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//===- LoopVectorize.cpp - A Loop Vectorizer ------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is the LLVM loop vectorizer. This pass modifies 'vectorizable' loops
// and generates target-independent LLVM-IR.
// The vectorizer uses the TargetTransformInfo analysis to estimate the costs
// of instructions in order to estimate the profitability of vectorization.
//
// The loop vectorizer combines consecutive loop iterations into a single
// 'wide' iteration. After this transformation the index is incremented
// by the SIMD vector width, and not by one.
//
// This pass has three parts:
// 1. The main loop pass that drives the different parts.
// 2. LoopVectorizationLegality - A unit that checks for the legality
// of the vectorization.
// 3. InnerLoopVectorizer - A unit that performs the actual
// widening of instructions.
// 4. LoopVectorizationCostModel - A unit that checks for the profitability
// of vectorization. It decides on the optimal vector width, which
// can be one, if vectorization is not profitable.
//
//===----------------------------------------------------------------------===//
//
// The reduction-variable vectorization is based on the paper:
// D. Nuzman and R. Henderson. Multi-platform Auto-vectorization.
//
// Variable uniformity checks are inspired by:
// Karrenberg, R. and Hack, S. Whole Function Vectorization.
//
// The interleaved access vectorization is based on the paper:
// Dorit Nuzman, Ira Rosen and Ayal Zaks. Auto-Vectorization of Interleaved
// Data for SIMD
//
// Other ideas/concepts are from:
// A. Zaks and D. Nuzman. Autovectorization in GCC-two years later.
//
// S. Maleki, Y. Gao, M. Garzaran, T. Wong and D. Padua. An Evaluation of
// Vectorizing Compilers.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Vectorize.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/CodeMetrics.h"
#include "llvm/Analysis/LoopAccessAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopIterator.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/ValueHandle.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Pass.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include <algorithm>
#include <map>
#include <tuple>
using namespace llvm;
using namespace llvm::PatternMatch;
#define LV_NAME "loop-vectorize"
#define DEBUG_TYPE LV_NAME
STATISTIC(LoopsVectorized, "Number of loops vectorized");
STATISTIC(LoopsAnalyzed, "Number of loops analyzed for vectorization");
static cl::opt<bool>
EnableIfConversion("enable-if-conversion", cl::init(true), cl::Hidden,
cl::desc("Enable if-conversion during vectorization."));
/// We don't vectorize loops with a known constant trip count below this number.
static cl::opt<unsigned>
TinyTripCountVectorThreshold("vectorizer-min-trip-count", cl::init(16),
cl::Hidden,
cl::desc("Don't vectorize loops with a constant "
"trip count that is smaller than this "
"value."));
/// This enables versioning on the strides of symbolically striding memory
/// accesses in code like the following.
/// for (i = 0; i < N; ++i)
/// A[i * Stride1] += B[i * Stride2] ...
///
/// Will be roughly translated to
/// if (Stride1 == 1 && Stride2 == 1) {
/// for (i = 0; i < N; i+=4)
/// A[i:i+3] += ...
/// } else
/// ...
static cl::opt<bool> EnableMemAccessVersioning(
"enable-mem-access-versioning", cl::init(true), cl::Hidden,
cl::desc("Enable symblic stride memory access versioning"));
static cl::opt<bool> EnableInterleavedMemAccesses(
"enable-interleaved-mem-accesses", cl::init(false), cl::Hidden,
cl::desc("Enable vectorization on interleaved memory accesses in a loop"));
/// Maximum factor for an interleaved memory access.
static cl::opt<unsigned> MaxInterleaveGroupFactor(
"max-interleave-group-factor", cl::Hidden,
cl::desc("Maximum factor for an interleaved access group (default = 8)"),
cl::init(8));
/// We don't interleave loops with a known constant trip count below this
/// number.
static const unsigned TinyTripCountInterleaveThreshold = 128;
static cl::opt<unsigned> ForceTargetNumScalarRegs(
"force-target-num-scalar-regs", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's number of scalar registers."));
static cl::opt<unsigned> ForceTargetNumVectorRegs(
"force-target-num-vector-regs", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's number of vector registers."));
/// Maximum vectorization interleave count.
