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//===- CloneFunction.cpp - Clone a function into another function ---------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// 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/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.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/MDBuilder.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <map>
using namespace llvm;
#define DEBUG_TYPE "clone-function"
/// See comments in Cloning.h.
BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, ValueToValueMapTy &VMap,
const Twine &NameSuffix, Function *F,
ClonedCodeInfo *CodeInfo,
DebugInfoFinder *DIFinder) {
DenseMap<const MDNode *, MDNode *> Cache;
BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
if (BB->hasName())
NewBB->setName(BB->getName() + NameSuffix);
bool hasCalls = false, hasDynamicAllocas = false;
Module *TheModule = F ? F->getParent() : nullptr;
// Loop over all instructions, and copy them over.
for (const Instruction &I : *BB) {
if (DIFinder && TheModule)
DIFinder->processInstruction(*TheModule, I);
Instruction *NewInst = I.clone();
if (I.hasName())
NewInst->setName(I.getName() + NameSuffix);
VMap[&I] = NewInst; // Add instruction map to value.
hasCalls |= (isa<CallInst>(I) && !isa<DbgInfoIntrinsic>(I));
if (const AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
if (!AI->isStaticAlloca()) {
hasDynamicAllocas = true;
if (CodeInfo) {
CodeInfo->ContainsCalls |= hasCalls;
CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
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,
CloneFunctionChangeType Changes,
SmallVectorImpl<ReturnInst *> &Returns,
const char *NameSuffix, ClonedCodeInfo *CodeInfo,
ValueMapTypeRemapper *TypeMapper,
ValueMaterializer *Materializer) {
assert(NameSuffix && "NameSuffix cannot be null!");
#ifndef NDEBUG
for (const Argument &I : OldFunc->args())
assert(VMap.count(&I) && "No mapping from source argument specified!");
bool ModuleLevelChanges = Changes > CloneFunctionChangeType::LocalChangesOnly;
// Copy all attributes other than those stored in the AttributeList. We need
// to remap the parameter indices of the AttributeList.
AttributeList NewAttrs = NewFunc->getAttributes();
// Fix up the personality function that got copied over.
if (OldFunc->hasPersonalityFn())
MapValue(OldFunc->getPersonalityFn(), VMap,
ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
TypeMapper, Materializer));
SmallVector<AttributeSet, 4> NewArgAttrs(NewFunc->arg_size());
AttributeList 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])) {
NewArgAttrs[NewArg->getArgNo()] =
AttributeList::get(NewFunc->getContext(), OldAttrs.getFnAttributes(),
OldAttrs.getRetAttributes(), NewArgAttrs));
// Everything else beyond this point deals with function instructions,
// so if we are dealing with a function declaration, we're done.
if (OldFunc->isDeclaration())
// When we remap instructions within the same module, we want to avoid
// duplicating inlined DISubprograms, so record all subprograms we find as we
// duplicate instructions and then freeze them in the MD map. We also record
// information about dbg.value and dbg.declare to avoid duplicating the
// types.
Optional<DebugInfoFinder> DIFinder;
// Track the subprogram attachment that needs to be cloned to fine-tune the
// mapping within the same module.
DISubprogram *SPClonedWithinModule = nullptr;
if (Changes < CloneFunctionChangeType::DifferentModule) {
assert((NewFunc->getParent() == nullptr ||
NewFunc->getParent() == OldFunc->getParent()) &&
"Expected NewFunc to have the same parent, or no parent");
// Need to find subprograms, types, and compile units.
SPClonedWithinModule = OldFunc->getSubprogram();
if (SPClonedWithinModule)
} else {
assert((NewFunc->getParent() == nullptr ||
NewFunc->getParent() != OldFunc->getParent()) &&
"Expected NewFunc to have different parents, or no parent");
if (Changes == CloneFunctionChangeType::DifferentModule) {
assert(NewFunc->getParent() &&
"Need parent of new function to maintain debug info invariants");
// Need to find all the compile units.
// 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 (const BasicBlock &BB : *OldFunc) {
// Create a new basic block and copy instructions into it!
BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo,
DIFinder ? &*DIFinder : nullptr);
// 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()))
if (Changes < CloneFunctionChangeType::DifferentModule &&
DIFinder->subprogram_count() > 0) {
// Turn on module-level changes, since we need to clone (some of) the
// debug info metadata.
