//
//===----------------------------------------------------------------------===//
-#include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Scalar/EarlyCSE.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/ScopedHashTable.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/RecyclingAllocator.h"
-#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include <deque>
using namespace llvm;
STATISTIC(NumCSECall, "Number of call instructions CSE'd");
STATISTIC(NumDSE, "Number of trivial dead stores removed");
-static unsigned getHash(const void *V) {
- return DenseMapInfo<const void*>::getHashValue(V);
-}
-
//===----------------------------------------------------------------------===//
// SimpleValue
//===----------------------------------------------------------------------===//
unsigned DenseMapInfo<CallValue>::getHashValue(CallValue Val) {
Instruction *Inst = Val.Inst;
- // Hash in all of the operands as pointers.
- unsigned Res = 0;
- for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i) {
- assert(!Inst->getOperand(i)->getType()->isMetadataTy() &&
- "Cannot value number calls with metadata operands");
- Res ^= getHash(Inst->getOperand(i)) << (i & 0xF);
- }
-
- // Mix in the opcode.
- return (Res << 1) ^ Inst->getOpcode();
+ // Hash all of the operands as pointers and mix in the opcode.
+ return hash_combine(
+ Inst->getOpcode(),
+ hash_combine_range(Inst->value_op_begin(), Inst->value_op_end()));
}
bool DenseMapInfo<CallValue>::isEqual(CallValue LHS, CallValue RHS) {
}
//===----------------------------------------------------------------------===//
-// EarlyCSE pass.
+// EarlyCSE implementation
//===----------------------------------------------------------------------===//
namespace {
-
/// \brief A simple and fast domtree-based CSE pass.
///
/// This pass does a simple depth-first walk over the dominator tree,
/// canonicalize things as it goes. It is intended to be fast and catch obvious
/// cases so that instcombine and other passes are more effective. It is
/// expected that a later pass of GVN will catch the interesting/hard cases.
-class EarlyCSE : public FunctionPass {
+class EarlyCSE {
public:
- const DataLayout *DL;
- const TargetLibraryInfo *TLI;
- const TargetTransformInfo *TTI;
- DominatorTree *DT;
- AssumptionCache *AC;
+ const TargetLibraryInfo &TLI;
+ const TargetTransformInfo &TTI;
+ DominatorTree &DT;
+ AssumptionCache &AC;
typedef RecyclingAllocator<
BumpPtrAllocator, ScopedHashTableVal<SimpleValue, Value *>> AllocatorTy;
typedef ScopedHashTable<SimpleValue, Value *, DenseMapInfo<SimpleValue>,
/// As we walk down the domtree, we look to see if instructions are in this:
/// if so, we replace them with what we find, otherwise we insert them so
/// that dominated values can succeed in their lookup.
- ScopedHTType *AvailableValues;
+ ScopedHTType AvailableValues;
- /// \brief A scoped hash table of the current values of loads.
+ /// A scoped hash table of the current values of previously encounted memory
+ /// locations.
///
- /// This allows us to get efficient access to dominating loads when we have
- /// a fully redundant load. In addition to the most recent load, we keep
- /// track of a generation count of the read, which is compared against the
- /// current generation count. The current generation count is incremented
+ /// This allows us to get efficient access to dominating loads or stores when
+ /// we have a fully redundant load. In addition to the most recent load, we
+ /// keep track of a generation count of the read, which is compared against
+ /// the current generation count. The current generation count is incremented
/// after every possibly writing memory operation, which ensures that we only
- /// CSE loads with other loads that have no intervening store.
- typedef RecyclingAllocator<
- BumpPtrAllocator,
- ScopedHashTableVal<Value *, std::pair<Value *, unsigned>>>
+ /// CSE loads with other loads that have no intervening store. Ordering
+ /// events (such as fences or atomic instructions) increment the generation
+ /// count as well; essentially, we model these as writes to all possible
+ /// locations. Note that atomic and/or volatile loads and stores can be
+ /// present the table; it is the responsibility of the consumer to inspect
+ /// the atomicity/volatility if needed.
