//===- CloneFunction.cpp - Clone a function into another function ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the CloneFunctionInto interface, which is used as the
// low-level function cloner. This is used by the CloneFunction and function
// inliner to do the dirty work of copying the body of a function around.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <map>
using namespace llvm;
// CloneBasicBlock - See comments in Cloning.h
BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
ValueToValueMapTy &VMap,
const Twine &NameSuffix, Function *F,
ClonedCodeInfo *CodeInfo) {
BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
// Loop over all instructions, and copy them over.
for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
II != IE; ++II) {
Instruction *NewInst = II->clone();
if (II->hasName())
NewInst->setName(II->getName()+NameSuffix);
NewBB->getInstList().push_back(NewInst);
VMap[II] = NewInst; // Add instruction map to value.
hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
if (isa<ConstantInt>(AI->getArraySize()))
hasStaticAllocas = true;
else
hasDynamicAllocas = true;
}
}
if (CodeInfo) {
CodeInfo->ContainsCalls |= hasCalls;
CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
BB != &BB->getParent()->getEntryBlock();
}
return NewBB;
}
// Clone OldFunc into NewFunc, transforming the old arguments into references to
// VMap values.
//
void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
ValueToValueMapTy &VMap,
bool ModuleLevelChanges,
SmallVectorImpl<ReturnInst*> &Returns,
const char *NameSuffix, ClonedCodeInfo *CodeInfo,
ValueMapTypeRemapper *TypeMapper,
ValueMaterializer *Materializer) {
assert(NameSuffix && "NameSuffix cannot be null!");
#ifndef NDEBUG
for (Function::const_arg_iterator I = OldFunc->arg_begin(),
E = OldFunc->arg_end(); I != E; ++I)
assert(VMap.count(I) && "No mapping from source argument specified!");
#endif
// Copy all attributes other than those stored in the AttributeSet. We need
// to remap the parameter indices of the AttributeSet.
AttributeSet NewAttrs = NewFunc->getAttributes();
NewFunc->copyAttributesFrom(OldFunc);
NewFunc->setAttributes(NewAttrs);
AttributeSet OldAttrs = OldFunc->getAttributes();
// Clone any argument attributes that are present in the VMap.
for (const Argument &OldArg : OldFunc->args())
if (Argument *NewArg = dyn_cast<Argument>(VMap[&OldArg])) {
AttributeSet attrs =
OldAttrs.getParamAttributes(OldArg.getArgNo() + 1);
if (attrs.getNumSlots() > 0)
NewArg->addAttr(attrs);
}
NewFunc->setAttributes(
NewFunc->getAttributes()
.addAttributes(NewFunc->getContext(), AttributeSet::ReturnIndex,
OldAttrs.getRetAttributes())
.addAttributes(NewFunc->getContext(), AttributeSet::FunctionIndex,
OldAttrs.getFnAttributes()));
// Loop over all of the basic blocks in the function, cloning them as
// appropriate. Note that we save BE this way in order to handle cloning of
// recursive functions into themselves.
//
for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
BI != BE; ++BI) {
const BasicBlock &BB = *BI;
// Create a new basic block and copy instructions into it!
BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo);
// Add basic block mapping.
VMap[&BB] = CBB;
// It is only legal to clone a function if a block address within that
// function is never referenced outside of the function. Given that, we
// want to map block addresses from the old function to block addresses in
// the clone. (This is different from the generic ValueMapper
// implementation, which generates an invalid blockaddress when
// cloning a function.)
if (BB.hasAddressTaken()) {
Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
const_cast<BasicBlock*>(&BB));
VMap[OldBBAddr] = BlockAddress::get(NewFunc, CBB);
}
// Note return instructions for the caller.
if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
Returns.push_back(RI);
}
// Loop over all of the instructions in the function, fixing up operand
// references as we go. This uses VMap to do all the hard work.
for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]),
BE = NewFunc->end(); BB != BE; ++BB)
// Loop over all instructions, fixing each one as we find it...
