//
//===----------------------------------------------------------------------===//
-#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/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 <deque>
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<const void*>::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<Instruction*>::getEmptyKey() ||
- Inst == DenseMapInfo<Instruction*>::getTombstoneKey();
- }
-
- static bool canHandle(Instruction *Inst) {
- return isa<CastInst>(Inst) || isa<BinaryOperator>(Inst) ||
- isa<GetElementPtrInst>(Inst) || isa<CmpInst>(Inst) ||
- isa<SelectInst>(Inst) || isa<ExtractElementInst>(Inst) ||
- isa<InsertElementInst>(Inst) || isa<ShuffleVectorInst>(Inst) ||
- isa<ExtractValueInst>(Inst) || isa<InsertValueInst>(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<SimpleValue> {
- 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<Instruction *>::getEmptyKey() ||
+ Inst == DenseMapInfo<Instruction *>::getTombstoneKey();
+ }
+
+ static bool canHandle(Instruction *Inst) {
+ // This can only handle non-void readnone functions.
+ if (CallInst *CI = dyn_cast<CallInst>(Inst))
+ return CI->doesNotAccessMemory() && !CI->getType()->isVoidTy();
+ return isa<CastInst>(Inst) || isa<BinaryOperator>(Inst) ||
+ isa<GetElementPtrInst>(Inst) || isa<CmpInst>(Inst) ||
+ isa<SelectInst>(Inst) || isa<ExtractElementInst>(Inst) ||
+ isa<InsertElementInst>(Inst) || isa<ShuffleVectorInst>(Inst) ||
+ isa<ExtractValueInst>(Inst) || isa<InsertValueInst>(Inst);
+ }
};
+}
-template<> struct DenseMapInfo<SimpleValue> {
+namespace llvm {
+template <> struct DenseMapInfo<SimpleValue> {
static inline SimpleValue getEmptyKey() {
- return SimpleValue::get(DenseMapInfo<Instruction*>::getEmptyKey());
+ return DenseMapInfo<Instruction *>::getEmptyKey();
}
static inline SimpleValue getTombstoneKey() {
- return SimpleValue::get(DenseMapInfo<Instruction*>::getTombstoneKey());
+ return DenseMapInfo<Instruction *>::getTombstoneKey();
}
static unsigned getHashValue(SimpleValue Val);
static bool isEqual(SimpleValue LHS, SimpleValue RHS);
unsigned DenseMapInfo<SimpleValue>::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<BinaryOperator>(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<CastInst>(Inst))
- Res ^= getHash(CI->getType());
- else if (CmpInst *CI = dyn_cast<CmpInst>(Inst))
- Res ^= CI->getPredicate();
- else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(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<InsertValueInst>(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<BinaryOperator>(Inst) || isa<GetElementPtrInst>(Inst) ||
- isa<SelectInst>(Inst) || isa<ExtractElementInst>(Inst) ||
- isa<InsertElementInst>(Inst) || isa<ShuffleVectorInst>(Inst)) &&
- "Invalid/unknown instruction");
+ if (isa<OverflowingBinaryOperator>(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<CmpInst>(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<CastInst>(Inst))
+ return hash_combine(CI->getOpcode(), CI->getType(), CI->getOperand(0));
+
+ if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Inst))
+ return hash_combine(EVI->getOpcode(), EVI->getOperand(0),
+ hash_combine_range(EVI->idx_begin(), EVI->idx_end()));
+
+ if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(Inst))
+ return hash_combine(IVI->getOpcode(), IVI->getOperand(0),
+ IVI->getOperand(1),
+ hash_combine_range(IVI->idx_begin(), IVI->idx_end()));
+
+ assert((isa<CallInst>(Inst) || isa<BinaryOperator>(Inst) ||
+ isa<GetElementPtrInst>(Inst) || isa<SelectInst>(Inst) ||
+ isa<ExtractElementInst>(Inst) || isa<InsertElementInst>(Inst) ||
+ isa<ShuffleVectorInst>(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<SimpleValue>::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<BinaryOperator>(LHSI)) {
+ if (!LHSBinOp->isCommutative())
+ return false;
+
+ assert(isa<BinaryOperator>(RHSI) &&
+ "same opcode, but different instruction type?");
+ BinaryOperator *RHSBinOp = cast<BinaryOperator>(RHSI);
+
+ // Check overflow attributes
+ if (isa<OverflowingBinaryOperator>(LHSBinOp)) {
+ assert(isa<OverflowingBinaryOperator>(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<CmpInst>(LHSI)) {
+ assert(isa<CmpInst>(RHSI) &&
+ "same opcode, but different instruction type?");
+ CmpInst *RHSCmp = cast<CmpInst>(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<Instruction*>::getEmptyKey() ||
- Inst == DenseMapInfo<Instruction*>::getTombstoneKey();
- }
-
- static bool canHandle(Instruction *Inst) {
- if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
- return !LI->isVolatile();
- if (CallInst *CI = dyn_cast<CallInst>(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<Instruction *>::getEmptyKey() ||
+ Inst == DenseMapInfo<Instruction *>::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<CallInst>(Inst);
+ if (!CI || !CI->onlyReadsMemory())
+ return false;
+ return true;
+ }
+};
}
namespace llvm {
- // MemoryValue is POD.
