1 //===- CloneFunction.cpp - Clone a function into another function ---------===//
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 // 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/Constants.h"
18 #include "llvm/DerivedTypes.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Function.h"
21 #include "llvm/Support/CFG.h"
22 #include "ValueMapper.h"
23 #include "llvm/Transforms/Utils/Local.h"
26 // CloneBasicBlock - See comments in Cloning.h
27 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
28 std::map<const Value*, Value*> &ValueMap,
29 const char *NameSuffix, Function *F,
30 ClonedCodeInfo *CodeInfo) {
31 BasicBlock *NewBB = new BasicBlock("", F);
32 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
34 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
36 // Loop over all instructions, and copy them over.
37 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
39 Instruction *NewInst = II->clone();
41 NewInst->setName(II->getName()+NameSuffix);
42 NewBB->getInstList().push_back(NewInst);
43 ValueMap[II] = NewInst; // Add instruction map to value.
45 hasCalls |= isa<CallInst>(II);
46 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
47 if (isa<ConstantInt>(AI->getArraySize()))
48 hasStaticAllocas = true;
50 hasDynamicAllocas = true;
55 CodeInfo->ContainsCalls |= hasCalls;
56 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator());
57 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
58 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
59 BB != &BB->getParent()->front();
64 // Clone OldFunc into NewFunc, transforming the old arguments into references to
67 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
68 std::map<const Value*, Value*> &ValueMap,
69 std::vector<ReturnInst*> &Returns,
70 const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
71 assert(NameSuffix && "NameSuffix cannot be null!");
74 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
75 E = OldFunc->arg_end(); I != E; ++I)
76 assert(ValueMap.count(I) && "No mapping from source argument specified!");
79 // Loop over all of the basic blocks in the function, cloning them as
80 // appropriate. Note that we save BE this way in order to handle cloning of
81 // recursive functions into themselves.
83 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
85 const BasicBlock &BB = *BI;
87 // Create a new basic block and copy instructions into it!
88 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
90 ValueMap[&BB] = CBB; // Add basic block mapping.
92 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
93 Returns.push_back(RI);
96 // Loop over all of the instructions in the function, fixing up operand
97 // references as we go. This uses ValueMap to do all the hard work.
99 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
100 BE = NewFunc->end(); BB != BE; ++BB)
101 // Loop over all instructions, fixing each one as we find it...
102 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
103 RemapInstruction(II, ValueMap);
106 /// CloneFunction - Return a copy of the specified function, but without
107 /// embedding the function into another module. Also, any references specified
108 /// in the ValueMap are changed to refer to their mapped value instead of the
109 /// original one. If any of the arguments to the function are in the ValueMap,
110 /// the arguments are deleted from the resultant function. The ValueMap is
111 /// updated to include mappings from all of the instructions and basicblocks in
112 /// the function from their old to new values.
114 Function *llvm::CloneFunction(const Function *F,
115 std::map<const Value*, Value*> &ValueMap,
116 ClonedCodeInfo *CodeInfo) {
117 std::vector<const Type*> ArgTypes;
119 // The user might be deleting arguments to the function by specifying them in
120 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
122 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
124 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
125 ArgTypes.push_back(I->getType());
127 // Create a new function type...
128 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
129 ArgTypes, F->getFunctionType()->isVarArg());
131 // Create the new function...
132 Function *NewF = new Function(FTy, F->getLinkage(), F->getName());
134 // Loop over the arguments, copying the names of the mapped arguments over...
135 Function::arg_iterator DestI = NewF->arg_begin();
136 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
138 if (ValueMap.count(I) == 0) { // Is this argument preserved?
139 DestI->setName(I->getName()); // Copy the name over...
140 ValueMap[I] = DestI++; // Add mapping to ValueMap
143 std::vector<ReturnInst*> Returns; // Ignore returns cloned...
144 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
151 /// PruningFunctionCloner - This class is a private class used to implement
152 /// the CloneAndPruneFunctionInto method.
153 struct PruningFunctionCloner {
155 const Function *OldFunc;
156 std::map<const Value*, Value*> &ValueMap;
157 std::vector<ReturnInst*> &Returns;
158 const char *NameSuffix;
159 ClonedCodeInfo *CodeInfo;
162 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
163 std::map<const Value*, Value*> &valueMap,
164 std::vector<ReturnInst*> &returns,
165 const char *nameSuffix,
166 ClonedCodeInfo *codeInfo)
167 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
168 NameSuffix(nameSuffix), CodeInfo(codeInfo) {
171 /// CloneBlock - The specified block is found to be reachable, clone it and
172 /// anything that it can reach.
173 void CloneBlock(const BasicBlock *BB);
176 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
177 /// mapping its operands through ValueMap if they are available.