+ struct LoadValue {
+ Value *Data;
+ unsigned Generation;
+ int MatchingId;
+ bool IsAtomic;
+ LoadValue()
+ : Data(nullptr), Generation(0), MatchingId(-1), IsAtomic(false) {}
+ LoadValue(Value *Data, unsigned Generation, unsigned MatchingId,
+ bool IsAtomic)
+ : Data(Data), Generation(Generation), MatchingId(MatchingId),
+ IsAtomic(IsAtomic) {}
+ };
+ typedef RecyclingAllocator<BumpPtrAllocator,
+ ScopedHashTableVal<Value *, LoadValue>>
LoadMapAllocator;
- typedef ScopedHashTable<Value *, std::pair<Value *, unsigned>,
- DenseMapInfo<Value *>, LoadMapAllocator> LoadHTType;
- LoadHTType *AvailableLoads;
+ typedef ScopedHashTable<Value *, LoadValue, DenseMapInfo<Value *>,
+ LoadMapAllocator> LoadHTType;
+ LoadHTType AvailableLoads;
/// \brief A scoped hash table of the current values of read-only call
/// values.
///
/// It uses the same generation count as loads.
typedef ScopedHashTable<CallValue, std::pair<Value *, unsigned>> CallHTType;
- CallHTType *AvailableCalls;
+ CallHTType AvailableCalls;
/// \brief This is the current generation of the memory value.
unsigned CurrentGeneration;
- static char ID;
- explicit EarlyCSE() : FunctionPass(ID) {
- initializeEarlyCSEPass(*PassRegistry::getPassRegistry());
- }
+ /// \brief Set up the EarlyCSE runner for a particular function.
+ EarlyCSE(const TargetLibraryInfo &TLI, const TargetTransformInfo &TTI,
+ DominatorTree &DT, AssumptionCache &AC)
+ : TLI(TLI), TTI(TTI), DT(DT), AC(AC), CurrentGeneration(0) {}
- bool runOnFunction(Function &F) override;
+ bool run();
private:
// Almost a POD, but needs to call the constructors for the scoped hash
// scope gets popped when the NodeScope is destroyed.
class NodeScope {
public:
- NodeScope(ScopedHTType *availableValues, LoadHTType *availableLoads,
- CallHTType *availableCalls)
- : Scope(*availableValues), LoadScope(*availableLoads),
- CallScope(*availableCalls) {}
+ NodeScope(ScopedHTType &AvailableValues, LoadHTType &AvailableLoads,
+ CallHTType &AvailableCalls)
+ : Scope(AvailableValues), LoadScope(AvailableLoads),
+ CallScope(AvailableCalls) {}
private:
- NodeScope(const NodeScope &) LLVM_DELETED_FUNCTION;
- void operator=(const NodeScope &) LLVM_DELETED_FUNCTION;
+ NodeScope(const NodeScope &) = delete;
+ void operator=(const NodeScope &) = delete;
ScopedHTType::ScopeTy Scope;
LoadHTType::ScopeTy LoadScope;
// children do not need to be store spearately.
class StackNode {
public:
- StackNode(ScopedHTType *availableValues, LoadHTType *availableLoads,
- CallHTType *availableCalls, unsigned cg, DomTreeNode *n,
+ StackNode(ScopedHTType &AvailableValues, LoadHTType &AvailableLoads,
+ CallHTType &AvailableCalls, unsigned cg, DomTreeNode *n,
DomTreeNode::iterator child, DomTreeNode::iterator end)
: CurrentGeneration(cg), ChildGeneration(cg), Node(n), ChildIter(child),
- EndIter(end), Scopes(availableValues, availableLoads, availableCalls),
+ EndIter(end), Scopes(AvailableValues, AvailableLoads, AvailableCalls),
Processed(false) {}
// Accessors.
void process() { Processed = true; }
private:
- StackNode(const StackNode &) LLVM_DELETED_FUNCTION;
- void operator=(const StackNode &) LLVM_DELETED_FUNCTION;
+ StackNode(const StackNode &) = delete;
+ void operator=(const StackNode &) = delete;
// Members.
unsigned CurrentGeneration;
/// stores and intrinsic loads and stores defined by the target.
