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llvm-6502/lib/Transforms/Vectorize/BBVectorize.cpp
Hal Finkel 282969ed36 Precompute SCEV pointer analysis prior to instruction fusion in BBVectorize. 
When both a load/store and its address computation are being vectorized, it can
happen that the address-computation vectorization destroys SCEV's ability
to analyize the relative pointer offsets. As a result (like with the aliasing
analysis info), we need to precompute the necessary information prior to
instruction fusing.

This was found during stress testing (running through the test suite with a very
low required chain length); unfortunately, I don't have a small test case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159332 91177308-0d34-0410-b5e6-96231b3b80d8
2012-06-28 05:42:45 +00:00

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//===- BBVectorize.cpp - A Basic-Block Vectorizer -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a basic-block vectorization pass. The algorithm was
// inspired by that used by the Vienna MAP Vectorizor by Franchetti and Kral,
// et al. It works by looking for chains of pairable operations and then
// pairing them.
//
//===----------------------------------------------------------------------===//
#define BBV_NAME "bb-vectorize"
#define DEBUG_TYPE BBV_NAME
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Intrinsics.h"
#include "llvm/LLVMContext.h"
#include "llvm/Metadata.h"
#include "llvm/Pass.h"
#include "llvm/Type.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Vectorize.h"
#include <algorithm>
#include <map>
using namespace llvm;
static cl::opt<unsigned>
ReqChainDepth("bb-vectorize-req-chain-depth", cl::init(6), cl::Hidden,
cl::desc("The required chain depth for vectorization"));
static cl::opt<unsigned>
SearchLimit("bb-vectorize-search-limit", cl::init(400), cl::Hidden,
cl::desc("The maximum search distance for instruction pairs"));
static cl::opt<bool>
SplatBreaksChain("bb-vectorize-splat-breaks-chain", cl::init(false), cl::Hidden,
cl::desc("Replicating one element to a pair breaks the chain"));
static cl::opt<unsigned>
VectorBits("bb-vectorize-vector-bits", cl::init(128), cl::Hidden,
cl::desc("The size of the native vector registers"));
static cl::opt<unsigned>
MaxIter("bb-vectorize-max-iter", cl::init(0), cl::Hidden,
cl::desc("The maximum number of pairing iterations"));
static cl::opt<bool>
Pow2LenOnly("bb-vectorize-pow2-len-only", cl::init(false), cl::Hidden,
cl::desc("Don't try to form non-2^n-length vectors"));
static cl::opt<unsigned>
MaxInsts("bb-vectorize-max-instr-per-group", cl::init(500), cl::Hidden,
cl::desc("The maximum number of pairable instructions per group"));
static cl::opt<unsigned>
MaxCandPairsForCycleCheck("bb-vectorize-max-cycle-check-pairs", cl::init(200),
cl::Hidden, cl::desc("The maximum number of candidate pairs with which to use"
" a full cycle check"));
static cl::opt<bool>
NoBools("bb-vectorize-no-bools", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize boolean (i1) values"));
static cl::opt<bool>
NoInts("bb-vectorize-no-ints", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize integer values"));
static cl::opt<bool>
NoFloats("bb-vectorize-no-floats", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize floating-point values"));
static cl::opt<bool>
NoPointers("bb-vectorize-no-pointers", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize pointer values"));
static cl::opt<bool>
NoCasts("bb-vectorize-no-casts", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize casting (conversion) operations"));
static cl::opt<bool>
NoMath("bb-vectorize-no-math", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize floating-point math intrinsics"));
static cl::opt<bool>
NoFMA("bb-vectorize-no-fma", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize the fused-multiply-add intrinsic"));
static cl::opt<bool>
NoSelect("bb-vectorize-no-select", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize select instructions"));
static cl::opt<bool>
NoCmp("bb-vectorize-no-cmp", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize comparison instructions"));
static cl::opt<bool>
NoGEP("bb-vectorize-no-gep", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize getelementptr instructions"));
static cl::opt<bool>
NoMemOps("bb-vectorize-no-mem-ops", cl::init(false), cl::Hidden,
cl::desc("Don't try to vectorize loads and stores"));
static cl::opt<bool>
AlignedOnly("bb-vectorize-aligned-only", cl::init(false), cl::Hidden,
cl::desc("Only generate aligned loads and stores"));
static cl::opt<bool>
NoMemOpBoost("bb-vectorize-no-mem-op-boost",
cl::init(false), cl::Hidden,
cl::desc("Don't boost the chain-depth contribution of loads and stores"));
static cl::opt<bool>
FastDep("bb-vectorize-fast-dep", cl::init(false), cl::Hidden,
cl::desc("Use a fast instruction dependency analysis"));
#ifndef NDEBUG
static cl::opt<bool>
DebugInstructionExamination("bb-vectorize-debug-instruction-examination",
cl::init(false), cl::Hidden,
cl::desc("When debugging is enabled, output information on the"
" instruction-examination process"));
static cl::opt<bool>
DebugCandidateSelection("bb-vectorize-debug-candidate-selection",
cl::init(false), cl::Hidden,
cl::desc("When debugging is enabled, output information on the"
" candidate-selection process"));
static cl::opt<bool>
DebugPairSelection("bb-vectorize-debug-pair-selection",
cl::init(false), cl::Hidden,
cl::desc("When debugging is enabled, output information on the"
" pair-selection process"));
static cl::opt<bool>
DebugCycleCheck("bb-vectorize-debug-cycle-check",
cl::init(false), cl::Hidden,
cl::desc("When debugging is enabled, output information on the"
" cycle-checking process"));
#endif
STATISTIC(NumFusedOps, "Number of operations fused by bb-vectorize");
namespace {
struct BBVectorize : public BasicBlockPass {
static char ID; // Pass identification, replacement for typeid
const VectorizeConfig Config;
BBVectorize(const VectorizeConfig &C = VectorizeConfig())
: BasicBlockPass(ID), Config(C) {
initializeBBVectorizePass(*PassRegistry::getPassRegistry());
}
BBVectorize(Pass *P, const VectorizeConfig &C)
: BasicBlockPass(ID), Config(C) {
AA = &P->getAnalysis<AliasAnalysis>();
SE = &P->getAnalysis<ScalarEvolution>();
TD = P->getAnalysisIfAvailable<TargetData>();
}
typedef std::pair<Value *, Value *> ValuePair;
typedef std::pair<ValuePair, size_t> ValuePairWithDepth;
typedef std::pair<ValuePair, ValuePair> VPPair; // A ValuePair pair
typedef std::pair<std::multimap<Value *, Value *>::iterator,
std::multimap<Value *, Value *>::iterator> VPIteratorPair;
typedef std::pair<std::multimap<ValuePair, ValuePair>::iterator,
std::multimap<ValuePair, ValuePair>::iterator>
VPPIteratorPair;
AliasAnalysis *AA;
ScalarEvolution *SE;
TargetData *TD;
// FIXME: const correct?
bool vectorizePairs(BasicBlock &BB, bool NonPow2Len = false);
bool getCandidatePairs(BasicBlock &BB,
BasicBlock::iterator &Start,
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts, bool NonPow2Len);
void computeConnectedPairs(std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs);
void buildDepMap(BasicBlock &BB,
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
DenseSet<ValuePair> &PairableInstUsers);
void choosePairs(std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
DenseSet<ValuePair> &PairableInstUsers,
DenseMap<Value *, Value *>& ChosenPairs);
void fuseChosenPairs(BasicBlock &BB,
std::vector<Value *> &PairableInsts,
DenseMap<Value *, Value *>& ChosenPairs);
bool isInstVectorizable(Instruction *I, bool &IsSimpleLoadStore);
bool areInstsCompatible(Instruction *I, Instruction *J,
bool IsSimpleLoadStore, bool NonPow2Len);
bool trackUsesOfI(DenseSet<Value *> &Users,
AliasSetTracker &WriteSet, Instruction *I,
Instruction *J, bool UpdateUsers = true,
std::multimap<Value *, Value *> *LoadMoveSet = 0);
void computePairsConnectedTo(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
ValuePair P);
bool pairsConflict(ValuePair P, ValuePair Q,
DenseSet<ValuePair> &PairableInstUsers,
std::multimap<ValuePair, ValuePair> *PairableInstUserMap = 0);
bool pairWillFormCycle(ValuePair P,
std::multimap<ValuePair, ValuePair> &PairableInstUsers,
DenseSet<ValuePair> &CurrentPairs);
void pruneTreeFor(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
DenseSet<ValuePair> &PairableInstUsers,
std::multimap<ValuePair, ValuePair> &PairableInstUserMap,
DenseMap<Value *, Value *> &ChosenPairs,
DenseMap<ValuePair, size_t> &Tree,
DenseSet<ValuePair> &PrunedTree, ValuePair J,
bool UseCycleCheck);
void buildInitialTreeFor(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
DenseSet<ValuePair> &PairableInstUsers,
DenseMap<Value *, Value *> &ChosenPairs,
DenseMap<ValuePair, size_t> &Tree, ValuePair J);
void findBestTreeFor(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
DenseSet<ValuePair> &PairableInstUsers,
std::multimap<ValuePair, ValuePair> &PairableInstUserMap,
DenseMap<Value *, Value *> &ChosenPairs,
DenseSet<ValuePair> &BestTree, size_t &BestMaxDepth,
size_t &BestEffSize, VPIteratorPair ChoiceRange,
bool UseCycleCheck);
Value *getReplacementPointerInput(LLVMContext& Context, Instruction *I,
Instruction *J, unsigned o, bool FlipMemInputs);
void fillNewShuffleMask(LLVMContext& Context, Instruction *J,
unsigned MaskOffset, unsigned NumInElem,
unsigned NumInElem1, unsigned IdxOffset,
std::vector<Constant*> &Mask);
Value *getReplacementShuffleMask(LLVMContext& Context, Instruction *I,
Instruction *J);
bool expandIEChain(LLVMContext& Context, Instruction *I, Instruction *J,
unsigned o, Value *&LOp, unsigned numElemL,
Type *ArgTypeL, Type *ArgTypeR,
unsigned IdxOff = 0);
Value *getReplacementInput(LLVMContext& Context, Instruction *I,
Instruction *J, unsigned o, bool FlipMemInputs);
void getReplacementInputsForPair(LLVMContext& Context, Instruction *I,
Instruction *J, SmallVector<Value *, 3> &ReplacedOperands,
bool FlipMemInputs);
void replaceOutputsOfPair(LLVMContext& Context, Instruction *I,
Instruction *J, Instruction *K,
Instruction *&InsertionPt, Instruction *&K1,
Instruction *&K2, bool FlipMemInputs);
void collectPairLoadMoveSet(BasicBlock &BB,
DenseMap<Value *, Value *> &ChosenPairs,
std::multimap<Value *, Value *> &LoadMoveSet,
Instruction *I);
void collectLoadMoveSet(BasicBlock &BB,
std::vector<Value *> &PairableInsts,
DenseMap<Value *, Value *> &ChosenPairs,
std::multimap<Value *, Value *> &LoadMoveSet);
void collectPtrInfo(std::vector<Value *> &PairableInsts,
DenseMap<Value *, Value *> &ChosenPairs,
DenseSet<Value *> &LowPtrInsts);
bool canMoveUsesOfIAfterJ(BasicBlock &BB,
std::multimap<Value *, Value *> &LoadMoveSet,
Instruction *I, Instruction *J);
void moveUsesOfIAfterJ(BasicBlock &BB,
std::multimap<Value *, Value *> &LoadMoveSet,
Instruction *&InsertionPt,
Instruction *I, Instruction *J);
void combineMetadata(Instruction *K, const Instruction *J);
bool vectorizeBB(BasicBlock &BB) {
bool changed = false;
// Iterate a sufficient number of times to merge types of size 1 bit,
// then 2 bits, then 4, etc. up to half of the target vector width of the
// target vector register.
