/// Handle frees of entire structures whose dependency is a store
/// to a field of that structure.
static bool handleFree(CallInst *F, AliasAnalysis *AA,
MemoryDependenceResults *MD, DominatorTree *DT,
const TargetLibraryInfo *TLI,
InstOverlapIntervalsTy &IOL,
DenseMap<Instruction*, size_t> *InstrOrdering) {
bool MadeChange = false;
MemoryLocation Loc = MemoryLocation(F->getOperand(0));
SmallVector<BasicBlock *, 16> Blocks;
Blocks.push_back(F->getParent());
const DataLayout &DL = F->getModule()->getDataLayout();
while (!Blocks.empty()) {
BasicBlock *BB = Blocks.pop_back_val();
Instruction *InstPt = BB->getTerminator();
if (BB == F->getParent()) InstPt = F;
MemDepResult Dep =
MD->getPointerDependencyFrom(Loc, false, InstPt->getIterator(), BB);
while (Dep.isDef() || Dep.isClobber()) {
Instruction *Dependency = Dep.getInst();
if (!hasMemoryWrite(Dependency, *TLI) || !isRemovable(Dependency))
break;
Value *DepPointer =
GetUnderlyingObject(getStoredPointerOperand(Dependency), DL);
// Check for aliasing.
if (!AA->isMustAlias(F->getArgOperand(0), DepPointer))
break;
DEBUG(dbgs() << "DSE: Dead Store to soon to be freed memory:\n DEAD: "
<< *Dependency << '\n');
// DCE instructions only used to calculate that store.
BasicBlock::iterator BBI(Dependency);
deleteDeadInstruction(Dependency, &BBI, *MD, *TLI, IOL, InstrOrdering);
++NumFastStores;
MadeChange = true;
// Inst's old Dependency is now deleted. Compute the next dependency,
// which may also be dead, as in
// s[0] = 0;
// s[1] = 0; // This has just been deleted.
// free(s);
Dep = MD->getPointerDependencyFrom(Loc, false, BBI, BB);
}
if (Dep.isNonLocal())
findUnconditionalPreds(Blocks, BB, DT);
}
return MadeChange;
}
DataDependence::DepInfo DataDependence::getDepInfo(MemDepResult dep) {
if (dep.isClobber())
return DepInfo(dep.getInst(), Clobber);
if (dep.isDef())
return DepInfo(dep.getInst(), Def);
if (dep.isNonFuncLocal())
return DepInfo(dep.getInst(), NonFuncLocal);
if (dep.isUnknown())
return DepInfo(dep.getInst(), Unknown);
if (dep.isNonLocal())
return DepInfo(dep.getInst(), NonLocal);
llvm_unreachable("unknown dependence type");
}
/// HandleFree - Handle frees of entire structures whose dependency is a store
/// to a field of that structure.
bool DSE::HandleFree(CallInst *F) {
bool MadeChange = false;
MemoryLocation Loc = MemoryLocation(F->getOperand(0));
SmallVector<BasicBlock *, 16> Blocks;
Blocks.push_back(F->getParent());
const DataLayout &DL = F->getModule()->getDataLayout();
while (!Blocks.empty()) {
BasicBlock *BB = Blocks.pop_back_val();
Instruction *InstPt = BB->getTerminator();
if (BB == F->getParent()) InstPt = F;
MemDepResult Dep = MD->getPointerDependencyFrom(Loc, false, InstPt, BB);
while (Dep.isDef() || Dep.isClobber()) {
Instruction *Dependency = Dep.getInst();
if (!hasMemoryWrite(Dependency, *TLI) || !isRemovable(Dependency))
break;
Value *DepPointer =
GetUnderlyingObject(getStoredPointerOperand(Dependency), DL);
// Check for aliasing.
if (!AA->isMustAlias(F->getArgOperand(0), DepPointer))
break;
Instruction *Next = std::next(BasicBlock::iterator(Dependency));
// DCE instructions only used to calculate that store
DeleteDeadInstruction(Dependency, *MD, *TLI);
++NumFastStores;
MadeChange = true;
// Inst's old Dependency is now deleted. Compute the next dependency,
// which may also be dead, as in
// s[0] = 0;
// s[1] = 0; // This has just been deleted.