static const unsigned MaxInterleaveFactor = 16;
static cl::opt<unsigned> ForceTargetMaxScalarInterleaveFactor(
"force-target-max-scalar-interleave", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's max interleave factor for "
"scalar loops."));
static cl::opt<unsigned> ForceTargetMaxVectorInterleaveFactor(
"force-target-max-vector-interleave", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's max interleave factor for "
"vectorized loops."));
static cl::opt<unsigned> ForceTargetInstructionCost(
"force-target-instruction-cost", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's expected cost for "
"an instruction to a single constant value. Mostly "
"useful for getting consistent testing."));
static cl::opt<unsigned> SmallLoopCost(
"small-loop-cost", cl::init(20), cl::Hidden,
cl::desc(
"The cost of a loop that is considered 'small' by the interleaver."));
static cl::opt<bool> LoopVectorizeWithBlockFrequency(
"loop-vectorize-with-block-frequency", cl::init(false), cl::Hidden,
cl::desc("Enable the use of the block frequency analysis to access PGO "
"heuristics minimizing code growth in cold regions and being more "
"aggressive in hot regions."));
// Runtime interleave loops for load/store throughput.
static cl::opt<bool> EnableLoadStoreRuntimeInterleave(
"enable-loadstore-runtime-interleave", cl::init(true), cl::Hidden,
cl::desc(
"Enable runtime interleaving until load/store ports are saturated"));
/// The number of stores in a loop that are allowed to need predication.
static cl::opt<unsigned> NumberOfStoresToPredicate(
"vectorize-num-stores-pred", cl::init(1), cl::Hidden,
cl::desc("Max number of stores to be predicated behind an if."));
static cl::opt<bool> EnableIndVarRegisterHeur(
"enable-ind-var-reg-heur", cl::init(true), cl::Hidden,
cl::desc("Count the induction variable only once when interleaving"));
static cl::opt<bool> EnableCondStoresVectorization(
"enable-cond-stores-vec", cl::init(false), cl::Hidden,
cl::desc("Enable if predication of stores during vectorization."));
static cl::opt<unsigned> MaxNestedScalarReductionIC(
"max-nested-scalar-reduction-interleave", cl::init(2), cl::Hidden,
cl::desc("The maximum interleave count to use when interleaving a scalar "
"reduction in a nested loop."));
namespace {
// Forward declarations.
class LoopVectorizationLegality;
class LoopVectorizationCostModel;
class LoopVectorizeHints;
/// \brief This modifies LoopAccessReport to initialize message with
/// loop-vectorizer-specific part.
class VectorizationReport : public LoopAccessReport {
public:
VectorizationReport(Instruction *I = nullptr)
: LoopAccessReport("loop not vectorized: ", I) {}
/// \brief This allows promotion of the loop-access analysis report into the
/// loop-vectorizer report. It modifies the message to add the
/// loop-vectorizer-specific part of the message.
explicit VectorizationReport(const LoopAccessReport &R)
: LoopAccessReport(Twine("loop not vectorized: ") + R.str(),
R.getInstr()) {}
};
/// A helper function for converting Scalar types to vector types.
/// If the incoming type is void, we return void. If the VF is 1, we return
/// the scalar type.
static Type* ToVectorTy(Type *Scalar, unsigned VF) {
if (Scalar->isVoidTy() || VF == 1)
return Scalar;
return VectorType::get(Scalar, VF);
}
/// InnerLoopVectorizer vectorizes loops which contain only one basic
/// block to a specified vectorization factor (VF).
/// This class performs the widening of scalars into vectors, or multiple
/// scalars. This class also implements the following features:
/// * It inserts an epilogue loop for handling loops that don't have iteration
/// counts that are known to be a multiple of the vectorization factor.
/// * It handles the code generation for reduction variables.
/// * Scalarization (implementation using scalars) of un-vectorizable
/// instructions.
/// InnerLoopVectorizer does not perform any vectorization-legality
/// checks, and relies on the caller to check for the different legality
/// aspects. The InnerLoopVectorizer relies on the
/// LoopVectorizationLegality class to provide information about the induction
/// and reduction variables that were found to a given vectorization factor.
class InnerLoopVectorizer {
public:
InnerLoopVectorizer(Loop *OrigLoop, ScalarEvolution *SE, LoopInfo *LI,
DominatorTree *DT, const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI, unsigned VecWidth,
unsigned UnrollFactor)
: OrigLoop(OrigLoop), SE(SE), LI(LI), DT(DT), TLI(TLI), TTI(TTI),
VF(VecWidth), UF(UnrollFactor), Builder(SE->getContext()),
Induction(nullptr), OldInduction(nullptr), WidenMap(UnrollFactor),
Legal(nullptr), AddedSafetyChecks(false) {}
// Perform the actual loop widening (vectorization).
void vectorize(LoopVectorizationLegality *L) {
Legal = L;
// Create a new empty loop. Unlink the old loop and connect the new one.
createEmptyLoop();
// Widen each instruction in the old loop to a new one in the new loop.