unsigned n = 1;
for (unsigned v = 2;
v <= Config.VectorBits && (!Config.MaxIter || n <= Config.MaxIter);
v *= 2, ++n) {
DEBUG(dbgs() << "BBV: fusing loop #" << n <<
" for " << BB.getName() << " in " <<
BB.getParent()->getName() << "...\n");
if (vectorizePairs(BB))
changed = true;
else
break;
}
if (changed && !Pow2LenOnly) {
++n;
for (; !Config.MaxIter || n <= Config.MaxIter; ++n) {
DEBUG(dbgs() << "BBV: fusing for non-2^n-length vectors loop #: " <<
n << " for " << BB.getName() << " in " <<
BB.getParent()->getName() << "...\n");
if (!vectorizePairs(BB, true)) break;
}
}
DEBUG(dbgs() << "BBV: done!\n");
return changed;
}
virtual bool runOnBasicBlock(BasicBlock &BB) {
AA = &getAnalysis<AliasAnalysis>();
SE = &getAnalysis<ScalarEvolution>();
TD = getAnalysisIfAvailable<TargetData>();
return vectorizeBB(BB);
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
BasicBlockPass::getAnalysisUsage(AU);
AU.addRequired<AliasAnalysis>();
AU.addRequired<ScalarEvolution>();
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<ScalarEvolution>();
AU.setPreservesCFG();
}
static inline VectorType *getVecTypeForPair(Type *ElemTy, Type *Elem2Ty) {
assert(ElemTy->getScalarType() == Elem2Ty->getScalarType() &&
"Cannot form vector from incompatible scalar types");
Type *STy = ElemTy->getScalarType();
unsigned numElem;
if (VectorType *VTy = dyn_cast<VectorType>(ElemTy)) {
numElem = VTy->getNumElements();
} else {
numElem = 1;
}
if (VectorType *VTy = dyn_cast<VectorType>(Elem2Ty)) {
numElem += VTy->getNumElements();
} else {
numElem += 1;
}
return VectorType::get(STy, numElem);
}
static inline void getInstructionTypes(Instruction *I,
Type *&T1, Type *&T2) {
if (isa<StoreInst>(I)) {
// For stores, it is the value type, not the pointer type that matters
// because the value is what will come from a vector register.
Value *IVal = cast<StoreInst>(I)->getValueOperand();
T1 = IVal->getType();
} else {
T1 = I->getType();
}
if (I->isCast())
T2 = cast<CastInst>(I)->getSrcTy();
else
T2 = T1;
}
// Returns the weight associated with the provided value. A chain of
// candidate pairs has a length given by the sum of the weights of its
// members (one weight per pair; the weight of each member of the pair
// is assumed to be the same). This length is then compared to the
// chain-length threshold to determine if a given chain is significant
// enough to be vectorized. The length is also used in comparing
// candidate chains where longer chains are considered to be better.
// Note: when this function returns 0, the resulting instructions are
// not actually fused.
inline size_t getDepthFactor(Value *V) {
// InsertElement and ExtractElement have a depth factor of zero. This is
// for two reasons: First, they cannot be usefully fused. Second, because
// the pass generates a lot of these, they can confuse the simple metric
// used to compare the trees in the next iteration. Thus, giving them a
// weight of zero allows the pass to essentially ignore them in
// subsequent iterations when looking for vectorization opportunities
// while still tracking dependency chains that flow through those
// instructions.
if (isa<InsertElementInst>(V) || isa<ExtractElementInst>(V))
return 0;
// Give a load or store half of the required depth so that load/store
// pairs will vectorize.
if (!Config.NoMemOpBoost && (isa<LoadInst>(V) || isa<StoreInst>(V)))
return Config.ReqChainDepth/2;
return 1;
}
// This determines the relative offset of two loads or stores, returning
// true if the offset could be determined to be some constant value.
// For example, if OffsetInElmts == 1, then J accesses the memory directly
// after I; if OffsetInElmts == -1 then I accesses the memory
// directly after J.
bool getPairPtrInfo(Instruction *I, Instruction *J,
Value *&IPtr, Value *&JPtr, unsigned &IAlignment, unsigned &JAlignment,
int64_t &OffsetInElmts) {
OffsetInElmts = 0;
if (isa<LoadInst>(I)) {
IPtr = cast<LoadInst>(I)->getPointerOperand();
JPtr = cast<LoadInst>(J)->getPointerOperand();
IAlignment = cast<LoadInst>(I)->getAlignment();
JAlignment = cast<LoadInst>(J)->getAlignment();
} else {
IPtr = cast<StoreInst>(I)->getPointerOperand();
JPtr = cast<StoreInst>(J)->getPointerOperand();
IAlignment = cast<StoreInst>(I)->getAlignment();
JAlignment = cast<StoreInst>(J)->getAlignment();
}
const SCEV *IPtrSCEV = SE->getSCEV(IPtr);
const SCEV *JPtrSCEV = SE->getSCEV(JPtr);
// If this is a trivial offset, then we'll get something like
// 1*sizeof(type). With target data, which we need anyway, this will get
// constant folded into a number.
const SCEV *OffsetSCEV = SE->getMinusSCEV(JPtrSCEV, IPtrSCEV);
if (const SCEVConstant *ConstOffSCEV =
dyn_cast<SCEVConstant>(OffsetSCEV)) {
ConstantInt *IntOff = ConstOffSCEV->getValue();
int64_t Offset = IntOff->getSExtValue();
Type *VTy = cast<PointerType>(IPtr->getType())->getElementType();
int64_t VTyTSS = (int64_t) TD->getTypeStoreSize(VTy);
Type *VTy2 = cast<PointerType>(JPtr->getType())->getElementType();
if (VTy != VTy2 && Offset < 0) {
int64_t VTy2TSS = (int64_t) TD->getTypeStoreSize(VTy2);
OffsetInElmts = Offset/VTy2TSS;
return (abs64(Offset) % VTy2TSS) == 0;
}
OffsetInElmts = Offset/VTyTSS;
return (abs64(Offset) % VTyTSS) == 0;
}
return false;
}
// Returns true if the provided CallInst represents an intrinsic that can
// be vectorized.
bool isVectorizableIntrinsic(CallInst* I) {
Function *F = I->getCalledFunction();
if (!F) return false;
unsigned IID = F->getIntrinsicID();
if (!IID) return false;
switch(IID) {
default:
return false;
case Intrinsic::sqrt:
case Intrinsic::powi:
case Intrinsic::sin:
case Intrinsic::cos:
case Intrinsic::log:
case Intrinsic::log2:
case Intrinsic::log10:
case Intrinsic::exp:
case Intrinsic::exp2:
case Intrinsic::pow:
return Config.VectorizeMath;
case Intrinsic::fma:
return Config.VectorizeFMA;
}
}
// Returns true if J is the second element in some pair referenced by
// some multimap pair iterator pair.
template <typename V>
bool isSecondInIteratorPair(V J, std::pair<
typename std::multimap<V, V>::iterator,
typename std::multimap<V, V>::iterator> PairRange) {
for (typename std::multimap<V, V>::iterator K = PairRange.first;
K != PairRange.second; ++K)
if (K->second == J) return true;
return false;
}
};
// This function implements one vectorization iteration on the provided
// basic block. It returns true if the block is changed.
bool BBVectorize::vectorizePairs(BasicBlock &BB, bool NonPow2Len) {
bool ShouldContinue;
BasicBlock::iterator Start = BB.getFirstInsertionPt();
std::vector<Value *> AllPairableInsts;
DenseMap<Value *, Value *> AllChosenPairs;
do {
std::vector<Value *> PairableInsts;
std::multimap<Value *, Value *> CandidatePairs;
ShouldContinue = getCandidatePairs(BB, Start, CandidatePairs,
PairableInsts, NonPow2Len);
if (PairableInsts.empty()) continue;
// Now we have a map of all of the pairable instructions and we need to
// select the best possible pairing. A good pairing is one such that the
// users of the pair are also paired. This defines a (directed) forest
// over the pairs such that two pairs are connected iff the second pair
// uses the first.
// Note that it only matters that both members of the second pair use some
// element of the first pair (to allow for splatting).
std::multimap<ValuePair, ValuePair> ConnectedPairs;
computeConnectedPairs(CandidatePairs, PairableInsts, ConnectedPairs);
if (ConnectedPairs.empty()) continue;
// Build the pairable-instruction dependency map
DenseSet<ValuePair> PairableInstUsers;
buildDepMap(BB, CandidatePairs, PairableInsts, PairableInstUsers);
// There is now a graph of the connected pairs. For each variable, pick
// the pairing with the largest tree meeting the depth requirement on at
// least one branch. Then select all pairings that are part of that tree
// and remove them from the list of available pairings and pairable
// variables.
DenseMap<Value *, Value *> ChosenPairs;
choosePairs(CandidatePairs, PairableInsts, ConnectedPairs,
PairableInstUsers, ChosenPairs);
if (ChosenPairs.empty()) continue;
AllPairableInsts.insert(AllPairableInsts.end(), PairableInsts.begin(),
PairableInsts.end());
AllChosenPairs.insert(ChosenPairs.begin(), ChosenPairs.end());
} while (ShouldContinue);
if (AllChosenPairs.empty()) return false;
NumFusedOps += AllChosenPairs.size();
// A set of pairs has now been selected. It is now necessary to replace the
// paired instructions with vector instructions. For this procedure each
// operand must be replaced with a vector operand. This vector is formed
// by using build_vector on the old operands. The replaced values are then
// replaced with a vector_extract on the result. Subsequent optimization
// passes should coalesce the build/extract combinations.
fuseChosenPairs(BB, AllPairableInsts, AllChosenPairs);
// It is important to cleanup here so that future iterations of this
// function have less work to do.