178 Constant *ConstantFoldMappedInstruction(const Instruction *I);
182 /// CloneBlock - The specified block is found to be reachable, clone it and
183 /// anything that it can reach.
184 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB) {
185 Value *&BBEntry = ValueMap[BB];
187 // Have we already cloned this block?
190 // Nope, clone it now.
192 BBEntry = NewBB = new BasicBlock();
193 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
195 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
197 // Loop over all instructions, and copy them over, DCE'ing as we go. This
198 // loop doesn't include the terminator.
199 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
201 // If this instruction constant folds, don't bother cloning the instruction,
202 // instead, just add the constant to the value map.
203 if (Constant *C = ConstantFoldMappedInstruction(II)) {
208 Instruction *NewInst = II->clone();
210 NewInst->setName(II->getName()+NameSuffix);
211 NewBB->getInstList().push_back(NewInst);
212 ValueMap[II] = NewInst; // Add instruction map to value.
214 hasCalls |= isa<CallInst>(II);
215 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
216 if (isa<ConstantInt>(AI->getArraySize()))
217 hasStaticAllocas = true;
219 hasDynamicAllocas = true;
223 // Finally, clone over the terminator.
224 const TerminatorInst *OldTI = BB->getTerminator();
225 bool TerminatorDone = false;
226 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
227 if (BI->isConditional()) {
228 // If the condition was a known constant in the callee...
229 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
230 // Or is a known constant in the caller...
232 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
234 // Constant fold to uncond branch!
236 BasicBlock *Dest = BI->getSuccessor(!Cond->getBoolValue());
237 ValueMap[OldTI] = new BranchInst(Dest, NewBB);
239 TerminatorDone = true;
242 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
243 // If switching on a value known constant in the caller.
244 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
245 if (Cond == 0) // Or known constant after constant prop in the callee...
246 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
247 if (Cond) { // Constant fold to uncond branch!
248 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
249 ValueMap[OldTI] = new BranchInst(Dest, NewBB);
251 TerminatorDone = true;
255 if (!TerminatorDone) {
256 Instruction *NewInst = OldTI->clone();
257 if (OldTI->hasName())
258 NewInst->setName(OldTI->getName()+NameSuffix);
259 NewBB->getInstList().push_back(NewInst);
260 ValueMap[OldTI] = NewInst; // Add instruction map to value.
262 // Recursively clone any reachable successor blocks.
263 const TerminatorInst *TI = BB->getTerminator();
264 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
265 CloneBlock(TI->getSuccessor(i));
269 CodeInfo->ContainsCalls |= hasCalls;
270 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
271 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
272 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
273 BB != &BB->getParent()->front();
276 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
277 Returns.push_back(RI);
280 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
281 /// mapping its operands through ValueMap if they are available.
282 Constant *PruningFunctionCloner::
283 ConstantFoldMappedInstruction(const Instruction *I) {
284 if (isa<CmpInst>(I)) {
285 if (Constant *Op0 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(0),
287 if (Constant *Op1 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(1),
289 return ConstantExpr::getCompare(cast<CmpInst>(I)->getPredicate(), Op0,
292 } else if (isa<BinaryOperator>(I) || isa<ShiftInst>(I)) {
293 if (Constant *Op0 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(0),
295 if (Constant *Op1 = dyn_cast_or_null<Constant>(MapValue(I->getOperand(1),
297 return ConstantExpr::get(I->getOpcode(), Op0, Op1);
301 std::vector<Constant*> Ops;
302 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
303 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
307 return 0; // All operands not constant!
309 return ConstantFoldInstOperands(I, Ops);
312 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
313 /// except that it does some simple constant prop and DCE on the fly. The
314 /// effect of this is to copy significantly less code in cases where (for
315 /// example) a function call with constant arguments is inlined, and those
316 /// constant arguments cause a significant amount of code in the callee to be
317 /// dead. Since this doesn't produce an exactly copy of the input, it can't be
318 /// used for things like CloneFunction or CloneModule.
319 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
320 std::map<const Value*, Value*> &ValueMap,
321 std::vector<ReturnInst*> &Returns,
322 const char *NameSuffix,
323 ClonedCodeInfo *CodeInfo) {
324 assert(NameSuffix && "NameSuffix cannot be null!");
327 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
328 E = OldFunc->arg_end(); II != E; ++II)
329 assert(ValueMap.count(II) && "No mapping from source argument specified!");
332 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
333 NameSuffix, CodeInfo);
335 // Clone the entry block, and anything recursively reachable from it.
336 PFC.CloneBlock(&OldFunc->getEntryBlock());
338 // Loop over all of the basic blocks in the old function. If the block was
339 // reachable, we have cloned it and the old block is now in the value map:
340 // insert it into the new function in the right order. If not, ignore it.
342 // Defer PHI resolution until rest of function is resolved.
343 std::vector<const PHINode*> PHIToResolve;
344 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
346 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
347 if (NewBB == 0) continue; // Dead block.