// FIXME: Metadata effectively owned by a function should be made
// local, and only that local metadata should be cloned.
ModuleLevelChanges = true;
auto mapToSelfIfNew = [&VMap](MDNode *N) {
// Avoid clobbering an existing mapping.
(void)VMap.MD().try_emplace(N, N);
// Avoid cloning types, compile units, and (other) subprograms.
for (DISubprogram *ISP : DIFinder->subprograms())
if (ISP != SPClonedWithinModule)
for (DICompileUnit *CU : DIFinder->compile_units())
for (DIType *Type : DIFinder->types())
} else {
assert(!SPClonedWithinModule &&
"Subprogram should be in DIFinder->subprogram_count()...");
const auto RemapFlag = ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges;
// Duplicate the metadata that is attached to the cloned function.
// Subprograms/CUs/types that were already mapped to themselves won't be
// duplicated.
SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
for (auto MD : MDs) {
NewFunc->addMetadata(MD.first, *MapMetadata(MD.second, VMap, RemapFlag,
TypeMapper, Materializer));
// Loop over all of the instructions in the new 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->front()])->getIterator(),
BE = NewFunc->end();
BB != BE; ++BB)
// Loop over all instructions, fixing each one as we find it...
for (Instruction &II : *BB)
RemapInstruction(&II, VMap, RemapFlag, TypeMapper, Materializer);
// Only update ! for DifferentModule (not CloneModule). In the
// same module, the compile unit will already be listed (or not). When
// cloning a module, CloneModule() will handle creating the named metadata.
if (Changes != CloneFunctionChangeType::DifferentModule)
// Update ! with compile units added to the new module if this
// function is being cloned in isolation.
// FIXME: This is making global / module-level changes, which doesn't seem
// like the right encapsulation Consider dropping the requirement to update
// ! (either obsoleting the node, or restricting it to
// non-discardable compile units) instead of discovering compile units by
// visiting the metadata attached to global values, which would allow this
// code to be deleted. Alternatively, perhaps give responsibility for this
// update to CloneFunctionInto's callers.
auto *NewModule = NewFunc->getParent();
auto *NMD = NewModule->getOrInsertNamedMetadata("");
// Avoid multiple insertions of the same DICompileUnit to NMD.
SmallPtrSet<const void *, 8> Visited;
for (auto *Operand : NMD->operands())
for (auto *Unit : DIFinder->compile_units()) {
MDNode *MappedUnit =
MapMetadata(Unit, VMap, RF_None, TypeMapper, Materializer);
if (Visited.insert(MappedUnit).second)
/// Return a copy of the specified function and add it to that function's
/// 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(Function *F, ValueToValueMapTy &VMap,
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 (const Argument &I : F->args())
if (VMap.count(&I) == 0) // Haven't mapped the argument to anything yet?
// Create a new function type...
FunctionType *FTy =
FunctionType::get(F->getFunctionType()->getReturnType(), ArgTypes,
// Create the new function...
Function *NewF = Function::Create(FTy, F->getLinkage(), F->getAddressSpace(),
F->getName(), F->getParent());
// Loop over the arguments, copying the names of the mapped arguments over...
Function::arg_iterator DestI = NewF->arg_begin();
for (const Argument &I : F->args())
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, CloneFunctionChangeType::LocalChangesOnly,
Returns, "", CodeInfo);
return NewF;
namespace {
/// This is a private class used to implement CloneAndPruneFunctionInto.
struct PruningFunctionCloner {
Function *NewFunc;
const Function *OldFunc;
ValueToValueMapTy &VMap;
bool ModuleLevelChanges;
const char *NameSuffix;
ClonedCodeInfo *CodeInfo;
PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
ValueToValueMapTy &valueMap, bool moduleLevelChanges,
const char *nameSuffix, ClonedCodeInfo *codeInfo)
: NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap),
ModuleLevelChanges(moduleLevelChanges), NameSuffix(nameSuffix),
CodeInfo(codeInfo) {}
/// The specified block is found to be reachable, clone it and
/// anything that it can reach.
void CloneBlock(const BasicBlock *BB, BasicBlock::const_iterator StartingInst,
std::vector<const BasicBlock *> &ToClone);
} // namespace
/// The specified block is found to be reachable, clone it and
/// anything that it can reach.
