1 //===- CloneFunction.cpp - Clone a function into another function ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the CloneFunctionInto interface, which is used as the
11 // low-level function cloner. This is used by the CloneFunction and function
12 // inliner to do the dirty work of copying the body of a function around.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/Transforms/Utils/Cloning.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/Analysis/ConstantFolding.h"
19 #include "llvm/Analysis/InstructionSimplify.h"
20 #include "llvm/IR/CFG.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/DebugInfo.h"
23 #include "llvm/IR/DerivedTypes.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/IR/GlobalVariable.h"
26 #include "llvm/IR/Instructions.h"
27 #include "llvm/IR/IntrinsicInst.h"
28 #include "llvm/IR/LLVMContext.h"
29 #include "llvm/IR/Metadata.h"
30 #include "llvm/IR/Module.h"
31 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
32 #include "llvm/Transforms/Utils/Local.h"
33 #include "llvm/Transforms/Utils/ValueMapper.h"
38 // CloneBasicBlock - See comments in Cloning.h
39 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
40 ValueToValueMapTy &VMap,
41 const Twine &NameSuffix, Function *F,
42 ClonedCodeInfo *CodeInfo) {
43 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
44 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
46 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
48 // Loop over all instructions, and copy them over.
49 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
51 Instruction *NewInst = II->clone();
53 NewInst->setName(II->getName()+NameSuffix);
54 NewBB->getInstList().push_back(NewInst);
55 VMap[II] = NewInst; // Add instruction map to value.
57 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
58 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
59 if (isa<ConstantInt>(AI->getArraySize()))
60 hasStaticAllocas = true;
62 hasDynamicAllocas = true;
67 CodeInfo->ContainsCalls |= hasCalls;
68 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
69 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
70 BB != &BB->getParent()->getEntryBlock();
75 // Clone OldFunc into NewFunc, transforming the old arguments into references to
78 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
79 ValueToValueMapTy &VMap,
80 bool ModuleLevelChanges,
81 SmallVectorImpl<ReturnInst*> &Returns,
82 const char *NameSuffix, ClonedCodeInfo *CodeInfo,
83 ValueMapTypeRemapper *TypeMapper,
84 ValueMaterializer *Materializer) {
85 assert(NameSuffix && "NameSuffix cannot be null!");
88 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
89 E = OldFunc->arg_end(); I != E; ++I)
90 assert(VMap.count(I) && "No mapping from source argument specified!");
93 // Copy all attributes other than those stored in the AttributeSet. We need
94 // to remap the parameter indices of the AttributeSet.
95 AttributeSet NewAttrs = NewFunc->getAttributes();
96 NewFunc->copyAttributesFrom(OldFunc);
97 NewFunc->setAttributes(NewAttrs);
99 AttributeSet OldAttrs = OldFunc->getAttributes();
100 // Clone any argument attributes that are present in the VMap.
101 for (const Argument &OldArg : OldFunc->args())
102 if (Argument *NewArg = dyn_cast<Argument>(VMap[&OldArg])) {
104 OldAttrs.getParamAttributes(OldArg.getArgNo() + 1);
105 if (attrs.getNumSlots() > 0)
106 NewArg->addAttr(attrs);
109 NewFunc->setAttributes(
110 NewFunc->getAttributes()
111 .addAttributes(NewFunc->getContext(), AttributeSet::ReturnIndex,
112 OldAttrs.getRetAttributes())
113 .addAttributes(NewFunc->getContext(), AttributeSet::FunctionIndex,
114 OldAttrs.getFnAttributes()));
116 // Loop over all of the basic blocks in the function, cloning them as
117 // appropriate. Note that we save BE this way in order to handle cloning of
118 // recursive functions into themselves.
120 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
122 const BasicBlock &BB = *BI;
124 // Create a new basic block and copy instructions into it!
125 BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo);
127 // Add basic block mapping.