// free(s);
Dep = MD->getPointerDependencyFrom(Loc, false, Next, BB);
}
if (Dep.isNonLocal())
FindUnconditionalPreds(Blocks, BB, DT);
}
return MadeChange;
}
/// processMemCpy - perform simplification of memcpy's. If we have memcpy A
/// which copies X to Y, and memcpy B which copies Y to Z, then we can rewrite
/// B to be a memcpy from X to Z (or potentially a memmove, depending on
/// circumstances). This allows later passes to remove the first memcpy
/// altogether.
bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
// We can only optimize non-volatile memcpy's.
if (M->isVolatile()) return false;
// If the source and destination of the memcpy are the same, then zap it.
if (M->getSource() == M->getDest()) {
MD->removeInstruction(M);
M->eraseFromParent();
return false;
}
// If copying from a constant, try to turn the memcpy into a memset.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(M->getSource()))
if (GV->isConstant() && GV->hasDefinitiveInitializer())
if (Value *ByteVal = isBytewiseValue(GV->getInitializer())) {
IRBuilder<> Builder(M);
Builder.CreateMemSet(M->getRawDest(), ByteVal, M->getLength(),
M->getAlignment(), false);
MD->removeInstruction(M);
M->eraseFromParent();
++NumCpyToSet;
return true;
}
MemDepResult DepInfo = MD->getDependency(M);
// Try to turn a partially redundant memset + memcpy into
// memcpy + smaller memset. We don't need the memcpy size for this.
if (DepInfo.isClobber())
if (MemSetInst *MDep = dyn_cast<MemSetInst>(DepInfo.getInst()))
if (processMemSetMemCpyDependence(M, MDep))
return true;
// The optimizations after this point require the memcpy size.
ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
if (!CopySize) return false;
// There are four possible optimizations we can do for memcpy:
// a) memcpy-memcpy xform which exposes redundance for DSE.
// b) call-memcpy xform for return slot optimization.
// c) memcpy from freshly alloca'd space or space that has just started its
// lifetime copies undefined data, and we can therefore eliminate the
// memcpy in favor of the data that was already at the destination.
// d) memcpy from a just-memset'd source can be turned into memset.
if (DepInfo.isClobber()) {
if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) {
if (performCallSlotOptzn(M, M->getDest(), M->getSource(),
CopySize->getZExtValue(), M->getAlignment(),
C)) {
MD->removeInstruction(M);
M->eraseFromParent();
return true;
}
}
}
AliasAnalysis::Location SrcLoc = AliasAnalysis::getLocationForSource(M);
MemDepResult SrcDepInfo = MD->getPointerDependencyFrom(SrcLoc, true,
M, M->getParent());
if (SrcDepInfo.isClobber()) {
if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst()))
return processMemCpyMemCpyDependence(M, MDep);
} else if (SrcDepInfo.isDef()) {
Instruction *I = SrcDepInfo.getInst();
bool hasUndefContents = false;
if (isa<AllocaInst>(I)) {
hasUndefContents = true;
} else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
if (II->getIntrinsicID() == Intrinsic::lifetime_start)
if (ConstantInt *LTSize = dyn_cast<ConstantInt>(II->getArgOperand(0)))
if (LTSize->getZExtValue() >= CopySize->getZExtValue())
hasUndefContents = true;
}
if (hasUndefContents) {
MD->removeInstruction(M);
M->eraseFromParent();
++NumMemCpyInstr;
return true;
}
}
if (SrcDepInfo.isClobber())
if (MemSetInst *MDep = dyn_cast<MemSetInst>(SrcDepInfo.getInst()))
if (performMemCpyToMemSetOptzn(M, MDep)) {
MD->removeInstruction(M);
M->eraseFromParent();
++NumCpyToSet;
return true;
}
return false;
}
bool DSE::runOnBasicBlock(BasicBlock &BB) {
bool MadeChange = false;
// Do a top-down walk on the BB.