for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
RemapInstruction(II, VMap,
ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
TypeMapper, Materializer);
}
// Find the MDNode which corresponds to the DISubprogram data that described F.
static MDNode* FindSubprogram(const Function *F, DebugInfoFinder &Finder) {
for (DISubprogram Subprogram : Finder.subprograms()) {
if (Subprogram.describes(F)) return Subprogram;
}
return nullptr;
}
// Add an operand to an existing MDNode. The new operand will be added at the
// back of the operand list.
static void AddOperand(MDNode *Node, Value *Operand) {
SmallVector<Value*, 16> Operands;
for (unsigned i = 0; i < Node->getNumOperands(); i++) {
Operands.push_back(Node->getOperand(i));
}
Operands.push_back(Operand);
MDNode *NewNode = MDNode::get(Node->getContext(), Operands);
Node->replaceAllUsesWith(NewNode);
}
// Clone the module-level debug info associated with OldFunc. The cloned data
// will point to NewFunc instead.
static void CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
ValueToValueMapTy &VMap) {
DebugInfoFinder Finder;
Finder.processModule(*OldFunc->getParent());
const MDNode *OldSubprogramMDNode = FindSubprogram(OldFunc, Finder);
if (!OldSubprogramMDNode) return;
// Ensure that OldFunc appears in the map.
// (if it's already there it must point to NewFunc anyway)
VMap[OldFunc] = NewFunc;
DISubprogram NewSubprogram(MapValue(OldSubprogramMDNode, VMap));
for (DICompileUnit CU : Finder.compile_units()) {
DIArray Subprograms(CU.getSubprograms());
// If the compile unit's function list contains the old function, it should
// also contain the new one.
for (unsigned i = 0; i < Subprograms.getNumElements(); i++) {
if ((MDNode*)Subprograms.getElement(i) == OldSubprogramMDNode) {
AddOperand(Subprograms, NewSubprogram);
}
}
}
}
/// CloneFunction - Return a copy of the specified function, but without
/// embedding the function into another module. Also, any references specified
/// in the VMap are changed to refer to their mapped value instead of the
/// original one. If any of the arguments to the function are in the VMap,
/// the arguments are deleted from the resultant function. The VMap is
/// updated to include mappings from all of the instructions and basicblocks in
/// the function from their old to new values.
///
Function *llvm::CloneFunction(const Function *F, ValueToValueMapTy &VMap,
bool ModuleLevelChanges,
ClonedCodeInfo *CodeInfo) {
std::vector<Type*> ArgTypes;
// The user might be deleting arguments to the function by specifying them in
// the VMap. If so, we need to not add the arguments to the arg ty vector
//
for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
I != E; ++I)
if (VMap.count(I) == 0) // Haven't mapped the argument to anything yet?
ArgTypes.push_back(I->getType());
// Create a new function type...
FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
ArgTypes, F->getFunctionType()->isVarArg());
// Create the new function...
Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
// Loop over the arguments, copying the names of the mapped arguments over...
Function::arg_iterator DestI = NewF->arg_begin();
for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
I != E; ++I)
if (VMap.count(I) == 0) { // Is this argument preserved?
DestI->setName(I->getName()); // Copy the name over...
VMap[I] = DestI++; // Add mapping to VMap
}
if (ModuleLevelChanges)
CloneDebugInfoMetadata(NewF, F, VMap);
SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
CloneFunctionInto(NewF, F, VMap, ModuleLevelChanges, Returns, "", CodeInfo);
return NewF;
}
namespace {
/// PruningFunctionCloner - This class is a private class used to implement
/// the CloneAndPruneFunctionInto method.
struct PruningFunctionCloner {
Function *NewFunc;
const Function *OldFunc;
ValueToValueMapTy &VMap;
bool ModuleLevelChanges;
const char *NameSuffix;
ClonedCodeInfo *CodeInfo;
const DataLayout *DL;
public:
PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
ValueToValueMapTy &valueMap,
bool moduleLevelChanges,
const char *nameSuffix,
ClonedCodeInfo *codeInfo,
const DataLayout *DL)
: NewFunc(newFunc), OldFunc(oldFunc),
VMap(valueMap), ModuleLevelChanges(moduleLevelChanges),
NameSuffix(nameSuffix), CodeInfo(codeInfo), DL(DL) {
}
/// CloneBlock - The specified block is found to be reachable, clone it and
/// anything that it can reach.