130 // It is only legal to clone a function if a block address within that
131 // function is never referenced outside of the function. Given that, we
132 // want to map block addresses from the old function to block addresses in
133 // the clone. (This is different from the generic ValueMapper
134 // implementation, which generates an invalid blockaddress when
135 // cloning a function.)
136 if (BB.hasAddressTaken()) {
137 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
138 const_cast<BasicBlock*>(&BB));
139 VMap[OldBBAddr] = BlockAddress::get(NewFunc, CBB);
142 // Note return instructions for the caller.
143 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
144 Returns.push_back(RI);
147 // Loop over all of the instructions in the function, fixing up operand
148 // references as we go. This uses VMap to do all the hard work.
149 for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]),
150 BE = NewFunc->end(); BB != BE; ++BB)
151 // Loop over all instructions, fixing each one as we find it...
152 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
153 RemapInstruction(II, VMap,
154 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
155 TypeMapper, Materializer);
158 // Find the MDNode which corresponds to the DISubprogram data that described F.
159 static MDNode* FindSubprogram(const Function *F, DebugInfoFinder &Finder) {
160 for (DISubprogram Subprogram : Finder.subprograms()) {
161 if (Subprogram.describes(F)) return Subprogram;
166 // Add an operand to an existing MDNode. The new operand will be added at the
167 // back of the operand list.
168 static void AddOperand(MDNode *Node, Value *Operand) {
169 SmallVector<Value*, 16> Operands;
170 for (unsigned i = 0; i < Node->getNumOperands(); i++) {
171 Operands.push_back(Node->getOperand(i));
173 Operands.push_back(Operand);
174 MDNode *NewNode = MDNode::get(Node->getContext(), Operands);
175 Node->replaceAllUsesWith(NewNode);
178 // Clone the module-level debug info associated with OldFunc. The cloned data
179 // will point to NewFunc instead.
180 static void CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
181 ValueToValueMapTy &VMap) {
182 DebugInfoFinder Finder;
183 Finder.processModule(*OldFunc->getParent());
185 const MDNode *OldSubprogramMDNode = FindSubprogram(OldFunc, Finder);
186 if (!OldSubprogramMDNode) return;
188 // Ensure that OldFunc appears in the map.
189 // (if it's already there it must point to NewFunc anyway)
190 VMap[OldFunc] = NewFunc;
191 DISubprogram NewSubprogram(MapValue(OldSubprogramMDNode, VMap));
193 for (DICompileUnit CU : Finder.compile_units()) {
194 DIArray Subprograms(CU.getSubprograms());
196 // If the compile unit's function list contains the old function, it should
197 // also contain the new one.
198 for (unsigned i = 0; i < Subprograms.getNumElements(); i++) {
199 if ((MDNode*)Subprograms.getElement(i) == OldSubprogramMDNode) {
200 AddOperand(Subprograms, NewSubprogram);
206 /// CloneFunction - Return a copy of the specified function, but without
207 /// embedding the function into another module. Also, any references specified
208 /// in the VMap are changed to refer to their mapped value instead of the
209 /// original one. If any of the arguments to the function are in the VMap,
210 /// the arguments are deleted from the resultant function. The VMap is
211 /// updated to include mappings from all of the instructions and basicblocks in
212 /// the function from their old to new values.
214 Function *llvm::CloneFunction(const Function *F, ValueToValueMapTy &VMap,
215 bool ModuleLevelChanges,
216 ClonedCodeInfo *CodeInfo) {
217 std::vector<Type*> ArgTypes;
219 // The user might be deleting arguments to the function by specifying them in
220 // the VMap. If so, we need to not add the arguments to the arg ty vector
222 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
224 if (VMap.count(I) == 0) // Haven't mapped the argument to anything yet?
225 ArgTypes.push_back(I->getType());
227 // Create a new function type...
228 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
229 ArgTypes, F->getFunctionType()->isVarArg());
231 // Create the new function...
232 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
234 // Loop over the arguments, copying the names of the mapped arguments over...