(void) SimplifyInstructionsInBlock(&BB, TD);
return true;
}
// This function returns true if the provided instruction is capable of being
// fused into a vector instruction. This determination is based only on the
// type and other attributes of the instruction.
bool BBVectorize::isInstVectorizable(Instruction *I,
bool &IsSimpleLoadStore) {
IsSimpleLoadStore = false;
if (CallInst *C = dyn_cast<CallInst>(I)) {
if (!isVectorizableIntrinsic(C))
return false;
} else if (LoadInst *L = dyn_cast<LoadInst>(I)) {
// Vectorize simple loads if possbile:
IsSimpleLoadStore = L->isSimple();
if (!IsSimpleLoadStore || !Config.VectorizeMemOps)
return false;
} else if (StoreInst *S = dyn_cast<StoreInst>(I)) {
// Vectorize simple stores if possbile:
IsSimpleLoadStore = S->isSimple();
if (!IsSimpleLoadStore || !Config.VectorizeMemOps)
return false;
} else if (CastInst *C = dyn_cast<CastInst>(I)) {
// We can vectorize casts, but not casts of pointer types, etc.
if (!Config.VectorizeCasts)
return false;
Type *SrcTy = C->getSrcTy();
if (!SrcTy->isSingleValueType())
return false;
Type *DestTy = C->getDestTy();
if (!DestTy->isSingleValueType())
return false;
} else if (isa<SelectInst>(I)) {
if (!Config.VectorizeSelect)
return false;
} else if (isa<CmpInst>(I)) {
if (!Config.VectorizeCmp)
return false;
} else if (GetElementPtrInst *G = dyn_cast<GetElementPtrInst>(I)) {
if (!Config.VectorizeGEP)
return false;
// Currently, vector GEPs exist only with one index.
if (G->getNumIndices() != 1)
return false;
} else if (!(I->isBinaryOp() || isa<ShuffleVectorInst>(I) ||
isa<ExtractElementInst>(I) || isa<InsertElementInst>(I))) {
return false;
}
// We can't vectorize memory operations without target data
if (TD == 0 && IsSimpleLoadStore)
return false;
Type *T1, *T2;
getInstructionTypes(I, T1, T2);
// Not every type can be vectorized...
if (!(VectorType::isValidElementType(T1) || T1->isVectorTy()) ||
!(VectorType::isValidElementType(T2) || T2->isVectorTy()))
return false;
if (T1->getScalarSizeInBits() == 1 && T2->getScalarSizeInBits() == 1) {
if (!Config.VectorizeBools)
return false;
} else {
if (!Config.VectorizeInts
&& (T1->isIntOrIntVectorTy() || T2->isIntOrIntVectorTy()))
return false;
}
if (!Config.VectorizeFloats
&& (T1->isFPOrFPVectorTy() || T2->isFPOrFPVectorTy()))
return false;
// Don't vectorize target-specific types.
if (T1->isX86_FP80Ty() || T1->isPPC_FP128Ty() || T1->isX86_MMXTy())
return false;
if (T2->isX86_FP80Ty() || T2->isPPC_FP128Ty() || T2->isX86_MMXTy())
return false;
if ((!Config.VectorizePointers || TD == 0) &&
(T1->getScalarType()->isPointerTy() ||
T2->getScalarType()->isPointerTy()))
return false;
if (T1->getPrimitiveSizeInBits() >= Config.VectorBits ||
T2->getPrimitiveSizeInBits() >= Config.VectorBits)
return false;
return true;
}
// This function returns true if the two provided instructions are compatible
// (meaning that they can be fused into a vector instruction). This assumes
// that I has already been determined to be vectorizable and that J is not
// in the use tree of I.
bool BBVectorize::areInstsCompatible(Instruction *I, Instruction *J,
bool IsSimpleLoadStore, bool NonPow2Len) {
DEBUG(if (DebugInstructionExamination) dbgs() << "BBV: looking at " << *I <<
" <-> " << *J << "\n");
// Loads and stores can be merged if they have different alignments,
// but are otherwise the same.
if (!J->isSameOperationAs(I, Instruction::CompareIgnoringAlignment |
(NonPow2Len ? Instruction::CompareUsingScalarTypes : 0)))
return false;
Type *IT1, *IT2, *JT1, *JT2;
getInstructionTypes(I, IT1, IT2);
getInstructionTypes(J, JT1, JT2);
unsigned MaxTypeBits = std::max(
IT1->getPrimitiveSizeInBits() + JT1->getPrimitiveSizeInBits(),
IT2->getPrimitiveSizeInBits() + JT2->getPrimitiveSizeInBits());
if (MaxTypeBits > Config.VectorBits)
return false;
// FIXME: handle addsub-type operations!
if (IsSimpleLoadStore) {
Value *IPtr, *JPtr;
unsigned IAlignment, JAlignment;
int64_t OffsetInElmts = 0;
if (getPairPtrInfo(I, J, IPtr, JPtr, IAlignment, JAlignment,
OffsetInElmts) && abs64(OffsetInElmts) == 1) {
if (Config.AlignedOnly) {
Type *aTypeI = isa<StoreInst>(I) ?
cast<StoreInst>(I)->getValueOperand()->getType() : I->getType();
Type *aTypeJ = isa<StoreInst>(J) ?
cast<StoreInst>(J)->getValueOperand()->getType() : J->getType();
// An aligned load or store is possible only if the instruction
// with the lower offset has an alignment suitable for the
// vector type.
unsigned BottomAlignment = IAlignment;
if (OffsetInElmts < 0) BottomAlignment = JAlignment;
Type *VType = getVecTypeForPair(aTypeI, aTypeJ);
unsigned VecAlignment = TD->getPrefTypeAlignment(VType);
if (BottomAlignment < VecAlignment)
return false;
}
} else {
return false;
}
}
// The powi intrinsic is special because only the first argument is
// vectorized, the second arguments must be equal.
CallInst *CI = dyn_cast<CallInst>(I);
Function *FI;
if (CI && (FI = CI->getCalledFunction()) &&
FI->getIntrinsicID() == Intrinsic::powi) {
Value *A1I = CI->getArgOperand(1),
*A1J = cast<CallInst>(J)->getArgOperand(1);
const SCEV *A1ISCEV = SE->getSCEV(A1I),
*A1JSCEV = SE->getSCEV(A1J);
return (A1ISCEV == A1JSCEV);
}
return true;
}
// Figure out whether or not J uses I and update the users and write-set
// structures associated with I. Specifically, Users represents the set of
// instructions that depend on I. WriteSet represents the set
// of memory locations that are dependent on I. If UpdateUsers is true,
// and J uses I, then Users is updated to contain J and WriteSet is updated
// to contain any memory locations to which J writes. The function returns
// true if J uses I. By default, alias analysis is used to determine
// whether J reads from memory that overlaps with a location in WriteSet.
// If LoadMoveSet is not null, then it is a previously-computed multimap
// where the key is the memory-based user instruction and the value is
// the instruction to be compared with I. So, if LoadMoveSet is provided,
// then the alias analysis is not used. This is necessary because this
// function is called during the process of moving instructions during
// vectorization and the results of the alias analysis are not stable during
// that process.
bool BBVectorize::trackUsesOfI(DenseSet<Value *> &Users,
AliasSetTracker &WriteSet, Instruction *I,
Instruction *J, bool UpdateUsers,
std::multimap<Value *, Value *> *LoadMoveSet) {
bool UsesI = false;
// This instruction may already be marked as a user due, for example, to
// being a member of a selected pair.
if (Users.count(J))
UsesI = true;
if (!UsesI)
for (User::op_iterator JU = J->op_begin(), JE = J->op_end();
JU != JE; ++JU) {
Value *V = *JU;
if (I == V || Users.count(V)) {
UsesI = true;
break;
}
}
if (!UsesI && J->mayReadFromMemory()) {
if (LoadMoveSet) {
VPIteratorPair JPairRange = LoadMoveSet->equal_range(J);
UsesI = isSecondInIteratorPair<Value*>(I, JPairRange);
} else {
for (AliasSetTracker::iterator W = WriteSet.begin(),
WE = WriteSet.end(); W != WE; ++W) {
if (W->aliasesUnknownInst(J, *AA)) {
UsesI = true;
break;
}
}
}
}
if (UsesI && UpdateUsers) {
if (J->mayWriteToMemory()) WriteSet.add(J);
Users.insert(J);
}
return UsesI;
}
// This function iterates over all instruction pairs in the provided
// basic block and collects all candidate pairs for vectorization.
bool BBVectorize::getCandidatePairs(BasicBlock &BB,
BasicBlock::iterator &Start,
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts, bool NonPow2Len) {
BasicBlock::iterator E = BB.end();
if (Start == E) return false;
bool ShouldContinue = false, IAfterStart = false;
for (BasicBlock::iterator I = Start++; I != E; ++I) {
if (I == Start) IAfterStart = true;
bool IsSimpleLoadStore;
if (!isInstVectorizable(I, IsSimpleLoadStore)) continue;
// Look for an instruction with which to pair instruction *I...
DenseSet<Value *> Users;
AliasSetTracker WriteSet(*AA);
bool JAfterStart = IAfterStart;
BasicBlock::iterator J = llvm::next(I);
for (unsigned ss = 0; J != E && ss <= Config.SearchLimit; ++J, ++ss) {
if (J == Start) JAfterStart = true;
// Determine if J uses I, if so, exit the loop.
bool UsesI = trackUsesOfI(Users, WriteSet, I, J, !Config.FastDep);
if (Config.FastDep) {
// Note: For this heuristic to be effective, independent operations
// must tend to be intermixed. This is likely to be true from some
// kinds of grouped loop unrolling (but not the generic LLVM pass),
// but otherwise may require some kind of reordering pass.
// When using fast dependency analysis,
// stop searching after first use:
if (UsesI) break;
} else {
if (UsesI) continue;
}
// J does not use I, and comes before the first use of I, so it can be
// merged with I if the instructions are compatible.
if (!areInstsCompatible(I, J, IsSimpleLoadStore, NonPow2Len)) continue;
// J is a candidate for merging with I.
if (!PairableInsts.size() ||
PairableInsts[PairableInsts.size()-1] != I) {
PairableInsts.push_back(I);
}
CandidatePairs.insert(ValuePair(I, J));
// The next call to this function must start after the last instruction
// selected during this invocation.
if (JAfterStart) {
Start = llvm::next(J);
IAfterStart = JAfterStart = false;
}
DEBUG(if (DebugCandidateSelection) dbgs() << "BBV: candidate pair "
<< *I << " <-> " << *J << "\n");
// If we have already found too many pairs, break here and this function
// will be called again starting after the last instruction selected
// during this invocation.
if (PairableInsts.size() >= Config.MaxInsts) {
ShouldContinue = true;
break;
}
}
if (ShouldContinue)
break;
}
DEBUG(dbgs() << "BBV: found " << PairableInsts.size()
<< " instructions with candidate pairs\n");
return ShouldContinue;
}
// Finds candidate pairs connected to the pair P = <PI, PJ>. This means that
// it looks for pairs such that both members have an input which is an
// output of PI or PJ.
void BBVectorize::computePairsConnectedTo(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
ValuePair P) {
StoreInst *SI, *SJ;
// For each possible pairing for this variable, look at the uses of
// the first value...
for (Value::use_iterator I = P.first->use_begin(),
E = P.first->use_end(); I != E; ++I) {
if (isa<LoadInst>(*I)) {
// A pair cannot be connected to a load because the load only takes one
// operand (the address) and it is a scalar even after vectorization.
continue;
} else if ((SI = dyn_cast<StoreInst>(*I)) &&
P.first == SI->getPointerOperand()) {
// Similarly, a pair cannot be connected to a store through its
// pointer operand.
continue;
}
VPIteratorPair IPairRange = CandidatePairs.equal_range(*I);
// For each use of the first variable, look for uses of the second
// variable...
for (Value::use_iterator J = P.second->use_begin(),
E2 = P.second->use_end(); J != E2; ++J) {
if ((SJ = dyn_cast<StoreInst>(*J)) &&
P.second == SJ->getPointerOperand())
continue;
VPIteratorPair JPairRange = CandidatePairs.equal_range(*J);
// Look for <I, J>:
if (isSecondInIteratorPair<Value*>(*J, IPairRange))
ConnectedPairs.insert(VPPair(P, ValuePair(*I, *J)));
// Look for <J, I>:
if (isSecondInIteratorPair<Value*>(*I, JPairRange))
ConnectedPairs.insert(VPPair(P, ValuePair(*J, *I)));
}
if (Config.SplatBreaksChain) continue;
// Look for cases where just the first value in the pair is used by
// both members of another pair (splatting).