349 // Add the new block to the new function.
350 NewFunc->getBasicBlockList().push_back(NewBB);
352 // Loop over all of the instructions in the block, fixing up operand
353 // references as we go. This uses ValueMap to do all the hard work.
355 BasicBlock::iterator I = NewBB->begin();
357 // Handle PHI nodes specially, as we have to remove references to dead
359 if (PHINode *PN = dyn_cast<PHINode>(I)) {
360 // Skip over all PHI nodes, remembering them for later.
361 BasicBlock::const_iterator OldI = BI->begin();
362 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
363 PHIToResolve.push_back(cast<PHINode>(OldI));
366 // Otherwise, remap the rest of the instructions normally.
367 for (; I != NewBB->end(); ++I)
368 RemapInstruction(I, ValueMap);
371 // Defer PHI resolution until rest of function is resolved, PHI resolution
372 // requires the CFG to be up-to-date.
373 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
374 const PHINode *OPN = PHIToResolve[phino];
375 unsigned NumPreds = OPN->getNumIncomingValues();
376 const BasicBlock *OldBB = OPN->getParent();
377 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
379 // Map operands for blocks that are live and remove operands for blocks
381 for (; phino != PHIToResolve.size() &&
382 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
383 OPN = PHIToResolve[phino];
384 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
385 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
386 if (BasicBlock *MappedBlock =
387 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
388 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
389 assert(InVal && "Unknown input value?");
390 PN->setIncomingValue(pred, InVal);
391 PN->setIncomingBlock(pred, MappedBlock);
393 PN->removeIncomingValue(pred, false);
394 --pred, --e; // Revisit the next entry.
399 // The loop above has removed PHI entries for those blocks that are dead
400 // and has updated others. However, if a block is live (i.e. copied over)
401 // but its terminator has been changed to not go to this block, then our
402 // phi nodes will have invalid entries. Update the PHI nodes in this
404 PHINode *PN = cast<PHINode>(NewBB->begin());
405 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
406 if (NumPreds != PN->getNumIncomingValues()) {
407 assert(NumPreds < PN->getNumIncomingValues());
408 // Count how many times each predecessor comes to this block.
409 std::map<BasicBlock*, unsigned> PredCount;
410 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
414 // Figure out how many entries to remove from each PHI.
415 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
416 ++PredCount[PN->getIncomingBlock(i)];
418 // At this point, the excess predecessor entries are positive in the
419 // map. Loop over all of the PHIs and remove excess predecessor
421 BasicBlock::iterator I = NewBB->begin();
422 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
423 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
424 E = PredCount.end(); PCI != E; ++PCI) {
425 BasicBlock *Pred = PCI->first;
426 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
427 PN->removeIncomingValue(Pred, false);
432 // If the loops above have made these phi nodes have 0 or 1 operand,
433 // replace them with undef or the input value. We must do this for
434 // correctness, because 0-operand phis are not valid.
435 PN = cast<PHINode>(NewBB->begin());
436 if (PN->getNumIncomingValues() == 0) {
437 BasicBlock::iterator I = NewBB->begin();
438 BasicBlock::const_iterator OldI = OldBB->begin();
439 while ((PN = dyn_cast<PHINode>(I++))) {
440 Value *NV = UndefValue::get(PN->getType());
441 PN->replaceAllUsesWith(NV);
442 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
444 PN->eraseFromParent();
447 } else if (PN->getNumIncomingValues() == 1) {
448 BasicBlock::iterator I = NewBB->begin();
449 BasicBlock::const_iterator OldI = OldBB->begin();
450 while ((PN = dyn_cast<PHINode>(I++))) {
451 Value *NV = PN->getIncomingValue(0);
452 PN->replaceAllUsesWith(NV);
453 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
455 PN->eraseFromParent();
461 // Now that the inlined function body has been fully constructed, go through
462 // and zap unconditional fall-through branches. This happen all the time when
463 // specializing code: code specialization turns conditional branches into
464 // uncond branches, and this code folds them.
465 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
466 while (I != NewFunc->end()) {
467 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
468 if (!BI || BI->isConditional()) { ++I; continue; }
470 BasicBlock *Dest = BI->getSuccessor(0);
471 if (!Dest->getSinglePredecessor()) { ++I; continue; }
473 // We know all single-entry PHI nodes in the inlined function have been
474 // removed, so we just need to splice the blocks.
475 BI->eraseFromParent();
477 // Move all the instructions in the succ to the pred.
478 I->getInstList().splice(I->end(), Dest->getInstList());
480 // Make all PHI nodes that referred to Dest now refer to I as their source.
481 Dest->replaceAllUsesWith(I);
483 // Remove the dest block.
484 Dest->eraseFromParent();
486 // Do not increment I, iteratively merge all things this block branches to.