void PruningFunctionCloner::CloneBlock(
const BasicBlock *BB, BasicBlock::const_iterator StartingInst,
std::vector<const BasicBlock *> &ToClone) {
WeakTrackingVH &BBEntry = VMap[BB];
// Have we already cloned this block?
if (BBEntry)
// 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 = StartingInst, 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, BB->getModule()->getDataLayout())) {
// On the off-chance that this simplifies to an instruction in the old
// function, map it back into the new function.
if (NewFunc != OldFunc)
if (Value *MappedV = VMap.lookup(V))
V = MappedV;
if (!NewInst->mayHaveSideEffects()) {
VMap[&*II] = V;
if (II->hasName())
NewInst->setName(II->getName() + NameSuffix);
VMap[&*II] = NewInst; // Add instruction map to value.
hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
if (CodeInfo)
if (auto *CB = dyn_cast<CallBase>(&*II))
if (CB->hasOperandBundles())
if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
if (isa<ConstantInt>(AI->getArraySize()))
hasStaticAllocas = true;
hasDynamicAllocas = true;
// Finally, clone over the terminator.
const Instruction *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.lookup(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);
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.lookup(SI->getCondition());
Cond = dyn_cast_or_null<ConstantInt>(V);
if (Cond) { // Constant fold to uncond branch!
SwitchInst::ConstCaseHandle Case = *SI->findCaseValue(Cond);
BasicBlock *Dest = const_cast<BasicBlock *>(Case.getCaseSuccessor());
VMap[OldTI] = BranchInst::Create(Dest, NewBB);
TerminatorDone = true;
if (!TerminatorDone) {
Instruction *NewInst = OldTI->clone();
if (OldTI->hasName())
NewInst->setName(OldTI->getName() + NameSuffix);
VMap[OldTI] = NewInst; // Add instruction map to value.
if (CodeInfo)
if (auto *CB = dyn_cast<CallBase>(OldTI))
if (CB->hasOperandBundles())
// Recursively clone any reachable successor blocks.
append_range(ToClone, successors(BB->getTerminator()));
if (CodeInfo) {
CodeInfo->ContainsCalls |= hasCalls;
CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
CodeInfo->ContainsDynamicAllocas |=
hasStaticAllocas && BB != &BB->getParent()->front();
/// This works like CloneAndPruneFunctionInto, except that it does not clone the
/// entire function. Instead it starts at an instruction provided by the caller
/// and copies (and prunes) only the code reachable from that instruction.
void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
const Instruction *StartingInst,
ValueToValueMapTy &VMap,
bool ModuleLevelChanges,
SmallVectorImpl<ReturnInst *> &Returns,
const char *NameSuffix,
ClonedCodeInfo *CodeInfo) {
assert(NameSuffix && "NameSuffix cannot be null!");
ValueMapTypeRemapper *TypeMapper = nullptr;
ValueMaterializer *Materializer = nullptr;
#ifndef NDEBUG
// If the cloning starts at the beginning of the function, verify that
// the function arguments are mapped.
if (!StartingInst)
for (const Argument &II : OldFunc->args())
assert(VMap.count(&II) && "No mapping from source argument specified!");
PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
NameSuffix, CodeInfo);
const BasicBlock *StartingBB;
if (StartingInst)
StartingBB = StartingInst->getParent();
else {
StartingBB = &OldFunc->getEntryBlock();
StartingInst = &StartingBB->front();
// Clone the entry block, and anything recursively reachable from it.
std::vector<const BasicBlock *> CloneWorklist;
PFC.CloneBlock(StartingBB, StartingInst->getIterator(), CloneWorklist);
while (!CloneWorklist.empty()) {
const BasicBlock *BB = CloneWorklist.back();
PFC.CloneBlock(BB, BB->begin(), 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 (const BasicBlock &BI : *OldFunc) {
Value *V = VMap.lookup(&BI);
BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
if (!NewBB)
continue; // Dead block.
// Add the new block to the new function.