for (Value::use_iterator J = P.first->use_begin(); J != E; ++J) {
if ((SJ = dyn_cast<StoreInst>(*J)) &&
P.first == SJ->getPointerOperand())
continue;
if (isSecondInIteratorPair<Value*>(*J, IPairRange))
ConnectedPairs.insert(VPPair(P, ValuePair(*I, *J)));
}
}
if (Config.SplatBreaksChain) return;
// Look for cases where just the second value in the pair is used by
// both members of another pair (splatting).
for (Value::use_iterator I = P.second->use_begin(),
E = P.second->use_end(); I != E; ++I) {
if (isa<LoadInst>(*I))
continue;
else if ((SI = dyn_cast<StoreInst>(*I)) &&
P.second == SI->getPointerOperand())
continue;
VPIteratorPair IPairRange = CandidatePairs.equal_range(*I);
for (Value::use_iterator J = P.second->use_begin(); J != E; ++J) {
if ((SJ = dyn_cast<StoreInst>(*J)) &&
P.second == SJ->getPointerOperand())
continue;
if (isSecondInIteratorPair<Value*>(*J, IPairRange))
ConnectedPairs.insert(VPPair(P, ValuePair(*I, *J)));
}
}
}
// This function figures out which pairs are connected. Two pairs are
// connected if some output of the first pair forms an input to both members
// of the second pair.
void BBVectorize::computeConnectedPairs(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs) {
for (std::vector<Value *>::iterator PI = PairableInsts.begin(),
PE = PairableInsts.end(); PI != PE; ++PI) {
VPIteratorPair choiceRange = CandidatePairs.equal_range(*PI);
for (std::multimap<Value *, Value *>::iterator P = choiceRange.first;
P != choiceRange.second; ++P)
computePairsConnectedTo(CandidatePairs, PairableInsts,
ConnectedPairs, *P);
}
DEBUG(dbgs() << "BBV: found " << ConnectedPairs.size()
<< " pair connections.\n");
}
// This function builds a set of use tuples such that <A, B> is in the set
// if B is in the use tree of A. If B is in the use tree of A, then B
// depends on the output of A.
void BBVectorize::buildDepMap(
BasicBlock &BB,
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
DenseSet<ValuePair> &PairableInstUsers) {
DenseSet<Value *> IsInPair;
for (std::multimap<Value *, Value *>::iterator C = CandidatePairs.begin(),
E = CandidatePairs.end(); C != E; ++C) {
IsInPair.insert(C->first);
IsInPair.insert(C->second);
}
// Iterate through the basic block, recording all Users of each
// pairable instruction.
BasicBlock::iterator E = BB.end();
for (BasicBlock::iterator I = BB.getFirstInsertionPt(); I != E; ++I) {
if (IsInPair.find(I) == IsInPair.end()) continue;
DenseSet<Value *> Users;
AliasSetTracker WriteSet(*AA);
for (BasicBlock::iterator J = llvm::next(I); J != E; ++J)
(void) trackUsesOfI(Users, WriteSet, I, J);
for (DenseSet<Value *>::iterator U = Users.begin(), E = Users.end();
U != E; ++U)
PairableInstUsers.insert(ValuePair(I, *U));
}
}
// Returns true if an input to pair P is an output of pair Q and also an
// input of pair Q is an output of pair P. If this is the case, then these
// two pairs cannot be simultaneously fused.
bool BBVectorize::pairsConflict(ValuePair P, ValuePair Q,
DenseSet<ValuePair> &PairableInstUsers,
std::multimap<ValuePair, ValuePair> *PairableInstUserMap) {
// Two pairs are in conflict if they are mutual Users of eachother.
bool QUsesP = PairableInstUsers.count(ValuePair(P.first, Q.first)) ||
PairableInstUsers.count(ValuePair(P.first, Q.second)) ||
PairableInstUsers.count(ValuePair(P.second, Q.first)) ||
PairableInstUsers.count(ValuePair(P.second, Q.second));
bool PUsesQ = PairableInstUsers.count(ValuePair(Q.first, P.first)) ||
PairableInstUsers.count(ValuePair(Q.first, P.second)) ||
PairableInstUsers.count(ValuePair(Q.second, P.first)) ||
PairableInstUsers.count(ValuePair(Q.second, P.second));
if (PairableInstUserMap) {
// FIXME: The expensive part of the cycle check is not so much the cycle
// check itself but this edge insertion procedure. This needs some
// profiling and probably a different data structure (same is true of
// most uses of std::multimap).
if (PUsesQ) {
VPPIteratorPair QPairRange = PairableInstUserMap->equal_range(Q);
if (!isSecondInIteratorPair(P, QPairRange))
PairableInstUserMap->insert(VPPair(Q, P));
}
if (QUsesP) {
VPPIteratorPair PPairRange = PairableInstUserMap->equal_range(P);
if (!isSecondInIteratorPair(Q, PPairRange))
PairableInstUserMap->insert(VPPair(P, Q));
}
}
return (QUsesP && PUsesQ);
}
// This function walks the use graph of current pairs to see if, starting
// from P, the walk returns to P.
bool BBVectorize::pairWillFormCycle(ValuePair P,
std::multimap<ValuePair, ValuePair> &PairableInstUserMap,
DenseSet<ValuePair> &CurrentPairs) {
DEBUG(if (DebugCycleCheck)
dbgs() << "BBV: starting cycle check for : " << *P.first << " <-> "
<< *P.second << "\n");
// A lookup table of visisted pairs is kept because the PairableInstUserMap
// contains non-direct associations.
DenseSet<ValuePair> Visited;
SmallVector<ValuePair, 32> Q;
// General depth-first post-order traversal:
Q.push_back(P);
do {
ValuePair QTop = Q.pop_back_val();
Visited.insert(QTop);
DEBUG(if (DebugCycleCheck)
dbgs() << "BBV: cycle check visiting: " << *QTop.first << " <-> "
<< *QTop.second << "\n");
VPPIteratorPair QPairRange = PairableInstUserMap.equal_range(QTop);
for (std::multimap<ValuePair, ValuePair>::iterator C = QPairRange.first;
C != QPairRange.second; ++C) {
if (C->second == P) {
DEBUG(dbgs()
<< "BBV: rejected to prevent non-trivial cycle formation: "
<< *C->first.first << " <-> " << *C->first.second << "\n");
return true;
}
if (CurrentPairs.count(C->second) && !Visited.count(C->second))
Q.push_back(C->second);
}
} while (!Q.empty());
return false;
}
// This function builds the initial tree of connected pairs with the
// pair J at the root.
void BBVectorize::buildInitialTreeFor(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
DenseSet<ValuePair> &PairableInstUsers,
DenseMap<Value *, Value *> &ChosenPairs,
DenseMap<ValuePair, size_t> &Tree, ValuePair J) {
// Each of these pairs is viewed as the root node of a Tree. The Tree
// is then walked (depth-first). As this happens, we keep track of
// the pairs that compose the Tree and the maximum depth of the Tree.
SmallVector<ValuePairWithDepth, 32> Q;
// General depth-first post-order traversal:
Q.push_back(ValuePairWithDepth(J, getDepthFactor(J.first)));
do {
ValuePairWithDepth QTop = Q.back();
// Push each child onto the queue:
bool MoreChildren = false;
size_t MaxChildDepth = QTop.second;
VPPIteratorPair qtRange = ConnectedPairs.equal_range(QTop.first);
for (std::multimap<ValuePair, ValuePair>::iterator k = qtRange.first;
k != qtRange.second; ++k) {
// Make sure that this child pair is still a candidate:
bool IsStillCand = false;
VPIteratorPair checkRange =
CandidatePairs.equal_range(k->second.first);
for (std::multimap<Value *, Value *>::iterator m = checkRange.first;
m != checkRange.second; ++m) {
if (m->second == k->second.second) {
IsStillCand = true;
break;
}
}
if (IsStillCand) {
DenseMap<ValuePair, size_t>::iterator C = Tree.find(k->second);
if (C == Tree.end()) {
size_t d = getDepthFactor(k->second.first);
Q.push_back(ValuePairWithDepth(k->second, QTop.second+d));
MoreChildren = true;
} else {
MaxChildDepth = std::max(MaxChildDepth, C->second);
}
}
}
if (!MoreChildren) {
// Record the current pair as part of the Tree:
Tree.insert(ValuePairWithDepth(QTop.first, MaxChildDepth));
Q.pop_back();
}
} while (!Q.empty());
}
// Given some initial tree, prune it by removing conflicting pairs (pairs
// that cannot be simultaneously chosen for vectorization).
void BBVectorize::pruneTreeFor(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
DenseSet<ValuePair> &PairableInstUsers,
std::multimap<ValuePair, ValuePair> &PairableInstUserMap,
DenseMap<Value *, Value *> &ChosenPairs,
DenseMap<ValuePair, size_t> &Tree,
DenseSet<ValuePair> &PrunedTree, ValuePair J,
bool UseCycleCheck) {
SmallVector<ValuePairWithDepth, 32> Q;
// General depth-first post-order traversal:
Q.push_back(ValuePairWithDepth(J, getDepthFactor(J.first)));
do {
ValuePairWithDepth QTop = Q.pop_back_val();
PrunedTree.insert(QTop.first);
// Visit each child, pruning as necessary...
DenseMap<ValuePair, size_t> BestChildren;
VPPIteratorPair QTopRange = ConnectedPairs.equal_range(QTop.first);
for (std::multimap<ValuePair, ValuePair>::iterator K = QTopRange.first;
K != QTopRange.second; ++K) {
DenseMap<ValuePair, size_t>::iterator C = Tree.find(K->second);
if (C == Tree.end()) continue;
// This child is in the Tree, now we need to make sure it is the
// best of any conflicting children. There could be multiple
// conflicting children, so first, determine if we're keeping
// this child, then delete conflicting children as necessary.
// It is also necessary to guard against pairing-induced
// dependencies. Consider instructions a .. x .. y .. b
// such that (a,b) are to be fused and (x,y) are to be fused
// but a is an input to x and b is an output from y. This
// means that y cannot be moved after b but x must be moved
// after b for (a,b) to be fused. In other words, after
// fusing (a,b) we have y .. a/b .. x where y is an input
// to a/b and x is an output to a/b: x and y can no longer
// be legally fused. To prevent this condition, we must
// make sure that a child pair added to the Tree is not
// both an input and output of an already-selected pair.
// Pairing-induced dependencies can also form from more complicated
// cycles. The pair vs. pair conflicts are easy to check, and so
// that is done explicitly for "fast rejection", and because for
// child vs. child conflicts, we may prefer to keep the current
// pair in preference to the already-selected child.