for (BasicBlock::iterator BBI = BB.begin(), BBE = BB.end(); BBI != BBE; ) {
Instruction *Inst = BBI++;
// Handle 'free' calls specially.
if (CallInst *F = isFreeCall(Inst, TLI)) {
MadeChange |= HandleFree(F);
continue;
}
// If we find something that writes memory, get its memory dependence.
if (!hasMemoryWrite(Inst, TLI))
continue;
MemDepResult InstDep = MD->getDependency(Inst);
// Ignore any store where we can't find a local dependence.
// FIXME: cross-block DSE would be fun. :)
if (!InstDep.isDef() && !InstDep.isClobber())
continue;
// If we're storing the same value back to a pointer that we just
// loaded from, then the store can be removed.
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
if (LoadInst *DepLoad = dyn_cast<LoadInst>(InstDep.getInst())) {
if (SI->getPointerOperand() == DepLoad->getPointerOperand() &&
SI->getOperand(0) == DepLoad && isRemovable(SI)) {
DEBUG(dbgs() << "DSE: Remove Store Of Load from same pointer:\n "
<< "LOAD: " << *DepLoad << "\n STORE: " << *SI << '\n');
// DeleteDeadInstruction can delete the current instruction. Save BBI
// in case we need it.
WeakVH NextInst(BBI);
DeleteDeadInstruction(SI, *MD, TLI);
if (!NextInst) // Next instruction deleted.
BBI = BB.begin();
else if (BBI != BB.begin()) // Revisit this instruction if possible.
--BBI;
++NumFastStores;
MadeChange = true;
continue;
}
}
}
// Figure out what location is being stored to.
AliasAnalysis::Location Loc = getLocForWrite(Inst, *AA);
// If we didn't get a useful location, fail.
if (!Loc.Ptr)
continue;
while (InstDep.isDef() || InstDep.isClobber()) {
// Get the memory clobbered by the instruction we depend on. MemDep will
// skip any instructions that 'Loc' clearly doesn't interact with. If we
// end up depending on a may- or must-aliased load, then we can't optimize
// away the store and we bail out. However, if we depend on on something
// that overwrites the memory location we *can* potentially optimize it.
//
// Find out what memory location the dependent instruction stores.
Instruction *DepWrite = InstDep.getInst();
AliasAnalysis::Location DepLoc = getLocForWrite(DepWrite, *AA);
// If we didn't get a useful location, or if it isn't a size, bail out.
if (!DepLoc.Ptr)
break;
// If we find a write that is a) removable (i.e., non-volatile), b) is
// completely obliterated by the store to 'Loc', and c) which we know that
// 'Inst' doesn't load from, then we can remove it.
if (isRemovable(DepWrite) &&
!isPossibleSelfRead(Inst, Loc, DepWrite, *AA)) {
int64_t InstWriteOffset, DepWriteOffset;
OverwriteResult OR = isOverwrite(Loc, DepLoc, *AA,
DepWriteOffset, InstWriteOffset);
if (OR == OverwriteComplete) {
DEBUG(dbgs() << "DSE: Remove Dead Store:\n DEAD: "
<< *DepWrite << "\n KILLER: " << *Inst << '\n');
// Delete the store and now-dead instructions that feed it.
DeleteDeadInstruction(DepWrite, *MD, TLI);
++NumFastStores;
MadeChange = true;
// DeleteDeadInstruction can delete the current instruction in loop
// cases, reset BBI.
