60#include <forward_list>
66#define LLE_OPTION "loop-load-elim"
67#define DEBUG_TYPE LLE_OPTION
70 "runtime-check-per-loop-load-elim",
cl::Hidden,
71 cl::desc(
"Max number of memchecks allowed per eliminated load on average"),
76 cl::desc(
"The maximum number of SCEV checks allowed for Loop "
79STATISTIC(NumLoopLoadEliminted,
"Number of loads eliminated by LLE");
84struct StoreToLoadForwardingCandidate {
89 : Load(Load), Store(Store) {}
96 Value *LoadPtr =
Load->getPointerOperand();
99 auto &
DL =
Load->getParent()->getModule()->getDataLayout();
103 DL.getTypeSizeInBits(LoadType) ==
105 "Should be a known dependence");
107 int64_t StrideLoad =
getPtrStride(PSE, LoadType, LoadPtr, L).value_or(0);
108 int64_t StrideStore =
getPtrStride(PSE, LoadType, StorePtr, L).value_or(0);
109 if (!StrideLoad || !StrideStore || StrideLoad != StrideStore)
119 if (std::abs(StrideLoad) != 1)
122 unsigned TypeByteSize =
DL.getTypeAllocSize(
const_cast<Type *
>(LoadType));
124 auto *LoadPtrSCEV = cast<SCEVAddRecExpr>(PSE.
getSCEV(LoadPtr));
125 auto *StorePtrSCEV = cast<SCEVAddRecExpr>(PSE.
getSCEV(StorePtr));
129 auto *Dist = dyn_cast<SCEVConstant>(
133 const APInt &Val = Dist->getAPInt();
134 return Val == TypeByteSize * StrideLoad;
137 Value *getLoadPtr()
const {
return Load->getPointerOperand(); }
141 const StoreToLoadForwardingCandidate &Cand) {
142 OS << *Cand.Store <<
" -->\n";
156 L->getLoopLatches(Latches);
164 return Load->getParent() != L->getHeader();
170class LoadEliminationForLoop {
175 :
L(
L), LI(LI), LAI(LAI), DT(DT),
BFI(
BFI), PSI(PSI), PSE(LAI.getPSE()) {}
182 std::forward_list<StoreToLoadForwardingCandidate>
184 std::forward_list<StoreToLoadForwardingCandidate> Candidates;
196 for (
const auto &Dep : *Deps) {
198 Instruction *Destination = Dep.getDestination(LAI);
202 if (isa<LoadInst>(Source))
203 LoadsWithUnknownDepedence.
insert(Source);
204 if (isa<LoadInst>(Destination))
205 LoadsWithUnknownDepedence.
insert(Destination);
209 if (Dep.isBackward())
215 assert(Dep.isForward() &&
"Needs to be a forward dependence");
217 auto *
Store = dyn_cast<StoreInst>(Source);
220 auto *
Load = dyn_cast<LoadInst>(Destination);
227 Store->getParent()->getModule()->getDataLayout()))
230 Candidates.emplace_front(Load, Store);
233 if (!LoadsWithUnknownDepedence.
empty())
234 Candidates.remove_if([&](
const StoreToLoadForwardingCandidate &
C) {
235 return LoadsWithUnknownDepedence.
count(
C.Load);
243 auto I = InstOrder.find(Inst);
244 assert(
I != InstOrder.end() &&
"No index for instruction");
267 void removeDependencesFromMultipleStores(
268 std::forward_list<StoreToLoadForwardingCandidate> &Candidates) {
271 using LoadToSingleCandT =
273 LoadToSingleCandT LoadToSingleCand;
275 for (
const auto &Cand : Candidates) {
277 LoadToSingleCandT::iterator Iter;
279 std::tie(Iter, NewElt) =
280 LoadToSingleCand.
insert(std::make_pair(Cand.Load, &Cand));
282 const StoreToLoadForwardingCandidate *&OtherCand = Iter->second;
284 if (OtherCand ==
nullptr)
290 if (Cand.Store->getParent() == OtherCand->Store->getParent() &&
291 Cand.isDependenceDistanceOfOne(PSE, L) &&
292 OtherCand->isDependenceDistanceOfOne(PSE, L)) {
294 if (getInstrIndex(OtherCand->Store) < getInstrIndex(Cand.Store))
301 Candidates.remove_if([&](
const StoreToLoadForwardingCandidate &Cand) {
302 if (LoadToSingleCand[Cand.Load] != &Cand) {
304 dbgs() <<
"Removing from candidates: \n"
306 <<
" The load may have multiple stores forwarding to "
319 bool needsChecking(
unsigned PtrIdx1,
unsigned PtrIdx2,
326 return ((PtrsWrittenOnFwdingPath.