// Handle PHI nodes specially, as we have to remove references to dead
// blocks.
for (const PHINode &PN : BI.phis()) {
// PHI nodes may have been remapped to non-PHI nodes by the caller or
// during the cloning process.
if (isa<PHINode>(VMap[&PN]))
// 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,
TypeMapper, Materializer);
// 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.lookup(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; // 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 = pred_size(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 (BasicBlock *Pred : predecessors(NewBB))
// Figure out how many entries to remove from each PHI.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++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 (const auto &PCI : PredCount) {
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());
assert(VMap[&*OldI] == PN && "VMap mismatch");
VMap[&*OldI] = NV;
// 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
// WeakTrackingVH 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).
const DataLayout &DL = NewFunc->getParent()->getDataLayout();
SmallSetVector<const Value *, 8> Worklist;
for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
if (isa<PHINode>(VMap[PHIToResolve[Idx]]))
// Note that we must test the size on each iteration, the worklist can grow.
for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) {
const Value *OrigV = Worklist[Idx];
auto *I = dyn_cast_or_null<Instruction>(VMap.lookup(OrigV));
if (!I)
// Skip over non-intrinsic callsites, we don't want to remove any nodes from
// the CGSCC.
CallBase *CB = dyn_cast<CallBase>(I);
if (CB && CB->getCalledFunction() &&
// See if this instruction simplifies.
Value *SimpleV = SimplifyInstruction(I, DL);
if (!SimpleV)
// Stash away all the uses of the old instruction so we can check them for
// recursive simplifications after a RAUW. This is cheaper than checking all
// uses of To on the recursive step in most cases.
for (const User *U : OrigV->users())
// Replace the instruction with its simplified value.
// If the original instruction had no side effects, remove it.
if (isInstructionTriviallyDead(I))
VMap[OrigV] = I;
// Now that the inlined function body has been fully constructed, go through
// and zap unconditional fall-through branches. This happens 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[StartingBB])->getIterator();
Function::iterator I = Begin;
while (I != NewFunc->end()) {
// 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.
// Do the folding before we check if the block is dead since we want code
// like
// bb:
// br i1 undef, label %bb, label %bb
// to be simplified to
// bb:
// br label %bb
// before we call I->getSinglePredecessor().
// 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_empty(&*I) || I->getSinglePredecessor() == &*I)) {
BasicBlock *DeadBB = &*I++;
BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
if (!BI || BI->isConditional()) {
BasicBlock *Dest = BI->getSuccessor(0);
if (!Dest->getSinglePredecessor()) {
// We shouldn't be able to get single-entry PHI nodes here, as instsimplify
// above should have zapped all of them..
// We know all single-entry PHI nodes in the inlined function have been
// removed, so we just need to splice the blocks.
// Make all PHI nodes that referred to Dest now refer to I as their source.
// Move all the instructions in the succ to the pred.
I->getInstList().splice(I->end(), Dest->getInstList());
// Remove the dest block.
// Do not increment I, iteratively merge all things this block branches to.
// Make a final pass over the basic blocks from the 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[StartingBB])->getIterator(),
E = NewFunc->end();
I != E; ++I)
if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
/// 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, Instruction *TheCall) {
CloneAndPruneIntoFromInst(NewFunc, OldFunc, &OldFunc->front().front(), VMap,
ModuleLevelChanges, Returns, NameSuffix, CodeInfo);
/// Remaps instructions in \p Blocks using the mapping in \p VMap.
void llvm::remapInstructionsInBlocks(
const SmallVectorImpl<BasicBlock *> &Blocks, ValueToValueMapTy &VMap) {
// Rewrite the code to refer to itself.
for (auto *BB : Blocks)
for (auto &Inst : *BB)
RemapInstruction(&Inst, VMap,
RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
/// Clones a loop \p OrigLoop. Returns the loop and the blocks in \p
/// Blocks.
/// Updates LoopInfo and DominatorTree assuming the loop is dominated by block
/// \p LoopDomBB. Insert the new blocks before block specified in \p Before.
Loop *llvm::cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
Loop *OrigLoop, ValueToValueMapTy &VMap,
const Twine &NameSuffix, LoopInfo *LI,
DominatorTree *DT,
SmallVectorImpl<BasicBlock *> &Blocks) {
Function *F = OrigLoop->getHeader()->getParent();
Loop *ParentLoop = OrigLoop->getParentLoop();
DenseMap<Loop *, Loop *> LMap;
Loop *NewLoop = LI->AllocateLoop();
LMap[OrigLoop] = NewLoop;
if (ParentLoop)
BasicBlock *OrigPH = OrigLoop->getLoopPreheader();
assert(OrigPH && "No preheader");
BasicBlock *NewPH = CloneBasicBlock(OrigPH, VMap, NameSuffix, F);
// To rename the loop PHIs.
