1 //===- EarlyCSE.cpp - Simple and fast CSE pass ----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass performs a simple dominator tree walk that eliminates trivially
11 // redundant instructions.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Transforms/Scalar.h"
16 #include "llvm/ADT/Hashing.h"
17 #include "llvm/ADT/ScopedHashTable.h"
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/Analysis/AssumptionCache.h"
20 #include "llvm/Analysis/InstructionSimplify.h"
21 #include "llvm/Analysis/TargetTransformInfo.h"
22 #include "llvm/IR/DataLayout.h"
23 #include "llvm/IR/Dominators.h"
24 #include "llvm/IR/Instructions.h"
25 #include "llvm/IR/IntrinsicInst.h"
26 #include "llvm/IR/PatternMatch.h"
27 #include "llvm/Pass.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/RecyclingAllocator.h"
30 #include "llvm/Analysis/TargetLibraryInfo.h"
31 #include "llvm/Transforms/Utils/Local.h"
34 using namespace llvm::PatternMatch;
36 #define DEBUG_TYPE "early-cse"
38 STATISTIC(NumSimplify, "Number of instructions simplified or DCE'd");
39 STATISTIC(NumCSE, "Number of instructions CSE'd");
40 STATISTIC(NumCSELoad, "Number of load instructions CSE'd");
41 STATISTIC(NumCSECall, "Number of call instructions CSE'd");
42 STATISTIC(NumDSE, "Number of trivial dead stores removed");
44 static unsigned getHash(const void *V) {
45 return DenseMapInfo<const void*>::getHashValue(V);
48 //===----------------------------------------------------------------------===//
50 //===----------------------------------------------------------------------===//
53 /// \brief Struct representing the available values in the scoped hash table.
57 SimpleValue(Instruction *I) : Inst(I) {
58 assert((isSentinel() || canHandle(I)) && "Inst can't be handled!");
61 bool isSentinel() const {
62 return Inst == DenseMapInfo<Instruction *>::getEmptyKey() ||
63 Inst == DenseMapInfo<Instruction *>::getTombstoneKey();
66 static bool canHandle(Instruction *Inst) {
67 // This can only handle non-void readnone functions.
68 if (CallInst *CI = dyn_cast<CallInst>(Inst))
69 return CI->doesNotAccessMemory() && !CI->getType()->isVoidTy();
70 return isa<CastInst>(Inst) || isa<BinaryOperator>(Inst) ||
71 isa<GetElementPtrInst>(Inst) || isa<CmpInst>(Inst) ||
72 isa<SelectInst>(Inst) || isa<ExtractElementInst>(Inst) ||
73 isa<InsertElementInst>(Inst) || isa<ShuffleVectorInst>(Inst) ||
74 isa<ExtractValueInst>(Inst) || isa<InsertValueInst>(Inst);
80 template <> struct DenseMapInfo<SimpleValue> {
81 static inline SimpleValue getEmptyKey() {
82 return DenseMapInfo<Instruction *>::getEmptyKey();
84 static inline SimpleValue getTombstoneKey() {
85 return DenseMapInfo<Instruction *>::getTombstoneKey();
87 static unsigned getHashValue(SimpleValue Val);
88 static bool isEqual(SimpleValue LHS, SimpleValue RHS);
92 unsigned DenseMapInfo<SimpleValue>::getHashValue(SimpleValue Val) {
93 Instruction *Inst = Val.Inst;
94 // Hash in all of the operands as pointers.
