 // If the module has a symbol table, they might be referring to the malloc
245 // and free functions. If this is the case, grab the method pointers that
246 // the module is using.
248 // Lookup %malloc and %free in the symbol table, for later use. If they
249 // don't exist, or are not external, we do not worry about converting calls
250 // to that function into the appropriate instruction.
252 const PointerType *MallocType = // Get the type for malloc
253 PointerType::get(MethodType::get(PointerType::get(Type::SByteTy),
254 vector<const Type*>(1, Type::UIntTy), false));
255 Malloc = cast_or_null<Method>(ST->lookup(MallocType, "malloc"));
256 if (Malloc && !Malloc->isExternal())
257 Malloc = 0; // Don't mess with locally defined versions of the fn
259 const PointerType *FreeType = // Get the type for free
260 PointerType::get(MethodType::get(Type::VoidTy,
261 vector<const Type*>(1, PointerType::get(Type::SByteTy)), false));
262 Free = cast_or_null<Method>(ST->lookup(FreeType, "free"));
263 if (Free && !Free->isExternal())
264 Free = 0; // Don't mess with locally defined versions of the fn
267 // Check the symbol table for superfluous type entries...
269 // Grab the 'type' plane of the module symbol...
270 SymbolTable::iterator STI = ST->find(Type::TypeTy);
271 if (STI != ST->end()) {
272 // Loop over all entries in the type plane...
273 SymbolTable::VarMap &Plane = STI->second;
274 for (SymbolTable::VarMap::iterator PI = Plane.begin(); PI != Plane.end();)
275 if (ShouldNukeSymtabEntry(*PI)) { // Should we remove this entry?
276 #if MAP_IS_NOT_BRAINDEAD
277 PI = Plane.erase(PI); // STD C++ Map should support this!
279 Plane.erase(PI); // Alas, GCC 2.95.3 doesn't *SIGH*
293 // doOneCleanupPass - Do one pass over the input method, fixing stuff up.
295 bool CleanupGCCOutput::doOneCleanupPass(Method *M) {
296 bool Changed = false;
297 for (Method::iterator MI = M->begin(), ME = M->end(); MI != ME; ++MI) {
298 BasicBlock *BB = *MI;
299 BasicBlock::InstListType &BIL = BB->getInstList();
301 for (BasicBlock::iterator BI = BB->begin(); BI != BB->end();) {
302 Instruction *I = *BI;
304 if (CallInst *CI = dyn_cast<CallInst>(I)) {
305 if (CI->getCalledValue() == Malloc) { // Replace call to malloc?
306 MallocInst *MallocI = new MallocInst(PtrArrSByte, CI->getOperand(1),
309 BI = BIL.insert(BI, MallocI)+1;
310 ReplaceInstWithInst(BIL, BI, new CastInst(MallocI, PtrSByte));
312 continue; // Skip the ++BI
313 } else if (CI->getCalledValue() == Free) { // Replace call to free?
314 ReplaceInstWithInst(BIL, BI, new FreeInst(CI->getOperand(1)));
316 continue; // Skip the ++BI
328 // FixCastsAndPHIs - The LLVM GCC has a tendancy to intermix Cast instructions
329 // in with the PHI nodes. These cast instructions are potentially there for two
330 // different reasons:
332 // 1. The cast could be for an early PHI, and be accidentally inserted before
333 // another PHI node. In this case, the PHI node should be moved to the end
334 // of the PHI nodes in the basic block. We know that it is this case if
335 // the source for the cast is a PHI node in this basic block.
337 // 2. If not #1, the cast must be a source argument for one of the PHI nodes
338 // in the current basic block. If this is the case, the cast should be
339 // lifted into the basic block for the appropriate predecessor.
341 static inline bool FixCastsAndPHIs(BasicBlock *BB) {
342 bool Changed = false;
344 BasicBlock::iterator InsertPos = BB->begin();
346 // Find the end of the interesting instructions...
347 while (isa<PHINode>(*InsertPos) || isa<CastInst>(*InsertPos)) ++InsertPos;
349 // Back the InsertPos up to right after the last PHI node.
350 while (InsertPos != BB->begin() && isa<CastInst>(*(InsertPos-1))) --InsertPos;
352 // No PHI nodes, quick exit.
353 if (InsertPos == BB->begin()) return false;
355 // Loop over all casts trapped between the PHI's...