235 Function::arg_iterator DestI = NewF->arg_begin();
236 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
238 if (VMap.count(I) == 0) { // Is this argument preserved?
239 DestI->setName(I->getName()); // Copy the name over...
240 VMap[I] = DestI++; // Add mapping to VMap
243 if (ModuleLevelChanges)
244 CloneDebugInfoMetadata(NewF, F, VMap);
246 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
247 CloneFunctionInto(NewF, F, VMap, ModuleLevelChanges, Returns, "", CodeInfo);
254 /// PruningFunctionCloner - This class is a private class used to implement
255 /// the CloneAndPruneFunctionInto method.
256 struct PruningFunctionCloner {
258 const Function *OldFunc;
259 ValueToValueMapTy &VMap;
260 bool ModuleLevelChanges;
261 const char *NameSuffix;
262 ClonedCodeInfo *CodeInfo;
263 const DataLayout *DL;
265 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
266 ValueToValueMapTy &valueMap,
267 bool moduleLevelChanges,
268 const char *nameSuffix,
269 ClonedCodeInfo *codeInfo,
270 const DataLayout *DL)
271 : NewFunc(newFunc), OldFunc(oldFunc),
272 VMap(valueMap), ModuleLevelChanges(moduleLevelChanges),
273 NameSuffix(nameSuffix), CodeInfo(codeInfo), DL(DL) {
276 /// CloneBlock - The specified block is found to be reachable, so clone it
278 void CloneBlock(const BasicBlock *BB,
280 std::vector<const BasicBlock *> &ToClone,
281 std::set<const BasicBlock *> &OrigBBs);
285 /// CloneBlock - The specified block is found to be reachable, so clone it
287 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
289 std::vector<const BasicBlock *> &ToClone,
290 std::set<const BasicBlock *> &OrigBBs) {
292 // Remove BB from list of blocks to clone.
293 // When it was not in the list, it has been cloned already, so
294 // don't clone again.
295 if (!OrigBBs.erase(BB)) return;
297 // Nope, clone it now.
299 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
301 // Loop over all instructions, and copy them over, DCE'ing as we go. This
302 // loop doesn't include the terminator.
303 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
305 Instruction *NewInst = II->clone();
307 // Eagerly remap operands to the newly cloned instruction, except for PHI
308 // nodes for which we defer processing until we update the CFG.
309 if (!isa<PHINode>(NewInst)) {
310 RemapInstruction(NewInst, VMap,
311 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
313 // If we can simplify this instruction to some other value, simply add
314 // a mapping to that value rather than inserting a new instruction into
316 if (Value *V = SimplifyInstruction(NewInst, DL)) {
317 // On the off-chance that this simplifies to an instruction in the old
318 // function, map it back into the new function.
319 if (Value *MappedV = VMap.lookup(V))
329 NewInst->setName(II->getName()+NameSuffix);
330 VMap[II] = NewInst; // Add instruction map to value.
331 NewBB->getInstList().push_back(NewInst);
332 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
333 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
334 if (isa<ConstantInt>(AI->getArraySize()))
335 hasStaticAllocas = true;
337 hasDynamicAllocas = true;
341 // Finally, clone over the terminator.
342 const TerminatorInst *OldTI = BB->getTerminator();
343 bool TerminatorDone = false;
344 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
345 if (BI->isConditional()) {
346 // If the condition was a known constant in the callee...
347 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
348 // Or is a known constant in the caller...
350 Value *V = VMap[BI->getCondition()];
351 Cond = dyn_cast_or_null<ConstantInt>(V);
354 // Constant fold to uncond branch!
356 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
357 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
358 ToClone.push_back(Dest);
359 TerminatorDone = true;
362 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
363 // If switching on a value known constant in the caller.
364 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
365 if (!Cond) { // Or known constant after constant prop in the callee...