void CloneBlock(const BasicBlock *BB,
std::vector<const BasicBlock*> &ToClone);
};
}
/// CloneBlock - The specified block is found to be reachable, clone it and
/// anything that it can reach.
void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
std::vector<const BasicBlock*> &ToClone){
WeakVH &BBEntry = VMap[BB];
// Have we already cloned this block?
if (BBEntry) return;
// Nope, clone it now.
BasicBlock *NewBB;
BBEntry = NewBB = BasicBlock::Create(BB->getContext());
if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
// It is only legal to clone a function if a block address within that
// function is never referenced outside of the function. Given that, we
// want to map block addresses from the old function to block addresses in
// the clone. (This is different from the generic ValueMapper
// implementation, which generates an invalid blockaddress when
// cloning a function.)
//
// Note that we don't need to fix the mapping for unreachable blocks;
// the default mapping there is safe.
if (BB->hasAddressTaken()) {
Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
const_cast<BasicBlock*>(BB));
VMap[OldBBAddr] = BlockAddress::get(NewFunc, NewBB);
}
bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
// Loop over all instructions, and copy them over, DCE'ing as we go. This
// loop doesn't include the terminator.
for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
II != IE; ++II) {
Instruction *NewInst = II->clone();
// Eagerly remap operands to the newly cloned instruction, except for PHI
// nodes for which we defer processing until we update the CFG.
if (!isa<PHINode>(NewInst)) {
RemapInstruction(NewInst, VMap,
ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
// If we can simplify this instruction to some other value, simply add
// a mapping to that value rather than inserting a new instruction into
// the basic block.
if (Value *V = SimplifyInstruction(NewInst, DL)) {
// On the off-chance that this simplifies to an instruction in the old
// function, map it back into the new function.
if (Value *MappedV = VMap.lookup(V))
V = MappedV;
VMap[II] = V;
delete NewInst;
continue;
}
}
if (II->hasName())
NewInst->setName(II->getName()+NameSuffix);
VMap[II] = NewInst; // Add instruction map to value.
NewBB->getInstList().push_back(NewInst);
hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
if (isa<ConstantInt>(AI->getArraySize()))
hasStaticAllocas = true;
else
hasDynamicAllocas = true;
}
}
// Finally, clone over the terminator.
const TerminatorInst *OldTI = BB->getTerminator();
bool TerminatorDone = false;
if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
if (BI->isConditional()) {
// If the condition was a known constant in the callee...
ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
// Or is a known constant in the caller...
if (!Cond) {
Value *V = VMap[BI->getCondition()];
Cond = dyn_cast_or_null<ConstantInt>(V);
}
// Constant fold to uncond branch!
if (Cond) {
BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
VMap[OldTI] = BranchInst::Create(Dest, NewBB);
ToClone.push_back(Dest);
TerminatorDone = true;
}
}
} else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
// If switching on a value known constant in the caller.
ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
if (!Cond) { // Or known constant after constant prop in the callee...
Value *V = VMap[SI->getCondition()];
Cond = dyn_cast_or_null<ConstantInt>(V);
}
if (Cond) { // Constant fold to uncond branch!
SwitchInst::ConstCaseIt Case = SI->findCaseValue(Cond);
BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
VMap[OldTI] = BranchInst::Create(Dest, NewBB);
ToClone.push_back(Dest);
TerminatorDone = true;
}
}
if (!TerminatorDone) {
Instruction *NewInst = OldTI->clone();
if (OldTI->hasName())
NewInst->setName(OldTI->getName()+NameSuffix);
NewBB->getInstList().push_back(NewInst);
VMap[OldTI] = NewInst; // Add instruction map to value.