BBI = Inst;
if (BBI != BB.begin())
--BBI;
break;
} else if (OR == OverwriteEnd && isShortenable(DepWrite)) {
// TODO: base this on the target vector size so that if the earlier
// store was too small to get vector writes anyway then its likely
// a good idea to shorten it
// Power of 2 vector writes are probably always a bad idea to optimize
// as any store/memset/memcpy is likely using vector instructions so
// shortening it to not vector size is likely to be slower
MemIntrinsic* DepIntrinsic = cast<MemIntrinsic>(DepWrite);
unsigned DepWriteAlign = DepIntrinsic->getAlignment();
if (llvm::isPowerOf2_64(InstWriteOffset) ||
((DepWriteAlign != 0) && InstWriteOffset % DepWriteAlign == 0)) {
DEBUG(dbgs() << "DSE: Remove Dead Store:\n OW END: "
<< *DepWrite << "\n KILLER (offset "
<< InstWriteOffset << ", "
<< DepLoc.Size << ")"
<< *Inst << '\n');
Value* DepWriteLength = DepIntrinsic->getLength();
Value* TrimmedLength = ConstantInt::get(DepWriteLength->getType(),
InstWriteOffset -
DepWriteOffset);
DepIntrinsic->setLength(TrimmedLength);
MadeChange = true;
}
}
}
// If this is a may-aliased store that is clobbering the store value, we
// can keep searching past it for another must-aliased pointer that stores
// to the same location. For example, in:
// store -> P
// store -> Q
// store -> P
// we can remove the first store to P even though we don't know if P and Q
// alias.
if (DepWrite == &BB.front()) break;
// Can't look past this instruction if it might read 'Loc'.
if (AA->getModRefInfo(DepWrite, Loc) & AliasAnalysis::Ref)
break;
InstDep = MD->getPointerDependencyFrom(Loc, false, DepWrite, &BB);
}
}
// If this block ends in a return, unwind, or unreachable, all allocas are
// dead at its end, which means stores to them are also dead.
if (BB.getTerminator()->getNumSuccessors() == 0)
MadeChange |= handleEndBlock(BB);
return MadeChange;
}
void DSWP::buildPDG(Loop *L) {
//Initialize PDG
for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
BasicBlock *BB = *bi;
for (BasicBlock::iterator ui = BB->begin(); ui != BB->end(); ui++) {
Instruction *inst = &(*ui);
//standardlize the name for all expr
if (util.hasNewDef(inst)) {
inst->setName(util.genId());
dname[inst] = inst->getNameStr();
} else {
dname[inst] = util.genId();
}
pdg[inst] = new vector<Edge>();
rev[inst] = new vector<Edge>();
}
}
//LoopInfo &li = getAnalysis<LoopInfo>();
/*
* Memory dependency analysis
*/
MemoryDependenceAnalysis &mda = getAnalysis<MemoryDependenceAnalysis>();
for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
BasicBlock *BB = *bi;
for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ii++) {
Instruction *inst = &(*ii);
//data dependence = register dependence + memory dependence
//begin register dependence
for (Value::use_iterator ui = ii->use_begin(); ui != ii->use_end(); ui++) {
if (Instruction *user = dyn_cast<Instruction>(*ui)) {
addEdge(inst, user, REG);
}
}
//finish register dependence
//begin memory dependence
MemDepResult mdr = mda.getDependency(inst);
//TODO not sure clobbers mean!!