95 if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Inst)) {
96 Value *LHS = BinOp->getOperand(0);
97 Value *RHS = BinOp->getOperand(1);
98 if (BinOp->isCommutative() && BinOp->getOperand(0) > BinOp->getOperand(1))
101 if (isa<OverflowingBinaryOperator>(BinOp)) {
102 // Hash the overflow behavior
104 BinOp->hasNoSignedWrap() * OverflowingBinaryOperator::NoSignedWrap |
105 BinOp->hasNoUnsignedWrap() *
106 OverflowingBinaryOperator::NoUnsignedWrap;
107 return hash_combine(BinOp->getOpcode(), Overflow, LHS, RHS);
110 return hash_combine(BinOp->getOpcode(), LHS, RHS);
113 if (CmpInst *CI = dyn_cast<CmpInst>(Inst)) {
114 Value *LHS = CI->getOperand(0);
115 Value *RHS = CI->getOperand(1);
116 CmpInst::Predicate Pred = CI->getPredicate();
117 if (Inst->getOperand(0) > Inst->getOperand(1)) {
119 Pred = CI->getSwappedPredicate();
121 return hash_combine(Inst->getOpcode(), Pred, LHS, RHS);
124 if (CastInst *CI = dyn_cast<CastInst>(Inst))
125 return hash_combine(CI->getOpcode(), CI->getType(), CI->getOperand(0));
127 if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Inst))
128 return hash_combine(EVI->getOpcode(), EVI->getOperand(0),
129 hash_combine_range(EVI->idx_begin(), EVI->idx_end()));
131 if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(Inst))
132 return hash_combine(IVI->getOpcode(), IVI->getOperand(0),
134 hash_combine_range(IVI->idx_begin(), IVI->idx_end()));
136 assert((isa<CallInst>(Inst) || isa<BinaryOperator>(Inst) ||
137 isa<GetElementPtrInst>(Inst) || isa<SelectInst>(Inst) ||
138 isa<ExtractElementInst>(Inst) || isa<InsertElementInst>(Inst) ||
139 isa<ShuffleVectorInst>(Inst)) &&
140 "Invalid/unknown instruction");
142 // Mix in the opcode.
145 hash_combine_range(Inst->value_op_begin(), Inst->value_op_end()));
148 bool DenseMapInfo<SimpleValue>::isEqual(SimpleValue LHS, SimpleValue RHS) {
149 Instruction *LHSI = LHS.Inst, *RHSI = RHS.Inst;
151 if (LHS.isSentinel() || RHS.isSentinel())
154 if (LHSI->getOpcode() != RHSI->getOpcode())
156 if (LHSI->isIdenticalTo(RHSI))
159 // If we're not strictly identical, we still might be a commutable instruction
160 if (BinaryOperator *LHSBinOp = dyn_cast<BinaryOperator>(LHSI)) {
161 if (!LHSBinOp->isCommutative())
164 assert(isa<BinaryOperator>(RHSI) &&
165 "same opcode, but different instruction type?");
166 BinaryOperator *RHSBinOp = cast<BinaryOperator>(RHSI);
168 // Check overflow attributes
169 if (isa<OverflowingBinaryOperator>(LHSBinOp)) {
170 assert(isa<OverflowingBinaryOperator>(RHSBinOp) &&
171 "same opcode, but different operator type?");
172 if (LHSBinOp->hasNoUnsignedWrap() != RHSBinOp->hasNoUnsignedWrap() ||
173 LHSBinOp->hasNoSignedWrap() != RHSBinOp->hasNoSignedWrap())
178 return LHSBinOp->getOperand(0) == RHSBinOp->getOperand(1) &&
179 LHSBinOp->getOperand(1) == RHSBinOp->getOperand(0);
181 if (CmpInst *LHSCmp = dyn_cast<CmpInst>(LHSI)) {
182 assert(isa<CmpInst>(RHSI) &&
183 "same opcode, but different instruction type?");
184 CmpInst *RHSCmp = cast<CmpInst>(RHSI);
186 return LHSCmp->getOperand(0) == RHSCmp->getOperand(1) &&
187 LHSCmp->getOperand(1) == RHSCmp->getOperand(0) &&
188 LHSCmp->getSwappedPredicate() == RHSCmp->getPredicate();
194 //===----------------------------------------------------------------------===//
196 //===----------------------------------------------------------------------===//
199 /// \brief Struct representing the available call values in the scoped hash
204 CallValue(Instruction *I) : Inst(I) {
205 assert((isSentinel() || canHandle(I)) && "Inst can't be handled!");
208 bool isSentinel() const {
209 return Inst == DenseMapInfo<Instruction *>::getEmptyKey() ||
210 Inst == DenseMapInfo<Instruction *>::getTombstoneKey();
213 static bool canHandle(Instruction *Inst) {
214 // Don't value number anything that returns void.
215 if (Inst->getType()->isVoidTy())
218 CallInst *CI = dyn_cast<CallInst>(Inst);
219 if (!CI || !CI->onlyReadsMemory())
227 template <> struct DenseMapInfo<CallValue> {
228 static inline CallValue getEmptyKey() {
229 return DenseMapInfo<Instruction *>::getEmptyKey();
231 static inline CallValue getTombstoneKey() {
232 return DenseMapInfo<Instruction *>::getTombstoneKey();
234 static unsigned getHashValue(CallValue Val);
235 static bool isEqual(CallValue LHS, CallValue RHS);
239 unsigned DenseMapInfo<CallValue>::getHashValue(CallValue Val) {
240 Instruction *Inst = Val.Inst;
241 // Hash in all of the operands as pointers.