366 Value *V = VMap[SI->getCondition()];
367 Cond = dyn_cast_or_null<ConstantInt>(V);
369 if (Cond) { // Constant fold to uncond branch!
370 SwitchInst::ConstCaseIt Case = SI->findCaseValue(Cond);
371 BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
372 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
373 ToClone.push_back(Dest);
374 TerminatorDone = true;
378 if (!TerminatorDone) {
379 Instruction *NewInst = OldTI->clone();
380 if (OldTI->hasName())
381 NewInst->setName(OldTI->getName()+NameSuffix);
382 NewBB->getInstList().push_back(NewInst);
383 VMap[OldTI] = NewInst; // Add instruction map to value.
385 // Recursively clone any reachable successor blocks.
386 const TerminatorInst *TI = BB->getTerminator();
387 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
388 ToClone.push_back(TI->getSuccessor(i));
392 CodeInfo->ContainsCalls |= hasCalls;
393 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
394 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
395 BB != &BB->getParent()->front();
399 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
400 /// except that it does some simple constant prop and DCE on the fly. The
401 /// effect of this is to copy significantly less code in cases where (for
402 /// example) a function call with constant arguments is inlined, and those
403 /// constant arguments cause a significant amount of code in the callee to be
404 /// dead. Since this doesn't produce an exact copy of the input, it can't be
405 /// used for things like CloneFunction or CloneModule.
406 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
407 ValueToValueMapTy &VMap,
408 bool ModuleLevelChanges,
409 SmallVectorImpl<ReturnInst*> &Returns,
410 const char *NameSuffix,
411 ClonedCodeInfo *CodeInfo,
412 const DataLayout *DL,
413 Instruction *TheCall) {
414 assert(NameSuffix && "NameSuffix cannot be null!");
417 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
418 E = OldFunc->arg_end(); II != E; ++II)
419 assert(VMap.count(II) && "No mapping from source argument specified!");
422 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
423 NameSuffix, CodeInfo, DL);
425 // Since all BB address references need to be known before block-by-block
426 // processing, we need to create all reachable blocks before processing
427 // them for instruction cloning and pruning. Some of these blocks may
428 // be removed due to later pruning.
429 std::vector<const BasicBlock*> CloneWorklist;
431 // OrigBBs consists of all blocks reachable from the entry
433 // This list will be pruned down by the CloneFunction() currently
434 // (March 2014) due to two optimizations:
435 // First, when a conditional branch target is known at compile-time,
436 // only the actual branch destination block needs to be cloned.
437 // Second, when a switch statement target is known at compile-time,
438 // only the actual case statement needs to be cloned.
439 std::set<const BasicBlock*> OrigBBs;
441 CloneWorklist.push_back(&OldFunc->getEntryBlock());
442 while (!CloneWorklist.empty()) {
443 const BasicBlock *BB = CloneWorklist.back();
444 CloneWorklist.pop_back();
446 // Don't revisit blocks.
450 BasicBlock *NewBB = BasicBlock::Create(BB->getContext());
451 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
453 // It is only legal to clone a function if a block address within that
454 // function is never referenced outside of the function. Given that, we
455 // want to map block addresses from the old function to block addresses in
456 // the clone. (This is different from the generic ValueMapper
457 // implementation, which generates an invalid blockaddress when
458 // cloning a function.)
460 // Note that we don't need to fix the mapping for unreachable blocks;
461 // the default mapping there is safe.
462 if (BB->hasAddressTaken()) {
463 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
464 const_cast<BasicBlock*>(BB));
465 VMap[OldBBAddr] = BlockAddress::get(NewFunc, NewBB);
470 // Iterate over all possible successors and add them to the CloneWorklist.
