| //===- 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/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/GlobalVariable.h" |
| #include "llvm/Function.h" |
| #include "llvm/LLVMContext.h" |
| #include "llvm/Metadata.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Transforms/Utils/ValueMapper.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Analysis/DebugInfo.h" |
| #include "llvm/ADT/SmallVector.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->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator()); |
| 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) { |
| 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 |
| |
| // Clone any attributes. |
| if (NewFunc->arg_size() == OldFunc->arg_size()) |
| NewFunc->copyAttributesFrom(OldFunc); |
| else { |
| //Some arguments were deleted with the VMap. Copy arguments one by one |
| for (Function::const_arg_iterator I = OldFunc->arg_begin(), |
| E = OldFunc->arg_end(); I != E; ++I) |
| if (Argument* Anew = dyn_cast<Argument>(VMap[I])) |
| Anew->addAttr( OldFunc->getAttributes() |
| .getParamAttributes(I->getArgNo() + 1)); |
| NewFunc->setAttributes(NewFunc->getAttributes() |
| .addAttr(0, OldFunc->getAttributes() |
| .getRetAttributes())); |
| NewFunc->setAttributes(NewFunc->getAttributes() |
| .addAttr(~0, OldFunc->getAttributes() |
| .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); |
| VMap[&BB] = CBB; // Add basic block mapping. |
| |
| 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); |
| } |
| |
| /// 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<const 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 |
| } |
| |
| 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; |
| SmallVectorImpl<ReturnInst*> &Returns; |
| const char *NameSuffix; |
| ClonedCodeInfo *CodeInfo; |
| const TargetData *TD; |
| public: |
| PruningFunctionCloner(Function *newFunc, const Function *oldFunc, |
| ValueToValueMapTy &valueMap, |
| bool moduleLevelChanges, |
| SmallVectorImpl<ReturnInst*> &returns, |
| const char *nameSuffix, |
| ClonedCodeInfo *codeInfo, |
| const TargetData *td) |
| : NewFunc(newFunc), OldFunc(oldFunc), |
| VMap(valueMap), ModuleLevelChanges(moduleLevelChanges), |
| Returns(returns), NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) { |
| } |
| |
| /// 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); |
| |
| public: |
| /// ConstantFoldMappedInstruction - Constant fold the specified instruction, |
| /// mapping its operands through VMap if they are available. |
| Constant *ConstantFoldMappedInstruction(const Instruction *I); |
| }; |
| } |
| |
| /// 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){ |
| TrackingVH<Value> &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); |
| |
| 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) { |
| // If this instruction constant folds, don't bother cloning the instruction, |
| // instead, just add the constant to the value map. |
| if (Constant *C = ConstantFoldMappedInstruction(II)) { |
| VMap[II] = C; |
| continue; |
| } |
| |
| 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; |
| } |
| } |
| |
| // 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 == 0) { |
| 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 == 0) { // 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! |
| BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond)); |
| 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->ContainsUnwinds |= isa<UnwindInst>(OldTI); |
| CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; |
| CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && |
| BB != &BB->getParent()->front(); |
| } |
| |
| if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator())) |
| Returns.push_back(RI); |
| } |
| |
| /// ConstantFoldMappedInstruction - Constant fold the specified instruction, |
| /// mapping its operands through VMap if they are available. |
| Constant *PruningFunctionCloner:: |
| ConstantFoldMappedInstruction(const Instruction *I) { |
| SmallVector<Constant*, 8> Ops; |
| for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) |
| if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i), |
| VMap, |
| ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges))) |
| Ops.push_back(Op); |
| else |
| return 0; // All operands not constant! |
| |
| if (const CmpInst *CI = dyn_cast<CmpInst>(I)) |
| return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1], |
| TD); |
| |
| if (const LoadInst *LI = dyn_cast<LoadInst>(I)) |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) |
| if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr) |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0))) |
| if (GV->isConstant() && GV->hasDefinitiveInitializer()) |
| return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), |
| CE); |
| |
| return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0], |
| Ops.size(), TD); |
| } |
| |
| /// 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 TargetData *TD, |
| 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, |
| Returns, NameSuffix, CodeInfo, TD); |
| |
| // 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 == 0) continue; // Dead block. |
| |
| // Add the new block to the new function. |
| NewFunc->getBasicBlockList().push_back(NewBB); |
| |
| // Loop over all of the instructions in the block, fixing up operand |
| // references as we go. This uses VMap to do all the hard work. |
| // |
| BasicBlock::iterator I = NewBB->begin(); |
| |
| DebugLoc TheCallDL; |
| if (TheCall) |
| TheCallDL = TheCall->getDebugLoc(); |
| |
| // Handle PHI nodes specially, as we have to remove references to dead |
| // blocks. |
| if (PHINode *PN = dyn_cast<PHINode>(I)) { |
| // Skip over all PHI nodes, remembering them for later. |
| BasicBlock::const_iterator OldI = BI->begin(); |
| for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) |
| PHIToResolve.push_back(cast<PHINode>(OldI)); |
| } |
| |
| // Otherwise, remap the rest of the instructions normally. |
| for (; I != NewBB->end(); ++I) |
| RemapInstruction(I, 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; |
| } |
| } |
| // NOTE: We cannot eliminate single entry phi nodes here, because of |
| // VMap. Single entry phi nodes can have multiple VMap entries |
| // pointing at them. Thus, deleting one would require scanning the VMap |
| // to update any entries in it that would require that. This would be |
| // really slow. |
| } |
| |
| // 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 I = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]); |
| while (I != NewFunc->end()) { |
| BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator()); |
| if (!BI || BI->isConditional()) { ++I; continue; } |
| |
| // Note that we can't eliminate uncond branches if the destination has |
| // single-entry PHI nodes. Eliminating the single-entry phi nodes would |
| // require scanning the VMap to update any entries that point to the phi |
| // node. |
| BasicBlock *Dest = BI->getSuccessor(0); |
| if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) { |
| ++I; continue; |
| } |
| |
| // 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. |
| } |
| } |