VMap[OrigPH] = NewPH;
// Update LoopInfo.
if (ParentLoop)
ParentLoop->addBasicBlockToLoop(NewPH, *LI);
// Update DominatorTree.
DT->addNewBlock(NewPH, LoopDomBB);
for (Loop *CurLoop : OrigLoop->getLoopsInPreorder()) {
Loop *&NewLoop = LMap[CurLoop];
if (!NewLoop) {
NewLoop = LI->AllocateLoop();
// Establish the parent/child relationship.
Loop *OrigParent = CurLoop->getParentLoop();
assert(OrigParent && "Could not find the original parent loop");
Loop *NewParentLoop = LMap[OrigParent];
assert(NewParentLoop && "Could not find the new parent loop");
for (BasicBlock *BB : OrigLoop->getBlocks()) {
Loop *CurLoop = LI->getLoopFor(BB);
Loop *&NewLoop = LMap[CurLoop];
assert(NewLoop && "Expecting new loop to be allocated");
BasicBlock *NewBB = CloneBasicBlock(BB, VMap, NameSuffix, F);
VMap[BB] = NewBB;
// Update LoopInfo.
NewLoop->addBasicBlockToLoop(NewBB, *LI);
// Add DominatorTree node. After seeing all blocks, update to correct
// IDom.
DT->addNewBlock(NewBB, NewPH);
for (BasicBlock *BB : OrigLoop->getBlocks()) {
// Update loop headers.
Loop *CurLoop = LI->getLoopFor(BB);
if (BB == CurLoop->getHeader())
// Update DominatorTree.
BasicBlock *IDomBB = DT->getNode(BB)->getIDom()->getBlock();
// Move them physically from the end of the block list.
F->getBasicBlockList().splice(Before->getIterator(), F->getBasicBlockList(),
F->getBasicBlockList().splice(Before->getIterator(), F->getBasicBlockList(),
NewLoop->getHeader()->getIterator(), F->end());
return NewLoop;
/// Duplicate non-Phi instructions from the beginning of block up to
/// StopAt instruction into a split block between BB and its predecessor.
BasicBlock *llvm::DuplicateInstructionsInSplitBetween(
BasicBlock *BB, BasicBlock *PredBB, Instruction *StopAt,
ValueToValueMapTy &ValueMapping, DomTreeUpdater &DTU) {
assert(count(successors(PredBB), BB) == 1 &&
"There must be a single edge between PredBB and BB!");
// We are going to have to map operands from the original BB block to the new
// copy of the block 'NewBB'. If there are PHI nodes in BB, evaluate them to
// account for entry from PredBB.
BasicBlock::iterator BI = BB->begin();
for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
ValueMapping[PN] = PN->getIncomingValueForBlock(PredBB);
BasicBlock *NewBB = SplitEdge(PredBB, BB);
NewBB->setName(PredBB->getName() + ".split");
Instruction *NewTerm = NewBB->getTerminator();
// FIXME: SplitEdge does not yet take a DTU, so we include the split edge
// in the update set here.
DTU.applyUpdates({{DominatorTree::Delete, PredBB, BB},
{DominatorTree::Insert, PredBB, NewBB},
{DominatorTree::Insert, NewBB, BB}});
// Clone the non-phi instructions of BB into NewBB, keeping track of the
// mapping and using it to remap operands in the cloned instructions.
// Stop once we see the terminator too. This covers the case where BB's
// terminator gets replaced and StopAt == BB's terminator.
for (; StopAt != &*BI && BB->getTerminator() != &*BI; ++BI) {
Instruction *New = BI->clone();
ValueMapping[&*BI] = New;
// Remap operands to patch up intra-block references.