243 for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i) {
244 assert(!Inst->getOperand(i)->getType()->isMetadataTy() &&
245 "Cannot value number calls with metadata operands");
246 Res ^= getHash(Inst->getOperand(i)) << (i & 0xF);
249 // Mix in the opcode.
250 return (Res << 1) ^ Inst->getOpcode();
253 bool DenseMapInfo<CallValue>::isEqual(CallValue LHS, CallValue RHS) {
254 Instruction *LHSI = LHS.Inst, *RHSI = RHS.Inst;
255 if (LHS.isSentinel() || RHS.isSentinel())
257 return LHSI->isIdenticalTo(RHSI);
260 //===----------------------------------------------------------------------===//
261 // EarlyCSE implementation
262 //===----------------------------------------------------------------------===//
265 /// \brief A simple and fast domtree-based CSE pass.
267 /// This pass does a simple depth-first walk over the dominator tree,
268 /// eliminating trivially redundant instructions and using instsimplify to
269 /// canonicalize things as it goes. It is intended to be fast and catch obvious
270 /// cases so that instcombine and other passes are more effective. It is
271 /// expected that a later pass of GVN will catch the interesting/hard cases.
275 const DataLayout *DL;
276 const TargetLibraryInfo &TLI;
277 const TargetTransformInfo &TTI;
280 typedef RecyclingAllocator<
281 BumpPtrAllocator, ScopedHashTableVal<SimpleValue, Value *>> AllocatorTy;
282 typedef ScopedHashTable<SimpleValue, Value *, DenseMapInfo<SimpleValue>,
283 AllocatorTy> ScopedHTType;
285 /// \brief A scoped hash table of the current values of all of our simple
286 /// scalar expressions.
288 /// As we walk down the domtree, we look to see if instructions are in this:
289 /// if so, we replace them with what we find, otherwise we insert them so
290 /// that dominated values can succeed in their lookup.
291 ScopedHTType AvailableValues;
293 /// \brief A scoped hash table of the current values of loads.
295 /// This allows us to get efficient access to dominating loads when we have
296 /// a fully redundant load. In addition to the most recent load, we keep
297 /// track of a generation count of the read, which is compared against the
298 /// current generation count. The current generation count is incremented
299 /// after every possibly writing memory operation, which ensures that we only
300 /// CSE loads with other loads that have no intervening store.
301 typedef RecyclingAllocator<
303 ScopedHashTableVal<Value *, std::pair<Value *, unsigned>>>
305 typedef ScopedHashTable<Value *, std::pair<Value *, unsigned>,
306 DenseMapInfo<Value *>, LoadMapAllocator> LoadHTType;
307 LoadHTType AvailableLoads;
309 /// \brief A scoped hash table of the current values of read-only call
312 /// It uses the same generation count as loads.
313 typedef ScopedHashTable<CallValue, std::pair<Value *, unsigned>> CallHTType;
314 CallHTType AvailableCalls;
316 /// \brief This is the current generation of the memory value.
317 unsigned CurrentGeneration;
319 /// \brief Set up the EarlyCSE runner for a particular function.
320 EarlyCSE(Function &F, const DataLayout *DL, const TargetLibraryInfo &TLI,
321 const TargetTransformInfo &TTI, DominatorTree &DT,
323 : F(F), DL(DL), TLI(TLI), TTI(TTI), DT(DT), AC(AC), CurrentGeneration(0) {
329 // Almost a POD, but needs to call the constructors for the scoped hash
330 // tables so that a new scope gets pushed on. These are RAII so that the
331 // scope gets popped when the NodeScope is destroyed.
334 NodeScope(ScopedHTType &AvailableValues, LoadHTType &AvailableLoads,
335 CallHTType &AvailableCalls)
336 : Scope(AvailableValues), LoadScope(AvailableLoads),
337 CallScope(AvailableCalls) {}
340 NodeScope(const NodeScope &) LLVM_DELETED_FUNCTION;
341 void operator=(const NodeScope &) LLVM_DELETED_FUNCTION;
343 ScopedHTType::ScopeTy Scope;
344 LoadHTType::ScopeTy LoadScope;
345 CallHTType::ScopeTy CallScope;
348 // Contains all the needed information to create a stack for doing a depth
349 // first tranversal of the tree. This includes scopes for values, loads, and
350 // calls as well as the generation. There is a child iterator so that the
351 // children do not need to be store spearately.