class ParseMemoryInst {
public:
- ParseMemoryInst(Instruction *Inst, const TargetTransformInfo *TTI)
- : Load(false), Store(false), Vol(false), MayReadFromMemory(false),
- MayWriteToMemory(false), MatchingId(-1), Ptr(nullptr) {
- MayReadFromMemory = Inst->mayReadFromMemory();
- MayWriteToMemory = Inst->mayWriteToMemory();
- if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
- MemIntrinsicInfo Info;
- if (!TTI->getTgtMemIntrinsic(II, Info))
- return;
- if (Info.NumMemRefs == 1) {
- Store = Info.WriteMem;
- Load = Info.ReadMem;
- MatchingId = Info.MatchingId;
- MayReadFromMemory = Info.ReadMem;
- MayWriteToMemory = Info.WriteMem;
- Vol = Info.Vol;
- Ptr = Info.PtrVal;
- }
- } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
- Load = true;
- Vol = !LI->isSimple();
- Ptr = LI->getPointerOperand();
+ ParseMemoryInst(Instruction *Inst, const TargetTransformInfo &TTI)
+ : IsTargetMemInst(false), Inst(Inst) {
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst))
+ if (TTI.getTgtMemIntrinsic(II, Info) && Info.NumMemRefs == 1)
+ IsTargetMemInst = true;
+ }
+ bool isLoad() const {
+ if (IsTargetMemInst) return Info.ReadMem;
+ return isa<LoadInst>(Inst);
+ }
+ bool isStore() const {
+ if (IsTargetMemInst) return Info.WriteMem;
+ return isa<StoreInst>(Inst);
+ }
+ bool isAtomic() const {
+ if (IsTargetMemInst) {
+ assert(Info.IsSimple && "need to refine IsSimple in TTI");
+ return false;
+ }
+ return Inst->isAtomic();
+ }
+ bool isUnordered() const {
+ if (IsTargetMemInst) {
+ assert(Info.IsSimple && "need to refine IsSimple in TTI");
+ return true;
+ }
+ if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
+ return LI->isUnordered();
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ return SI->isUnordered();
+ }
+ // Conservative answer
+ return !Inst->isAtomic();
+ }
+
+ bool isVolatile() const {
+ if (IsTargetMemInst) {
+ assert(Info.IsSimple && "need to refine IsSimple in TTI");
+ return false;
+ }
+ if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
+ return LI->isVolatile();
} else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- Store = true;
- Vol = !SI->isSimple();
- Ptr = SI->getPointerOperand();
+ return SI->isVolatile();
}
+ // Conservative answer
+ return true;
}
- bool isLoad() { return Load; }
- bool isStore() { return Store; }
- bool isVolatile() { return Vol; }
- bool isMatchingMemLoc(const ParseMemoryInst &Inst) {
- return Ptr == Inst.Ptr && MatchingId == Inst.MatchingId;
+
+
+ bool isMatchingMemLoc(const ParseMemoryInst &Inst) const {
+ return (getPointerOperand() == Inst.getPointerOperand() &&
+ getMatchingId() == Inst.getMatchingId());
}
- bool isValid() { return Ptr != nullptr; }
- int getMatchingId() { return MatchingId; }
- Value *getPtr() { return Ptr; }
- bool mayReadFromMemory() { return MayReadFromMemory; }
- bool mayWriteToMemory() { return MayWriteToMemory; }
+ bool isValid() const { return getPointerOperand() != nullptr; }
- private:
- bool Load;
- bool Store;
- bool Vol;
- bool MayReadFromMemory;
- bool MayWriteToMemory;
// For regular (non-intrinsic) loads/stores, this is set to -1. For
// intrinsic loads/stores, the id is retrieved from the corresponding
// field in the MemIntrinsicInfo structure. That field contains
// non-negative values only.
