/*========================== begin_copyright_notice ============================

Copyright (C) 2017-2021 Intel Corporation

SPDX-License-Identifier: MIT

============================= end_copyright_notice ===========================*/

#include "Compiler/CISACodeGen/VectorProcess.hpp"
#include "Compiler/CISACodeGen/ShaderCodeGen.hpp"
#include "Compiler/CISACodeGen/EmitVISAPass.hpp"
#include "Compiler/CodeGenPublic.h"
#include "Compiler/IGCPassSupport.h"
#include "common/LLVMWarningsPush.hpp"
#include <llvm/IR/DataLayout.h>
#include <llvm/IR/Instructions.h>
#include <llvmWrapper/IR/IRBuilder.h>
#include <llvm/IR/InstIterator.h>
#include <llvm/Support/MathExtras.h>
#include <llvm/Transforms/Utils/Local.h>
#include <llvmWrapper/IR/DerivedTypes.h>
#include <llvmWrapper/Support/Alignment.h>
#include "common/LLVMWarningsPop.hpp"
#include "Probe/Assertion.h"

#include <utility>    // std::pair, std::make_pair

using namespace llvm;
using namespace IGC;
using IGCLLVM::FixedVectorType;

//
// Description of VectorPreProcess Pass
//   The purpose is both to legalize vector types and to reduce register
//   presure. Once this pass is done, there is no 3-element vector whose
//   element size < 4 bytes, that is, no <3 x i8>, no <3 x i16>. (But
//   we will have <3xi32> and <3xi64>.)
//
// 1. Split a vector load/stores with a large vector into ones with
//    smaller vectors or scalars; and make sure that the sub-vectors
//    are either multiple of DW, vector3, or their size is less than
//    4 bytes (see details in code).  Vector3 will be specially
//    handled later.
//    For example,
//        <16xi64> ---> four <4xi64>
//        <15xi32> ---> <8xi32>, <7xi32>
//        <13xi32> ---> <8xi32>, <5xi32>
//        <31xi16> ---> <16xi16>, <12xi16>, <3xi16>
//        <19xi16> ---> <16xi16>, <3xi16>
//        <39xi8>  ---> <32xi8>, <4xi8>, <3xi8>
//    Note that splitting keeps the vector element's type without
//    changing it.
//
//    Note that as 6/2020,
//      if size of vector element >= DW, the number of elements of the new vector
//      should be power of 2 except for vector3.  Thus, we should not see 5xi32,
//      7xi32, etc.  This makes code emit easier.
//
// 2. Special processing of 3-element vectors
//    If (vector element's size < 4 bytes)
//    {
//       3-element vector load  --> 2-element vector load + scalar load
//       3-element vector store --> 2-element vector store + scalar store.
//    }
//    Note that 3-element load could be optimized to 4-element load (check
//    details in the code).
//
//    for example,
//      (1) %1 = load <3 x i8> *p
//          converted into
//             %pv = bitcast p to <2 x i8>*  // %pv is type <2 x i8>*
//             %ps = (i8*)p + 2;             // %ps is type i8*
//             %2 = load <2 x i8> *pv
//             %3 = load i8 *ps
//          original vector %1 == (%2, %3)
//
//      (2) store <3 x i16> %1, <3 x i16> *p
//          converted into
//             %pv = bitcast p to <2 x i16>*  // %pv is type <2 x i16>*
//             %ps = (i16*)p + 2;             // %ps is type i16*
//             %new_v = (%1.x, %1.y)
//             store <2 x i16> %new_v, <2 x i16> *pv
//             store i16 %1.z i8 *ps
//
namespace
{
    // AbstractLoadInst and AbstractStoreInst abstract away the differences
    // between ldraw and Load and between storeraw and Store.
    // Note on usage: The Value* passed as the ptr paramter to the Create method
    // should be either the result of the getPointerOperand() method or the
    // CreateConstScalarGEP() method. Do not attempt to do arithmetic
    // (or pointer arithmetic) on these values.
    class AbstractLoadInst
    {
        Instruction* const m_inst;
        AbstractLoadInst(LoadInst* LI) : m_inst(LI) {}
        AbstractLoadInst(LdRawIntrinsic* LdRI) : m_inst(LdRI) {}