354 StackNode(ScopedHTType &AvailableValues, LoadHTType &AvailableLoads,
355 CallHTType &AvailableCalls, unsigned cg, DomTreeNode *n,
356 DomTreeNode::iterator child, DomTreeNode::iterator end)
357 : CurrentGeneration(cg), ChildGeneration(cg), Node(n), ChildIter(child),
358 EndIter(end), Scopes(AvailableValues, AvailableLoads, AvailableCalls),
362 unsigned currentGeneration() { return CurrentGeneration; }
363 unsigned childGeneration() { return ChildGeneration; }
364 void childGeneration(unsigned generation) { ChildGeneration = generation; }
365 DomTreeNode *node() { return Node; }
366 DomTreeNode::iterator childIter() { return ChildIter; }
367 DomTreeNode *nextChild() {
368 DomTreeNode *child = *ChildIter;
372 DomTreeNode::iterator end() { return EndIter; }
373 bool isProcessed() { return Processed; }
374 void process() { Processed = true; }
377 StackNode(const StackNode &) LLVM_DELETED_FUNCTION;
378 void operator=(const StackNode &) LLVM_DELETED_FUNCTION;
381 unsigned CurrentGeneration;
382 unsigned ChildGeneration;
384 DomTreeNode::iterator ChildIter;
385 DomTreeNode::iterator EndIter;
390 /// \brief Wrapper class to handle memory instructions, including loads,
391 /// stores and intrinsic loads and stores defined by the target.
392 class ParseMemoryInst {
394 ParseMemoryInst(Instruction *Inst, const TargetTransformInfo &TTI)
395 : Load(false), Store(false), Vol(false), MayReadFromMemory(false),
396 MayWriteToMemory(false), MatchingId(-1), Ptr(nullptr) {
397 MayReadFromMemory = Inst->mayReadFromMemory();
398 MayWriteToMemory = Inst->mayWriteToMemory();
399 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
400 MemIntrinsicInfo Info;
401 if (!TTI.getTgtMemIntrinsic(II, Info))
403 if (Info.NumMemRefs == 1) {
404 Store = Info.WriteMem;
406 MatchingId = Info.MatchingId;
407 MayReadFromMemory = Info.ReadMem;
408 MayWriteToMemory = Info.WriteMem;
412 } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
414 Vol = !LI->isSimple();
415 Ptr = LI->getPointerOperand();
416 } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
418 Vol = !SI->isSimple();
419 Ptr = SI->getPointerOperand();
422 bool isLoad() { return Load; }
423 bool isStore() { return Store; }
424 bool isVolatile() { return Vol; }
425 bool isMatchingMemLoc(const ParseMemoryInst &Inst) {
426 return Ptr == Inst.Ptr && MatchingId == Inst.MatchingId;
428 bool isValid() { return Ptr != nullptr; }
429 int getMatchingId() { return MatchingId; }
430 Value *getPtr() { return Ptr; }
431 bool mayReadFromMemory() { return MayReadFromMemory; }
432 bool mayWriteToMemory() { return MayWriteToMemory; }
438 bool MayReadFromMemory;
439 bool MayWriteToMemory;
440 // For regular (non-intrinsic) loads/stores, this is set to -1. For
441 // intrinsic loads/stores, the id is retrieved from the corresponding
442 // field in the MemIntrinsicInfo structure. That field contains
443 // non-negative values only.
448 bool processNode(DomTreeNode *Node);
450 Value *getOrCreateResult(Value *Inst, Type *ExpectedType) const {
451 if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
453 else if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
454 return SI->getValueOperand();
455 assert(isa<IntrinsicInst>(Inst) && "Instruction not supported");
456 return TTI.getOrCreateResultFromMemIntrinsic(cast<IntrinsicInst>(Inst),
462 bool EarlyCSE::processNode(DomTreeNode *Node) {
463 BasicBlock *BB = Node->getBlock();
465 // If this block has a single predecessor, then the predecessor is the parent
466 // of the domtree node and all of the live out memory values are still current
467 // in this block. If this block has multiple predecessors, then they could
468 // have invalidated the live-out memory values of our parent value. For now,
469 // just be conservative and invalidate memory if this block has multiple
471 if (!BB->getSinglePredecessor())
474 /// LastStore - Keep track of the last non-volatile store that we saw... for
475 /// as long as there in no instruction that reads memory. If we see a store
476 /// to the same location, we delete the dead store. This zaps trivial dead
477 /// stores which can occur in bitfield code among other things.