// Use the Legality module to find the induction and reduction variables.
vectorizeLoop();
// Register the new loop and update the analysis passes.
updateAnalysis();
}
// Return true if any runtime check is added.
bool IsSafetyChecksAdded() {
return AddedSafetyChecks;
}
virtual ~InnerLoopVectorizer() {}
protected:
/// A small list of PHINodes.
typedef SmallVector<PHINode*, 4> PhiVector;
/// When we unroll loops we have multiple vector values for each scalar.
/// This data structure holds the unrolled and vectorized values that
/// originated from one scalar instruction.
typedef SmallVector<Value*, 2> VectorParts;
// When we if-convert we need to create edge masks. We have to cache values
// so that we don't end up with exponential recursion/IR.
typedef DenseMap<std::pair<BasicBlock*, BasicBlock*>,
VectorParts> EdgeMaskCache;
/// \brief Add checks for strides that were assumed to be 1.
///
/// Returns the last check instruction and the first check instruction in the
/// pair as (first, last).
std::pair<Instruction *, Instruction *> addStrideCheck(Instruction *Loc);
/// Create an empty loop, based on the loop ranges of the old loop.
void createEmptyLoop();
/// Copy and widen the instructions from the old loop.
virtual void vectorizeLoop();
/// \brief The Loop exit block may have single value PHI nodes where the
/// incoming value is 'Undef'. While vectorizing we only handled real values
/// that were defined inside the loop. Here we fix the 'undef case'.
/// See PR14725.
void fixLCSSAPHIs();
/// A helper function that computes the predicate of the block BB, assuming
/// that the header block of the loop is set to True. It returns the *entry*
/// mask for the block BB.
VectorParts createBlockInMask(BasicBlock *BB);
/// A helper function that computes the predicate of the edge between SRC
/// and DST.
VectorParts createEdgeMask(BasicBlock *Src, BasicBlock *Dst);
/// A helper function to vectorize a single BB within the innermost loop.
void vectorizeBlockInLoop(BasicBlock *BB, PhiVector *PV);
/// Vectorize a single PHINode in a block. This method handles the induction
/// variable canonicalization. It supports both VF = 1 for unrolled loops and
/// arbitrary length vectors.
void widenPHIInstruction(Instruction *PN, VectorParts &Entry,
unsigned UF, unsigned VF, PhiVector *PV);
/// Insert the new loop to the loop hierarchy and pass manager
/// and update the analysis passes.
void updateAnalysis();
/// This instruction is un-vectorizable. Implement it as a sequence
/// of scalars. If \p IfPredicateStore is true we need to 'hide' each
/// scalarized instruction behind an if block predicated on the control
/// dependence of the instruction.
virtual void scalarizeInstruction(Instruction *Instr,
bool IfPredicateStore=false);
/// Vectorize Load and Store instructions,
virtual void vectorizeMemoryInstruction(Instruction *Instr);
/// Create a broadcast instruction. This method generates a broadcast
/// instruction (shuffle) for loop invariant values and for the induction
/// value. If this is the induction variable then we extend it to N, N+1, ...
/// this is needed because each iteration in the loop corresponds to a SIMD
/// element.
virtual Value *getBroadcastInstrs(Value *V);
/// This function adds (StartIdx, StartIdx + Step, StartIdx + 2*Step, ...)
/// to each vector element of Val. The sequence starts at StartIndex.
virtual Value *getStepVector(Value *Val, int StartIdx, Value *Step);
/// When we go over instructions in the basic block we rely on previous
/// values within the current basic block or on loop invariant values.
/// When we widen (vectorize) values we place them in the map. If the values
/// are not within the map, they have to be loop invariant, so we simply
/// broadcast them into a vector.
VectorParts &getVectorValue(Value *V);
/// Try to vectorize the interleaved access group that \p Instr belongs to.
void vectorizeInterleaveGroup(Instruction *Instr);
/// Generate a shuffle sequence that will reverse the vector Vec.
virtual Value *reverseVector(Value *Vec);
/// This is a helper class that holds the vectorizer state. It maps scalar
/// instructions to vector instructions. When the code is 'unrolled' then
/// then a single scalar value is mapped to multiple vector parts. The parts
/// are stored in the VectorPart type.
struct ValueMap {
/// C'tor. UnrollFactor controls the number of vectors ('parts') that
/// are mapped.