        LoadInst* getLoad() const
        {
            return cast<LoadInst>(m_inst);
        }
        LdRawIntrinsic* getLdRaw() const
        {
            return cast<LdRawIntrinsic>(m_inst);
        }
    public:
        Instruction* getInst() const
        {
            return m_inst;
        }
        unsigned int getAlignment() const
        {
            return isa<LoadInst>(m_inst) ? getLoad()->getAlignment() : getLdRaw()->getAlignment();
        }
        void setAlignment(unsigned int alignment)
        {
            if (isa<LoadInst>(m_inst))
            {
                getLoad()->setAlignment(IGCLLVM::getCorrectAlign(alignment));
            }
            else
            {
                getLdRaw()->setAlignment(alignment);
            }
        }
        Value* getPointerOperand() const
        {
            return isa<LoadInst>(m_inst) ? getLoad()->getPointerOperand() : getLdRaw()->getResourceValue();
        }
        bool getIsVolatile() const
        {
            return isa<LoadInst>(m_inst) ? getLoad()->isVolatile() : getLdRaw()->isVolatile();
        }
        Instruction* Create(Type* returnType)
        {
            return Create(returnType, getPointerOperand(), getAlignment(), getIsVolatile());
        }
        Instruction* Create(Type* returnType, Value* ptr, unsigned int alignment, bool isVolatile)
        {
            IRBuilder<> builder(m_inst);
            if (isa<LoadInst>(m_inst))
            {
                Type* newPtrType = PointerType::get(returnType, ptr->getType()->getPointerAddressSpace());
                ptr = builder.CreateBitCast(ptr, newPtrType);
                return builder.CreateAlignedLoad(ptr, IGCLLVM::getAlign(alignment), isVolatile);
            }
            else
            {
                LdRawIntrinsic* ldraw = getLdRaw();
                bool hasComputedOffset = ptr != ldraw->getResourceValue();
                Value* offsetVal = hasComputedOffset ? ptr : ldraw->getOffsetValue();
                ptr = ldraw->getResourceValue();
                Type* types[2] = { returnType , ptr->getType() };
                Value* args[4] = { ptr, offsetVal, builder.getInt32(alignment), builder.getInt1(isVolatile) };
                Function* newLdRawFunction =
                    GenISAIntrinsic::getDeclaration(ldraw->getModule(), ldraw->getIntrinsicID(), types);
                return builder.CreateCall(newLdRawFunction, args);
            }
        }
        // Emulates a GEP on a pointer of the scalar type of returnType.
        Value* CreateConstScalarGEP(Type* returnType, Value* ptr, uint32_t offset)
        {
            IRBuilder<> builder(m_inst);
            if (isa<LoadInst>(m_inst))
            {
                Type* ePtrType = PointerType::get(returnType->getScalarType(), ptr->getType()->getPointerAddressSpace());
                ptr = builder.CreateBitCast(ptr, ePtrType);
                return builder.CreateConstGEP1_32(ptr, offset);
            }
            else
            {
                Value* offsetInBytes = builder.getInt32(offset * returnType->getScalarSizeInBits() / 8);
                return builder.CreateAdd(offsetInBytes, getLdRaw()->getOffsetValue());
            }
        }
        static Optional<AbstractLoadInst> get(llvm::Value* value)
        {
            if (LoadInst * LI = dyn_cast<LoadInst>(value))
            {
                return Optional<AbstractLoadInst>(LI);
            }
            else if (LdRawIntrinsic * LdRI = dyn_cast<LdRawIntrinsic>(value))
            {
                return Optional<AbstractLoadInst>(LdRI);
            }
            else
            {
                return Optional<AbstractLoadInst>();
            }
        }
    };
    static bool isAbstractLoadInst(llvm::Value* value)
    {
        return isa<LoadInst>(value) || isa<LdRawIntrinsic>(value);
    }

    class AbstractStoreInst
    {
        Instruction* const m_inst;
        AbstractStoreInst(StoreInst* SI) : m_inst(SI) {}
        AbstractStoreInst(StoreRawIntrinsic* SRI) : m_inst(SRI) {}

        StoreInst* getStore() const
        {
            return cast<StoreInst>(m_inst);
        }
        StoreRawIntrinsic* getStoreRaw() const
        {
            return cast<StoreRawIntrinsic>(m_inst);
        }
    public:
        Instruction* getInst() const
        {
            return m_inst;
        }
        unsigned int getAlignment() const
        {
            return isa<StoreInst>(m_inst) ? getStore()->getAlignment() : getStoreRaw()->getAlignment();
        }
        void setAlignment(unsigned int alignment)
        {
            if (isa<StoreInst>(m_inst))
            {
                getStore()->setAlignment(IGCLLVM::getCorrectAlign(alignment));
            }
        }
        Value* getValueOperand() const
        {
            return isa<StoreInst>(m_inst) ? getStore()->getValueOperand() : getStoreRaw()->getArgOperand(2);
        }
        Value* getPointerOperand() const
        {
            return isa<StoreInst>(m_inst) ? getStore()->getPointerOperand() : getStoreRaw()->getArgOperand(0);
        }
        bool getIsVolatile() const
        {
            return isa<StoreInst>(m_inst) ? getStore()->isVolatile() : false;
        }
        Instruction* Create(Value* storedValue, Value* ptr, unsigned int alignment, bool isVolatile)
        {
            IRBuilder<> builder(m_inst);
            Type* newType = storedValue->getType();
            if (isa<StoreInst>(m_inst))
            {
                Type* newPtrType = PointerType::get(newType, ptr->getType()->getPointerAddressSpace());
                ptr = builder.CreateBitCast(ptr, newPtrType);
                return builder.CreateAlignedStore(storedValue, ptr, IGCLLVM::getAlign(alignment), isVolatile);
            }
            else
            {
                bool hasComputedOffset = ptr != getPointerOperand();
                Value* offset = hasComputedOffset ? ptr : getStoreRaw()->getArgOperand(1);
                ptr = getPointerOperand();
                Type* types[2] = { ptr->getType(), newType };
                Value* args[5] = { ptr, offset, storedValue, builder.getInt32(alignment), builder.getInt1(isVolatile) };
                Function* newStoreRawFunction =
                    GenISAIntrinsic::getDeclaration(getStoreRaw()->getModule(), getStoreRaw()->getIntrinsicID(), types);
                return builder.CreateCall(newStoreRawFunction, args);
            }
        }
        Instruction* Create(Value* storedValue)
        {
            return Create(storedValue, getPointerOperand(), getAlignment(), getIsVolatile());
        }
        // Emulates a GEP on a pointer of the scalar type of storedType.
        Value* CreateConstScalarGEP(Type* storedType, Value* ptr, uint32_t offset)
        {
            IRBuilder<> builder(m_inst);
            if (isa<StoreInst>(m_inst))
            {
                Type* ePtrType = PointerType::get(storedType->getScalarType(), ptr->getType()->getPointerAddressSpace());
                ptr = builder.CreateBitCast(ptr, ePtrType);
                return builder.CreateConstGEP1_32(ptr, offset);
            }
            else
            {
                Value* offsetInBytes = builder.getInt32(offset * storedType->getScalarSizeInBits() / 8);
                return builder.CreateAdd(offsetInBytes, getStoreRaw()->getArgOperand(1));
            }
        }
        static Optional<AbstractStoreInst> get(llvm::Value* value)
        {
            if (StoreInst * SI = dyn_cast<StoreInst>(value))
            {
                return Optional<AbstractStoreInst>(SI);
            }
            else if (StoreRawIntrinsic* SRI = dyn_cast<StoreRawIntrinsic>(value))
            {
                return Optional<AbstractStoreInst>(SRI);
            }
            return Optional<AbstractStoreInst>();
        }
    };