DenseSet<ValuePair> CurrentPairs;
bool CanAdd = true;
for (DenseMap<ValuePair, size_t>::iterator C2
= BestChildren.begin(), E2 = BestChildren.end();
C2 != E2; ++C2) {
if (C2->first.first == C->first.first ||
C2->first.first == C->first.second ||
C2->first.second == C->first.first ||
C2->first.second == C->first.second ||
pairsConflict(C2->first, C->first, PairableInstUsers,
UseCycleCheck ? &PairableInstUserMap : 0)) {
if (C2->second >= C->second) {
CanAdd = false;
break;
}
CurrentPairs.insert(C2->first);
}
}
if (!CanAdd) continue;
// Even worse, this child could conflict with another node already
// selected for the Tree. If that is the case, ignore this child.
for (DenseSet<ValuePair>::iterator T = PrunedTree.begin(),
E2 = PrunedTree.end(); T != E2; ++T) {
if (T->first == C->first.first ||
T->first == C->first.second ||
T->second == C->first.first ||
T->second == C->first.second ||
pairsConflict(*T, C->first, PairableInstUsers,
UseCycleCheck ? &PairableInstUserMap : 0)) {
CanAdd = false;
break;
}
CurrentPairs.insert(*T);
}
if (!CanAdd) continue;
// And check the queue too...
for (SmallVector<ValuePairWithDepth, 32>::iterator C2 = Q.begin(),
E2 = Q.end(); C2 != E2; ++C2) {
if (C2->first.first == C->first.first ||
C2->first.first == C->first.second ||
C2->first.second == C->first.first ||
C2->first.second == C->first.second ||
pairsConflict(C2->first, C->first, PairableInstUsers,
UseCycleCheck ? &PairableInstUserMap : 0)) {
CanAdd = false;
break;
}
CurrentPairs.insert(C2->first);
}
if (!CanAdd) continue;
// Last but not least, check for a conflict with any of the
// already-chosen pairs.
for (DenseMap<Value *, Value *>::iterator C2 =
ChosenPairs.begin(), E2 = ChosenPairs.end();
C2 != E2; ++C2) {
if (pairsConflict(*C2, C->first, PairableInstUsers,
UseCycleCheck ? &PairableInstUserMap : 0)) {
CanAdd = false;
break;
}
CurrentPairs.insert(*C2);
}
if (!CanAdd) continue;
// To check for non-trivial cycles formed by the addition of the
// current pair we've formed a list of all relevant pairs, now use a
// graph walk to check for a cycle. We start from the current pair and
// walk the use tree to see if we again reach the current pair. If we
// do, then the current pair is rejected.
// FIXME: It may be more efficient to use a topological-ordering
// algorithm to improve the cycle check. This should be investigated.
if (UseCycleCheck &&
pairWillFormCycle(C->first, PairableInstUserMap, CurrentPairs))
continue;
// This child can be added, but we may have chosen it in preference
// to an already-selected child. Check for this here, and if a
// conflict is found, then remove the previously-selected child
// before adding this one in its place.
for (DenseMap<ValuePair, size_t>::iterator C2
= BestChildren.begin(); C2 != BestChildren.end();) {
if (C2->first.first == C->first.first ||
C2->first.first == C->first.second ||
C2->first.second == C->first.first ||
C2->first.second == C->first.second ||
pairsConflict(C2->first, C->first, PairableInstUsers))
BestChildren.erase(C2++);
else
++C2;
}
BestChildren.insert(ValuePairWithDepth(C->first, C->second));
}
for (DenseMap<ValuePair, size_t>::iterator C
= BestChildren.begin(), E2 = BestChildren.end();
C != E2; ++C) {
size_t DepthF = getDepthFactor(C->first.first);
Q.push_back(ValuePairWithDepth(C->first, QTop.second+DepthF));
}
} while (!Q.empty());
}
// This function finds the best tree of mututally-compatible connected
// pairs, given the choice of root pairs as an iterator range.
void BBVectorize::findBestTreeFor(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
DenseSet<ValuePair> &PairableInstUsers,
std::multimap<ValuePair, ValuePair> &PairableInstUserMap,
DenseMap<Value *, Value *> &ChosenPairs,
DenseSet<ValuePair> &BestTree, size_t &BestMaxDepth,
size_t &BestEffSize, VPIteratorPair ChoiceRange,
bool UseCycleCheck) {
for (std::multimap<Value *, Value *>::iterator J = ChoiceRange.first;
J != ChoiceRange.second; ++J) {
// Before going any further, make sure that this pair does not
// conflict with any already-selected pairs (see comment below
// near the Tree pruning for more details).
DenseSet<ValuePair> ChosenPairSet;
bool DoesConflict = false;
for (DenseMap<Value *, Value *>::iterator C = ChosenPairs.begin(),
E = ChosenPairs.end(); C != E; ++C) {
if (pairsConflict(*C, *J, PairableInstUsers,
UseCycleCheck ? &PairableInstUserMap : 0)) {
DoesConflict = true;
break;
}
ChosenPairSet.insert(*C);
}
if (DoesConflict) continue;
if (UseCycleCheck &&
pairWillFormCycle(*J, PairableInstUserMap, ChosenPairSet))
continue;
DenseMap<ValuePair, size_t> Tree;
buildInitialTreeFor(CandidatePairs, PairableInsts, ConnectedPairs,
PairableInstUsers, ChosenPairs, Tree, *J);
// Because we'll keep the child with the largest depth, the largest
// depth is still the same in the unpruned Tree.
size_t MaxDepth = Tree.lookup(*J);
DEBUG(if (DebugPairSelection) dbgs() << "BBV: found Tree for pair {"
<< *J->first << " <-> " << *J->second << "} of depth " <<
MaxDepth << " and size " << Tree.size() << "\n");
// At this point the Tree has been constructed, but, may contain
// contradictory children (meaning that different children of
// some tree node may be attempting to fuse the same instruction).
// So now we walk the tree again, in the case of a conflict,
// keep only the child with the largest depth. To break a tie,
// favor the first child.
DenseSet<ValuePair> PrunedTree;
pruneTreeFor(CandidatePairs, PairableInsts, ConnectedPairs,
PairableInstUsers, PairableInstUserMap, ChosenPairs, Tree,
PrunedTree, *J, UseCycleCheck);
size_t EffSize = 0;
for (DenseSet<ValuePair>::iterator S = PrunedTree.begin(),
E = PrunedTree.end(); S != E; ++S)
EffSize += getDepthFactor(S->first);
DEBUG(if (DebugPairSelection)
dbgs() << "BBV: found pruned Tree for pair {"
<< *J->first << " <-> " << *J->second << "} of depth " <<
MaxDepth << " and size " << PrunedTree.size() <<
" (effective size: " << EffSize << ")\n");
if (MaxDepth >= Config.ReqChainDepth && EffSize > BestEffSize) {
BestMaxDepth = MaxDepth;
BestEffSize = EffSize;
BestTree = PrunedTree;
}
}
}
// Given the list of candidate pairs, this function selects those
// that will be fused into vector instructions.
void BBVectorize::choosePairs(
std::multimap<Value *, Value *> &CandidatePairs,
std::vector<Value *> &PairableInsts,
std::multimap<ValuePair, ValuePair> &ConnectedPairs,
DenseSet<ValuePair> &PairableInstUsers,
DenseMap<Value *, Value *>& ChosenPairs) {
bool UseCycleCheck =
CandidatePairs.size() <= Config.MaxCandPairsForCycleCheck;
std::multimap<ValuePair, ValuePair> PairableInstUserMap;
for (std::vector<Value *>::iterator I = PairableInsts.begin(),
E = PairableInsts.end(); I != E; ++I) {
// The number of possible pairings for this variable:
size_t NumChoices = CandidatePairs.count(*I);
if (!NumChoices) continue;
VPIteratorPair ChoiceRange = CandidatePairs.equal_range(*I);
// The best pair to choose and its tree:
size_t BestMaxDepth = 0, BestEffSize = 0;
DenseSet<ValuePair> BestTree;
findBestTreeFor(CandidatePairs, PairableInsts, ConnectedPairs,
PairableInstUsers, PairableInstUserMap, ChosenPairs,
BestTree, BestMaxDepth, BestEffSize, ChoiceRange,
UseCycleCheck);
// A tree has been chosen (or not) at this point. If no tree was
// chosen, then this instruction, I, cannot be paired (and is no longer
// considered).
DEBUG(if (BestTree.size() > 0)
dbgs() << "BBV: selected pairs in the best tree for: "
<< *cast<Instruction>(*I) << "\n");
for (DenseSet<ValuePair>::iterator S = BestTree.begin(),
SE2 = BestTree.end(); S != SE2; ++S) {
// Insert the members of this tree into the list of chosen pairs.
ChosenPairs.insert(ValuePair(S->first, S->second));
DEBUG(dbgs() << "BBV: selected pair: " << *S->first << " <-> " <<
*S->second << "\n");
// Remove all candidate pairs that have values in the chosen tree.
for (std::multimap<Value *, Value *>::iterator K =
CandidatePairs.begin(); K != CandidatePairs.end();) {
if (K->first == S->first || K->second == S->first ||
K->second == S->second || K->first == S->second) {
// Don't remove the actual pair chosen so that it can be used
// in subsequent tree selections.
if (!(K->first == S->first && K->second == S->second))
CandidatePairs.erase(K++);
else
++K;
} else {
++K;
}
}
}
}
DEBUG(dbgs() << "BBV: selected " << ChosenPairs.size() << " pairs.\n");
}
std::string getReplacementName(Instruction *I, bool IsInput, unsigned o,
unsigned n = 0) {
if (!I->hasName())
return "";
return (I->getName() + (IsInput ? ".v.i" : ".v.r") + utostr(o) +
(n > 0 ? "." + utostr(n) : "")).str();
}
// Returns the value that is to be used as the pointer input to the vector
// instruction that fuses I with J.
Value *BBVectorize::getReplacementPointerInput(LLVMContext& Context,
Instruction *I, Instruction *J, unsigned o,
bool FlipMemInputs) {
Value *IPtr, *JPtr;
unsigned IAlignment, JAlignment;
int64_t OffsetInElmts;
// Note: the analysis might fail here, that is why FlipMemInputs has
// been precomputed (OffsetInElmts must be unused here).
(void) getPairPtrInfo(I, J, IPtr, JPtr, IAlignment, JAlignment,
OffsetInElmts);
// The pointer value is taken to be the one with the lowest offset.
Value *VPtr;
if (!FlipMemInputs) {
VPtr = IPtr;
} else {
VPtr = JPtr;
}
Type *ArgTypeI = cast<PointerType>(IPtr->getType())->getElementType();
Type *ArgTypeJ = cast<PointerType>(JPtr->getType())->getElementType();
Type *VArgType = getVecTypeForPair(ArgTypeI, ArgTypeJ);
Type *VArgPtrType = PointerType::get(VArgType,
cast<PointerType>(IPtr->getType())->getAddressSpace());
return new BitCastInst(VPtr, VArgPtrType, getReplacementName(I, true, o),
/* insert before */ FlipMemInputs ? J : I);
}
void BBVectorize::fillNewShuffleMask(LLVMContext& Context, Instruction *J,
unsigned MaskOffset, unsigned NumInElem,
unsigned NumInElem1, unsigned IdxOffset,
std::vector<Constant*> &Mask) {
unsigned NumElem1 = cast<VectorType>(J->getType())->getNumElements();
for (unsigned v = 0; v < NumElem1; ++v) {
int m = cast<ShuffleVectorInst>(J)->getMaskValue(v);
if (m < 0) {
Mask[v+MaskOffset] = UndefValue::get(Type::getInt32Ty(Context));
} else {
unsigned mm = m + (int) IdxOffset;
if (m >= (int) NumInElem1)
mm += (int) NumInElem;
Mask[v+MaskOffset] =
ConstantInt::get(Type::getInt32Ty(Context), mm);
}
}
}
// Returns the value that is to be used as the vector-shuffle mask to the
// vector instruction that fuses I with J.
Value *BBVectorize::getReplacementShuffleMask(LLVMContext& Context,
Instruction *I, Instruction *J) {
// This is the shuffle mask. We need to append the second
// mask to the first, and the numbers need to be adjusted.