count(Ptr1) && CandLoadPtrs.
count(Ptr2)) ||
327 (PtrsWrittenOnFwdingPath.
count(Ptr2) && CandLoadPtrs.
count(Ptr1)));
355 [&](
const StoreToLoadForwardingCandidate &
A,
356 const StoreToLoadForwardingCandidate &
B) {
357 return getInstrIndex(
A.Load) <
358 getInstrIndex(
B.Load);
363 [&](
const StoreToLoadForwardingCandidate &
A,
364 const StoreToLoadForwardingCandidate &
B) {
365 return getInstrIndex(
A.Store) <
366 getInstrIndex(
B.Store);
376 if (
auto *S = dyn_cast<StoreInst>(
I))
377 PtrsWrittenOnFwdingPath.
insert(S->getPointerOperand());
380 std::for_each(MemInstrs.begin() + getInstrIndex(FirstStore) + 1,
381 MemInstrs.end(), InsertStorePtr);
382 std::for_each(MemInstrs.begin(), &MemInstrs[getInstrIndex(LastLoad)],
385 return PtrsWrittenOnFwdingPath;
394 findPointersWrittenOnForwardingPath(Candidates);
398 for (
const auto &Candidate : Candidates)
399 CandLoadPtrs.
insert(Candidate.getLoadPtr());
404 copy_if(AllChecks, std::back_inserter(Checks),
406 for (
auto PtrIdx1 :
Check.first->Members)
407 for (
auto PtrIdx2 :
Check.second->Members)
408 if (needsChecking(PtrIdx1, PtrIdx2, PtrsWrittenOnFwdingPath,
423 propagateStoredValueToLoadUsers(
const StoreToLoadForwardingCandidate &Cand,
440 Value *
Ptr = Cand.Load->getPointerOperand();
441 auto *PtrSCEV = cast<SCEVAddRecExpr>(PSE.
getSCEV(
Ptr));
442 auto *PH =
L->getLoopPreheader();
443 assert(PH &&
"Preheader should exist!");
444 Value *InitialPtr =
SEE.expandCodeFor(PtrSCEV->getStart(),
Ptr->getType(),
445 PH->getTerminator());
447 new LoadInst(Cand.Load->getType(), InitialPtr,
"load_initial",
448 false, Cand.Load->getAlign(),
449 PH->getTerminator()->getIterator());
452 PHI->insertBefore(
L->getHeader()->begin());
453 PHI->addIncoming(Initial, PH);
456 Type *StoreType = Cand.Store->getValueOperand()->getType();
460 assert(
DL.getTypeSizeInBits(LoadType) ==
DL.getTypeSizeInBits(StoreType) &&
461 "The type sizes should match!");
463 Value *StoreValue = Cand.Store->getValueOperand();
464 if (LoadType != StoreType)
466 "store_forward_cast",
467 Cand.Store->getIterator());
469 PHI->addIncoming(StoreValue,
L->getLoopLatch());
471 Cand.Load->replaceAllUsesWith(
PHI);
477 LLVM_DEBUG(
dbgs() <<
"\nIn \"" <<
L->getHeader()->getParent()->getName()
478 <<
"\" checking " << *L <<
"\n");
499 auto StoreToLoadDependences = findStoreToLoadDependences(LAI);
500 if (StoreToLoadDependences.empty())
509 removeDependencesFromMultipleStores(StoreToLoadDependences);
510 if (StoreToLoadDependences.empty())
515 for (
const StoreToLoadForwardingCandidate &Cand : StoreToLoadDependences) {
531 if (!Cand.isDependenceDistanceOfOne(PSE, L))
534 assert(isa<SCEVAddRecExpr>(PSE.
getSCEV(Cand.Load->getPointerOperand())) &&
535 "Loading from something other than indvar?");
537 isa<SCEVAddRecExpr>(PSE.
getSCEV(Cand.Store->getPointerOperand())) &&
538 "Storing to something other than indvar?");
544 <<
". Valid store-to-load forwarding across the loop backedge\n");
546 if (Candidates.
empty())
565 if (!