478 Instruction *LastStore = nullptr;
480 bool Changed = false;
482 // See if any instructions in the block can be eliminated. If so, do it. If
483 // not, add them to AvailableValues.
484 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
485 Instruction *Inst = I++;
487 // Dead instructions should just be removed.
488 if (isInstructionTriviallyDead(Inst, &TLI)) {
489 DEBUG(dbgs() << "EarlyCSE DCE: " << *Inst << '\n');
490 Inst->eraseFromParent();
496 // Skip assume intrinsics, they don't really have side effects (although
497 // they're marked as such to ensure preservation of control dependencies),
498 // and this pass will not disturb any of the assumption's control
500 if (match(Inst, m_Intrinsic<Intrinsic::assume>())) {
501 DEBUG(dbgs() << "EarlyCSE skipping assumption: " << *Inst << '\n');
505 // If the instruction can be simplified (e.g. X+0 = X) then replace it with
506 // its simpler value.
507 if (Value *V = SimplifyInstruction(Inst, DL, &TLI, &DT, &AC)) {
508 DEBUG(dbgs() << "EarlyCSE Simplify: " << *Inst << " to: " << *V << '\n');
509 Inst->replaceAllUsesWith(V);
510 Inst->eraseFromParent();
516 // If this is a simple instruction that we can value number, process it.
517 if (SimpleValue::canHandle(Inst)) {
518 // See if the instruction has an available value. If so, use it.
519 if (Value *V = AvailableValues.lookup(Inst)) {
520 DEBUG(dbgs() << "EarlyCSE CSE: " << *Inst << " to: " << *V << '\n');
521 Inst->replaceAllUsesWith(V);
522 Inst->eraseFromParent();
528 // Otherwise, just remember that this value is available.
529 AvailableValues.insert(Inst, Inst);
533 ParseMemoryInst MemInst(Inst, TTI);
534 // If this is a non-volatile load, process it.
535 if (MemInst.isValid() && MemInst.isLoad()) {
536 // Ignore volatile loads.
537 if (MemInst.isVolatile()) {
542 // If we have an available version of this load, and if it is the right
543 // generation, replace this instruction.
544 std::pair<Value *, unsigned> InVal =
545 AvailableLoads.lookup(MemInst.getPtr());
546 if (InVal.first != nullptr && InVal.second == CurrentGeneration) {
547 Value *Op = getOrCreateResult(InVal.first, Inst->getType());
549 DEBUG(dbgs() << "EarlyCSE CSE LOAD: " << *Inst
550 << " to: " << *InVal.first << '\n');
551 if (!Inst->use_empty())
552 Inst->replaceAllUsesWith(Op);
553 Inst->eraseFromParent();
560 // Otherwise, remember that we have this instruction.
561 AvailableLoads.insert(MemInst.getPtr(), std::pair<Value *, unsigned>(
562 Inst, CurrentGeneration));
567 // If this instruction may read from memory, forget LastStore.
568 // Load/store intrinsics will indicate both a read and a write to
569 // memory. The target may override this (e.g. so that a store intrinsic
570 // does not read from memory, and thus will be treated the same as a
571 // regular store for commoning purposes).
572 if (Inst->mayReadFromMemory() &&
573 !(MemInst.isValid() && !MemInst.mayReadFromMemory()))
576 // If this is a read-only call, process it.
577 if (CallValue::canHandle(Inst)) {
578 // If we have an available version of this call, and if it is the right
579 // generation, replace this instruction.
580 std::pair<Value *, unsigned> InVal = AvailableCalls.lookup(Inst);
581 if (InVal.first != nullptr && InVal.second == CurrentGeneration) {
582 DEBUG(dbgs() << "EarlyCSE CSE CALL: " << *Inst
583 << " to: " << *InVal.first << '\n');
584 if (!Inst->use_empty())
585 Inst->replaceAllUsesWith(InVal.first);
586 Inst->eraseFromParent();
592 // Otherwise, remember that we have this instruction.
593 AvailableCalls.insert(
594 Inst, std::pair<Value *, unsigned>(Inst, CurrentGeneration));
598 // Okay, this isn't something we can CSE at all. Check to see if it is
599 // something that could modify memory. If so, our available memory values
600 // cannot be used so bump the generation count.
601 if (Inst->mayWriteToMemory()) {
604 if (MemInst.isValid() && MemInst.isStore()) {
605 // We do a trivial form of DSE if there are two stores to the same
606 // location with no intervening loads. Delete the earlier store.
