X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FScalar%2FEarlyCSE.cpp;h=de539d53a4f55b3adf2c07da85d42d53c3031d0c;hb=45ef74f29c3cbccc33cbf05e0c26bdc029ce997b;hp=557cd6d2b53ef81a3e3c3ce6eae12c855cc10a57;hpb=8e7f0d70c7dd3864126c746378a7b928d57f971f;p=oota-llvm.git diff --git a/lib/Transforms/Scalar/EarlyCSE.cpp b/lib/Transforms/Scalar/EarlyCSE.cpp index 557cd6d2b53..de539d53a4f 100644 --- a/lib/Transforms/Scalar/EarlyCSE.cpp +++ b/lib/Transforms/Scalar/EarlyCSE.cpp @@ -12,71 +12,76 @@ // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "early-cse" -#include "llvm/Transforms/Scalar.h" -#include "llvm/Instructions.h" -#include "llvm/Pass.h" -#include "llvm/Analysis/Dominators.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/Target/TargetData.h" -#include "llvm/Transforms/Utils/Local.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/TargetTransformInfo.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/Pass.h" #include "llvm/Support/Debug.h" #include "llvm/Support/RecyclingAllocator.h" -#include "llvm/ADT/ScopedHashTable.h" -#include "llvm/ADT/Statistic.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Transforms/Scalar.h" +#include "llvm/Transforms/Utils/Local.h" +#include using namespace llvm; +using namespace llvm::PatternMatch; -STATISTIC(NumSimplify, "Number of insts simplified or DCE'd"); -STATISTIC(NumCSE, "Number of insts CSE'd"); -STATISTIC(NumCSEMem, "Number of load and call insts CSE'd"); +#define DEBUG_TYPE "early-cse" -static unsigned getHash(const void *V) { - return DenseMapInfo::getHashValue(V); -} +STATISTIC(NumSimplify, "Number of instructions simplified or DCE'd"); +STATISTIC(NumCSE, "Number of instructions CSE'd"); +STATISTIC(NumCSELoad, "Number of load instructions CSE'd"); +STATISTIC(NumCSECall, "Number of call instructions CSE'd"); +STATISTIC(NumDSE, "Number of trivial dead stores removed"); //===----------------------------------------------------------------------===// -// SimpleValue +// SimpleValue //===----------------------------------------------------------------------===// namespace { - /// SimpleValue - Instances of this struct represent available values in the - /// scoped hash table. - struct SimpleValue { - Instruction *Inst; - - bool isSentinel() const { - return Inst == DenseMapInfo::getEmptyKey() || - Inst == DenseMapInfo::getTombstoneKey(); - } - - static bool canHandle(Instruction *Inst) { - return isa(Inst) || isa(Inst) || - isa(Inst) || isa(Inst) || - isa(Inst) || isa(Inst) || - isa(Inst) || isa(Inst) || - isa(Inst) || isa(Inst); - } - - static SimpleValue get(Instruction *I) { - SimpleValue X; X.Inst = I; - assert((X.isSentinel() || canHandle(I)) && "Inst can't be handled!"); - return X; - } - }; -} +/// \brief Struct representing the available values in the scoped hash table. +struct SimpleValue { + Instruction *Inst; -namespace llvm { -// SimpleValue is POD. -template<> struct isPodLike { - static const bool value = true; + SimpleValue(Instruction *I) : Inst(I) { + assert((isSentinel() || canHandle(I)) && "Inst can't be handled!"); + } + + bool isSentinel() const { + return Inst == DenseMapInfo::getEmptyKey() || + Inst == DenseMapInfo::getTombstoneKey(); + } + + static bool canHandle(Instruction *Inst) { + // This can only handle non-void readnone functions. + if (CallInst *CI = dyn_cast(Inst)) + return CI->doesNotAccessMemory() && !CI->getType()->isVoidTy(); + return isa(Inst) || isa(Inst) || + isa(Inst) || isa(Inst) || + isa(Inst) || isa(Inst) || + isa(Inst) || isa(Inst) || + isa(Inst) || isa(Inst); + } }; +} -template<> struct DenseMapInfo { +namespace llvm { +template <> struct DenseMapInfo { static inline SimpleValue getEmptyKey() { - return SimpleValue::get(DenseMapInfo::getEmptyKey()); + return DenseMapInfo::getEmptyKey(); } static inline SimpleValue getTombstoneKey() { - return SimpleValue::get(DenseMapInfo::getTombstoneKey()); + return