- int MatchingId;
- Value *Ptr;
+ int getMatchingId() const {
+ if (IsTargetMemInst) return Info.MatchingId;
+ return -1;
+ }
+ Value *getPointerOperand() const {
+ if (IsTargetMemInst) return Info.PtrVal;
+ if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
+ return LI->getPointerOperand();
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ return SI->getPointerOperand();
+ }
+ return nullptr;
+ }
+ bool mayReadFromMemory() const {
+ if (IsTargetMemInst) return Info.ReadMem;
+ return Inst->mayReadFromMemory();
+ }
+ bool mayWriteToMemory() const {
+ if (IsTargetMemInst) return Info.WriteMem;
+ return Inst->mayWriteToMemory();
+ }
+
+ private:
+ bool IsTargetMemInst;
+ MemIntrinsicInfo Info;
+ Instruction *Inst;
};
bool processNode(DomTreeNode *Node);
- void getAnalysisUsage(AnalysisUsage &AU) const override {
- AU.addRequired<AssumptionCacheTracker>();
- AU.addRequired<DominatorTreeWrapperPass>();
- AU.addRequired<TargetLibraryInfoWrapperPass>();
- AU.addRequired<TargetTransformInfo>();
- AU.setPreservesCFG();
- }
-
Value *getOrCreateResult(Value *Inst, Type *ExpectedType) const {
if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
return LI;
else if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
return SI->getValueOperand();
assert(isa<IntrinsicInst>(Inst) && "Instruction not supported");
- return TTI->getOrCreateResultFromMemIntrinsic(cast<IntrinsicInst>(Inst),
- ExpectedType);
+ return TTI.getOrCreateResultFromMemIntrinsic(cast<IntrinsicInst>(Inst),
+ ExpectedType);
}
};
}
-char EarlyCSE::ID = 0;
-
-FunctionPass *llvm::createEarlyCSEPass() { return new EarlyCSE(); }
-
-INITIALIZE_PASS_BEGIN(EarlyCSE, "early-cse", "Early CSE", false, false)
-INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
-INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
-INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
-INITIALIZE_PASS_END(EarlyCSE, "early-cse", "Early CSE", false, false)
-
bool EarlyCSE::processNode(DomTreeNode *Node) {
BasicBlock *BB = Node->getBlock();
if (!BB->getSinglePredecessor())
++CurrentGeneration;
+ // If this node has a single predecessor which ends in a conditional branch,
+ // we can infer the value of the branch condition given that we took this
+ // path. We need the single predeccesor to ensure there's not another path
+ // which reaches this block where the condition might hold a different
+ // value. Since we're adding this to the scoped hash table (like any other
+ // def), it will have been popped if we encounter a future merge block.
+ if (BasicBlock *Pred = BB->getSinglePredecessor())
+ if (auto *BI = dyn_cast<BranchInst>(Pred->getTerminator()))
+ if (BI->isConditional())
+ if (auto *CondInst = dyn_cast<Instruction>(BI->getCondition()))
+ if (SimpleValue::canHandle(CondInst)) {
+ assert(BI->getSuccessor(0) == BB || BI->getSuccessor(1) == BB);
+ auto *ConditionalConstant = (BI->getSuccessor(0) == BB) ?
+ ConstantInt::getTrue(BB->getContext()) :
+ ConstantInt::getFalse(BB->getContext());
+ AvailableValues.insert(CondInst, ConditionalConstant);
+ DEBUG(dbgs() << "EarlyCSE CVP: Add conditional value for '"
+ << CondInst->getName() << "' as " << *ConditionalConstant
+ << " in " << BB->getName() << "\n");
+ // Replace all dominated uses with the known value
+ replaceDominatedUsesWith(CondInst, ConditionalConstant, DT,
+ BasicBlockEdge(Pred, BB));
+ }
+
/// LastStore - Keep track of the last non-volatile store that we saw... for
/// as long as there in no instruction that reads memory. If we see a store
/// to the same location, we delete the dead store. This zaps trivial dead
Instruction *LastStore = nullptr;
bool Changed = false;
+ const DataLayout &DL = BB->getModule()->getDataLayout();
// See if any instructions in the block can be eliminated. If so, do it. If
// not, add them to AvailableValues.
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) {
- Instruction *Inst = I++;
+ Instruction *Inst = &*I++;
// Dead instructions should just be removed.