356 BasicBlock::iterator I = BB->begin();
357 while (I != InsertPos) {
358 if (CastInst *CI = dyn_cast<CastInst>(*I)) { // Fix all cast instructions
359 Value *Src = CI->getOperand(0);
361 // Move the cast instruction to the current insert position...
362 --InsertPos; // New position for cast to go...
363 swap(*InsertPos, *I); // Cast goes down, PHI goes up
365 if (isa<PHINode>(Src) && // Handle case #1
366 cast<PHINode>(Src)->getParent() == BB) {
367 // We're done for case #1
368 } else { // Handle case #2
369 // In case #2, we have to do a few things:
370 // 1. Remove the cast from the current basic block.
371 // 2. Identify the PHI node that the cast is for.
372 // 3. Find out which predecessor the value is for.
373 // 4. Move the cast to the end of the basic block that it SHOULD be
376 // Remove the cast instruction from the basic block. The remove only
377 // invalidates iterators in the basic block that are AFTER the removed
378 // element. Because we just moved the CastInst to the InsertPos, no
379 // iterators get invalidated.
381 BB->getInstList().remove(InsertPos);
383 // Find the PHI node. Since this cast was generated specifically for a
384 // PHI node, there can only be a single PHI node using it.
386 assert(CI->use_size() == 1 && "Exactly one PHI node should use cast!");
387 PHINode *PN = cast<PHINode>(*CI->use_begin());
389 // Find out which operand of the PHI it is...
391 for (i = 0; i < PN->getNumIncomingValues(); ++i)
392 if (PN->getIncomingValue(i) == CI)
394 assert(i != PN->getNumIncomingValues() && "PHI doesn't use cast!");
396 // Get the predecessor the value is for...
397 BasicBlock *Pred = PN->getIncomingBlock(i);
399 // Reinsert the cast right before the terminator in Pred.
400 Pred->getInstList().insert(Pred->end()-1, CI);
411 // RefactorPredecessor - When we find out that a basic block is a repeated
412 // predecessor in a PHI node, we have to refactor the method until there is at
413 // most a single instance of a basic block in any predecessor list.
415 static inline void RefactorPredecessor(BasicBlock *BB, BasicBlock *Pred) {
416 Method *M = BB->getParent();
417 assert(find(BB->pred_begin(), BB->pred_end(), Pred) != BB->pred_end() &&
418 "Pred is not a predecessor of BB!");
420 // Create a new basic block, adding it to the end of the method.
421 BasicBlock *NewBB = new BasicBlock("", M);
423 // Add an unconditional branch to BB to the new block.
424 NewBB->getInstList().push_back(new BranchInst(BB));
426 // Get the terminator that causes a branch to BB from Pred.
427 TerminatorInst *TI = Pred->getTerminator();
429 // Find the first use of BB in the terminator...
430 User::op_iterator OI = find(TI->op_begin(), TI->op_end(), BB);
431 assert(OI != TI->op_end() && "Pred does not branch to BB!!!");
433 // Change the use of BB to point to the new stub basic block
436 // Now we need to loop through all of the PHI nodes in BB and convert their
437 // first incoming value for Pred to reference the new basic block instead.
439 for (BasicBlock::iterator I = BB->begin();
440 PHINode *PN = dyn_cast<PHINode>(*I); ++I) {
441 int BBIdx = PN->getBasicBlockIndex(Pred);
442 assert(BBIdx != -1 && "PHI node doesn't have an entry for Pred!");
444 // The value that used to look like it came from Pred now comes from NewBB
445 PN->setIncomingBlock((unsigned)BBIdx, NewBB);
450 // CheckIncomingValueFor - Make sure that the specified PHI node has an entry
451 // for the provided basic block. If it doesn't, add one and return true.