    static bool isAbstractStoreInst(llvm::Value* value)
    {
        GenIntrinsicInst* II = dyn_cast<GenIntrinsicInst>(value);
        return isa<StoreInst>(value) || (II && (II->getIntrinsicID() == GenISAIntrinsic::GenISA_storeraw_indexed ||
            II->getIntrinsicID() == GenISAIntrinsic::GenISA_storerawvector_indexed));
    }

    class VectorPreProcess : public FunctionPass
    {
    public:
        typedef SmallVector<Instruction*, 32> InstWorkVector;
        typedef SmallVector<Value*, 16> ValVector;
        // map from Vector value to its Component Values
        typedef DenseMap<Value*, ValVector> V2SMap;

        enum class VPConst {
            // If a vector's size is bigger than SPLIT_SIZE, split it into multiple
            // of SPLIT_SIZE (plus smaller sub-vectors or scalar if any).
            // With SPLIT_SIZE=32, we have the max vectors as below after this pass:
            //     <32 x i8>, 16xi16, 8xi32, or 4xi64!
            SPLIT_SIZE = 32,              // default, 32 bytes
            RAW_SPLIT_SIZE = 16
        };

        static char ID; // Pass identification, replacement for typeid
        VectorPreProcess()
            : FunctionPass(ID)
            , m_DL(nullptr)
            , m_C(nullptr)
            , m_WorkList()
            , m_Temps()
            , m_CGCtx(nullptr)
        {
            initializeVectorPreProcessPass(*PassRegistry::getPassRegistry());
        }

        StringRef getPassName() const override { return "VectorPreProcess"; }
        bool runOnFunction(Function& F) override;
        void getAnalysisUsage(AnalysisUsage& AU) const override
        {
            AU.setPreservesCFG();
            AU.addRequired<CodeGenContextWrapper>();
            AU.addRequired<MetaDataUtilsWrapper>();
            AU.addRequired<DominatorTreeWrapperPass>();
            AU.addRequired<PostDominatorTreeWrapperPass>();
        }

    private:

        void getOrGenScalarValues(
            Function& F, Value* VecVal, ValVector& scalars, Instruction*& availBeforeInst);
        void replaceAllVectorUsesWithScalars(Instruction* VI,
            ValVector& SVals);

        // Return true if V is created by InsertElementInst with const index.
        bool isValueCreatedOnlyByIEI(Value* V, InsertElementInst** IEInsts);
        // Return true if V is only used by ExtractElement with const index.
        bool isValueUsedOnlyByEEI(Value* V, ExtractElementInst** EEInsts);

        // Split load/store that cannot be re-layout or is too big.
        uint32_t getSplitByteSize(Instruction* I, WIAnalysisRunner& WI) const;
        bool splitLoadStore(Instruction* Inst, V2SMap& vecToSubVec, WIAnalysisRunner& WI);
        bool splitLoad(AbstractLoadInst& LI, V2SMap& vecToSubVec, WIAnalysisRunner& WI);
        bool splitStore(AbstractStoreInst& SI, V2SMap& vecToSubVec, WIAnalysisRunner& WI);
        bool splitVector3LoadStore(Instruction* Inst);
        // Simplify load/store instructions if possible. Return itself if no
        // simplification is performed.
        Instruction* simplifyLoadStore(Instruction* LI);
        void createSplitVectorTypes(
            Type* ETy,
            uint32_t NElts,
            uint32_t SplitSize,
            SmallVector<std::pair<Type*, uint32_t>, 8>& SplitInfo);

    private:
        const DataLayout* m_DL;
        LLVMContext* m_C;
        InstWorkVector m_WorkList;
        ValVector m_Temps;
        InstWorkVector m_Vector3List; // used for keep all 3-element vectors.
        IGC::CodeGenContext* m_CGCtx;
    };
}