DenseMapInfo::getTombstoneKey(); } static unsigned getHashValue(SimpleValue Val); static bool isEqual(SimpleValue LHS, SimpleValue RHS); @@ -85,34 +90,58 @@ template<> struct DenseMapInfo { unsigned DenseMapInfo::getHashValue(SimpleValue 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) - Res ^= getHash(Inst->getOperand(i)) << i; + if (BinaryOperator *BinOp = dyn_cast(Inst)) { + Value *LHS = BinOp->getOperand(0); + Value *RHS = BinOp->getOperand(1); + if (BinOp->isCommutative() && BinOp->getOperand(0) > BinOp->getOperand(1)) + std::swap(LHS, RHS); - if (CastInst *CI = dyn_cast(Inst)) - Res ^= getHash(CI->getType()); - else if (CmpInst *CI = dyn_cast(Inst)) - Res ^= CI->getPredicate(); - else if (const ExtractValueInst *EVI = dyn_cast(Inst)) { - for (ExtractValueInst::idx_iterator I = EVI->idx_begin(), - E = EVI->idx_end(); I != E; ++I) - Res ^= *I; - } else if (const InsertValueInst *IVI = dyn_cast(Inst)) { - for (InsertValueInst::idx_iterator I = IVI->idx_begin(), - E = IVI->idx_end(); I != E; ++I) - Res ^= *I; - } else { - // nothing extra to hash in. - assert((isa(Inst) || isa(Inst) || - isa(Inst) || isa(Inst) || - isa(Inst) || isa(Inst)) && - "Invalid/unknown instruction"); + if (isa(BinOp)) { + // Hash the overflow behavior + unsigned Overflow = + BinOp->hasNoSignedWrap() * OverflowingBinaryOperator::NoSignedWrap | + BinOp->hasNoUnsignedWrap() * + OverflowingBinaryOperator::NoUnsignedWrap; + return hash_combine(BinOp->getOpcode(), Overflow, LHS, RHS); + } + + return hash_combine(BinOp->getOpcode(), LHS, RHS); } + if (CmpInst *CI = dyn_cast(Inst)) { + Value *LHS = CI->getOperand(0); + Value *RHS = CI->getOperand(1); + CmpInst::Predicate Pred = CI->getPredicate(); + if (Inst->getOperand(0) > Inst->getOperand(1)) { + std::swap(LHS, RHS); + Pred = CI->getSwappedPredicate(); + } + return hash_combine(Inst->getOpcode(), Pred, LHS, RHS); + } + + if (CastInst *CI = dyn_cast(Inst)) + return hash_combine(CI->getOpcode(), CI->getType(), CI->getOperand(0)); + + if (const ExtractValueInst *EVI = dyn_cast(Inst)) + return hash_combine(EVI->getOpcode(), EVI->getOperand(0), + hash_combine_range(EVI->idx_begin(), EVI->idx_end())); + + if (const InsertValueInst *IVI = dyn_cast(Inst)) + return hash_combine(IVI->getOpcode(), IVI->getOperand(0), + IVI->getOperand(1), + hash_combine_range(IVI->idx_begin(), IVI->idx_end())); + + assert((isa(Inst) || isa(Inst) || + isa(Inst) || isa(Inst) || + isa(Inst) || isa(Inst) || + isa(Inst)) && + "Invalid/unknown instruction"); + // Mix in the opcode. - return (Res << 1) ^ Inst->getOpcode(); + return hash_combine( + Inst->getOpcode(), + hash_combine_range(Inst->value_op_begin(), Inst->value_op_end())); } bool DenseMapInfo::isEqual(SimpleValue LHS, SimpleValue RHS) { @@ -120,192 +149,383 @@ bool DenseMapInfo::isEqual(SimpleValue LHS, SimpleValue RHS) { if (LHS.isSentinel() || RHS.isSentinel()) return LHSI == RHSI; - - if (LHSI->getOpcode() != RHSI->getOpcode()) return false; - return LHSI->isIdenticalTo(RHSI); + + if (LHSI->getOpcode() != RHSI->getOpcode()) + return false; + if (LHSI->isIdenticalTo(RHSI)) + return true; + + // If we're not strictly identical, we still might be a commutable instruction + if (BinaryOperator *LHSBinOp = dyn_cast(LHSI)) { + if (!LHSBinOp->isCommutative()) + return false; + + assert(isa(RHSI) && + "same opcode, but different instruction type?"); + BinaryOperator *RHSBinOp = cast(RHSI); + + // Check overflow attributes + if (isa(LHSBinOp)) { + assert(isa(RHSBinOp) && + "same opcode, but different operator type?"); + if (LHSBinOp->hasNoUnsignedWrap() != RHSBinOp->hasNoUnsignedWrap() || + LHSBinOp->hasNoSignedWrap() != RHSBinOp->hasNoSignedWrap()) + return false; + } + + // Commuted equality + return LHSBinOp->getOperand(0) == RHSBinOp->getOperand(1) && + LHSBinOp->getOperand(1) == RHSBinOp->getOperand(0); + } + if (CmpInst *LHSCmp = dyn_cast(LHSI)) { + assert(isa(RHSI) && + "same opcode, but different instruction type?"); + CmpInst *RHSCmp = cast(RHSI); + // Commuted equality + return LHSCmp->getOperand(0) == RHSCmp->getOperand(1) && + LHSCmp->getOperand(1) == RHSCmp->getOperand(0) && + LHSCmp->getSwappedPredicate() == RHSCmp->getPredicate(); + } + + return false; } //===----------------------------------------------------------------------===// -// MemoryValue +// CallValue //===----------------------------------------------------------------------===// namespace { - /// MemoryValue - Instances of this struct represent available load and call - /// values in the scoped hash table. - struct MemoryValue { - Instruction *Inst; - - bool isSentinel() const { - return Inst == DenseMapInfo::getEmptyKey() || - Inst == DenseMapInfo::getTombstoneKey(); - } - - static bool canHandle(Instruction *Inst) { - if (LoadInst *LI = dyn_cast(Inst)) - return !LI->isVolatile(); - if (CallInst *CI = dyn_cast(Inst)) - return CI->onlyReadsMemory(); +/// \brief Struct representing the available call values in the scoped hash +/// table. +struct CallValue { + Instruction *Inst; + + CallValue(Instruction *I) : Inst(I) { + assert((isSentinel() || canHandle(I)) && "Inst can't be handled!"); + } + + bool isSentinel() const { + return Inst == DenseMapInfo::getEmptyKey() || + Inst == DenseMapInfo::getTombstoneKey(); + } + + static bool canHandle(Instruction *Inst) { + // Don't value number anything that returns void. + if (Inst->getType()->isVoidTy()) return false; - } - - static MemoryValue get(Instruction *I) { - MemoryValue X; X.Inst = I; - assert((X.isSentinel() || canHandle(I)) && "Inst can't be handled!"); - return X; - } - }; + + CallInst *CI = dyn_cast(Inst); + if (!CI || !CI->onlyReadsMemory()) + return false; + return true; + } +}; } namespace llvm { - // MemoryValue is POD. - template<> struct isPodLike { - static const bool value = true; - }; - - template<> struct DenseMapInfo { - static inline MemoryValue getEmptyKey() { - return MemoryValue::get(DenseMapInfo::getEmptyKey()); - } - static inline MemoryValue getTombstoneKey() { - return MemoryValue::get(DenseMapInfo::getTombstoneKey()); - } - static unsigned getHashValue(MemoryValue Val); - static bool isEqual(MemoryValue LHS, MemoryValue RHS); - }; +template <> struct DenseMapInfo { + static inline CallValue getEmptyKey() { + return DenseMapInfo::getEmptyKey(); + } + static inline CallValue getTombstoneKey() { + return DenseMapInfo::getTombstoneKey(); + } + static unsigned getHashValue(CallValue Val); + static bool isEqual(CallValue LHS, CallValue RHS); +}; } -unsigned DenseMapInfo::getHashValue(MemoryValue Val) { + +unsigned DenseMapInfo::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) - Res ^= getHash(Inst->getOperand(i)) << i; - // 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::isEqual(MemoryValue LHS, MemoryValue RHS) { +bool DenseMapInfo::isEqual(CallValue LHS, CallValue RHS) { Instruction *LHSI = LHS.Inst, *RHSI = RHS.Inst; - if (LHS.isSentinel() || RHS.isSentinel()) return LHSI == RHSI; - - if (LHSI->getOpcode() != RHSI->getOpcode()) return false; return LHSI->isIdenticalTo(RHSI); } - //===----------------------------------------------------------------------===// -// EarlyCSE pass. +// EarlyCSE implementation //===----------------------------------------------------------------------===// namespace { - -/// EarlyCSE - 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 EarlyCSE : public FunctionPass { +/// \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 EarlyCSE { public: - const TargetData *TD; - DominatorTree *DT; - typedef RecyclingAllocator > AllocatorTy; - typedef ScopedHashTable, + const TargetLibraryInfo &TLI; + const TargetTransformInfo &TTI; + DominatorTree &DT; + AssumptionCache &AC; + typedef RecyclingAllocator< + BumpPtrAllocator, ScopedHashTableVal> AllocatorTy; + typedef ScopedHashTable, AllocatorTy> ScopedHTType; - - /// AvailableValues - This scoped hash table contains the current values of - /// all of our simple scalar expressions. 