// Recursively clone any reachable successor blocks.
const TerminatorInst *TI = BB->getTerminator();
for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
ToClone.push_back(TI->getSuccessor(i));
}
if (CodeInfo) {
CodeInfo->ContainsCalls |= hasCalls;
CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
BB != &BB->getParent()->front();
}
}
/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
/// except that it does some simple constant prop and DCE on the fly. The
/// effect of this is to copy significantly less code in cases where (for
/// example) a function call with constant arguments is inlined, and those
/// constant arguments cause a significant amount of code in the callee to be
/// dead. Since this doesn't produce an exact copy of the input, it can't be
/// used for things like CloneFunction or CloneModule.
void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
ValueToValueMapTy &VMap,
bool ModuleLevelChanges,
SmallVectorImpl<ReturnInst*> &Returns,
const char *NameSuffix,
ClonedCodeInfo *CodeInfo,
const DataLayout *DL,
Instruction *TheCall) {
assert(NameSuffix && "NameSuffix cannot be null!");
#ifndef NDEBUG
for (Function::const_arg_iterator II = OldFunc->arg_begin(),
E = OldFunc->arg_end(); II != E; ++II)
assert(VMap.count(II) && "No mapping from source argument specified!");
#endif
PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
NameSuffix, CodeInfo, DL);
// Clone the entry block, and anything recursively reachable from it.
std::vector<const BasicBlock*> CloneWorklist;
CloneWorklist.push_back(&OldFunc->getEntryBlock());
while (!CloneWorklist.empty()) {
const BasicBlock *BB = CloneWorklist.back();
CloneWorklist.pop_back();
PFC.CloneBlock(BB, CloneWorklist);
}
// Loop over all of the basic blocks in the old function. If the block was
// reachable, we have cloned it and the old block is now in the value map:
// insert it into the new function in the right order. If not, ignore it.
//
// Defer PHI resolution until rest of function is resolved.
SmallVector<const PHINode*, 16> PHIToResolve;
for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
BI != BE; ++BI) {
Value *V = VMap[BI];
BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
if (!NewBB) continue; // Dead block.
// Add the new block to the new function.
NewFunc->getBasicBlockList().push_back(NewBB);
// Handle PHI nodes specially, as we have to remove references to dead
// blocks.
for (BasicBlock::const_iterator I = BI->begin(), E = BI->end(); I != E; ++I)
if (const PHINode *PN = dyn_cast<PHINode>(I))
PHIToResolve.push_back(PN);
else
break;
// Finally, remap the terminator instructions, as those can't be remapped
// until all BBs are mapped.
RemapInstruction(NewBB->getTerminator(), VMap,
ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
}
// Defer PHI resolution until rest of function is resolved, PHI resolution
// requires the CFG to be up-to-date.
for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
const PHINode *OPN = PHIToResolve[phino];
unsigned NumPreds = OPN->getNumIncomingValues();
const BasicBlock *OldBB = OPN->getParent();
BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
// Map operands for blocks that are live and remove operands for blocks
// that are dead.
for (; phino != PHIToResolve.size() &&
PHIToResolve[phino]->getParent() == OldBB; ++phino) {
OPN = PHIToResolve[phino];
PHINode *PN = cast<PHINode>(VMap[OPN]);
for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
Value *V = VMap[PN->getIncomingBlock(pred)];
if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
Value *InVal = MapValue(PN->getIncomingValue(pred),
VMap,
ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
assert(InVal && "Unknown input value?");
PN->setIncomingValue(pred, InVal);
PN->setIncomingBlock(pred, MappedBlock);
} else {
PN->removeIncomingValue(pred, false);
--pred, --e; // Revisit the next entry.
}
}
}
// The loop above has removed PHI entries for those blocks that are dead
// and has updated others. However, if a block is live (i.e. copied over)
// but its terminator has been changed to not go to this block, then our
// phi nodes will have invalid entries. Update the PHI nodes in this
// case.