for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
if (Instruction *Inst = dyn_cast<Instruction>(New->getOperand(i))) {
auto I = ValueMapping.find(Inst);
if (I != ValueMapping.end())
New->setOperand(i, I->second);
return NewBB;
void llvm::cloneNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes,
DenseMap<MDNode *, MDNode *> &ClonedScopes,
StringRef Ext, LLVMContext &Context) {
MDBuilder MDB(Context);
for (auto *ScopeList : NoAliasDeclScopes) {
for (auto &MDOperand : ScopeList->operands()) {
if (MDNode *MD = dyn_cast<MDNode>(MDOperand)) {
AliasScopeNode SNANode(MD);
std::string Name;
auto ScopeName = SNANode.getName();
if (!ScopeName.empty())
Name = (Twine(ScopeName) + ":" + Ext).str();
Name = std::string(Ext);
MDNode *NewScope = MDB.createAnonymousAliasScope(
const_cast<MDNode *>(SNANode.getDomain()), Name);
ClonedScopes.insert(std::make_pair(MD, NewScope));
void llvm::adaptNoAliasScopes(Instruction *I,
const DenseMap<MDNode *, MDNode *> &ClonedScopes,
LLVMContext &Context) {
auto CloneScopeList = [&](const MDNode *ScopeList) -> MDNode * {
bool NeedsReplacement = false;
SmallVector<Metadata *, 8> NewScopeList;
for (auto &MDOp : ScopeList->operands()) {
if (MDNode *MD = dyn_cast<MDNode>(MDOp)) {
if (auto *NewMD = ClonedScopes.lookup(MD)) {
NeedsReplacement = true;
if (NeedsReplacement)
return MDNode::get(Context, NewScopeList);
return nullptr;
if (auto *Decl = dyn_cast<NoAliasScopeDeclInst>(I))
if (auto *NewScopeList = CloneScopeList(Decl->getScopeList()))
auto replaceWhenNeeded = [&](unsigned MD_ID) {
if (const MDNode *CSNoAlias = I->getMetadata(MD_ID))
if (auto *NewScopeList = CloneScopeList(CSNoAlias))
I->setMetadata(MD_ID, NewScopeList);
void llvm::cloneAndAdaptNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes,
ArrayRef<BasicBlock *> NewBlocks,
LLVMContext &Context, StringRef Ext) {
if (NoAliasDeclScopes.empty())
DenseMap<MDNode *, MDNode *> ClonedScopes;
LLVM_DEBUG(dbgs() << "cloneAndAdaptNoAliasScopes: cloning "
<< NoAliasDeclScopes.size() << " node(s)\n");
cloneNoAliasScopes(NoAliasDeclScopes, ClonedScopes, Ext, Context);
// Identify instructions using metadata that needs adaptation
for (BasicBlock *NewBlock : NewBlocks)
for (Instruction &I : *NewBlock)
adaptNoAliasScopes(&I, ClonedScopes, Context);
void llvm::cloneAndAdaptNoAliasScopes(ArrayRef<MDNode *> NoAliasDeclScopes,
Instruction *IStart, Instruction *IEnd,
LLVMContext &Context, StringRef Ext) {
if (NoAliasDeclScopes.empty())
DenseMap<MDNode *, MDNode *> ClonedScopes;
LLVM_DEBUG(dbgs() << "cloneAndAdaptNoAliasScopes: cloning "
<< NoAliasDeclScopes.size() << " node(s)\n");
cloneNoAliasScopes(NoAliasDeclScopes, ClonedScopes, Ext, Context);
// Identify instructions using metadata that needs adaptation
assert(IStart->getParent() == IEnd->getParent() && "different basic block ?");
auto ItStart = IStart->getIterator();
auto ItEnd = IEnd->getIterator();
++ItEnd; // IEnd is included, increment ItEnd to get the end of the range
for (auto &I : llvm::make_range(ItStart, ItEnd))
adaptNoAliasScopes(&I, ClonedScopes, Context);
void llvm::identifyNoAliasScopesToClone(
ArrayRef<BasicBlock *> BBs, SmallVectorImpl<MDNode *> &NoAliasDeclScopes) {
for (BasicBlock *BB : BBs)
for (Instruction &I : *BB)
if (auto *Decl = dyn_cast<NoAliasScopeDeclInst>(&I))
void llvm::identifyNoAliasScopesToClone(
BasicBlock::iterator Start, BasicBlock::iterator End,
SmallVectorImpl<MDNode *> &NoAliasDeclScopes) {
for (Instruction &I : make_range(Start, End))
if (auto *Decl = dyn_cast<NoAliasScopeDeclInst>(&I))