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; - - typedef ScopedHashTable > MemHTType; - /// AvailableMemValues - This scoped hash table contains the current values of - /// loads and other read-only memory values. This allows us to get efficient - /// access to dominating loads we we find 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. - MemHTType *AvailableMemValues; - - /// CurrentGeneration - This is the current generation of the memory value. + + /// \brief A scoped hash table of the current values of all of our simple + /// scalar expressions. + /// + /// 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; + + /// \brief A scoped hash table of the current values of loads. + /// + /// 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 + /// after every possibly writing memory operation, which ensures that we only + /// CSE loads with other loads that have no intervening store. + struct LoadValue { + Value *Data; + unsigned Generation; + int MatchingId; + LoadValue() : Data(nullptr), Generation(0), MatchingId(-1) {} + LoadValue(Value *Data, unsigned Generation, unsigned MatchingId) + : Data(Data), Generation(Generation), MatchingId(MatchingId) {} + }; + typedef RecyclingAllocator> + LoadMapAllocator; + typedef ScopedHashTable, + 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> CallHTType; + CallHTType AvailableCalls; + + /// \brief This is the current generation of the memory value. unsigned CurrentGeneration; - - static char ID; - explicit EarlyCSE() : FunctionPass(ID) { - initializeEarlyCSEPass(*PassRegistry::getPassRegistry()); - } - bool runOnFunction(Function &F); + /// \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 run(); private: - + // Almost a POD, but needs to call the constructors for the scoped hash + // tables so that a new scope gets pushed on. These are RAII so that the + // scope gets popped when the NodeScope is destroyed. + class NodeScope { + public: + NodeScope(ScopedHTType &AvailableValues, LoadHTType &AvailableLoads, + CallHTType &AvailableCalls) + : Scope(AvailableValues), LoadScope(AvailableLoads), + CallScope(AvailableCalls) {} + + private: + NodeScope(const NodeScope &) = delete; + void operator=(const NodeScope &) = delete; + + ScopedHTType::ScopeTy Scope; + LoadHTType::ScopeTy LoadScope; + CallHTType::ScopeTy CallScope; + }; + + // Contains all the needed information to create a stack for doing a depth + // first tranversal of the tree. This includes scopes for values, loads, and + // calls as well as the generation. There is a child iterator so that the + // children do not need to be store spearately. + class StackNode { + public: + 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), + Processed(false) {} + + // Accessors. + unsigned currentGeneration() { return CurrentGeneration; } + unsigned childGeneration() { return ChildGeneration; } + void childGeneration(unsigned generation) { ChildGeneration = generation; } + DomTreeNode *node() { return Node; } + DomTreeNode::iterator childIter() { return ChildIter; } + DomTreeNode *nextChild() { + DomTreeNode *child = *ChildIter; + ++ChildIter; + return child; + } + DomTreeNode::iterator end() { return EndIter; } + bool isProcessed() { return Processed; } + void process() { Processed = true; } + + private: + StackNode(const StackNode &) = delete; + void operator=(const StackNode &) = delete; + + // Members. + unsigned CurrentGeneration; + unsigned ChildGeneration; + DomTreeNode *Node; + DomTreeNode::iterator ChildIter; + DomTreeNode::iterator EndIter; + NodeScope Scopes; + bool Processed; + }; + + /// \brief Wrapper class to handle memory