// Register pass to igc-opt
#define PASS_FLAG "igc-vectorpreprocess"
#define PASS_DESCRIPTION "Split loads/stores of big (or 3-element) vectors into smaller ones."
#define PASS_CFG_ONLY false
#define PASS_ANALYSIS false
IGC_INITIALIZE_PASS_BEGIN(VectorPreProcess, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
IGC_INITIALIZE_PASS_DEPENDENCY(CodeGenContextWrapper)
IGC_INITIALIZE_PASS_DEPENDENCY(MetaDataUtilsWrapper)
IGC_INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
IGC_INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
IGC_INITIALIZE_PASS_END(VectorPreProcess, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)

char VectorPreProcess::ID = 0;

FunctionPass* IGC::createVectorPreProcessPass()
{
    return new VectorPreProcess();
}

bool VectorPreProcess::isValueCreatedOnlyByIEI(Value* V, InsertElementInst** IEInsts)
{
    Value* ChainVal = V;
    while (!isa<UndefValue>(ChainVal))
    {
        InsertElementInst* IEI = dyn_cast<InsertElementInst>(ChainVal);
        if (!IEI || !isa<ConstantInt>(IEI->getOperand(2)))
        {
            return false;
        }
        ConstantInt* CInt = dyn_cast<ConstantInt>(IEI->getOperand(2));
        uint32_t idx = (uint32_t)CInt->getZExtValue();

        // Make sure the last IEI will be recorded if an element is
        // inserted multiple times.
        if (IEInsts[idx] == nullptr)
        {
            IEInsts[idx] = IEI;
        }

        ChainVal = IEI->getOperand(0);
    }
    return true;
}

bool VectorPreProcess::isValueUsedOnlyByEEI(Value* V, ExtractElementInst** EEInsts)
{
    for (Value::user_iterator UI = V->user_begin(), UE = V->user_end();
        UI != UE; ++UI)
    {
        ExtractElementInst* EEI = dyn_cast<ExtractElementInst>(*UI);
        if (!EEI ||
            (EEI->getOperand(0) != V) ||
            !isa<ConstantInt>(EEI->getOperand(1)))
        {
            return false;
        }
        ConstantInt* CInt = dyn_cast<ConstantInt>(EEI->getOperand(1));
        uint32_t idx = (uint32_t)CInt->getZExtValue();

        // Quit if there are multiple extract from the same index.
        if (EEInsts[idx] != nullptr)
        {
            return false;
        }
        EEInsts[idx] = EEI;
    }
    return true;
}

// SVals[0:NumElements] has all scalar elements of vector VI. This function
// tries to replace all uses of VI with SVals[...] if possible, If not
// possible, re-generate the vector from SVals at the BB of VI.
//
// This function also erase VI.
void VectorPreProcess::replaceAllVectorUsesWithScalars(Instruction* VI, ValVector& SVals)
{
    SmallVector<Instruction*, 8> ToBeDeleted;
    bool genVec = false;
    for (Value::user_iterator UI = VI->user_begin(), UE = VI->user_end(); UI != UE; ++UI)
    {
        ExtractElementInst* EEI = dyn_cast<ExtractElementInst>(*UI);
        if (!EEI)
        {
            genVec = true;
            continue;
        }
        ConstantInt* CI = dyn_cast<ConstantInt>(EEI->getOperand(1));
        if (!CI)
        {
            genVec = true;
            continue;
        }
        uint32_t ix = (uint32_t)CI->getZExtValue();
        EEI->replaceAllUsesWith(SVals[ix]);
        ToBeDeleted.push_back(EEI);
    }
    if (genVec)
    {
        Instruction* I;
        if (!isa<PHINode>(VI))
        {
            I = VI;
        }
        else
        {
            I = VI->getParent()->getFirstNonPHI();
        }
        IRBuilder<> Builder(I);
        VectorType* VTy = cast<VectorType>(VI->getType());
        Value* newVec = UndefValue::get(VTy);
        for (uint32_t i = 0, e = int_cast<uint32_t>(VTy->getNumElements()); i < e; ++i)
        {
            newVec = Builder.CreateInsertElement(
                newVec,
                SVals[i],
                Builder.getInt32(i),
                "scalarize");
        }
        // Replace old instruction with new one
        VI->replaceAllUsesWith(newVec);
    }
    for (uint32_t i = 0; i < ToBeDeleted.size(); ++i)
    {
        ToBeDeleted[i]->eraseFromParent();
    }