ValueMap(unsigned UnrollFactor) : UF(UnrollFactor) {}
/// \return True if 'Key' is saved in the Value Map.
bool has(Value *Key) const { return MapStorage.count(Key); }
/// Initializes a new entry in the map. Sets all of the vector parts to the
/// save value in 'Val'.
/// \return A reference to a vector with splat values.
VectorParts &splat(Value *Key, Value *Val) {
VectorParts &Entry = MapStorage[Key];
Entry.assign(UF, Val);
return Entry;
}
///\return A reference to the value that is stored at 'Key'.
VectorParts &get(Value *Key) {
VectorParts &Entry = MapStorage[Key];
if (Entry.empty())
Entry.resize(UF);
assert(Entry.size() == UF);
return Entry;
}
private:
/// The unroll factor. Each entry in the map stores this number of vector
/// elements.
unsigned UF;
/// Map storage. We use std::map and not DenseMap because insertions to a
/// dense map invalidates its iterators.
std::map<Value *, VectorParts> MapStorage;
};
/// The original loop.
Loop *OrigLoop;
/// Scev analysis to use.
ScalarEvolution *SE;
/// Loop Info.
LoopInfo *LI;
/// Dominator Tree.
DominatorTree *DT;
/// Alias Analysis.
AliasAnalysis *AA;
/// Target Library Info.
const TargetLibraryInfo *TLI;
/// Target Transform Info.
const TargetTransformInfo *TTI;
/// The vectorization SIMD factor to use. Each vector will have this many
/// vector elements.
unsigned VF;
protected:
/// The vectorization unroll factor to use. Each scalar is vectorized to this
/// many different vector instructions.
unsigned UF;
/// The builder that we use
IRBuilder<> Builder;
// --- Vectorization state ---
/// The vector-loop preheader.
BasicBlock *LoopVectorPreHeader;
/// The scalar-loop preheader.
BasicBlock *LoopScalarPreHeader;
/// Middle Block between the vector and the scalar.
BasicBlock *LoopMiddleBlock;
///The ExitBlock of the scalar loop.
BasicBlock *LoopExitBlock;
///The vector loop body.
SmallVector<BasicBlock *, 4> LoopVectorBody;
///The scalar loop body.
BasicBlock *LoopScalarBody;
/// A list of all bypass blocks. The first block is the entry of the loop.
SmallVector<BasicBlock *, 4> LoopBypassBlocks;
/// The new Induction variable which was added to the new block.
PHINode *Induction;
/// The induction variable of the old basic block.
PHINode *OldInduction;
/// Holds the extended (to the widest induction type) start index.
Value *ExtendedIdx;
/// Maps scalars to widened vectors.
ValueMap WidenMap;
EdgeMaskCache MaskCache;
LoopVectorizationLegality *Legal;
// Record whether runtime check is added.
bool AddedSafetyChecks;
};
class InnerLoopUnroller : public InnerLoopVectorizer {
public:
InnerLoopUnroller(Loop *OrigLoop, ScalarEvolution *SE, LoopInfo *LI,
DominatorTree *DT, const TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI, unsigned UnrollFactor)
: InnerLoopVectorizer(OrigLoop, SE, LI, DT, TLI, TTI, 1, UnrollFactor) {}
private:
void scalarizeInstruction(Instruction *Instr,
bool IfPredicateStore = false) override;
void vectorizeMemoryInstruction(Instruction *Instr) override;
Value *getBroadcastInstrs(Value *V) override;
Value *getStepVector(Value *Val, int StartIdx, Value *Step) override;
Value *reverseVector(Value *Vec) override;
};
/// \brief Look for a meaningful debug location on the instruction or it's
/// operands.
static Instruction *getDebugLocFromInstOrOperands(Instruction *I) {
if (!I)
return I;
DebugLoc Empty;
if (I->getDebugLoc() != Empty)
return I;
for (User::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI) {
if (Instruction *OpInst = dyn_cast<Instruction>(*OI))
if (OpInst->getDebugLoc() != Empty)
return OpInst;
}
return I;
}
/// \brief Set the debug location in the builder using the debug location in the
/// instruction.
static void setDebugLocFromInst(IRBuilder<> &B, const Value *Ptr) {
if (const Instruction *Inst = dyn_cast_or_null<Instruction>(Ptr))
B.SetCurrentDebugLocation(Inst->getDebugLoc());
else
B.SetCurrentDebugLocation(DebugLoc());
}
#ifndef NDEBUG
/// \return string containing a file name and a line # for the given loop.
static std::string getDebugLocString(const Loop *L) {
std::string Result;
if (L) {
raw_string_ostream OS(Result);
if (const DebugLoc LoopDbgLoc = L->getStartLoc())
LoopDbgLoc.print(OS);
else
// Just print the module name.