if (mdr.isDef()) {
Instruction *dep = mdr.getInst();
if (isa<LoadInst>(inst)) {
if (isa<StoreInst>(dep)) {
addEdge(dep, inst, DTRUE); //READ AFTER WRITE
}
}
if (isa<StoreInst>(inst)) {
if (isa<LoadInst>(dep)) {
addEdge(dep, inst, DANTI); //WRITE AFTER READ
}
if (isa<StoreInst>(dep)) {
addEdge(dep, inst, DOUT); //WRITE AFTER WRITE
}
}
//READ AFTER READ IS INSERT AFTER PDG BUILD
}
//end memory dependence
}//for ii
}//for bi
/*
* begin control dependence
*/
PostDominatorTree &pdt = getAnalysis<PostDominatorTree>();
//cout << pdt.getRootNode()->getBlock()->getNameStr() << endl;
/*
* alien code part 1
*/
LoopInfo *LI = &getAnalysis<LoopInfo>();
std::set<BranchInst*> backedgeParents;
for (Loop::block_iterator bi = L->getBlocks().begin(); bi
!= L->getBlocks().end(); bi++) {
BasicBlock *BB = *bi;
for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ii++) {
Instruction *inst = ii;
if (BranchInst *brInst = dyn_cast<BranchInst>(inst)) {
// get the loop this instruction (and therefore basic block) belongs to
Loop *instLoop = LI->getLoopFor(BB);
bool branchesToHeader = false;
for (int i = brInst->getNumSuccessors() - 1; i >= 0
&& !branchesToHeader; i--) {
// if the branch could exit, store it
if (LI->getLoopFor(brInst->getSuccessor(i)) != instLoop) {
branchesToHeader = true;
}
}
if (branchesToHeader) {
backedgeParents.insert(brInst);
}
}
}
}
//build information for predecessor of blocks in post dominator tree
for (Function::iterator bi = func->begin(); bi != func->end(); bi++) {
BasicBlock *BB = bi;
DomTreeNode *dn = pdt.getNode(BB);
for (DomTreeNode::iterator di = dn->begin(); di != dn->end(); di++) {
BasicBlock *CB = (*di)->getBlock();
pre[CB] = BB;
}
}
//
// //add dependency within a basicblock
// for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
// BasicBlock *BB = *bi;
// Instruction *pre = NULL;
// for (BasicBlock::iterator ui = BB->begin(); ui != BB->end(); ui++) {
// Instruction *inst = &(*ui);
// if (pre != NULL) {
// addEdge(pre, inst, CONTROL);
// }
// pre = inst;
// }
// }
// //the special kind of dependence need loop peeling ? I don't know whether this is needed
// for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
// BasicBlock *BB = *bi;
// for (succ_iterator PI = succ_begin(BB); PI != succ_end(BB); ++PI) {
// BasicBlock *succ = *PI;
//
// checkControlDependence(BB, succ, pdt);
// }
// }
/*
* alien code part 2
*/
// add normal control dependencies
// loop through each instruction
for (Loop::block_iterator bbIter = L->block_begin(); bbIter
!= L->block_end(); ++bbIter) {
BasicBlock *bb = *bbIter;
// check the successors of this basic block
if (BranchInst *branchInst = dyn_cast<BranchInst>(bb->getTerminator())) {
if (branchInst->getNumSuccessors() > 1) {
BasicBlock * succ = branchInst->getSuccessor(0);
// if the successor is nested shallower than the current basic block, continue
if (LI->getLoopDepth(bb) < LI->getLoopDepth(succ)) {
continue;
}
// otherwise, add all instructions to graph as control dependence
while (succ != NULL && succ != bb && LI->getLoopDepth(succ)
>= LI->getLoopDepth(bb)) {
Instruction *terminator = bb->getTerminator();
for (BasicBlock::iterator succInstIter = succ->begin(); &(*succInstIter)
!= succ->getTerminator(); ++succInstIter) {
addEdge(terminator, &(*succInstIter), CONTROL);
}
if (BranchInst *succBrInst = dyn_cast<BranchInst>(succ->getTerminator())) {
if (succBrInst->getNumSuccessors() > 1) {
addEdge(terminator, succ->getTerminator(),
CONTROL);
}
}
if (BranchInst *br = dyn_cast<BranchInst>(succ->getTerminator())) {
if (br->getNumSuccessors() == 1) {
succ = br->getSuccessor(0);
} else {
succ = NULL;
}
} else {
succ = NULL;
}
}
}
}
}
/*
* alien code part 3
*/
for (std::set<BranchInst*>::iterator exitIter = backedgeParents.begin(); exitIter != backedgeParents.end(); ++exitIter) {
BranchInst *exitBranch = *exitIter;
if (exitBranch->isConditional()) {
BasicBlock *header = LI->getLoopFor(exitBranch->getParent())->getHeader();
for (BasicBlock::iterator ctrlIter = header->begin(); ctrlIter != header->end(); ++ctrlIter) {
addEdge(exitBranch, &(*ctrlIter), CONTROL);
}
}
}
//end control dependence
}
/// processMemCpy - perform simplification of memcpy's. If we have memcpy A
/// which copies X to Y, and memcpy B which copies Y to Z, then we can rewrite
/// B to be a memcpy from X to Z (or potentially a memmove, depending on
/// circumstances). This allows later passes to remove the first memcpy
/// altogether.
bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
// We can only optimize non-volatile memcpy's.
if (M->isVolatile()) return false;
// If the source and destination of the memcpy are the same, then zap it.
if (M->getSource() == M->getDest()) {
MD->removeInstruction(M);
M->eraseFromParent();
return false;
}
// If copying from a constant, try to turn the memcpy into a memset.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(M->getSource()))
if (GV->isConstant() && GV->hasDefinitiveInitializer())
if (Value *ByteVal = isBytewiseValue(GV->getInitializer())) {
IRBuilder<> Builder(M);
Builder.CreateMemSet(M->getRawDest(), ByteVal, M->getLength(),
M->getAlignment(), false);
MD->removeInstruction(M);
M->eraseFromParent();
++NumCpyToSet;
return true;
}
// The optimizations after this point require the memcpy size.
ConstantInt *CopySize = dyn_cast<ConstantInt>(M->getLength());
if (CopySize == 0) return false;
// The are three possible optimizations we can do for memcpy:
// a) memcpy-memcpy xform which exposes redundance for DSE.
// b) call-memcpy xform for return slot optimization.
// c) memcpy from freshly alloca'd space copies undefined data, and we can
// therefore eliminate the memcpy in favor of the data that was already
// at the destination.
MemDepResult DepInfo = MD->getDependency(M);
if (DepInfo.isClobber()) {
if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) {
if (performCallSlotOptzn(M, M->getDest(), M->getSource(),
CopySize->getZExtValue(), M->getAlignment(),
C)) {
MD->removeInstruction(M);
M->eraseFromParent();
return true;
}
}
}
AliasAnalysis::Location SrcLoc = AliasAnalysis::getLocationForSource(M);
MemDepResult SrcDepInfo = MD->getPointerDependencyFrom(SrcLoc, true,
M, M->getParent());
if (SrcDepInfo.isClobber()) {
if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst()))
return processMemCpyMemCpyDependence(M, MDep, CopySize->getZExtValue());
} else if (SrcDepInfo.isDef()) {
if (isa<AllocaInst>(SrcDepInfo.getInst())) {
MD->removeInstruction(M);
M->eraseFromParent();
++NumMemCpyInstr;
return true;
}
}
return false;
}
bool AMDGPURewriteOutArguments::runOnFunction(Function &F) {
if (skipFunction(F))
return false;
// TODO: Could probably handle variadic functions.
if (F.isVarArg() || F.hasStructRetAttr() ||
AMDGPU::isEntryFunctionCC(F.getCallingConv()))
return false;
MDA = &getAnalysis<MemoryDependenceWrapperPass>().getMemDep();
unsigned ReturnNumRegs = 0;
SmallSet<int, 4> OutArgIndexes;
SmallVector<Type *, 4> ReturnTypes;
Type *RetTy = F.getReturnType();
if (!RetTy->isVoidTy()) {
ReturnNumRegs = DL->getTypeStoreSize(RetTy) / 4;
if (ReturnNumRegs >= MaxNumRetRegs)
return false;
ReturnTypes.push_back(RetTy);
}
SmallVector<Argument *, 4> OutArgs;
for (Argument &Arg : F.args()) {
if (isOutArgumentCandidate(Arg)) {
LLVM_DEBUG(dbgs() << "Found possible out argument " << Arg
<< " in function " << F.getName() << '\n');
OutArgs.push_back(&Arg);
}
}
if (OutArgs.empty())
return false;
using ReplacementVec = SmallVector<std::pair<Argument *, Value *>, 4>;
DenseMap<ReturnInst *, ReplacementVec> Replacements;
SmallVector<ReturnInst *, 4> Returns;
for (BasicBlock &BB : F) {
if (ReturnInst *RI = dyn_cast<ReturnInst>(&BB.back()))
Returns.push_back(RI);
}
if (Returns.empty())
return false;
bool Changing;
do {
Changing = false;
// Keep retrying if we are able to successfully eliminate an argument. This
// helps with cases with multiple arguments which may alias, such as in a
// sincos implemntation. If we have 2 stores to arguments, on the first
// attempt the MDA query will succeed for the second store but not the
// first. On the second iteration we've removed that out clobbering argument
// (by effectively moving it into another function) and will find the second
// argument is OK to move.