    // May have phi use, need to check if it's empty.
    if (VI->use_empty())
    {
        VI->eraseFromParent();
    }
}

void VectorPreProcess::createSplitVectorTypes(
    Type* ETy,
    uint32_t NElts,
    uint32_t SplitSize,
    SmallVector<std::pair<Type*, uint32_t>, 8>& SplitInfo)
{
    uint32_t ebytes = (unsigned int)ETy->getPrimitiveSizeInBits() / 8;
    if (ETy->isPointerTy())
    {
        ebytes = m_DL->getPointerTypeSize(ETy);
    }

    // todo: generalize splitting for cases whose element size is bigger than splitsize!
    if (IGC_IS_FLAG_ENABLED(EnableSplitUnalignedVector))
    {
        if (ebytes > SplitSize)
        {
            IGC_ASSERT(SplitSize);
            uint32_t M = NElts * ebytes / SplitSize;
            Type* Ty = IntegerType::get(ETy->getContext(), SplitSize * 8);
            SplitInfo.push_back(std::make_pair(Ty, M));
            return;
        }
    }

    // Both SplitSize and ebytes shall be a power of 2
    IGC_ASSERT(ebytes);
    IGC_ASSERT_MESSAGE((SplitSize % ebytes) == 0, "Internal Error: Wrong split size!");

    uint32_t E = SplitSize / ebytes; // split size in elements
    uint32_t N = NElts;  // the number of elements to be split

    IGC_ASSERT(E);

    // 1. Make sure splitting it by SplitSize as required
    uint32_t M = N / E;  // the number of subvectors for split size E
    if (M > 0)
    {
        Type* Ty = (E == 1) ? ETy : FixedVectorType::get(ETy, E);
        SplitInfo.push_back(std::make_pair(Ty, M));
    }
    N = N % E;
    E = E / 2;  // next split size

    // 2. The remaining elts are splitted if not power of 2 until N <= 4.
    while (N > 4)
    {
        IGC_ASSERT(E);

        M = N / E;  // the number of subvectors for split size E
        if (M > 0)
        {
            SplitInfo.push_back(std::make_pair(FixedVectorType::get(ETy, E), M));
        }
        // The remaining elts are to be split for next iteration.
        N = N % E;
        E = E / 2;  // next split size
    }

    // 3. A vector of 1|2|3|4 elements. No further splitting!
    if (N > 0)
    {
        Type* Ty = (N == 1) ? ETy : FixedVectorType::get(ETy, N);
        SplitInfo.push_back(std::make_pair(Ty, 1));
    }
}

uint32_t VectorPreProcess::getSplitByteSize(Instruction* I, WIAnalysisRunner& WI) const
{
    uint32_t bytes = 0;
    if (LoadInst* LI = dyn_cast<LoadInst>(I))
    {
        bytes = (uint32_t)VPConst::SPLIT_SIZE;
    }
    else if (StoreInst* SI = dyn_cast<StoreInst>(I))
    {
        bytes = (uint32_t)VPConst::SPLIT_SIZE;
    }
    else if (isa<LdRawIntrinsic>(I) || isa<StoreRawIntrinsic>(I))
    {
        bytes = (uint32_t)VPConst::RAW_SPLIT_SIZE;
    }
    else
    {
        bytes = (uint32_t)VPConst::SPLIT_SIZE;
    }
    if ((isa<LoadInst>(I) || isa<StoreInst>(I)) && WI.isUniform(I))
    {
        auto Alignment = isa<LoadInst>(I) ? cast<LoadInst>(I)->getAlignment()
                                          : cast<StoreInst>(I)->getAlignment();
        if (Alignment >= 16) {
            Type* ETy = (isa<LoadInst>(I)) ?
                cast<VectorType>(I->getType())->getElementType() :
                cast<VectorType>(cast<StoreInst>(I)->getValueOperand()->getType())->getElementType();

            bool SLM = getLoadStorePointerOperand(I)->getType()->getPointerAddressSpace()
                == ADDRESS_SPACE_LOCAL;
            uint32_t ebytes = (unsigned int)ETy->getPrimitiveSizeInBits() / 8;
            if (ETy->isPointerTy())
                ebytes = m_DL->getPointerTypeSize(ETy);
            // Limit to DW and QW element types to avoid generating vectors that
            // are too large (ideally, should be <= 32 elements currently).
            if (ebytes == 4 || ebytes == 8)
            {
                bytes = std::max(bytes, m_CGCtx->platform.getMaxBlockMsgSize(SLM));
            }
        }
    }
    return bytes;
}

bool VectorPreProcess::splitStore(
    AbstractStoreInst& ASI, V2SMap& vecToSubVec, WIAnalysisRunner& WI)
{
    Instruction* SI = ASI.getInst();
    Value* StoredVal = ASI.getValueOperand();
    VectorType* VTy = cast<VectorType>(StoredVal->getType());
    Type* ETy = VTy->getElementType();
    uint32_t nelts = int_cast<uint32_t>(VTy->getNumElements());