OS << L->getHeader()->getParent()->getParent()->getModuleIdentifier();
OS.flush();
}
return Result;
}
#endif
/// \brief Propagate known metadata from one instruction to another.
static void propagateMetadata(Instruction *To, const Instruction *From) {
SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
From->getAllMetadataOtherThanDebugLoc(Metadata);
for (auto M : Metadata) {
unsigned Kind = M.first;
// These are safe to transfer (this is safe for TBAA, even when we
// if-convert, because should that metadata have had a control dependency
// on the condition, and thus actually aliased with some other
// non-speculated memory access when the condition was false, this would be
// caught by the runtime overlap checks).
if (Kind != LLVMContext::MD_tbaa &&
Kind != LLVMContext::MD_alias_scope &&
Kind != LLVMContext::MD_noalias &&
Kind != LLVMContext::MD_fpmath)
continue;
To->setMetadata(Kind, M.second);
}
}
/// \brief Propagate known metadata from one instruction to a vector of others.
static void propagateMetadata(SmallVectorImpl<Value *> &To, const Instruction *From) {
for (Value *V : To)
if (Instruction *I = dyn_cast<Instruction>(V))
propagateMetadata(I, From);
}
/// \brief The group of interleaved loads/stores sharing the same stride and
/// close to each other.
///
/// Each member in this group has an index starting from 0, and the largest
/// index should be less than interleaved factor, which is equal to the absolute
/// value of the access's stride.
///
/// E.g. An interleaved load group of factor 4:
/// for (unsigned i = 0; i < 1024; i+=4) {
/// a = A[i]; // Member of index 0
/// b = A[i+1]; // Member of index 1
/// d = A[i+3]; // Member of index 3
/// ...
/// }
///
/// An interleaved store group of factor 4:
/// for (unsigned i = 0; i < 1024; i+=4) {
/// ...
/// A[i] = a; // Member of index 0
/// A[i+1] = b; // Member of index 1
/// A[i+2] = c; // Member of index 2
/// A[i+3] = d; // Member of index 3
/// }
///
/// Note: the interleaved load group could have gaps (missing members), but
/// the interleaved store group doesn't allow gaps.
class InterleaveGroup {
public:
InterleaveGroup(Instruction *Instr, int Stride, unsigned Align)
: Align(Align), SmallestKey(0), LargestKey(0), InsertPos(Instr) {
assert(Align && "The alignment should be non-zero");
Factor = std::abs(Stride);
assert(Factor > 1 && "Invalid interleave factor");
Reverse = Stride < 0;
Members[0] = Instr;
}
bool isReverse() const { return Reverse; }
unsigned getFactor() const { return Factor; }
unsigned getAlignment() const { return Align; }
unsigned getNumMembers() const { return Members.size(); }
/// \brief Try to insert a new member \p Instr with index \p Index and
/// alignment \p NewAlign. The index is related to the leader and it could be
/// negative if it is the new leader.
///
/// \returns false if the instruction doesn't belong to the group.
bool insertMember(Instruction *Instr, int Index, unsigned NewAlign) {
assert(NewAlign && "The new member's alignment should be non-zero");
int Key = Index + SmallestKey;
// Skip if there is already a member with the same index.
if (Members.count(Key))
return false;
if (Key > LargestKey) {
// The largest index is always less than the interleave factor.
if (Index >= static_cast<int>(Factor))
return false;
LargestKey = Key;
} else if (Key < SmallestKey) {
// The largest index is always less than the interleave factor.
if (LargestKey - Key >= static_cast<int>(Factor))
return false;
SmallestKey = Key;
}
// It's always safe to select the minimum alignment.
Align = std::min(Align, NewAlign);
Members[Key] = Instr;
return true;
}
/// \brief Get the member with the given index \p Index
///
/// \returns nullptr if contains no such member.