471 const TerminatorInst *Term = BB->getTerminator();
472 for (unsigned i = 0, e = Term->getNumSuccessors(); i != e; ++i) {
473 BasicBlock *Succ = Term->getSuccessor(i);
474 CloneWorklist.push_back(Succ);
478 // Now, fill only the reachable blocks with the cloned contents
480 assert(CloneWorklist.empty() && "Dirty worklist before re-use\n");
481 CloneWorklist.push_back(&OldFunc->getEntryBlock());
482 while (!CloneWorklist.empty()) {
483 const BasicBlock *BB = CloneWorklist.back();
484 CloneWorklist.pop_back();
485 PFC.CloneBlock(BB, cast<BasicBlock>(VMap[BB]), CloneWorklist,
489 // Removed BB's that were created that turned out to be prunable.
490 // Actual cloning may have found pruning opportunities since
491 // branch or switch statement target may have been known at compile-time.
492 // Alternatively we could write a routine CloneFunction and add a) a
493 // parameter to actually do the cloning and b) a return parameter that
494 // gives a list of blocks that need to be cloned also. Then we could
495 // call CloneFunction when we collect the blocks to call, but suppress
496 // cloning. And actually *do* the cloning in the while loop above. Also
497 // the cleanup here would become redundant, and so would be the OrigBBs.
498 for (std::set<const BasicBlock *>::iterator Oi = OrigBBs.begin(),
499 Oe = OrigBBs.end(); Oi != Oe; ++Oi) {
500 const BasicBlock *Orig = *Oi;
501 BasicBlock *NewBB = cast<BasicBlock>(VMap[Orig]);
506 // Loop over all of the basic blocks in the old function. If the block was
507 // reachable, we have cloned it and the old block is now in the value map:
508 // insert it into the new function in the right order. If not, ignore it.
510 // Defer PHI resolution until rest of function is resolved.
511 SmallVector<const PHINode*, 16> PHIToResolve;
512 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
515 BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
516 if (!NewBB) continue; // Dead block.
518 // Add the new block to the new function.
519 NewFunc->getBasicBlockList().push_back(NewBB);
521 // Handle PHI nodes specially, as we have to remove references to dead
523 for (BasicBlock::const_iterator I = BI->begin(), E = BI->end(); I != E; ++I)
524 if (const PHINode *PN = dyn_cast<PHINode>(I))
525 PHIToResolve.push_back(PN);
529 // Finally, remap the terminator instructions, as those can't be remapped
530 // until all BBs are mapped.
531 RemapInstruction(NewBB->getTerminator(), VMap,
532 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
535 // Defer PHI resolution until rest of function is resolved, PHI resolution
536 // requires the CFG to be up-to-date.
537 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
538 const PHINode *OPN = PHIToResolve[phino];
539 unsigned NumPreds = OPN->getNumIncomingValues();
540 const BasicBlock *OldBB = OPN->getParent();
541 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
543 // Map operands for blocks that are live and remove operands for blocks
545 for (; phino != PHIToResolve.size() &&
546 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
547 OPN = PHIToResolve[phino];
548 PHINode *PN = cast<PHINode>(VMap[OPN]);
549 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
550 Value *V = VMap[PN->getIncomingBlock(pred)];
551 if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
552 Value *InVal = MapValue(PN->getIncomingValue(pred),
554 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
555 assert(InVal && "Unknown input value?");
556 PN->setIncomingValue(pred, InVal);
557 PN->setIncomingBlock(pred, MappedBlock);
559 PN->removeIncomingValue(pred, false);
560 --pred, --e; // Revisit the next entry.
565 // The loop above has removed PHI entries for those blocks that are dead
566 // and has updated others. However, if a block is live (i.e. copied over)
567 // but its terminator has been changed to not go to this block, then our
568 // phi nodes will have invalid entries. Update the PHI nodes in this
570 PHINode *PN = cast<PHINode>(NewBB->begin());
571 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
572 if (NumPreds != PN->getNumIncomingValues()) {
573 assert(NumPreds < PN->getNumIncomingValues());
574 // Count how many times each predecessor comes to this block.
575 std::map<BasicBlock*, unsigned> PredCount;
576 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
580 // Figure out how many entries to remove from each PHI.