L->isLoopSimplifyForm()) {
573 "convergent calls\n");
577 auto *HeaderBB =
L->getHeader();
578 auto *
F = HeaderBB->getParent();
579 bool OptForSize =
F->hasOptSize() ||
581 PGSOQueryType::IRPass);
584 dbgs() <<
"Versioning is needed but not allowed when optimizing "
597 auto NoLongerGoodCandidate = [
this](
598 const StoreToLoadForwardingCandidate &Cand) {
599 return !isa<SCEVAddRecExpr>(
600 PSE.
getSCEV(Cand.Load->getPointerOperand())) ||
601 !isa<SCEVAddRecExpr>(
602 PSE.
getSCEV(Cand.Store->getPointerOperand()));
611 for (
const auto &Cand : Candidates)
612 propagateStoredValueToLoadUsers(Cand,
SEE);
613 NumLoopLoadEliminted += Candidates.size();
649 bool Changed =
false;
651 for (
Loop *TopLevelLoop : LI)
653 Changed |=
simplifyLoop(L, &DT, &LI, SE, AC,
nullptr,
false);
655 if (L->isInnermost())
660 for (
Loop *L : Worklist) {
662 if (!L->isRotatedForm() || !L->getExitingBlock())
665 LoadEliminationForLoop LEL(L, &LI, LAIs.
getInfo(*L), &DT, BFI, PSI);
666 Changed |= LEL.processLoop();
685 auto *BFI = (PSI && PSI->hasProfileSummary()) ?
for(const MachineOperand &MO :llvm::drop_begin(OldMI.operands(), Desc.getNumOperands()))
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
This file implements a class to represent arbitrary precision integral constant values and operations...
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
This file defines the DenseMap class.
This file builds on the ADT/GraphTraits.h file to build generic depth first graph iterator.
This is the interface for a simple mod/ref and alias analysis over globals.
This header provides classes for managing per-loop analyses.
static bool eliminateLoadsAcrossLoops(Function &F, LoopInfo &LI, DominatorTree &DT, BlockFrequencyInfo *BFI, ProfileSummaryInfo *PSI, ScalarEvolution *SE, AssumptionCache *AC, LoopAccessInfoManager &LAIs)
static cl::opt< unsigned > LoadElimSCEVCheckThreshold("loop-load-elimination-scev-check-threshold", cl::init(8), cl::Hidden, cl::desc("The maximum number of SCEV checks allowed for Loop " "Load Elimination"))
static bool isLoadConditional(LoadInst *Load, Loop *L)
Return true if the load is not executed on all paths in the loop.
static bool doesStoreDominatesAllLatches(BasicBlock *StoreBlock, Loop *L, DominatorTree *DT)
Check if the store dominates all latches, so as long as there is no intervening store this value will...
static cl::opt< unsigned > CheckPerElim("runtime-check-per-loop-load-elim", cl::Hidden, cl::desc("Max number of memchecks allowed per eliminated load on average"), cl::init(1))
This header defines the LoopLoadEliminationPass object.
Module.h This file contains the declarations for the Module class.
This header defines various interfaces for pass management in LLVM.
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file defines the SmallPtrSet class.
This file defines the SmallVector class.
This file defines the 'Statistic' class, which is designed to be an easy way to expose various metric...
#define STATISTIC(VARNAME, DESC)
Class for arbitrary precision integers.
A container for analyses that lazily runs them and caches their results.
PassT::Result & getResult(IRUnitT &IR, ExtraArgTs... ExtraArgs)
Get the result of an analysis pass for a given IR unit.
A function analysis which provides an AssumptionCache.
A cache of @llvm.assume calls within a function.
LLVM Basic Block Representation.
Analysis pass which computes BlockFrequencyInfo.
BlockFrequencyInfo pass uses BlockFrequencyInfoImpl implementation to estimate IR basic block frequen...
static bool isBitOrNoopPointerCastable(Type *SrcTy, Type *DestTy, const DataLayout &DL)
Check whether a bitcast, inttoptr, or ptrtoint cast between these types is valid and a no-op.
static CastInst * CreateBitOrPointerCast(Value *S, Type *Ty, const Twine &Name, BasicBlock::iterator InsertBefore)
Create a BitCast, a PtrToInt, or an IntToPTr cast instruction.
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Analysis pass which computes a DominatorTree.
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree.
bool dominates(const BasicBlock *BB, const Use &U) const
Return true if the (end of the) basic block BB dominates the use U.
An instruction for reading from memory.
This analysis provides dependence information for the memory accesses of a loop.
const LoopAccessInfo & getInfo(Loop &L)
Drive the analysis of memory accesses in the loop.
const MemoryDepChecker & getDepChecker() const
the Memory Dependence Checker which can determine the loop-independent and loop-carried dependences b...
const RuntimePointerChecking * getRuntimePointerChecking() const
const PredicatedScalarEvolution & getPSE() const
Used to add runtime SCEV checks.
bool hasConvergentOp() const
Return true if there is a convergent operation in the loop.
Analysis pass that exposes the LoopInfo for a function.
This class emits a version of the loop where run-time checks ensure that may-alias pointers can't ove...
Represents a single loop in the control flow graph.
const MachineFunction * getParent() const
Return the MachineFunction containing this basic block.
const DataLayout & getDataLayout() const
Return the DataLayout attached to the Module associated to this MF.
const SmallVectorImpl< Instruction * > & getMemoryInstructions() const
The vector of memory access instructions.
const SmallVectorImpl< Dependence > * getDependences() const
Returns the memory dependences.