    // splitInfo: Keep track of all pairs of (sub-vec type, #sub-vec).
    SmallVector<std::pair<Type*, uint32_t>, 8> splitInfo;
    bool isStoreInst = isa<StoreInst>(SI);
    uint32_t splitSize = getSplitByteSize(SI, WI);
    if (IGC_IS_FLAG_ENABLED(EnableSplitUnalignedVector))
    {
        // byte and word-aligned stores can only store a dword at a time.
        unsigned int alignment = ASI.getAlignment();
        if (isStoreInst && alignment < 4)
        {
            uint32_t newAlign = (uint32_t)IGCLLVM::getAlignmentValue(getKnownAlignment(ASI.getPointerOperand(), *m_DL));
            if (newAlign > alignment)
            {
                // For the same reason as Load, use DW-aligned for OCL stateful.
                StoreInst* aSI = dyn_cast<StoreInst>(SI);
                if (aSI && newAlign > 4 && isStatefulAddrSpace(aSI->getPointerAddressSpace()))
                {
                    newAlign = 4;
                }
                ASI.setAlignment(newAlign);
            }
        }
        bool needsDWordSplit =
            (!isStoreInst ||
                m_CGCtx->m_DriverInfo.splitUnalignedVectors() ||
                !WI.isUniform(ASI.getInst()))
            && ASI.getAlignment() < 4;
        if (needsDWordSplit)
        {
            splitSize = 4;
        }
    }
    createSplitVectorTypes(ETy, nelts, splitSize, splitInfo);

    // return if no split
    uint32_t len = splitInfo.size();
    if (len == 1 && splitInfo[0].second == 1)
    {
        return false;
    }

    ValVector& svals = vecToSubVec[StoredVal];
    if (svals.size() == 0)
    {
        // Need to create splitted values.
        Instruction* insertBeforeInst = nullptr;
        ValVector scalars(nelts, nullptr);
        getOrGenScalarValues(*SI->getParent()->getParent(),
            StoredVal, scalars, insertBeforeInst);
        insertBeforeInst = insertBeforeInst ? insertBeforeInst : SI;
        IRBuilder<> aBuilder(insertBeforeInst);

        Type* Ty1 = splitInfo[0].first;
        if (IGC_IS_FLAG_ENABLED(EnableSplitUnalignedVector))
        {
            if (ETy->getPrimitiveSizeInBits() > Ty1->getScalarSizeInBits())
            {
                std::vector<Value*> splitScalars;
                IGC_ASSERT(Ty1->getScalarSizeInBits());
                const uint32_t vectorSize = (unsigned int)ETy->getPrimitiveSizeInBits() / Ty1->getScalarSizeInBits();
                Type* splitType = FixedVectorType::get(Ty1, vectorSize);
                for (uint32_t i = 0; i < nelts; i++)
                {
                    Value* splitInst = aBuilder.CreateBitCast(scalars[i], splitType);
                    for (uint32_t j = 0; j < vectorSize; j++)
                    {
                        splitScalars.push_back(aBuilder.CreateExtractElement(splitInst, j));
                    }
                }
                scalars.resize(splitScalars.size());
                for (uint32_t i = 0; i < splitScalars.size(); i++)
                {
                    scalars[i] = splitScalars[i];
                }
            }
        }

        // Now generate svals
        for (uint32_t i = 0, Idx = 0; i < len; ++i)
        {
            Type* Ty1 = splitInfo[i].first;
            uint32_t len1 = splitInfo[i].second;
            VectorType* VTy1 = dyn_cast<VectorType>(Ty1);
            for (uint32_t j = 0; j < len1; ++j)
            {
                Value* subVec;
                if (!VTy1)
                {
                    subVec = scalars[Idx];
                    ++Idx;
                }
                else
                {
                    subVec = UndefValue::get(Ty1);
                    uint32_t n1 = int_cast<uint32_t>(VTy1->getNumElements());
                    for (uint32_t k = 0; k < n1; ++k)
                    {
                        subVec = aBuilder.CreateInsertElement(
                            subVec,
                            scalars[Idx],
                            aBuilder.getInt32(k));
                        ++Idx;
                    }
                }
                svals.push_back(subVec);
            }
        }
    }

    Value* Addr = ASI.getPointerOperand();
    uint32_t Align = ASI.getAlignment();
    bool IsVolatile = ASI.getIsVolatile();
    uint32_t eOffset = 0;
    uint32_t EBytes = int_cast<unsigned int>(m_DL->getTypeAllocSize(ETy));

    for (uint32_t i = 0, subIdx = 0; i < len; ++i)
    {
        Type* Ty1 = splitInfo[i].first;
        uint32_t len1 = splitInfo[i].second;
        VectorType* VTy1 = dyn_cast<VectorType>(Ty1);
        for (uint32_t j = 0; j < len1; ++j)
        {
            uint32_t vAlign = (uint32_t)MinAlign(Align, (uint32_t)eOffset * EBytes);
            Value* offsetAddr = ASI.CreateConstScalarGEP(svals[subIdx]->getType(), Addr, eOffset);
            Instruction* newST = ASI.Create(svals[subIdx], offsetAddr, vAlign, IsVolatile);
            eOffset += (VTy1 ? int_cast<uint32_t>(VTy1->getNumElements()) : 1);
            ++subIdx;