- if (isInstructionTriviallyDead(Inst, TLI)) {
+ if (isInstructionTriviallyDead(Inst, &TLI)) {
DEBUG(dbgs() << "EarlyCSE DCE: " << *Inst << '\n');
Inst->eraseFromParent();
Changed = true;
// If the instruction can be simplified (e.g. X+0 = X) then replace it with
// its simpler value.
- if (Value *V = SimplifyInstruction(Inst, DL, TLI, DT, AC)) {
+ if (Value *V = SimplifyInstruction(Inst, DL, &TLI, &DT, &AC)) {
DEBUG(dbgs() << "EarlyCSE Simplify: " << *Inst << " to: " << *V << '\n');
Inst->replaceAllUsesWith(V);
Inst->eraseFromParent();
// If this is a simple instruction that we can value number, process it.
if (SimpleValue::canHandle(Inst)) {
// See if the instruction has an available value. If so, use it.
- if (Value *V = AvailableValues->lookup(Inst)) {
+ if (Value *V = AvailableValues.lookup(Inst)) {
DEBUG(dbgs() << "EarlyCSE CSE: " << *Inst << " to: " << *V << '\n');
Inst->replaceAllUsesWith(V);
Inst->eraseFromParent();
}
// Otherwise, just remember that this value is available.
- AvailableValues->insert(Inst, Inst);
+ AvailableValues.insert(Inst, Inst);
continue;
}
ParseMemoryInst MemInst(Inst, TTI);
// If this is a non-volatile load, process it.
if (MemInst.isValid() && MemInst.isLoad()) {
- // Ignore volatile loads.
- if (MemInst.isVolatile()) {
+ // (conservatively) we can't peak past the ordering implied by this
+ // operation, but we can add this load to our set of available values
+ if (MemInst.isVolatile() || !MemInst.isUnordered()) {
LastStore = nullptr;
- continue;
+ ++CurrentGeneration;
}
// If we have an available version of this load, and if it is the right
// generation, replace this instruction.
- std::pair<Value *, unsigned> InVal =
- AvailableLoads->lookup(MemInst.getPtr());
- if (InVal.first != nullptr && InVal.second == CurrentGeneration) {
- Value *Op = getOrCreateResult(InVal.first, Inst->getType());
+ LoadValue InVal = AvailableLoads.lookup(MemInst.getPointerOperand());
+ if (InVal.Data != nullptr && InVal.Generation == CurrentGeneration &&
+ InVal.MatchingId == MemInst.getMatchingId() &&
+ // We don't yet handle removing loads with ordering of any kind.
+ !MemInst.isVolatile() && MemInst.isUnordered() &&
+ // We can't replace an atomic load with one which isn't also atomic.
+ InVal.IsAtomic >= MemInst.isAtomic()) {
+ Value *Op = getOrCreateResult(InVal.Data, Inst->getType());
if (Op != nullptr) {
DEBUG(dbgs() << "EarlyCSE CSE LOAD: " << *Inst
- << " to: " << *InVal.first << '\n');
+ << " to: " << *InVal.Data << '\n');
if (!Inst->use_empty())
Inst->replaceAllUsesWith(Op);
Inst->eraseFromParent();
}
// Otherwise, remember that we have this instruction.
- AvailableLoads->insert(MemInst.getPtr(), std::pair<Value *, unsigned>(
- Inst, CurrentGeneration));
+ AvailableLoads.insert(
+ MemInst.getPointerOperand(),
+ LoadValue(Inst, CurrentGeneration, MemInst.getMatchingId(),
+ MemInst.isAtomic()));
LastStore = nullptr;
continue;
}
if (CallValue::canHandle(Inst)) {
// If we have an available version of this call, and if it is the right
// generation, replace this instruction.
- std::pair<Value *, unsigned> InVal = AvailableCalls->lookup(Inst);
+ std::pair<Value *, unsigned> InVal = AvailableCalls.lookup(Inst);
if (InVal.first != nullptr && InVal.second == CurrentGeneration) {
DEBUG(dbgs() << "EarlyCSE CSE CALL: " << *Inst
<< " to: " << *InVal.first << '\n');
}
// Otherwise, remember that we have this instruction.