Instruction *getMember(unsigned Index) const {
int Key = SmallestKey + Index;
if (!Members.count(Key))
return nullptr;
return Members.find(Key)->second;
}
/// \brief Get the index for the given member. Unlike the key in the member
/// map, the index starts from 0.
unsigned getIndex(Instruction *Instr) const {
for (auto I : Members)
if (I.second == Instr)
return I.first - SmallestKey;
llvm_unreachable("InterleaveGroup contains no such member");
}
Instruction *getInsertPos() const { return InsertPos; }
void setInsertPos(Instruction *Inst) { InsertPos = Inst; }
private:
unsigned Factor; // Interleave Factor.
bool Reverse;
unsigned Align;
DenseMap<int, Instruction *> Members;
int SmallestKey;
int LargestKey;
// To avoid breaking dependences, vectorized instructions of an interleave
// group should be inserted at either the first load or the last store in
// program order.
//
// E.g. %even = load i32 // Insert Position
// %add = add i32 %even // Use of %even
// %odd = load i32
//
// store i32 %even
// %odd = add i32 // Def of %odd
// store i32 %odd // Insert Position
Instruction *InsertPos;
};
/// \brief Drive the analysis of interleaved memory accesses in the loop.
///
/// Use this class to analyze interleaved accesses only when we can vectorize
/// a loop. Otherwise it's meaningless to do analysis as the vectorization
/// on interleaved accesses is unsafe.
///
/// The analysis collects interleave groups and records the relationships
/// between the member and the group in a map.
class InterleavedAccessInfo {
public:
InterleavedAccessInfo(ScalarEvolution *SE, Loop *L, DominatorTree *DT)
: SE(SE), TheLoop(L), DT(DT) {}
~InterleavedAccessInfo() {
SmallSet<InterleaveGroup *, 4> DelSet;
// Avoid releasing a pointer twice.
for (auto &I : InterleaveGroupMap)
DelSet.insert(I.second);
for (auto *Ptr : DelSet)
delete Ptr;
}
/// \brief Analyze the interleaved accesses and collect them in interleave
/// groups. Substitute symbolic strides using \p Strides.
void analyzeInterleaving(const ValueToValueMap &Strides);
/// \brief Check if \p Instr belongs to any interleave group.
bool isInterleaved(Instruction *Instr) const {
return InterleaveGroupMap.count(Instr);
}
/// \brief Get the interleave group that \p Instr belongs to.
///
/// \returns nullptr if doesn't have such group.
InterleaveGroup *getInterleaveGroup(Instruction *Instr) const {
if (InterleaveGroupMap.count(Instr))
return InterleaveGroupMap.find(Instr)->second;
return nullptr;
}
private:
ScalarEvolution *SE;
Loop *TheLoop;
DominatorTree *DT;
/// Holds the relationships between the members and the interleave group.
DenseMap<Instruction *, InterleaveGroup *> InterleaveGroupMap;
/// \brief The descriptor for a strided memory access.
struct StrideDescriptor {
StrideDescriptor(int Stride, const SCEV *Scev, unsigned Size,
unsigned Align)
: Stride(Stride), Scev(Scev), Size(Size), Align(Align) {}
StrideDescriptor() : Stride(0), Scev(nullptr), Size(0), Align(0) {}
int Stride; // The access's stride. It is negative for a reverse access.
const SCEV *Scev; // The scalar expression of this access
unsigned Size; // The size of the memory object.
unsigned Align; // The alignment of this access.
};
/// \brief Create a new interleave group with the given instruction \p Instr,
/// stride \p Stride and alignment \p Align.
///
/// \returns the newly created interleave group.
InterleaveGroup *createInterleaveGroup(Instruction *Instr, int Stride,
unsigned Align) {
assert(!InterleaveGroupMap.count(Instr) &&
"Already in an interleaved access group");
InterleaveGroupMap[Instr] = new InterleaveGroup(Instr, Stride, Align);
return InterleaveGroupMap[Instr];
}
/// \brief Release the group and remove all the relationships.
void releaseGroup(InterleaveGroup *Group) {
for (unsigned i = 0; i < Group->getFactor(); i++)
if (Instruction *Member = Group->getMember(i))
InterleaveGroupMap.erase(Member);
delete Group;
}
/// \brief Collect all the accesses with a constant stride in program order.
void collectConstStridedAccesses(
MapVector<Instruction *, StrideDescriptor> &StrideAccesses,
const ValueToValueMap &Strides);
};
/// LoopVectorizationLegality checks if it is legal to vectorize a loop, and
/// to what vectorization factor.