instructions, including loads, + /// 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(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(Inst)) { + Load = true; + Vol = !LI->isSimple(); + Ptr = LI->getPointerOperand(); + } else if (StoreInst *SI = dyn_cast(Inst)) { + Store = true; + Vol = !SI->isSimple(); + Ptr = SI->getPointerOperand(); + } + } + bool isLoad() const { return Load; } + bool isStore() const { return Store; } + bool isVolatile() const { return Vol; } + bool isMatchingMemLoc(const ParseMemoryInst &Inst) const { + return Ptr == Inst.Ptr && MatchingId == Inst.MatchingId; + } + bool isValid() const { return Ptr != nullptr; } + int getMatchingId() const { return MatchingId; } + Value *getPtr() const { return Ptr; } + bool mayReadFromMemory() const { return MayReadFromMemory; } + bool mayWriteToMemory() const { return MayWriteToMemory; } + + 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; + }; + bool processNode(DomTreeNode *Node); - - // This transformation requires dominator postdominator info - virtual void getAnalysisUsage(AnalysisUsage &AU) const { - AU.addRequired(); - AU.setPreservesCFG(); + + Value *getOrCreateResult(Value *Inst, Type *ExpectedType) const { + if (LoadInst *LI = dyn_cast(Inst)) + return LI; + else if (StoreInst *SI = dyn_cast(Inst)) + return SI->getValueOperand(); + assert(isa(Inst) && "Instruction not supported"); + return TTI.getOrCreateResultFromMemIntrinsic(cast(Inst), + ExpectedType); } }; } -char EarlyCSE::ID = 0; - -// createEarlyCSEPass - The public interface to this file. -FunctionPass *llvm::createEarlyCSEPass() { - return new EarlyCSE(); -} - -INITIALIZE_PASS_BEGIN(EarlyCSE, "early-cse", "Early CSE", false, false) -INITIALIZE_PASS_DEPENDENCY(DominatorTree) -INITIALIZE_PASS_END(EarlyCSE, "early-cse", "Early CSE", false, false) - bool EarlyCSE::processNode(DomTreeNode *Node) { - // Define a scope in the scoped hash table. When we are done processing this - // domtree node and recurse back up to our parent domtree node, this will pop - // off all the values we install. - ScopedHTType::ScopeTy Scope(*AvailableValues); - - // Define a scope for the memory values so that anything we add will get - // popped when we recurse back up to our parent domtree node. - MemHTType::ScopeTy MemScope(*AvailableMemValues); - BasicBlock *BB = Node->getBlock(); - + // If this block has a single predecessor, then the predecessor is the parent // of the domtree node and all of the live out memory values are still current // in this block. If this block has multiple predecessors, then they could // have invalidated the live-out memory values of our parent value. For now, // just be conservative and invalidate memory if this block has multiple // predecessors. - if (BB->getSinglePredecessor() == 0) + 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(Pred->getTerminator())) + if (BI->isConditional()) + if (auto *CondInst = dyn_cast(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 + /// stores which can occur in bitfield code among other things. + 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++; - + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;) { + Instruction *Inst = &*I++; + // Dead instructions should just be removed. - if (isInstructionTriviallyDead(Inst)) { + if (isInstructionTriviallyDead(Inst, &TLI)) { DEBUG(dbgs() << "EarlyCSE DCE: " << *Inst << '\n'); Inst->eraseFromParent(); Changed = true; ++NumSimplify; continue; } - + + // Skip assume intrinsics, they don't really have side effects (although + // they're marked as such to ensure preservation of control dependencies), + // and this pass will not disturb any of the assumption's control + // dependencies. + if (match(Inst, m_Intrinsic())) { + DEBUG(dbgs() << "EarlyCSE skipping assumption: " << *Inst << '\n'); + continue; + } + // If the instruction can be simplified (e.g. X+0 = X) then replace it with // its simpler value. - if (Value *V = SimplifyInstruction(Inst, TD, DT)) { + if (Value *V = SimplifyInstruction(Inst, DL, &TLI, &DT, &AC)) { DEBUG(dbgs() << "EarlyCSE Simplify: " << *Inst << " to: " << *V << '\n'); Inst->replaceAllUsesWith(V); Inst->eraseFromParent(); @@ -313,11 +533,11 @@ bool EarlyCSE::processNode(DomTreeNode *Node) { ++NumSimplify; continue; } - + // 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(SimpleValue::get(Inst))) { + if (Value *V = AvailableValues.lookup(Inst)) { DEBUG(dbgs() << "EarlyCSE CSE: " << *Inst << " to: " << *V << '\n'); Inst->replaceAllUsesWith(V); Inst->eraseFromParent(); @@ -325,60 +545,255 @@ bool EarlyCSE::processNode(DomTreeNode *Node) { ++NumCSE; continue; } - + // Otherwise, just remember that this value is available. - AvailableValues->insert(SimpleValue::get(Inst), Inst); + AvailableValues.insert(Inst, Inst); continue; } - - // If this is a read-only memory value, process it. - if (MemoryValue::canHandle(Inst)) { - // If we have an available version of this value, and if it is the right + + ParseMemoryInst MemInst(Inst, TTI); + // If this is a non-volatile load, process it. + if (MemInst.isValid() && MemInst.isLoad()) { + // Ignore volatile loads. + if (MemInst.isVolatile()) { + LastStore = nullptr; + // Don't CSE across synchronization boundaries. + if (Inst->mayWriteToMemory()) + ++CurrentGeneration; + continue; + } + + // If we have an available version of this load, and if it is the right // generation, replace this instruction. - std::pair InVal = - AvailableMemValues->lookup(MemoryValue::get(Inst)); - if (InVal.first != 0 && InVal.second == CurrentGeneration) { - DEBUG(dbgs() << "EarlyCSE CSE MEM: " << *Inst << " to: " - << *InVal.first << '\n'); - if (!Inst->use_empty()) Inst->replaceAllUsesWith(InVal.first); + LoadValue InVal = AvailableLoads.lookup(MemInst.getPtr()); + if (InVal.Data != nullptr && InVal.Generation == CurrentGeneration && + InVal.MatchingId == MemInst.getMatchingId()) { + Value *Op = getOrCreateResult(InVal.Data, Inst->getType()); + if (Op != nullptr) { + DEBUG(dbgs() << "EarlyCSE CSE LOAD: " << *Inst + << " to: " << *InVal.Data << '\n'); + if (!Inst->use_empty()) + Inst->replaceAllUsesWith(Op); + Inst->eraseFromParent(); + Changed = true; + ++NumCSELoad; + continue; + } + } + + // Otherwise, remember that we have this instruction. + AvailableLoads.insert( + MemInst.getPtr(), + LoadValue(Inst, CurrentGeneration, MemInst.getMatchingId())); + LastStore = nullptr; + continue; + } + + // If this instruction may read from memory, forget LastStore. + // Load/store intrinsics will indicate both a read and a write to + // memory. The target may override this (e.g. so that a store intrinsic + // does not read from memory, and thus will be treated the same as a + // regular store for commoning purposes). + if (Inst->mayReadFromMemory() && + !(MemInst.isValid() && !MemInst.mayReadFromMemory())) + LastStore = nullptr; + + // If this is a read-only call, process it. + 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 InVal = AvailableCalls.lookup(Inst); + if (InVal.first != nullptr && InVal.second == CurrentGeneration) { + DEBUG(dbgs() << "EarlyCSE CSE CALL: " << *Inst + << " to: " << *InVal.first << '\n'); + if (!Inst->use_empty()) + Inst->replaceAllUsesWith(InVal.first); Inst->eraseFromParent(); Changed = true; - ++NumCSEMem; + ++NumCSECall; continue; } - + // Otherwise, remember that we have this instruction. - AvailableMemValues->insert(MemoryValue::get(Inst), - std::pair(Inst, CurrentGeneration)); + AvailableCalls.insert( + Inst, std::pair(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(Inst)) + if (FI->getOrdering() == Release) { + assert(Inst->mayReadFromMemory() && "relied on to prevent DSE above"); + 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 (Inst->mayWriteToMemory()) + if (Inst->mayWriteToMemory()) { ++CurrentGeneration; + + 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. + if (LastStore) { + ParseMemoryInst LastStoreMemInst(LastStore, TTI); + if (LastStoreMemInst.isMatchingMemLoc(MemInst)) { + DEBUG(dbgs() << "EarlyCSE DEAD STORE: " << *LastStore + << " due to: " << *Inst << '\n'); + LastStore->eraseFromParent(); + Changed = true; + ++NumDSE; + LastStore = nullptr; + } + // fallthrough - we can exploit information about this store + } + + // Okay, we just invalidated anything we knew about loaded values. Try + // to salvage *something* by remembering that the stored value is a live + // 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(), + LoadValue(Inst, CurrentGeneration, MemInst.getMatchingId())); + + // Remember that this was the last store we saw for DSE. + if (!MemInst.isVolatile()) + LastStore = Inst; + } + } } - + + return Changed; +} + +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.llvm.org/pipermail/llvm-commits/Week-of-Mon-20120116/135228.html + std::deque nodesToProcess; + + bool Changed = false; + + // Process the root node. + nodesToProcess.push_back(new StackNode( + AvailableValues, AvailableLoads, AvailableCalls, CurrentGeneration, + DT.getRootNode(), DT.getRootNode()->begin(), DT.getRootNode()->end())); + + // Save the current generation. unsigned LiveOutGeneration = CurrentGeneration; - for (DomTreeNode::iterator I = Node->begin(), E = Node->end(); I != E; ++I) { - Changed |= processNode(*I); - // Pop any generation changes off the stack from the recursive walk. - CurrentGeneration = LiveOutGeneration; - } + + // Process the stack. + while (!nodesToProcess.empty()) { + // Grab the first item off the stack. Set the current generation, remove + // the node from the stack, and process it. + StackNode *NodeToProcess = nodesToProcess.back(); + + // Initialize class members. + CurrentGeneration = NodeToProcess->currentGeneration(); + + // Check if the node needs to be processed. + if (!NodeToProcess->isProcessed()) { + // Process the node. + Changed |= processNode(NodeToProcess->node()); + NodeToProcess->childGeneration(CurrentGeneration); + NodeToProcess->process(); + } else if (NodeToProcess->childIter() != NodeToProcess->end()) { + // Push the next child onto the stack. + DomTreeNode *child = NodeToProcess->nextChild(); + nodesToProcess.push_back( + new StackNode(AvailableValues, AvailableLoads, AvailableCalls, + NodeToProcess->childGeneration(), child, child->begin(), + child->end())); + } else { + // It has been processed, and there are no more children to process, + // so delete it and pop it off the stack. + delete NodeToProcess; + nodesToProcess.pop_back(); + } + } // while (!nodes...) + + // Reset the current generation. + CurrentGeneration = LiveOutGeneration; + return Changed; } +PreservedAnalyses EarlyCSEPass::run(Function &F, + AnalysisManager *AM) { + auto &TLI = AM->getResult(F); + auto &TTI = AM->getResult(F); + auto &DT = AM->getResult(F); + auto &AC = AM->getResult(F); -bool EarlyCSE::runOnFunction(Function &F) { - TD = getAnalysisIfAvailable(); - DT = &getAnalysis(); - ScopedHTType AVTable; - AvailableValues = &AVTable; + EarlyCSE CSE(TLI, TTI, DT, AC); - MemHTType MemTable; - AvailableMemValues = &MemTable; - - CurrentGeneration = 0; - return processNode(DT->getRootNode()); + 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(); + 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().getTLI(); + auto &TTI = getAnalysis().getTTI(F); + auto &DT = getAnalysis().getDomTree(); + auto &AC = getAnalysis().getAssumptionCache(F); + + EarlyCSE CSE(TLI, TTI, DT, AC); + + return CSE.run(); + } + + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.addRequired(); + AU.addRequired(); + AU.addRequired(); + AU.addRequired(); + AU.addPreserved(); + 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)