DenseMap< Instruction *, unsigned > generateInstructionOrderMap() const
Generate a mapping between the memory instructions and their indices according to program order.
An analysis over an "inner" IR unit that provides access to an analysis manager over a "outer" IR uni...
static PHINode * Create(Type *Ty, unsigned NumReservedValues, const Twine &NameStr, BasicBlock::iterator InsertBefore)
Constructors - NumReservedValues is a hint for the number of incoming edges that this phi node will h...
An interface layer with SCEV used to manage how we see SCEV expressions for values in the context of ...
ScalarEvolution * getSE() const
Returns the ScalarEvolution analysis used.
const SCEVPredicate & getPredicate() const
const SCEV * getSCEV(Value *V)
Returns the SCEV expression of V, in the context of the current SCEV predicate.
A set of analyses that are preserved following a run of a transformation pass.
static PreservedAnalyses all()
Construct a special preserved set that preserves all passes.
void preserve()
Mark an analysis as preserved.
An analysis pass based on the new PM to deliver ProfileSummaryInfo.
Analysis providing profile information.
void printChecks(raw_ostream &OS, const SmallVectorImpl< RuntimePointerCheck > &Checks, unsigned Depth=0) const
Print Checks.
const SmallVectorImpl< RuntimePointerCheck > & getChecks() const
Returns the checks that generateChecks created.
const PointerInfo & getPointerInfo(unsigned PtrIdx) const
Return PointerInfo for pointer at index PtrIdx.
This class uses information about analyze scalars to rewrite expressions in canonical form.
virtual unsigned getComplexity() const
Returns the estimated complexity of this predicate.
virtual bool isAlwaysTrue() const =0
Returns true if the predicate is always true.
Analysis pass that exposes the ScalarEvolution for a function.
The main scalar evolution driver.
const SCEV * getMinusSCEV(const SCEV *LHS, const SCEV *RHS, SCEV::NoWrapFlags Flags=SCEV::FlagAnyWrap, unsigned Depth=0)
Return LHS-RHS.
A templated base class for SmallPtrSet which provides the typesafe interface that is common across al...
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements.
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
void push_back(const T &Elt)
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
An instruction for storing to memory.
The instances of the Type class are immutable: once they are created, they are never changed.
unsigned getPointerAddressSpace() const
Get the address space of this pointer or pointer vector type.
LLVM Value Representation.
Type * getType() const
All values are typed, get the type of this value.
This class implements an extremely fast bulk output stream that can only output to a stream.
raw_ostream & indent(unsigned NumSpaces)
indent - Insert 'NumSpaces' spaces.
@ C
The default llvm calling convention, compatible with C.
initializer< Ty > init(const Ty &Val)
This is an optimization pass for GlobalISel generic memory operations.
bool simplifyLoop(Loop *L, DominatorTree *DT, LoopInfo *LI, ScalarEvolution *SE, AssumptionCache *AC, MemorySSAUpdater *MSSAU, bool PreserveLCSSA)
Simplify each loop in a loop nest recursively.
auto min_element(R &&Range)
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly.
std::pair< const RuntimeCheckingPtrGroup *, const RuntimeCheckingPtrGroup * > RuntimePointerCheck
A memcheck which made up of a pair of grouped pointers.
bool shouldOptimizeForSize(const MachineFunction *MF, ProfileSummaryInfo *PSI, const MachineBlockFrequencyInfo *BFI, PGSOQueryType QueryType=PGSOQueryType::Other)
Returns true if machine function MF is suggested to be size-optimized based on the profile.
OutputIt copy_if(R &&Range, OutputIt Out, UnaryPredicate P)
Provide wrappers to std::copy_if which take ranges instead of having to pass begin/end explicitly.
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
std::optional< int64_t > getPtrStride(PredicatedScalarEvolution &PSE, Type *AccessTy, Value *Ptr, const Loop *Lp, const DenseMap< Value *, const SCEV * > &StridesMap=DenseMap< Value *, const SCEV * >(), bool Assume=false, bool ShouldCheckWrap=true)
If the pointer has a constant stride return it in units of the access type size.
auto max_element(R &&Range)
raw_ostream & operator<<(raw_ostream &OS, const APFixedPoint &FX)
void erase_if(Container &C, UnaryPredicate P)
Provide a container algorithm similar to C++ Library Fundamentals v2's erase_if which is equivalent t...
iterator_range< df_iterator< T > > depth_first(const T &G)
Type * getLoadStoreType(Value *I)
A helper function that returns the type of a load or store instruction.
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM)
TrackingVH< Value > PointerValue
Holds the pointer value that we need to check.