Type *ArgTypeI = I->getType();
Type *ArgTypeJ = J->getType();
Type *VArgType = getVecTypeForPair(ArgTypeI, ArgTypeJ);
unsigned NumElemI = cast<VectorType>(ArgTypeI)->getNumElements();
// Get the total number of elements in the fused vector type.
// By definition, this must equal the number of elements in
// the final mask.
unsigned NumElem = cast<VectorType>(VArgType)->getNumElements();
std::vector<Constant*> Mask(NumElem);
Type *OpTypeI = I->getOperand(0)->getType();
unsigned NumInElemI = cast<VectorType>(OpTypeI)->getNumElements();
Type *OpTypeJ = J->getOperand(0)->getType();
unsigned NumInElemJ = cast<VectorType>(OpTypeJ)->getNumElements();
// The fused vector will be:
// -----------------------------------------------------
// | NumInElemI | NumInElemJ | NumInElemI | NumInElemJ |
// -----------------------------------------------------
// from which we'll extract NumElem total elements (where the first NumElemI
// of them come from the mask in I and the remainder come from the mask
// in J.
// For the mask from the first pair...
fillNewShuffleMask(Context, I, 0, NumInElemJ, NumInElemI,
0, Mask);
// For the mask from the second pair...
fillNewShuffleMask(Context, J, NumElemI, NumInElemI, NumInElemJ,
NumInElemI, Mask);
return ConstantVector::get(Mask);
}
bool BBVectorize::expandIEChain(LLVMContext& Context, Instruction *I,
Instruction *J, unsigned o, Value *&LOp,
unsigned numElemL,
Type *ArgTypeL, Type *ArgTypeH,
unsigned IdxOff) {
bool ExpandedIEChain = false;
if (InsertElementInst *LIE = dyn_cast<InsertElementInst>(LOp)) {
// If we have a pure insertelement chain, then this can be rewritten
// into a chain that directly builds the larger type.
bool PureChain = true;
InsertElementInst *LIENext = LIE;
do {
if (!isa<UndefValue>(LIENext->getOperand(0)) &&
!isa<InsertElementInst>(LIENext->getOperand(0))) {
PureChain = false;
break;
}
} while ((LIENext =
dyn_cast<InsertElementInst>(LIENext->getOperand(0))));
if (PureChain) {
SmallVector<Value *, 8> VectElemts(numElemL,
UndefValue::get(ArgTypeL->getScalarType()));
InsertElementInst *LIENext = LIE;
do {
unsigned Idx =
cast<ConstantInt>(LIENext->getOperand(2))->getSExtValue();
VectElemts[Idx] = LIENext->getOperand(1);
} while ((LIENext =
dyn_cast<InsertElementInst>(LIENext->getOperand(0))));
LIENext = 0;
Value *LIEPrev = UndefValue::get(ArgTypeH);
for (unsigned i = 0; i < numElemL; ++i) {
if (isa<UndefValue>(VectElemts[i])) continue;
LIENext = InsertElementInst::Create(LIEPrev, VectElemts[i],
ConstantInt::get(Type::getInt32Ty(Context),
i + IdxOff),
getReplacementName(I, true, o, i+1));
LIENext->insertBefore(J);
LIEPrev = LIENext;
}
LOp = LIENext ? (Value*) LIENext : UndefValue::get(ArgTypeH);
ExpandedIEChain = true;
}
}
return ExpandedIEChain;
}
// Returns the value to be used as the specified operand of the vector
// instruction that fuses I with J.
Value *BBVectorize::getReplacementInput(LLVMContext& Context, Instruction *I,
Instruction *J, unsigned o, bool FlipMemInputs) {
Value *CV0 = ConstantInt::get(Type::getInt32Ty(Context), 0);
Value *CV1 = ConstantInt::get(Type::getInt32Ty(Context), 1);
// Compute the fused vector type for this operand
Type *ArgTypeI = I->getOperand(o)->getType();
Type *ArgTypeJ = J->getOperand(o)->getType();
VectorType *VArgType = getVecTypeForPair(ArgTypeI, ArgTypeJ);
Instruction *L = I, *H = J;
Type *ArgTypeL = ArgTypeI, *ArgTypeH = ArgTypeJ;
if (FlipMemInputs) {
L = J;
H = I;
ArgTypeL = ArgTypeJ;
ArgTypeH = ArgTypeI;
}
unsigned numElemL;
if (ArgTypeL->isVectorTy())
numElemL = cast<VectorType>(ArgTypeL)->getNumElements();
else
numElemL = 1;
unsigned numElemH;
if (ArgTypeH->isVectorTy())
numElemH = cast<VectorType>(ArgTypeH)->getNumElements();
else
numElemH = 1;
Value *LOp = L->getOperand(o);
Value *HOp = H->getOperand(o);
unsigned numElem = VArgType->getNumElements();
// First, we check if we can reuse the "original" vector outputs (if these
// exist). We might need a shuffle.
ExtractElementInst *LEE = dyn_cast<ExtractElementInst>(LOp);
ExtractElementInst *HEE = dyn_cast<ExtractElementInst>(HOp);
ShuffleVectorInst *LSV = dyn_cast<ShuffleVectorInst>(LOp);
ShuffleVectorInst *HSV = dyn_cast<ShuffleVectorInst>(HOp);
// FIXME: If we're fusing shuffle instructions, then we can't apply this
// optimization. The input vectors to the shuffle might be a different
// length from the shuffle outputs. Unfortunately, the replacement
// shuffle mask has already been formed, and the mask entries are sensitive
// to the sizes of the inputs.
bool IsSizeChangeShuffle =
isa<ShuffleVectorInst>(L) &&
(LOp->getType() != L->getType() || HOp->getType() != H->getType());
if ((LEE || LSV) && (HEE || HSV) && !IsSizeChangeShuffle) {
// We can have at most two unique vector inputs.
bool CanUseInputs = true;
Value *I1, *I2 = 0;
if (LEE) {
I1 = LEE->getOperand(0);
} else {
I1 = LSV->getOperand(0);
I2 = LSV->getOperand(1);
if (I2 == I1 || isa<UndefValue>(I2))
I2 = 0;
}
if (HEE) {
Value *I3 = HEE->getOperand(0);
if (!I2 && I3 != I1)
I2 = I3;
else if (I3 != I1 && I3 != I2)
CanUseInputs = false;
} else {
Value *I3 = HSV->getOperand(0);
if (!I2 && I3 != I1)
I2 = I3;
else if (I3 != I1 && I3 != I2)
CanUseInputs = false;
if (CanUseInputs) {
Value *I4 = HSV->getOperand(1);
if (!isa<UndefValue>(I4)) {
if (!I2 && I4 != I1)
I2 = I4;
else if (I4 != I1 && I4 != I2)
CanUseInputs = false;
}
}
}
if (CanUseInputs) {
unsigned LOpElem =
cast<VectorType>(cast<Instruction>(LOp)->getOperand(0)->getType())
->getNumElements();
unsigned HOpElem =
cast<VectorType>(cast<Instruction>(HOp)->getOperand(0)->getType())
->getNumElements();
// We have one or two input vectors. We need to map each index of the
// operands to the index of the original vector.
SmallVector<std::pair<int, int>, 8> II(numElem);
for (unsigned i = 0; i < numElemL; ++i) {
int Idx, INum;
if (LEE) {
Idx =
cast<ConstantInt>(LEE->getOperand(1))->getSExtValue();
INum = LEE->getOperand(0) == I1 ? 0 : 1;
} else {
Idx = LSV->getMaskValue(i);
if (Idx < (int) LOpElem) {
INum = LSV->getOperand(0) == I1 ? 0 : 1;
} else {
Idx -= LOpElem;
INum = LSV->getOperand(1) == I1 ? 0 : 1;
}
}
II[i] = std::pair<int, int>(Idx, INum);
}
for (unsigned i = 0; i < numElemH; ++i) {
int Idx, INum;
if (HEE) {
Idx =
cast<ConstantInt>(HEE->getOperand(1))->getSExtValue();
INum = HEE->getOperand(0) == I1 ? 0 : 1;
} else {
Idx = HSV->getMaskValue(i);
if (Idx < (int) HOpElem) {
INum = HSV->getOperand(0) == I1 ? 0 : 1;
} else {
Idx -= HOpElem;
INum = HSV->getOperand(1) == I1 ? 0 : 1;
}
}
II[i + numElemL] = std::pair<int, int>(Idx, INum);
}
// We now have an array which tells us from which index of which
// input vector each element of the operand comes.
VectorType *I1T = cast<VectorType>(I1->getType());
unsigned I1Elem = I1T->getNumElements();
if (!I2) {
// In this case there is only one underlying vector input. Check for
// the trivial case where we can use the input directly.
if (I1Elem == numElem) {
bool ElemInOrder = true;
for (unsigned i = 0; i < numElem; ++i) {
if (II[i].first != (int) i && II[i].first != -1) {
ElemInOrder = false;
break;
}
}
if (ElemInOrder)
return I1;
}
// A shuffle is needed.
std::vector<Constant *> Mask(numElem);
for (unsigned i = 0; i < numElem; ++i) {
int Idx = II[i].first;
if (Idx == -1)
Mask[i] = UndefValue::get(Type::getInt32Ty(Context));
else
Mask[i] = ConstantInt::get(Type::getInt32Ty(Context), Idx);
}
Instruction *S =
new ShuffleVectorInst(I1, UndefValue::get(I1T),
ConstantVector::get(Mask),
getReplacementName(I, true, o));
S->insertBefore(J);
return S;
}
VectorType *I2T = cast<VectorType>(I2->getType());
unsigned I2Elem = I2T->getNumElements();
// This input comes from two distinct vectors. The first step is to
// make sure that both vectors are the same length. If not, the
// smaller one will need to grow before they can be shuffled together.
if (I1Elem < I2Elem) {
std::vector<Constant *> Mask(I2Elem);
unsigned v = 0;
for (; v < I1Elem; ++v)
Mask[v] = ConstantInt::get(Type::getInt32Ty(Context), v);
for (; v < I2Elem; ++v)
Mask[v] = UndefValue::get(Type::getInt32Ty(Context));
Instruction *NewI1 =
new ShuffleVectorInst(I1, UndefValue::get(I1T),
ConstantVector::get(Mask),
getReplacementName(I, true, o, 1));
NewI1->insertBefore(J);
I1 = NewI1;
I1T = I2T;
I1Elem = I2Elem;
} else if (I1Elem > I2Elem) {
std::vector<Constant *> Mask(I1Elem);
unsigned v = 0;
for (; v < I2Elem; ++v)
Mask[v] = ConstantInt::get(Type::getInt32Ty(Context), v);
for (; v < I1Elem; ++v)
Mask[v] = UndefValue::get(Type::getInt32Ty(Context));
Instruction *NewI2 =
new ShuffleVectorInst(I2, UndefValue::get(I2T),
ConstantVector::get(Mask),
getReplacementName(I, true, o, 1));
NewI2->insertBefore(J);
I2 = NewI2;
I2T = I1T;
I2Elem = I1Elem;
}
// Now that both I1 and I2 are the same length we can shuffle them
// together (and use the result).
std::vector<Constant *> Mask(numElem);
for (unsigned v = 0; v < numElem; ++v) {
if (II[v].first == -1) {
Mask[v] = UndefValue::get(Type::getInt32Ty(Context));
} else {
int Idx = II[v].first + II[v].second * I1Elem;
Mask[v] = ConstantInt::get(Type::getInt32Ty(Context), Idx);
}
}
Instruction *NewOp =
new ShuffleVectorInst(I1, I2, ConstantVector::get(Mask),
getReplacementName(I, true, o));
NewOp->insertBefore(J);
return NewOp;
}
}
Type *ArgType = ArgTypeL;
if (numElemL < numElemH) {
if (numElemL == 1 && expandIEChain(Context, I, J, o, HOp, numElemH,
ArgTypeL, VArgType, 1)) {
// This is another short-circuit case: we're combining a scalar into
// a vector that is formed by an IE chain. We've just expanded the IE
// chain, now insert the scalar and we're done.