PHINode *PN = cast<PHINode>(NewBB->begin());
NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
if (NumPreds != PN->getNumIncomingValues()) {
assert(NumPreds < PN->getNumIncomingValues());
// Count how many times each predecessor comes to this block.
std::map<BasicBlock*, unsigned> PredCount;
for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
PI != E; ++PI)
--PredCount[*PI];
// Figure out how many entries to remove from each PHI.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
++PredCount[PN->getIncomingBlock(i)];
// At this point, the excess predecessor entries are positive in the
// map. Loop over all of the PHIs and remove excess predecessor
// entries.
BasicBlock::iterator I = NewBB->begin();
for (; (PN = dyn_cast<PHINode>(I)); ++I) {
for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
E = PredCount.end(); PCI != E; ++PCI) {
BasicBlock *Pred = PCI->first;
for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
PN->removeIncomingValue(Pred, false);
}
}
}
// If the loops above have made these phi nodes have 0 or 1 operand,
// replace them with undef or the input value. We must do this for
// correctness, because 0-operand phis are not valid.
PN = cast<PHINode>(NewBB->begin());
if (PN->getNumIncomingValues() == 0) {
BasicBlock::iterator I = NewBB->begin();
BasicBlock::const_iterator OldI = OldBB->begin();
while ((PN = dyn_cast<PHINode>(I++))) {
Value *NV = UndefValue::get(PN->getType());
PN->replaceAllUsesWith(NV);
assert(VMap[OldI] == PN && "VMap mismatch");
VMap[OldI] = NV;
PN->eraseFromParent();
++OldI;
}
}
}
// Make a second pass over the PHINodes now that all of them have been
// remapped into the new function, simplifying the PHINode and performing any
// recursive simplifications exposed. This will transparently update the
// WeakVH in the VMap. Notably, we rely on that so that if we coalesce
// two PHINodes, the iteration over the old PHIs remains valid, and the
// mapping will just map us to the new node (which may not even be a PHI
// node).
for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
if (PHINode *PN = dyn_cast<PHINode>(VMap[PHIToResolve[Idx]]))
recursivelySimplifyInstruction(PN, DL);
// Now that the inlined function body has been fully constructed, go through
// and zap unconditional fall-through branches. This happen all the time when
// specializing code: code specialization turns conditional branches into
// uncond branches, and this code folds them.
Function::iterator Begin = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]);
Function::iterator I = Begin;
while (I != NewFunc->end()) {
// Check if this block has become dead during inlining or other
// simplifications. Note that the first block will appear dead, as it has
// not yet been wired up properly.
if (I != Begin && (pred_begin(I) == pred_end(I) ||
I->getSinglePredecessor() == I)) {
BasicBlock *DeadBB = I++;
DeleteDeadBlock(DeadBB);
continue;
}
// We need to simplify conditional branches and switches with a constant
// operand. We try to prune these out when cloning, but if the
// simplification required looking through PHI nodes, those are only
// available after forming the full basic block. That may leave some here,
// and we still want to prune the dead code as early as possible.
ConstantFoldTerminator(I);
BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
if (!BI || BI->isConditional()) { ++I; continue; }
BasicBlock *Dest = BI->getSuccessor(0);
if (!Dest->getSinglePredecessor()) {
++I; continue;
}
// We shouldn't be able to get single-entry PHI nodes here, as instsimplify
// above should have zapped all of them..
assert(!isa<PHINode>(Dest->begin()));
// We know all single-entry PHI nodes in the inlined function have been
// removed, so we just need to splice the blocks.
BI->eraseFromParent();
// Make all PHI nodes that referred to Dest now refer to I as their source.
Dest->replaceAllUsesWith(I);
// Move all the instructions in the succ to the pred.
I->getInstList().splice(I->end(), Dest->getInstList());
// Remove the dest block.
Dest->eraseFromParent();
// Do not increment I, iteratively merge all things this block branches to.
}
// Make a final pass over the basic blocks from theh old function to gather
// any return instructions which survived folding. We have to do this here
// because we can iteratively remove and merge returns above.
for (Function::iterator I = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]),
E = NewFunc->end();
I != E; ++I)
if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
Returns.push_back(RI);
}