- AvailableCalls->insert(
+ AvailableCalls.insert(
Inst, std::pair<Value *, unsigned>(Inst, CurrentGeneration));
continue;
}
+ // A release fence requires that all stores complete before it, but does
+ // not prevent the reordering of following loads 'before' the fence. As a
+ // result, we don't need to consider it as writing to memory and don't need
+ // to advance the generation. We do need to prevent DSE across the fence,
+ // but that's handled above.
+ if (FenceInst *FI = dyn_cast<FenceInst>(Inst))
+ if (FI->getOrdering() == Release) {
+ assert(Inst->mayReadFromMemory() && "relied on to prevent DSE above");
+ continue;
+ }
+
+ // write back DSE - If we write back the same value we just loaded from
+ // the same location and haven't passed any intervening writes or ordering
+ // operations, we can remove the write. The primary benefit is in allowing
+ // the available load table to remain valid and value forward past where
+ // the store originally was.
+ if (MemInst.isValid() && MemInst.isStore()) {
+ LoadValue InVal = AvailableLoads.lookup(MemInst.getPointerOperand());
+ if (InVal.Data &&
+ InVal.Data == getOrCreateResult(Inst, InVal.Data->getType()) &&
+ InVal.Generation == CurrentGeneration &&
+ InVal.MatchingId == MemInst.getMatchingId() &&
+ // We don't yet handle removing stores with ordering of any kind.
+ !MemInst.isVolatile() && MemInst.isUnordered()) {
+ assert((!LastStore ||
+ ParseMemoryInst(LastStore, TTI).getPointerOperand() ==
+ MemInst.getPointerOperand()) &&
+ "can't have an intervening store!");
+ DEBUG(dbgs() << "EarlyCSE DSE (writeback): " << *Inst << '\n');
+ Inst->eraseFromParent();
+ Changed = true;
+ ++NumDSE;
+ // We can avoid incrementing the generation count since we were able
+ // to eliminate this store.
+ continue;
+ }
+ }
+
// Okay, this isn't something we can CSE at all. Check to see if it is
// something that could modify memory. If so, our available memory values
// cannot be used so bump the generation count.
if (MemInst.isValid() && MemInst.isStore()) {
// We do a trivial form of DSE if there are two stores to the same
// location with no intervening loads. Delete the earlier store.
+ // At the moment, we don't remove ordered stores, but do remove
+ // unordered atomic stores. There's no special requirement (for
+ // unordered atomics) about removing atomic stores only in favor of
+ // other atomic stores since we we're going to execute the non-atomic
+ // one anyway and the atomic one might never have become visible.
if (LastStore) {
ParseMemoryInst LastStoreMemInst(LastStore, TTI);
+ assert(LastStoreMemInst.isUnordered() &&
+ !LastStoreMemInst.isVolatile() &&
+ "Violated invariant");
if (LastStoreMemInst.isMatchingMemLoc(MemInst)) {
DEBUG(dbgs() << "EarlyCSE DEAD STORE: " << *LastStore
<< " due to: " << *Inst << '\n');
// version of the pointer. It is safe to forward from volatile stores
// to non-volatile loads, so we don't have to check for volatility of
// the store.
- AvailableLoads->insert(MemInst.getPtr(), std::pair<Value *, unsigned>(
- Inst, CurrentGeneration));
-
- // Remember that this was the last store we saw for DSE.
- if (!MemInst.isVolatile())
+ AvailableLoads.insert(
+ MemInst.getPointerOperand(),
+ LoadValue(Inst, CurrentGeneration, MemInst.getMatchingId(),
+ MemInst.isAtomic()));
+
+ // Remember that this was the last unordered store we saw for DSE. We
+ // don't yet handle DSE on ordered or volatile stores since we don't
+ // have a good way to model the ordering requirement for following
+ // passes once the store is removed. We could insert a fence, but
+ // since fences are slightly stronger than stores in their ordering,
+ // it's not clear this is a profitable transform. Another option would
+ // be to merge the ordering with that of the post dominating store.