453 static inline void CheckIncomingValueFor(PHINode *PN, BasicBlock *BB) {
454 if (PN->getBasicBlockIndex(BB) != -1) return; // Already has value
457 const Type *Ty = PN->getType();
459 if (const PointerType *PT = dyn_cast<PointerType>(Ty))
460 NewVal = ConstPoolPointerNull::get(PT);
461 else if (Ty == Type::BoolTy)
462 NewVal = ConstPoolBool::True;
463 else if (Ty == Type::FloatTy || Ty == Type::DoubleTy)
464 NewVal = ConstPoolFP::get(Ty, 42);
465 else if (Ty->isIntegral())
466 NewVal = ConstPoolInt::get(Ty, 42);
468 assert(NewVal && "Unknown PHI node type!");
469 PN->addIncoming(NewVal, BB);
472 // fixLocalProblems - Loop through the method and fix problems with the PHI
473 // nodes in the current method. The two problems that are handled are:
475 // 1. PHI nodes with multiple entries for the same predecessor. GCC sometimes
476 // generates code that looks like this:
478 // bb7: br bool %cond1004, label %bb8, label %bb8
479 // bb8: %reg119 = phi uint [ 0, %bb7 ], [ 1, %bb7 ]
481 // which is completely illegal LLVM code. To compensate for this, we insert
482 // an extra basic block, and convert the code to look like this:
484 // bb7: br bool %cond1004, label %bbX, label %bb8
486 // bb8: %reg119 = phi uint [ 0, %bbX ], [ 1, %bb7 ]
489 // 2. PHI nodes with fewer arguments than predecessors.
490 // These can be generated by GCC if a variable is uninitalized over a path
491 // in the CFG. We fix this by adding an entry for the missing predecessors
492 // that is initialized to either 42 for a numeric/FP value, or null if it's
493 // a pointer value. This problem can be generated by code that looks like
501 static bool fixLocalProblems(Method *M) {
502 bool Changed = false;
503 // Don't use iterators because invalidation gets messy...
504 for (unsigned MI = 0; MI < M->size(); ++MI) {
505 BasicBlock *BB = M->getBasicBlocks()[MI];
507 Changed |= FixCastsAndPHIs(BB);
509 if (isa<PHINode>(BB->front())) {
510 const vector<BasicBlock*> Preds(BB->pred_begin(), BB->pred_end());
512 // Handle Problem #1. Sort the list of predecessors so that it is easy to
513 // decide whether or not duplicate predecessors exist.
514 vector<BasicBlock*> SortedPreds(Preds);
515 sort(SortedPreds.begin(), SortedPreds.end());
517 // Loop over the predecessors, looking for adjacent BB's that are equal.
518 BasicBlock *LastOne = 0;
519 for (unsigned i = 0; i < Preds.size(); ++i) {
520 if (SortedPreds[i] == LastOne) { // Found a duplicate.
521 RefactorPredecessor(BB, SortedPreds[i]);
524 LastOne = SortedPreds[i];
527 // Loop over all of the PHI nodes in the current BB. These PHI nodes are
528 // guaranteed to be at the beginning of the basic block.
530 for (BasicBlock::iterator I = BB->begin();
531 PHINode *PN = dyn_cast<PHINode>(*I); ++I) {
533 // Handle problem #2.
534 if (PN->getNumIncomingValues() != Preds.size()) {
535 assert(PN->getNumIncomingValues() <= Preds.size() &&
536 "Can't handle extra arguments to PHI nodes!");
537 for (unsigned i = 0; i < Preds.size(); ++i)
538 CheckIncomingValueFor(PN, Preds[i]);
550 // doPerMethodWork - This method simplifies the specified method hopefully.
552 bool CleanupGCCOutput::doPerMethodWork(Method *M) {
553 bool Changed = fixLocalProblems(M);
554 while (doOneCleanupPass(M)) Changed = true;
556 FUT.doPerMethodWork(M);
560 bool CleanupGCCOutput::doPassFinalization(Module *M) {
561 bool Changed = false;
562 FUT.doPassFinalization(M);
564 if (M->hasSymbolTable()) {
565 SymbolTable *ST = M->getSymbolTable();
566 const set<const Type *> &UsedTypes = FUT.getTypes();
568 // Check the symbol table for superfluous type entries that aren't used in
571 // Grab the 'type' plane of the module symbol...
572 SymbolTable::iterator STI = ST->find(Type::TypeTy);
573 if (STI != ST->end()) {
574 // Loop over all entries in the type plane...
575 SymbolTable::VarMap &Plane = STI->second;
576 for (SymbolTable::VarMap::iterator PI = Plane.begin(); PI != Plane.end();)
577 if (!UsedTypes.count(cast<Type>(PI->second))) {
578 #if MAP_IS_NOT_BRAINDEAD
579 PI = Plane.erase(PI); // STD C++ Map should support this!
581 Plane.erase(PI); // Alas, GCC 2.95.3 doesn't *SIGH*
582 PI = Plane.begin(); // N^2 algorithms are fun. :(