Instruction *S = InsertElementInst::Create(HOp, LOp, CV0,
getReplacementName(I, true, o));
S->insertBefore(J);
return S;
} else if (!expandIEChain(Context, I, J, o, LOp, numElemL, ArgTypeL,
ArgTypeH)) {
// The two vector inputs to the shuffle must be the same length,
// so extend the smaller vector to be the same length as the larger one.
Instruction *NLOp;
if (numElemL > 1) {
std::vector<Constant *> Mask(numElemH);
unsigned v = 0;
for (; v < numElemL; ++v)
Mask[v] = ConstantInt::get(Type::getInt32Ty(Context), v);
for (; v < numElemH; ++v)
Mask[v] = UndefValue::get(Type::getInt32Ty(Context));
NLOp = new ShuffleVectorInst(LOp, UndefValue::get(ArgTypeL),
ConstantVector::get(Mask),
getReplacementName(I, true, o, 1));
} else {
NLOp = InsertElementInst::Create(UndefValue::get(ArgTypeH), LOp, CV0,
getReplacementName(I, true, o, 1));
}
NLOp->insertBefore(J);
LOp = NLOp;
}
ArgType = ArgTypeH;
} else if (numElemL > numElemH) {
if (numElemH == 1 && expandIEChain(Context, I, J, o, LOp, numElemL,
ArgTypeH, VArgType)) {
Instruction *S =
InsertElementInst::Create(LOp, HOp,
ConstantInt::get(Type::getInt32Ty(Context),
numElemL),
getReplacementName(I, true, o));
S->insertBefore(J);
return S;
} else if (!expandIEChain(Context, I, J, o, HOp, numElemH, ArgTypeH,
ArgTypeL)) {
Instruction *NHOp;
if (numElemH > 1) {
std::vector<Constant *> Mask(numElemL);
unsigned v = 0;
for (; v < numElemH; ++v)
Mask[v] = ConstantInt::get(Type::getInt32Ty(Context), v);
for (; v < numElemL; ++v)
Mask[v] = UndefValue::get(Type::getInt32Ty(Context));
NHOp = new ShuffleVectorInst(HOp, UndefValue::get(ArgTypeH),
ConstantVector::get(Mask),
getReplacementName(I, true, o, 1));
} else {
NHOp = InsertElementInst::Create(UndefValue::get(ArgTypeL), HOp, CV0,
getReplacementName(I, true, o, 1));
}
NHOp->insertBefore(J);
HOp = NHOp;
}
}
if (ArgType->isVectorTy()) {
unsigned numElem = cast<VectorType>(VArgType)->getNumElements();
std::vector<Constant*> Mask(numElem);
for (unsigned v = 0; v < numElem; ++v) {
unsigned Idx = v;
// If the low vector was expanded, we need to skip the extra
// undefined entries.
if (v >= numElemL && numElemH > numElemL)
Idx += (numElemH - numElemL);
Mask[v] = ConstantInt::get(Type::getInt32Ty(Context), Idx);
}
Instruction *BV = new ShuffleVectorInst(LOp, HOp,
ConstantVector::get(Mask),
getReplacementName(I, true, o));
BV->insertBefore(J);
return BV;
}
Instruction *BV1 = InsertElementInst::Create(
UndefValue::get(VArgType), LOp, CV0,
getReplacementName(I, true, o, 1));
BV1->insertBefore(I);
Instruction *BV2 = InsertElementInst::Create(BV1, HOp, CV1,
getReplacementName(I, true, o, 2));
BV2->insertBefore(J);
return BV2;
}
// This function creates an array of values that will be used as the inputs
// to the vector instruction that fuses I with J.
void BBVectorize::getReplacementInputsForPair(LLVMContext& Context,
Instruction *I, Instruction *J,
SmallVector<Value *, 3> &ReplacedOperands,
bool FlipMemInputs) {
unsigned NumOperands = I->getNumOperands();
for (unsigned p = 0, o = NumOperands-1; p < NumOperands; ++p, --o) {
// Iterate backward so that we look at the store pointer
// first and know whether or not we need to flip the inputs.
if (isa<LoadInst>(I) || (o == 1 && isa<StoreInst>(I))) {
// This is the pointer for a load/store instruction.
ReplacedOperands[o] = getReplacementPointerInput(Context, I, J, o,
FlipMemInputs);
continue;
} else if (isa<CallInst>(I)) {
Function *F = cast<CallInst>(I)->getCalledFunction();
unsigned IID = F->getIntrinsicID();
if (o == NumOperands-1) {
BasicBlock &BB = *I->getParent();
Module *M = BB.getParent()->getParent();
Type *ArgTypeI = I->getType();
Type *ArgTypeJ = J->getType();
Type *VArgType = getVecTypeForPair(ArgTypeI, ArgTypeJ);
ReplacedOperands[o] = Intrinsic::getDeclaration(M,
(Intrinsic::ID) IID, VArgType);
continue;
} else if (IID == Intrinsic::powi && o == 1) {
// The second argument of powi is a single integer and we've already
// checked that both arguments are equal. As a result, we just keep
// I's second argument.
ReplacedOperands[o] = I->getOperand(o);
continue;
}
} else if (isa<ShuffleVectorInst>(I) && o == NumOperands-1) {
ReplacedOperands[o] = getReplacementShuffleMask(Context, I, J);
continue;
}
ReplacedOperands[o] =
getReplacementInput(Context, I, J, o, FlipMemInputs);
}
}
// This function creates two values that represent the outputs of the
// original I and J instructions. These are generally vector shuffles
// or extracts. In many cases, these will end up being unused and, thus,
// eliminated by later passes.
void BBVectorize::replaceOutputsOfPair(LLVMContext& Context, Instruction *I,
Instruction *J, Instruction *K,
Instruction *&InsertionPt,
Instruction *&K1, Instruction *&K2,
bool FlipMemInputs) {
if (isa<StoreInst>(I)) {
AA->replaceWithNewValue(I, K);
AA->replaceWithNewValue(J, K);
} else {
Type *IType = I->getType();
Type *JType = J->getType();
VectorType *VType = getVecTypeForPair(IType, JType);
unsigned numElem = VType->getNumElements();
unsigned numElemI, numElemJ;
if (IType->isVectorTy())
numElemI = cast<VectorType>(IType)->getNumElements();
else
numElemI = 1;
if (JType->isVectorTy())
numElemJ = cast<VectorType>(JType)->getNumElements();
else
numElemJ = 1;
if (IType->isVectorTy()) {
std::vector<Constant*> Mask1(numElemI), Mask2(numElemI);
for (unsigned v = 0; v < numElemI; ++v) {
Mask1[v] = ConstantInt::get(Type::getInt32Ty(Context), v);
Mask2[v] = ConstantInt::get(Type::getInt32Ty(Context), numElemJ+v);
}
K1 = new ShuffleVectorInst(K, UndefValue::get(VType),
ConstantVector::get(
FlipMemInputs ? Mask2 : Mask1),
getReplacementName(K, false, 1));
} else {
Value *CV0 = ConstantInt::get(Type::getInt32Ty(Context), 0);
Value *CV1 = ConstantInt::get(Type::getInt32Ty(Context), numElem-1);
K1 = ExtractElementInst::Create(K, FlipMemInputs ? CV1 : CV0,
getReplacementName(K, false, 1));
}
if (JType->isVectorTy()) {
std::vector<Constant*> Mask1(numElemJ), Mask2(numElemJ);
for (unsigned v = 0; v < numElemJ; ++v) {
Mask1[v] = ConstantInt::get(Type::getInt32Ty(Context), v);
Mask2[v] = ConstantInt::get(Type::getInt32Ty(Context), numElemI+v);
}
K2 = new ShuffleVectorInst(K, UndefValue::get(VType),
ConstantVector::get(
FlipMemInputs ? Mask1 : Mask2),
getReplacementName(K, false, 2));
} else {
Value *CV0 = ConstantInt::get(Type::getInt32Ty(Context), 0);
Value *CV1 = ConstantInt::get(Type::getInt32Ty(Context), numElem-1);
K2 = ExtractElementInst::Create(K, FlipMemInputs ? CV0 : CV1,
getReplacementName(K, false, 2));
}
K1->insertAfter(K);
K2->insertAfter(K1);
InsertionPt = K2;
}
}
// Move all uses of the function I (including pairing-induced uses) after J.
bool BBVectorize::canMoveUsesOfIAfterJ(BasicBlock &BB,
std::multimap<Value *, Value *> &LoadMoveSet,
Instruction *I, Instruction *J) {
// Skip to the first instruction past I.
BasicBlock::iterator L = llvm::next(BasicBlock::iterator(I));
DenseSet<Value *> Users;
AliasSetTracker WriteSet(*AA);
for (; cast<Instruction>(L) != J; ++L)
(void) trackUsesOfI(Users, WriteSet, I, L, true, &LoadMoveSet);
assert(cast<Instruction>(L) == J &&
"Tracking has not proceeded far enough to check for dependencies");
// If J is now in the use set of I, then trackUsesOfI will return true
// and we have a dependency cycle (and the fusing operation must abort).
return !trackUsesOfI(Users, WriteSet, I, J, true, &LoadMoveSet);
}
// Move all uses of the function I (including pairing-induced uses) after J.
void BBVectorize::moveUsesOfIAfterJ(BasicBlock &BB,
std::multimap<Value *, Value *> &LoadMoveSet,
Instruction *&InsertionPt,
Instruction *I, Instruction *J) {
// Skip to the first instruction past I.
BasicBlock::iterator L = llvm::next(BasicBlock::iterator(I));
DenseSet<Value *> Users;
AliasSetTracker WriteSet(*AA);
for (; cast<Instruction>(L) != J;) {
if (trackUsesOfI(Users, WriteSet, I, L, true, &LoadMoveSet)) {
// Move this instruction
Instruction *InstToMove = L; ++L;
DEBUG(dbgs() << "BBV: moving: " << *InstToMove <<
" to after " << *InsertionPt << "\n");
InstToMove->removeFromParent();
InstToMove->insertAfter(InsertionPt);
InsertionPt = InstToMove;
} else {
++L;
}
}
}
// Collect all load instruction that are in the move set of a given first
// pair member. These loads depend on the first instruction, I, and so need
// to be moved after J (the second instruction) when the pair is fused.
void BBVectorize::collectPairLoadMoveSet(BasicBlock &BB,
DenseMap<Value *, Value *> &ChosenPairs,
std::multimap<Value *, Value *> &LoadMoveSet,
Instruction *I) {
// Skip to the first instruction past I.