for (Argument *OutArg : OutArgs) {
bool ThisReplaceable = true;
SmallVector<std::pair<ReturnInst *, StoreInst *>, 4> ReplaceableStores;
Type *ArgTy = OutArg->getType()->getPointerElementType();
// Skip this argument if converting it will push us over the register
// count to return limit.
// TODO: This is an approximation. When legalized this could be more. We
// can ask TLI for exactly how many.
unsigned ArgNumRegs = DL->getTypeStoreSize(ArgTy) / 4;
if (ArgNumRegs + ReturnNumRegs > MaxNumRetRegs)
continue;
// An argument is convertible only if all exit blocks are able to replace
// it.
for (ReturnInst *RI : Returns) {
BasicBlock *BB = RI->getParent();
MemDepResult Q = MDA->getPointerDependencyFrom(MemoryLocation(OutArg),
true, BB->end(), BB, RI);
StoreInst *SI = nullptr;
if (Q.isDef())
SI = dyn_cast<StoreInst>(Q.getInst());
if (SI) {
LLVM_DEBUG(dbgs() << "Found out argument store: " << *SI << '\n');
ReplaceableStores.emplace_back(RI, SI);
} else {
ThisReplaceable = false;
break;
}
}
if (!ThisReplaceable)
continue; // Try the next argument candidate.
for (std::pair<ReturnInst *, StoreInst *> Store : ReplaceableStores) {
Value *ReplVal = Store.second->getValueOperand();
auto &ValVec = Replacements[Store.first];
if (llvm::find_if(ValVec,
[OutArg](const std::pair<Argument *, Value *> &Entry) {
return Entry.first == OutArg;}) != ValVec.end()) {
LLVM_DEBUG(dbgs()
<< "Saw multiple out arg stores" << *OutArg << '\n');
// It is possible to see stores to the same argument multiple times,
// but we expect these would have been optimized out already.
ThisReplaceable = false;
break;
}
ValVec.emplace_back(OutArg, ReplVal);
Store.second->eraseFromParent();
}
if (ThisReplaceable) {
ReturnTypes.push_back(ArgTy);
OutArgIndexes.insert(OutArg->getArgNo());
++NumOutArgumentsReplaced;
Changing = true;
}
}
} while (Changing);
if (Replacements.empty())
return false;
LLVMContext &Ctx = F.getParent()->getContext();
StructType *NewRetTy = StructType::create(Ctx, ReturnTypes, F.getName());
FunctionType *NewFuncTy = FunctionType::get(NewRetTy,
F.getFunctionType()->params(),
F.isVarArg());
LLVM_DEBUG(dbgs() << "Computed new return type: " << *NewRetTy << '\n');
Function *NewFunc = Function::Create(NewFuncTy, Function::PrivateLinkage,
F.getName() + ".body");
F.getParent()->getFunctionList().insert(F.getIterator(), NewFunc);
NewFunc->copyAttributesFrom(&F);
NewFunc->setComdat(F.getComdat());
// We want to preserve the function and param attributes, but need to strip
// off any return attributes, e.g. zeroext doesn't make sense with a struct.