608 ParseMemoryInst LastStoreMemInst(LastStore, TTI);
609 if (LastStoreMemInst.isMatchingMemLoc(MemInst)) {
610 DEBUG(dbgs() << "EarlyCSE DEAD STORE: " << *LastStore
611 << " due to: " << *Inst << '\n');
612 LastStore->eraseFromParent();
617 // fallthrough - we can exploit information about this store
620 // Okay, we just invalidated anything we knew about loaded values. Try
621 // to salvage *something* by remembering that the stored value is a live
622 // version of the pointer. It is safe to forward from volatile stores
623 // to non-volatile loads, so we don't have to check for volatility of
625 AvailableLoads.insert(MemInst.getPtr(), std::pair<Value *, unsigned>(
626 Inst, CurrentGeneration));
628 // Remember that this was the last store we saw for DSE.
629 if (!MemInst.isVolatile())
638 bool EarlyCSE::run() {
639 // Note, deque is being used here because there is significant performance
640 // gains over vector when the container becomes very large due to the
641 // specific access patterns. For more information see the mailing list
642 // discussion on this:
643 // http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120116/135228.html
644 std::deque<StackNode *> nodesToProcess;
646 bool Changed = false;
648 // Process the root node.
649 nodesToProcess.push_back(new StackNode(
650 AvailableValues, AvailableLoads, AvailableCalls, CurrentGeneration,
651 DT.getRootNode(), DT.getRootNode()->begin(), DT.getRootNode()->end()));
653 // Save the current generation.
654 unsigned LiveOutGeneration = CurrentGeneration;
656 // Process the stack.
657 while (!nodesToProcess.empty()) {
658 // Grab the first item off the stack. Set the current generation, remove
659 // the node from the stack, and process it.
660 StackNode *NodeToProcess = nodesToProcess.back();
662 // Initialize class members.
663 CurrentGeneration = NodeToProcess->currentGeneration();
665 // Check if the node needs to be processed.
666 if (!NodeToProcess->isProcessed()) {
668 Changed |= processNode(NodeToProcess->node());
669 NodeToProcess->childGeneration(CurrentGeneration);
670 NodeToProcess->process();
671 } else if (NodeToProcess->childIter() != NodeToProcess->end()) {
672 // Push the next child onto the stack.
673 DomTreeNode *child = NodeToProcess->nextChild();
674 nodesToProcess.push_back(
675 new StackNode(AvailableValues, AvailableLoads, AvailableCalls,
676 NodeToProcess->childGeneration(), child, child->begin(),
679 // It has been processed, and there are no more children to process,
680 // so delete it and pop it off the stack.
681 delete NodeToProcess;
682 nodesToProcess.pop_back();
684 } // while (!nodes...)
686 // Reset the current generation.
687 CurrentGeneration = LiveOutGeneration;
693 /// \brief A simple and fast domtree-based CSE pass.
695 /// This pass does a simple depth-first walk over the dominator tree,
696 /// eliminating trivially redundant instructions and using instsimplify to
697 /// canonicalize things as it goes. It is intended to be fast and catch obvious
698 /// cases so that instcombine and other passes are more effective. It is
699 /// expected that a later pass of GVN will catch the interesting/hard cases.
700 class EarlyCSELegacyPass : public FunctionPass {
704 EarlyCSELegacyPass() : FunctionPass(ID) {
705 initializeEarlyCSELegacyPassPass(*PassRegistry::getPassRegistry());
708 bool runOnFunction(Function &F) override {
709 if (skipOptnoneFunction(F))
712 DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
713 auto *DL = DLP ? &DLP->getDataLayout() : nullptr;
714 auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
715 auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI();
716 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
717 auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
719 EarlyCSE CSE(F, DL, TLI, TTI, DT, AC);
724 void getAnalysisUsage(AnalysisUsage &AU) const override {
725 AU.addRequired<AssumptionCacheTracker>();
726 AU.addRequired<DominatorTreeWrapperPass>();
727 AU.addRequired<TargetLibraryInfoWrapperPass>();
728 AU.addRequired<TargetTransformInfoWrapperPass>();
729 AU.setPreservesCFG();
734 char EarlyCSELegacyPass::ID = 0;
736 FunctionPass *llvm::createEarlyCSEPass() { return new EarlyCSELegacyPass(); }
738 INITIALIZE_PASS_BEGIN(EarlyCSELegacyPass, "early-cse", "Early CSE", false,
740 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
741 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
742 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
743 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
744 INITIALIZE_PASS_END(EarlyCSELegacyPass, "early-cse", "Early CSE", false, false)