581 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
582 ++PredCount[PN->getIncomingBlock(i)];
584 // At this point, the excess predecessor entries are positive in the
585 // map. Loop over all of the PHIs and remove excess predecessor
587 BasicBlock::iterator I = NewBB->begin();
588 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
589 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
590 E = PredCount.end(); PCI != E; ++PCI) {
591 BasicBlock *Pred = PCI->first;
592 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
593 PN->removeIncomingValue(Pred, false);
598 // If the loops above have made these phi nodes have 0 or 1 operand,
599 // replace them with undef or the input value. We must do this for
600 // correctness, because 0-operand phis are not valid.
601 PN = cast<PHINode>(NewBB->begin());
602 if (PN->getNumIncomingValues() == 0) {
603 BasicBlock::iterator I = NewBB->begin();
604 BasicBlock::const_iterator OldI = OldBB->begin();
605 while ((PN = dyn_cast<PHINode>(I++))) {
606 Value *NV = UndefValue::get(PN->getType());
607 PN->replaceAllUsesWith(NV);
608 assert(VMap[OldI] == PN && "VMap mismatch");
610 PN->eraseFromParent();
616 // Make a second pass over the PHINodes now that all of them have been
617 // remapped into the new function, simplifying the PHINode and performing any
618 // recursive simplifications exposed. This will transparently update the
619 // WeakVH in the VMap. Notably, we rely on that so that if we coalesce
620 // two PHINodes, the iteration over the old PHIs remains valid, and the
621 // mapping will just map us to the new node (which may not even be a PHI
623 for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
624 if (PHINode *PN = dyn_cast<PHINode>(VMap[PHIToResolve[Idx]]))
625 recursivelySimplifyInstruction(PN, DL);
627 // Now that the inlined function body has been fully constructed, go through
628 // and zap unconditional fall-through branches. This happen all the time when
629 // specializing code: code specialization turns conditional branches into
630 // uncond branches, and this code folds them.
631 Function::iterator Begin = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]);
632 Function::iterator I = Begin;
633 while (I != NewFunc->end()) {
634 // Check if this block has become dead during inlining or other
635 // simplifications. Note that the first block will appear dead, as it has
636 // not yet been wired up properly.
637 if (I != Begin && (pred_begin(I) == pred_end(I) ||
638 I->getSinglePredecessor() == I)) {
639 BasicBlock *DeadBB = I++;
640 DeleteDeadBlock(DeadBB);
644 // We need to simplify conditional branches and switches with a constant
645 // operand. We try to prune these out when cloning, but if the
646 // simplification required looking through PHI nodes, those are only
647 // available after forming the full basic block. That may leave some here,
648 // and we still want to prune the dead code as early as possible.
649 ConstantFoldTerminator(I);
651 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
652 if (!BI || BI->isConditional()) { ++I; continue; }
654 BasicBlock *Dest = BI->getSuccessor(0);
655 if (!Dest->getSinglePredecessor()) {
659 // We shouldn't be able to get single-entry PHI nodes here, as instsimplify
660 // above should have zapped all of them..
661 assert(!isa<PHINode>(Dest->begin()));
663 // We know all single-entry PHI nodes in the inlined function have been
664 // removed, so we just need to splice the blocks.
665 BI->eraseFromParent();
667 // Make all PHI nodes that referred to Dest now refer to I as their source.
668 Dest->replaceAllUsesWith(I);
670 // Move all the instructions in the succ to the pred.
671 I->getInstList().splice(I->end(), Dest->getInstList());
673 // Remove the dest block.
674 Dest->eraseFromParent();
676 // Do not increment I, iteratively merge all things this block branches to.
679 // Make a final pass over the basic blocks from theh old function to gather
680 // any return instructions which survived folding. We have to do this here
681 // because we can iteratively remove and merge returns above.
682 for (Function::iterator I = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]),
685 if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
686 Returns.push_back(RI);