BasicBlock::iterator L = llvm::next(BasicBlock::iterator(I));
DenseSet<Value *> Users;
AliasSetTracker WriteSet(*AA);
// Note: We cannot end the loop when we reach J because J could be moved
// farther down the use chain by another instruction pairing. Also, J
// could be before I if this is an inverted input.
for (BasicBlock::iterator E = BB.end(); cast<Instruction>(L) != E; ++L) {
if (trackUsesOfI(Users, WriteSet, I, L)) {
if (L->mayReadFromMemory())
LoadMoveSet.insert(ValuePair(L, I));
}
}
}
// In cases where both load/stores and the computation of their pointers
// are chosen for vectorization, we can end up in a situation where the
// aliasing analysis starts returning different query results as the
// process of fusing instruction pairs continues. Because the algorithm
// relies on finding the same use trees here as were found earlier, we'll
// need to precompute the necessary aliasing information here and then
// manually update it during the fusion process.
void BBVectorize::collectLoadMoveSet(BasicBlock &BB,
std::vector<Value *> &PairableInsts,
DenseMap<Value *, Value *> &ChosenPairs,
std::multimap<Value *, Value *> &LoadMoveSet) {
for (std::vector<Value *>::iterator PI = PairableInsts.begin(),
PIE = PairableInsts.end(); PI != PIE; ++PI) {
DenseMap<Value *, Value *>::iterator P = ChosenPairs.find(*PI);
if (P == ChosenPairs.end()) continue;
Instruction *I = cast<Instruction>(P->first);
collectPairLoadMoveSet(BB, ChosenPairs, LoadMoveSet, I);
}
}
// As with the aliasing information, SCEV can also change because of
// vectorization. This information is used to compute relative pointer
// offsets; the necessary information will be cached here prior to
// fusion.
void BBVectorize::collectPtrInfo(std::vector<Value *> &PairableInsts,
DenseMap<Value *, Value *> &ChosenPairs,
DenseSet<Value *> &LowPtrInsts) {
for (std::vector<Value *>::iterator PI = PairableInsts.begin(),
PIE = PairableInsts.end(); PI != PIE; ++PI) {
DenseMap<Value *, Value *>::iterator P = ChosenPairs.find(*PI);
if (P == ChosenPairs.end()) continue;
Instruction *I = cast<Instruction>(P->first);
Instruction *J = cast<Instruction>(P->second);
if (!isa<LoadInst>(I) && !isa<StoreInst>(I))
continue;
Value *IPtr, *JPtr;
unsigned IAlignment, JAlignment;
int64_t OffsetInElmts;
if (!getPairPtrInfo(I, J, IPtr, JPtr, IAlignment, JAlignment,
OffsetInElmts) || abs64(OffsetInElmts) != 1)
llvm_unreachable("Pre-fusion pointer analysis failed");
Value *LowPI = (OffsetInElmts > 0) ? I : J;
LowPtrInsts.insert(LowPI);
}
}
// When the first instruction in each pair is cloned, it will inherit its
// parent's metadata. This metadata must be combined with that of the other
// instruction in a safe way.
void BBVectorize::combineMetadata(Instruction *K, const Instruction *J) {
SmallVector<std::pair<unsigned, MDNode*>, 4> Metadata;
K->getAllMetadataOtherThanDebugLoc(Metadata);
for (unsigned i = 0, n = Metadata.size(); i < n; ++i) {
unsigned Kind = Metadata[i].first;
MDNode *JMD = J->getMetadata(Kind);
MDNode *KMD = Metadata[i].second;
switch (Kind) {
default:
K->setMetadata(Kind, 0); // Remove unknown metadata
break;
case LLVMContext::MD_tbaa:
K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
break;
case LLVMContext::MD_fpmath:
K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD));
break;
}
}
}
// This function fuses the chosen instruction pairs into vector instructions,
// taking care preserve any needed scalar outputs and, then, it reorders the
// remaining instructions as needed (users of the first member of the pair
// need to be moved to after the location of the second member of the pair
// because the vector instruction is inserted in the location of the pair's
// second member).
void BBVectorize::fuseChosenPairs(BasicBlock &BB,
std::vector<Value *> &PairableInsts,
DenseMap<Value *, Value *> &ChosenPairs) {
LLVMContext& Context = BB.getContext();
// During the vectorization process, the order of the pairs to be fused
// could be flipped. So we'll add each pair, flipped, into the ChosenPairs
// list. After a pair is fused, the flipped pair is removed from the list.
std::vector<ValuePair> FlippedPairs;
FlippedPairs.reserve(ChosenPairs.size());
for (DenseMap<Value *, Value *>::iterator P = ChosenPairs.begin(),
E = ChosenPairs.end(); P != E; ++P)
FlippedPairs.push_back(ValuePair(P->second, P->first));
for (std::vector<ValuePair>::iterator P = FlippedPairs.begin(),
E = FlippedPairs.end(); P != E; ++P)
ChosenPairs.insert(*P);
std::multimap<Value *, Value *> LoadMoveSet;
collectLoadMoveSet(BB, PairableInsts, ChosenPairs, LoadMoveSet);
DenseSet<Value *> LowPtrInsts;
collectPtrInfo(PairableInsts, ChosenPairs, LowPtrInsts);
DEBUG(dbgs() << "BBV: initial: \n" << BB << "\n");
for (BasicBlock::iterator PI = BB.getFirstInsertionPt(); PI != BB.end();) {
DenseMap<Value *, Value *>::iterator P = ChosenPairs.find(PI);
if (P == ChosenPairs.end()) {
++PI;
continue;
}
if (getDepthFactor(P->first) == 0) {
// These instructions are not really fused, but are tracked as though
// they are. Any case in which it would be interesting to fuse them
// will be taken care of by InstCombine.
--NumFusedOps;
++PI;
continue;
}
Instruction *I = cast<Instruction>(P->first),
*J = cast<Instruction>(P->second);
DEBUG(dbgs() << "BBV: fusing: " << *I <<
" <-> " << *J << "\n");
// Remove the pair and flipped pair from the list.
DenseMap<Value *, Value *>::iterator FP = ChosenPairs.find(P->second);
assert(FP != ChosenPairs.end() && "Flipped pair not found in list");
ChosenPairs.erase(FP);
ChosenPairs.erase(P);
if (!canMoveUsesOfIAfterJ(BB, LoadMoveSet, I, J)) {
DEBUG(dbgs() << "BBV: fusion of: " << *I <<
" <-> " << *J <<
" aborted because of non-trivial dependency cycle\n");
--NumFusedOps;
++PI;
continue;
}
bool FlipMemInputs = false;
if (isa<LoadInst>(I) || isa<StoreInst>(I))
FlipMemInputs = (LowPtrInsts.find(I) == LowPtrInsts.end());
unsigned NumOperands = I->getNumOperands();
SmallVector<Value *, 3> ReplacedOperands(NumOperands);
getReplacementInputsForPair(Context, I, J, ReplacedOperands,
FlipMemInputs);
// Make a copy of the original operation, change its type to the vector
// type and replace its operands with the vector operands.
Instruction *K = I->clone();
if (I->hasName()) K->takeName(I);
if (!isa<StoreInst>(K))
K->mutateType(getVecTypeForPair(I->getType(), J->getType()));
combineMetadata(K, J);
for (unsigned o = 0; o < NumOperands; ++o)
K->setOperand(o, ReplacedOperands[o]);
// If we've flipped the memory inputs, make sure that we take the correct
// alignment.
if (FlipMemInputs) {
if (isa<StoreInst>(K))
cast<StoreInst>(K)->setAlignment(cast<StoreInst>(J)->getAlignment());
else
cast<LoadInst>(K)->setAlignment(cast<LoadInst>(J)->getAlignment());
}
K->insertAfter(J);
// Instruction insertion point:
Instruction *InsertionPt = K;
Instruction *K1 = 0, *K2 = 0;
replaceOutputsOfPair(Context, I, J, K, InsertionPt, K1, K2,
FlipMemInputs);
// The use tree of the first original instruction must be moved to after
// the location of the second instruction. The entire use tree of the
// first instruction is disjoint from the input tree of the second
// (by definition), and so commutes with it.
moveUsesOfIAfterJ(BB, LoadMoveSet, InsertionPt, I, J);
if (!isa<StoreInst>(I)) {
I->replaceAllUsesWith(K1);
J->replaceAllUsesWith(K2);
AA->replaceWithNewValue(I, K1);
AA->replaceWithNewValue(J, K2);
}
// Instructions that may read from memory may be in the load move set.
// Once an instruction is fused, we no longer need its move set, and so
// the values of the map never need to be updated. However, when a load
// is fused, we need to merge the entries from both instructions in the
// pair in case those instructions were in the move set of some other
// yet-to-be-fused pair. The loads in question are the keys of the map.
if (I->mayReadFromMemory()) {
std::vector<ValuePair> NewSetMembers;
VPIteratorPair IPairRange = LoadMoveSet.equal_range(I);
VPIteratorPair JPairRange = LoadMoveSet.equal_range(J);
for (std::multimap<Value *, Value *>::iterator N = IPairRange.first;
N != IPairRange.second; ++N)
NewSetMembers.push_back(ValuePair(K, N->second));
for (std::multimap<Value *, Value *>::iterator N = JPairRange.first;
N != JPairRange.second; ++N)
NewSetMembers.push_back(ValuePair(K, N->second));
for (std::vector<ValuePair>::iterator A = NewSetMembers.begin(),
AE = NewSetMembers.end(); A != AE; ++A)
LoadMoveSet.insert(*A);
}
// Before removing I, set the iterator to the next instruction.
PI = llvm::next(BasicBlock::iterator(I));
if (cast<Instruction>(PI) == J)
++PI;
SE->forgetValue(I);
SE->forgetValue(J);
I->eraseFromParent();
J->eraseFromParent();
}
DEBUG(dbgs() << "BBV: final: \n" << BB << "\n");
}
}
char BBVectorize::ID = 0;
static const char bb_vectorize_name[] = "Basic-Block Vectorization";
INITIALIZE_PASS_BEGIN(BBVectorize, BBV_NAME, bb_vectorize_name, false, false)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
INITIALIZE_PASS_END(BBVectorize, BBV_NAME, bb_vectorize_name, false, false)
BasicBlockPass *llvm::createBBVectorizePass(const VectorizeConfig &C) {
return new BBVectorize(C);
}
bool
llvm::vectorizeBasicBlock(Pass *P, BasicBlock &BB, const VectorizeConfig &C) {
BBVectorize BBVectorizer(P, C);
return BBVectorizer.vectorizeBB(BB);
}
//===----------------------------------------------------------------------===//
VectorizeConfig::VectorizeConfig() {
VectorBits = ::VectorBits;
VectorizeBools = !::NoBools;
VectorizeInts = !::NoInts;
VectorizeFloats = !::NoFloats;
VectorizePointers = !::NoPointers;
VectorizeCasts = !::NoCasts;
VectorizeMath = !::NoMath;
VectorizeFMA = !::NoFMA;
VectorizeSelect = !::NoSelect;
VectorizeCmp = !::NoCmp;
VectorizeGEP = !::NoGEP;
VectorizeMemOps = !::NoMemOps;
AlignedOnly = ::AlignedOnly;
ReqChainDepth= ::ReqChainDepth;
SearchLimit = ::SearchLimit;
MaxCandPairsForCycleCheck = ::MaxCandPairsForCycleCheck;
SplatBreaksChain = ::SplatBreaksChain;
MaxInsts = ::MaxInsts;
MaxIter = ::MaxIter;
Pow2LenOnly = ::Pow2LenOnly;
NoMemOpBoost = ::NoMemOpBoost;
FastDep = ::FastDep;
}
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