/// This class does not look at the profitability of vectorization, only the
/// legality. This class has two main kinds of checks:
/// * Memory checks - The code in canVectorizeMemory checks if vectorization
/// will change the order of memory accesses in a way that will change the
/// correctness of the program.
/// * Scalars checks - The code in canVectorizeInstrs and canVectorizeMemory
/// checks for a number of different conditions, such as the availability of a
/// single induction variable, that all types are supported and vectorize-able,
/// etc. This code reflects the capabilities of InnerLoopVectorizer.
/// This class is also used by InnerLoopVectorizer for identifying
/// induction variable and the different reduction variables.
class LoopVectorizationLegality {
public:
LoopVectorizationLegality(Loop *L, ScalarEvolution *SE, DominatorTree *DT,
TargetLibraryInfo *TLI, AliasAnalysis *AA,
Function *F, const TargetTransformInfo *TTI,
LoopAccessAnalysis *LAA)
: NumPredStores(0), TheLoop(L), SE(SE), TLI(TLI), TheFunction(F),
TTI(TTI), DT(DT), LAA(LAA), LAI(nullptr), InterleaveInfo(SE, L, DT),
Induction(nullptr), WidestIndTy(nullptr), HasFunNoNaNAttr(false) {}
/// This enum represents the kinds of inductions that we support.
enum InductionKind {
IK_NoInduction, ///< Not an induction variable.
IK_IntInduction, ///< Integer induction variable. Step = C.
IK_PtrInduction ///< Pointer induction var. Step = C / sizeof(elem).
};
/// A struct for saving information about induction variables.
struct InductionInfo {
InductionInfo(Value *Start, InductionKind K, ConstantInt *Step)
: StartValue(Start), IK(K), StepValue(Step) {
assert(IK != IK_NoInduction && "Not an induction");
assert(StartValue && "StartValue is null");
assert(StepValue && !StepValue->isZero() && "StepValue is zero");
assert((IK != IK_PtrInduction || StartValue->getType()->isPointerTy()) &&
"StartValue is not a pointer for pointer induction");
assert((IK != IK_IntInduction || StartValue->getType()->isIntegerTy()) &&
"StartValue is not an integer for integer induction");
assert(StepValue->getType()->isIntegerTy() &&
"StepValue is not an integer");
}
InductionInfo()
: StartValue(nullptr), IK(IK_NoInduction), StepValue(nullptr) {}
/// Get the consecutive direction. Returns:
/// 0 - unknown or non-consecutive.
/// 1 - consecutive and increasing.
/// -1 - consecutive and decreasing.
int getConsecutiveDirection() const {
if (StepValue && (StepValue->isOne() || StepValue->isMinusOne()))
return StepValue->getSExtValue();
return 0;
}
/// Compute the transformed value of Index at offset StartValue using step
/// StepValue.
/// For integer induction, returns StartValue + Index * StepValue.
/// For pointer induction, returns StartValue[Index * StepValue].
/// FIXME: The newly created binary instructions should contain nsw/nuw
/// flags, which can be found from the original scalar operations.
Value *transform(IRBuilder<> &B, Value *Index) const {
switch (IK) {
case IK_IntInduction:
assert(Index->getType() == StartValue->getType() &&
"Index type does not match StartValue type");
if (StepValue->isMinusOne())
return B.CreateSub(StartValue, Index);
if (!StepValue->isOne())
Index = B.CreateMul(Index, StepValue);
return B.CreateAdd(StartValue, Index);
case IK_PtrInduction:
assert(Index->getType() == StepValue->getType() &&
"Index type does not match StepValue type");
if (StepValue->isMinusOne())
Index = B.CreateNeg(Index);
else if (!StepValue->isOne())
Index = B.CreateMul(Index, StepValue);
return B.CreateGEP(nullptr, StartValue, Index);
case IK_NoInduction:
return nullptr;
}
llvm_unreachable("invalid enum");
}
/// Start value.
TrackingVH<Value> StartValue;
/// Induction kind.
InductionKind IK;
/// Step value.
ConstantInt *StepValue;
};
/// ReductionList contains the reduction descriptors for all
/// of the reductions that were found in the loop.
typedef DenseMap<PHINode *, RecurrenceDescriptor> ReductionList;
/// InductionList saves induction variables and maps them to the
/// induction descriptor.
typedef MapVector<PHINode*, InductionInfo> InductionList;
/// Returns true if it is legal to vectorize this loop.