+ if (MemInst.isUnordered() && !MemInst.isVolatile())
LastStore = Inst;
+ else
+ LastStore = nullptr;
}
}
}
return Changed;
}
-bool EarlyCSE::runOnFunction(Function &F) {
- if (skipOptnoneFunction(F))
- return false;
-
+bool EarlyCSE::run() {
// Note, deque is being used here because there is significant performance
// gains over vector when the container becomes very large due to the
// specific access patterns. For more information see the mailing list
// discussion on this:
- // http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120116/135228.html
+ // http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20120116/135228.html
std::deque<StackNode *> nodesToProcess;
- DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
- DL = DLP ? &DLP->getDataLayout() : nullptr;
- TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
- TTI = &getAnalysis<TargetTransformInfo>();
- DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
- AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
-
- // Tables that the pass uses when walking the domtree.
- ScopedHTType AVTable;
- AvailableValues = &AVTable;
- LoadHTType LoadTable;
- AvailableLoads = &LoadTable;
- CallHTType CallTable;
- AvailableCalls = &CallTable;
-
- CurrentGeneration = 0;
bool Changed = false;
// Process the root node.
nodesToProcess.push_back(new StackNode(
AvailableValues, AvailableLoads, AvailableCalls, CurrentGeneration,
- DT->getRootNode(), DT->getRootNode()->begin(), DT->getRootNode()->end()));
+ DT.getRootNode(), DT.getRootNode()->begin(), DT.getRootNode()->end()));
// Save the current generation.
unsigned LiveOutGeneration = CurrentGeneration;
return Changed;
}
+
+PreservedAnalyses EarlyCSEPass::run(Function &F,
+ AnalysisManager<Function> *AM) {
+ auto &TLI = AM->getResult<TargetLibraryAnalysis>(F);
+ auto &TTI = AM->getResult<TargetIRAnalysis>(F);
+ auto &DT = AM->getResult<DominatorTreeAnalysis>(F);
+ auto &AC = AM->getResult<AssumptionAnalysis>(F);
+
+ EarlyCSE CSE(TLI, TTI, DT, AC);
+
+ if (!CSE.run())
+ return PreservedAnalyses::all();
+
+ // CSE preserves the dominator tree because it doesn't mutate the CFG.
+ // FIXME: Bundle this with other CFG-preservation.
+ PreservedAnalyses PA;
+ PA.preserve<DominatorTreeAnalysis>();
+ return PA;
+}
+
+namespace {
+/// \brief A simple and fast domtree-based CSE pass.
+///
+/// This pass does a simple depth-first walk over the dominator tree,
+/// eliminating trivially redundant instructions and using instsimplify to
+/// canonicalize things as it goes. It is intended to be fast and catch obvious
+/// cases so that instcombine and other passes are more effective. It is
+/// expected that a later pass of GVN will catch the interesting/hard cases.
+class EarlyCSELegacyPass : public FunctionPass {
+public:
+ static char ID;
+
+ EarlyCSELegacyPass() : FunctionPass(ID) {
+ initializeEarlyCSELegacyPassPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnFunction(Function &F) override {
+ if (skipOptnoneFunction(F))
+ return false;
+
+ auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+ auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+ auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
+
+ EarlyCSE CSE(TLI, TTI, DT, AC);
+
+ return CSE.run();
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.addRequired<AssumptionCacheTracker>();
+ AU.addRequired<DominatorTreeWrapperPass>();
+ AU.addRequired<TargetLibraryInfoWrapperPass>();
+ AU.addRequired<TargetTransformInfoWrapperPass>();
+ AU.addPreserved<GlobalsAAWrapperPass>();
+ AU.setPreservesCFG();
+ }
+};
+}
+
+char EarlyCSELegacyPass::ID = 0;
+
+FunctionPass *llvm::createEarlyCSEPass() { return new EarlyCSELegacyPass(); }
+
+INITIALIZE_PASS_BEGIN(EarlyCSELegacyPass, "early-cse", "Early CSE", false,
+ false)
+INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_END(EarlyCSELegacyPass, "early-cse", "Early CSE", false, false)
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