- template<> struct isPodLike<MemoryValue> {
- static const bool value = true;
- };
-
- template<> struct DenseMapInfo<MemoryValue> {
- static inline MemoryValue getEmptyKey() {
- return MemoryValue::get(DenseMapInfo<Instruction*>::getEmptyKey());
- }
- static inline MemoryValue getTombstoneKey() {
- return MemoryValue::get(DenseMapInfo<Instruction*>::getTombstoneKey());
- }
- static unsigned getHashValue(MemoryValue Val);
- static bool isEqual(MemoryValue LHS, MemoryValue RHS);
- };
+template <> struct DenseMapInfo<CallValue> {
+ static inline CallValue getEmptyKey() {
+ return DenseMapInfo<Instruction *>::getEmptyKey();
+ }
+ static inline CallValue getTombstoneKey() {
+ return DenseMapInfo<Instruction *>::getTombstoneKey();
+ }
+ static unsigned getHashValue(CallValue Val);
+ static bool isEqual(CallValue LHS, CallValue RHS);
+};
}
-unsigned DenseMapInfo<MemoryValue>::getHashValue(MemoryValue Val) {
+
+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)
- 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<MemoryValue>::isEqual(MemoryValue LHS, MemoryValue RHS) {
+bool DenseMapInfo<CallValue>::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<BumpPtrAllocator,
- ScopedHashTableVal<SimpleValue, Value*> > AllocatorTy;
- typedef ScopedHashTable<SimpleValue, Value*, DenseMapInfo<SimpleValue>,
+ Function &F;
+ const TargetLibraryInfo &TLI;
+ const TargetTransformInfo &TTI;
+ DominatorTree &DT;
+ AssumptionCache &AC;
+ typedef RecyclingAllocator<
+ BumpPtrAllocator, ScopedHashTableVal<SimpleValue, Value *>> AllocatorTy;
+ typedef ScopedHashTable<SimpleValue, Value *, DenseMapInfo<SimpleValue>,
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<MemoryValue, std::pair<Value*, unsigned> > 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.
+ typedef RecyclingAllocator<
+ BumpPtrAllocator,
+ ScopedHashTableVal<Value *, std::pair<Value *, unsigned>>>
+ LoadMapAllocator;
+ typedef ScopedHashTable<Value *, std::pair<Value *, unsigned>,
+ 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;
+
+ /// \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(Function &F, const TargetLibraryInfo &TLI,
+ const TargetTransformInfo &TTI, DominatorTree &DT,
+ AssumptionCache &AC)
+ : F(F), 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<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();
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ Store = true;
+ Vol = !SI->isSimple();
+ Ptr = SI->getPointerOperand();
+ }
+ }
+ 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 isValid() { return Ptr != nullptr; }
+ int getMatchingId() { return MatchingId; }
+ Value *getPtr() { return Ptr; }
+ bool mayReadFromMemory() { return MayReadFromMemory; }
+ bool mayWriteToMemory() { 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<DominatorTree>();
- 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);
}
};
}
-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<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
+ /// 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; ) {
+ 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<Intrinsic::assume>())) {
+ 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();
++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();
++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<Value*, unsigned> 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);
+ std::pair<Value *, unsigned> InVal =
+ AvailableLoads.lookup(MemInst.getPtr());
+ if (InVal.first != nullptr && InVal.second == CurrentGeneration) {
+ Value *Op = getOrCreateResult(InVal.first, Inst->getType());
+ if (Op != nullptr) {
+ DEBUG(dbgs() << "EarlyCSE CSE LOAD: " << *Inst
+ << " to: " << *InVal.first << '\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(), std::pair<Value *, unsigned>(
+ Inst, CurrentGeneration));
+ 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<Value *, unsigned> 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<Value*, unsigned>(Inst, CurrentGeneration));
+ AvailableCalls.insert(
+ Inst, std::pair<Value *, unsigned>(Inst, CurrentGeneration));
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(), std::pair<Value *, unsigned>(
+ Inst, CurrentGeneration));
+
+ // 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<StackNode *> 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<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(F, TLI, TTI, DT, AC);
-bool EarlyCSE::runOnFunction(Function &F) {
- TD = getAnalysisIfAvailable<TargetData>();
- DT = &getAnalysis<DominatorTree>();
- ScopedHTType AVTable;
- AvailableValues = &AVTable;
+ if (!CSE.run())
+ return PreservedAnalyses::all();
- MemHTType MemTable;
- AvailableMemValues = &MemTable;
-
- CurrentGeneration = 0;
- return processNode(DT->getRootNode());
+ // 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(F, 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.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)