            // If this is a new 3-element vector, add it into m_Vector3List
            if (VTy1 && VTy1->getNumElements() == 3)
            {
                m_Vector3List.push_back(newST);
            }
        }
    }

    SI->eraseFromParent();

    // Since Load is processed later, stop optimizing if inst is Load.
    Instruction* inst = dyn_cast<Instruction>(StoredVal);
    bool keepLI = inst && isAbstractLoadInst(inst) &&
        (vecToSubVec.find(inst) != vecToSubVec.end());
    while (inst && !keepLI && inst->use_empty())
    {
        Instruction* next = nullptr;
        if (InsertElementInst * IEI = dyn_cast<InsertElementInst>(inst))
        {
            next = dyn_cast<Instruction>(IEI->getOperand(0));
        }

        inst->eraseFromParent();
        inst = next;
        keepLI = inst && isAbstractLoadInst(inst) &&
            (vecToSubVec.find(inst) != vecToSubVec.end());
    }
    return true;
}

bool VectorPreProcess::splitLoad(
    AbstractLoadInst& ALI, V2SMap& vecToSubVec, WIAnalysisRunner& WI)
{
    Instruction* LI = ALI.getInst();
    bool isLdRaw = isa<LdRawIntrinsic>(LI);
    VectorType* VTy = cast<VectorType>(LI->getType());
    Type* ETy = VTy->getElementType();
    uint32_t nelts = int_cast<uint32_t>(VTy->getNumElements());

    // Split a vector type into multiple sub-types:
    //       'len0' number of sub-vectors of type 'vecTy0'
    //       'len1' number of sub-vectors of type 'vecTy1'
    //       ...
    // SplitInfo : all pairs, each of which is (sub-vector's type, #sub-vectors).
    SmallVector< std::pair<Type*, uint32_t>, 8 > splitInfo;
    uint32_t splitSize = getSplitByteSize(LI, WI);
    if (IGC_IS_FLAG_ENABLED(EnableSplitUnalignedVector))
    {
        // byte and word-aligned loads can only load a dword at a time.
        unsigned int alignment = ALI.getAlignment();
        if (!isLdRaw && alignment < 4)
        {
            uint32_t newAlign = (uint32_t)IGCLLVM::getAlignmentValue(getKnownAlignment(ALI.getPointerOperand(), *m_DL));
            if (newAlign > alignment)
            {
                //  For OCL stateful, the base can be as little as DW-aligned. To be safe,
                //  need to use DW-aligned. For example,
                //       % 0 = add i32 0, 16
                //       % 4 = inttoptr i32 % 0 to <8 x i16> addrspace(131073) *
                //       %5 = load <8 x i16>, <8 x i16> addrspace(131073) * %4, align 2
                //  newAlign from getKnownAlignment() is 16. But we can only set align to 4 as
                //  the base of this stateful could be just DW-aligned.
                LoadInst* aLI = dyn_cast<LoadInst>(LI);
                if (aLI && newAlign > 4 && isStatefulAddrSpace(aLI->getPointerAddressSpace()))
                {
                    newAlign = 4;
                }
                ALI.setAlignment(newAlign);
            }
        }

        if ((isLdRaw || !WI.isUniform(ALI.getInst())) && ALI.getAlignment() < 4)
            splitSize = 4;
    }
    createSplitVectorTypes(ETy, nelts, splitSize, splitInfo);

    // return if no split
    uint32_t len = splitInfo.size();
    if (len == 1 &&  splitInfo[0].second == 1)
    {
        return false;
    }

    Value* Addr = ALI.getPointerOperand();
    uint32_t Align = ALI.getAlignment();
    bool IsVolatile = ALI.getIsVolatile();

    uint32_t eOffset = 0;
    uint32_t EBytes = int_cast<unsigned int>(m_DL->getTypeAllocSize(ETy));

    // Create a map entry for LI
    ValVector& svals = vecToSubVec[LI];

    for (uint32_t i = 0; i < len; ++i)
    {
        Type* Ty1 = splitInfo[i].first;
        uint32_t len1 = splitInfo[i].second;
        VectorType* VTy1 = dyn_cast<VectorType>(Ty1);
        for (uint32_t j = 0; j < len1; ++j)
        {
            uint32_t vAlign = (uint32_t)MinAlign(Align, eOffset * EBytes);
            Value* offsetAddr = ALI.CreateConstScalarGEP(Ty1, Addr, eOffset);
            Instruction* I = ALI.Create(Ty1, offsetAddr, vAlign, IsVolatile);
            eOffset += (VTy1 ? int_cast<uint32_t>(VTy1->getNumElements()) : 1);

            svals.push_back(I);

            // If this is a new 3-element vector, add it into m_Vector3List
            if (VTy1 && VTy1->getNumElements() == 3)
            {
                m_Vector3List.push_back(I);
            }
        }
    }

    if (IGC_IS_FLAG_ENABLED(EnableSplitUnalignedVector))
    {
        if (svals[0]->getType()->getPrimitiveSizeInBits() < ETy->getPrimitiveSizeInBits())
        {
            const unsigned int denominator = (unsigned int)svals[0]->getType()->getPrimitiveSizeInBits();
            IGC_ASSERT(0 < denominator);

            const uint32_t scalarsPerElement = (unsigned int)ETy->getPrimitiveSizeInBits() / denominator;
            IGC_ASSERT(1 < scalarsPerElement);
            IGC_ASSERT((svals.size() % scalarsPerElement) == 0);