NewFunc->stealArgumentListFrom(F);
AttrBuilder RetAttrs;
RetAttrs.addAttribute(Attribute::SExt);
RetAttrs.addAttribute(Attribute::ZExt);
RetAttrs.addAttribute(Attribute::NoAlias);
NewFunc->removeAttributes(AttributeList::ReturnIndex, RetAttrs);
// TODO: How to preserve metadata?
// Move the body of the function into the new rewritten function, and replace
// this function with a stub.
NewFunc->getBasicBlockList().splice(NewFunc->begin(), F.getBasicBlockList());
for (std::pair<ReturnInst *, ReplacementVec> &Replacement : Replacements) {
ReturnInst *RI = Replacement.first;
IRBuilder<> B(RI);
B.SetCurrentDebugLocation(RI->getDebugLoc());
int RetIdx = 0;
Value *NewRetVal = UndefValue::get(NewRetTy);
Value *RetVal = RI->getReturnValue();
if (RetVal)
NewRetVal = B.CreateInsertValue(NewRetVal, RetVal, RetIdx++);
for (std::pair<Argument *, Value *> ReturnPoint : Replacement.second) {
Argument *Arg = ReturnPoint.first;
Value *Val = ReturnPoint.second;
Type *EltTy = Arg->getType()->getPointerElementType();
if (Val->getType() != EltTy) {
Type *EffectiveEltTy = EltTy;
if (StructType *CT = dyn_cast<StructType>(EltTy)) {
assert(CT->getNumElements() == 1);
EffectiveEltTy = CT->getElementType(0);
}
if (DL->getTypeSizeInBits(EffectiveEltTy) !=
DL->getTypeSizeInBits(Val->getType())) {
assert(isVec3ToVec4Shuffle(EffectiveEltTy, Val->getType()));
Val = B.CreateShuffleVector(Val, UndefValue::get(Val->getType()),
{ 0, 1, 2 });
}
Val = B.CreateBitCast(Val, EffectiveEltTy);
// Re-create single element composite.
if (EltTy != EffectiveEltTy)
Val = B.CreateInsertValue(UndefValue::get(EltTy), Val, 0);
}
NewRetVal = B.CreateInsertValue(NewRetVal, Val, RetIdx++);
}
if (RetVal)
RI->setOperand(0, NewRetVal);
else {
B.CreateRet(NewRetVal);
RI->eraseFromParent();
}
}
SmallVector<Value *, 16> StubCallArgs;
for (Argument &Arg : F.args()) {
if (OutArgIndexes.count(Arg.getArgNo())) {
// It's easier to preserve the type of the argument list. We rely on
// DeadArgumentElimination to take care of these.
StubCallArgs.push_back(UndefValue::get(Arg.getType()));
} else {
StubCallArgs.push_back(&Arg);
}
}
BasicBlock *StubBB = BasicBlock::Create(Ctx, "", &F);
IRBuilder<> B(StubBB);
CallInst *StubCall = B.CreateCall(NewFunc, StubCallArgs);
int RetIdx = RetTy->isVoidTy() ? 0 : 1;
for (Argument &Arg : F.args()) {
if (!OutArgIndexes.count(Arg.getArgNo()))
continue;
PointerType *ArgType = cast<PointerType>(Arg.getType());
auto *EltTy = ArgType->getElementType();
unsigned Align = Arg.getParamAlignment();
if (Align == 0)
Align = DL->getABITypeAlignment(EltTy);
Value *Val = B.CreateExtractValue(StubCall, RetIdx++);
Type *PtrTy = Val->getType()->getPointerTo(ArgType->getAddressSpace());
// We can peek through bitcasts, so the type may not match.
Value *PtrVal = B.CreateBitCast(&Arg, PtrTy);
B.CreateAlignedStore(Val, PtrVal, Align);
}
if (!RetTy->isVoidTy()) {
B.CreateRet(B.CreateExtractValue(StubCall, 0));
} else {
B.CreateRetVoid();
}
// The function is now a stub we want to inline.
F.addFnAttr(Attribute::AlwaysInline);
++NumOutArgumentFunctionsReplaced;
return true;
}