/// This does not mean that it is profitable to vectorize this
/// loop, only that it is legal to do so.
bool canVectorize();
/// Returns the Induction variable.
PHINode *getInduction() { return Induction; }
/// Returns the reduction variables found in the loop.
ReductionList *getReductionVars() { return &Reductions; }
/// Returns the induction variables found in the loop.
InductionList *getInductionVars() { return &Inductions; }
/// Returns the widest induction type.
Type *getWidestInductionType() { return WidestIndTy; }
/// Returns True if V is an induction variable in this loop.
bool isInductionVariable(const Value *V);
/// Return true if the block BB needs to be predicated in order for the loop
/// to be vectorized.
bool blockNeedsPredication(BasicBlock *BB);
/// Check if this pointer is consecutive when vectorizing. This happens
/// when the last index of the GEP is the induction variable, or that the
/// pointer itself is an induction variable.
/// This check allows us to vectorize A[idx] into a wide load/store.
/// Returns:
/// 0 - Stride is unknown or non-consecutive.
/// 1 - Address is consecutive.
/// -1 - Address is consecutive, and decreasing.
int isConsecutivePtr(Value *Ptr);
/// Returns true if the value V is uniform within the loop.
bool isUniform(Value *V);
/// Returns true if this instruction will remain scalar after vectorization.
bool isUniformAfterVectorization(Instruction* I) { return Uniforms.count(I); }
/// Returns the information that we collected about runtime memory check.
const RuntimePointerChecking *getRuntimePointerChecking() const {
return LAI->getRuntimePointerChecking();
}
const LoopAccessInfo *getLAI() const {
return LAI;
}
/// \brief Check if \p Instr belongs to any interleaved access group.
bool isAccessInterleaved(Instruction *Instr) {
return InterleaveInfo.isInterleaved(Instr);
}
/// \brief Get the interleaved access group that \p Instr belongs to.
const InterleaveGroup *getInterleavedAccessGroup(Instruction *Instr) {
return InterleaveInfo.getInterleaveGroup(Instr);
}
unsigned getMaxSafeDepDistBytes() { return LAI->getMaxSafeDepDistBytes(); }
bool hasStride(Value *V) { return StrideSet.count(V); }
bool mustCheckStrides() { return !StrideSet.empty(); }
SmallPtrSet<Value *, 8>::iterator strides_begin() {
return StrideSet.begin();
}
SmallPtrSet<Value *, 8>::iterator strides_end() { return StrideSet.end(); }
/// Returns true if the target machine supports masked store operation
/// for the given \p DataType and kind of access to \p Ptr.
bool isLegalMaskedStore(Type *DataType, Value *Ptr) {
return TTI->isLegalMaskedStore(DataType, isConsecutivePtr(Ptr));
}
/// Returns true if the target machine supports masked load operation
/// for the given \p DataType and kind of access to \p Ptr.
bool isLegalMaskedLoad(Type *DataType, Value *Ptr) {
return TTI->isLegalMaskedLoad(DataType, isConsecutivePtr(Ptr));
}
/// Returns true if vector representation of the instruction \p I
/// requires mask.
bool isMaskRequired(const Instruction* I) {
return (MaskedOp.count(I) != 0);
}
unsigned getNumStores() const {
return LAI->getNumStores();
}
unsigned getNumLoads() const {
return LAI->getNumLoads();
}
unsigned getNumPredStores() const {
return NumPredStores;
}
private:
/// Check if a single basic block loop is vectorizable.
/// At this point we know that this is a loop with a constant trip count
/// and we only need to check individual instructions.
bool canVectorizeInstrs();
/// When we vectorize loops we may change the order in which
/// we read and write from memory. This method checks if it is
/// legal to vectorize the code, considering only memory constrains.
/// Returns true if the loop is vectorizable
bool canVectorizeMemory();
/// Return true if we can vectorize this loop using the IF-conversion
/// transformation.
bool canVectorizeWithIfConvert();
/// Collect the variables that need to stay uniform after vectorization.
void collectLoopUniforms();
/// Return true if all of the instructions in the block can be speculatively
/// executed. \p SafePtrs is a list of addresses that are known to be legal
/// and we know that we can read from them without segfault.
bool blockCanBePredicated(BasicBlock *BB, SmallPtrSetImpl<Value *> &SafePtrs);