            ValVector mergedScalars;
            IRBuilder<> builder(LI->getParent());
            Instruction* nextInst = LI->getNextNode();
            if (nextInst)
            {
                builder.SetInsertPoint(nextInst);
            }
            Value* undef = UndefValue::get(FixedVectorType::get(svals[0]->getType(), scalarsPerElement));
            for (uint32_t i = 0; i < svals.size() / scalarsPerElement; i++)
            {
                Value* newElement = undef;
                for (uint32_t j = 0; j < scalarsPerElement; j++)
                {
                    newElement = builder.CreateInsertElement(newElement, svals[i * scalarsPerElement + j], j);
                }
                mergedScalars.push_back(builder.CreateBitCast(newElement, ETy));
            }
            svals.clear();
            svals.append(mergedScalars.begin(), mergedScalars.end());
        }
    }
    // Put LI in m_Temps for post-processing.
    //
    // LI may be used only in store. If so, no need to re-generate the original
    // vector as load and store will use the same set of sub-vectors. So, we delay
    // generating the original vector until all stores are processed. Doing so,
    // we re-generate the original vector only if it is necessary and thus avoid
    // unnecesary insert/extract instructions.
    m_Temps.push_back(LI);
    return true;
}

bool VectorPreProcess::splitLoadStore(
    Instruction* Inst, V2SMap& vecToSubVec, WIAnalysisRunner& WI)
{
    Optional<AbstractLoadInst> ALI = AbstractLoadInst::get(Inst);
    Optional<AbstractStoreInst> ASI = AbstractStoreInst::get(Inst);
    IGC_ASSERT_MESSAGE((ALI || ASI), "Inst should be either load or store");
    Type* Ty = ALI ? ALI->getInst()->getType() : ASI->getValueOperand()->getType();
    VectorType* VTy = dyn_cast<VectorType>(Ty);
    if (!VTy)
    {
        return false;
    }

    if (VTy->getNumElements() == 3)
    {
        // Handle 3-element vector later.
        m_Vector3List.push_back(Inst);
        return false;
    }

    Value* V = ALI ? ALI->getInst() : ASI->getValueOperand();
    bool isInMap = vecToSubVec.find(V) != vecToSubVec.end();

    // Only LI could be processed already.
    bool processed = ALI && isInMap;
    if (processed)
    {
        return false;
    }

    // Do splitting

    // If it is a store and its stored value is from a load that
    // has not been splitted yet, then splitting the load first
    // so that the stored value will be directly from loaded values
    // without adding insert/extract instructions.
    Optional<AbstractLoadInst> aALI = (ASI && !isInMap) ? AbstractLoadInst::get(V) : ALI;

    if (aALI)
    {
        splitLoad(aALI.getValue(), vecToSubVec, WI);
    }

    if (ASI)
    {
        splitStore(ASI.getValue(), vecToSubVec, WI);
    }
    return true;
}

// For a vector3 whose element size < 4 bytes, will split them into one whose
// size is multiple of DW and one whose size is less than DW; If the size is
// less than DW, make sure it is either 1 Byte or 2 bytes.  After this, for
// vector size < 4, it must be either 1 byte or 2 bytes, never 3  bytes.
// This function also splits vector3s with an element size of 8 bytes if
// ldraw or storeraw is being used since neither of those messages support
// payloads larger than 4 DW.
bool VectorPreProcess::splitVector3LoadStore(Instruction* Inst)
{
    Optional<AbstractLoadInst> optionalALI = AbstractLoadInst::get(Inst);
    AbstractLoadInst* ALI = optionalALI ? optionalALI.getPointer() : nullptr;
    Optional<AbstractStoreInst> optionalASI = AbstractStoreInst::get(Inst);
    AbstractStoreInst* ASI = optionalASI ? optionalASI.getPointer() : nullptr;
    IGC_ASSERT_MESSAGE((optionalALI || optionalASI), "Inst should be either load or store");
    Type* Ty = ALI ? ALI->getInst()->getType() : ASI->getValueOperand()->getType();
    VectorType* VTy = dyn_cast<VectorType>(Ty);
    IGC_ASSERT_MESSAGE(nullptr != VTy, "Inst should be a 3-element vector load/store!");
    IGC_ASSERT_MESSAGE(VTy->getNumElements() == 3, "Inst should be a 3-element vector load/store!");

    Type* eTy = VTy->getElementType();
    uint32_t etyBytes = int_cast<unsigned int>(m_DL->getTypeAllocSize(eTy));
    // total size of vector in bytes;
    //uint32_t sz = VTy->getNumElements() * etyBytes;
    GenIntrinsicInst* II = dyn_cast<GenIntrinsicInst>(Inst);
    bool isStoreRaw = II &&
        (II->getIntrinsicID() == GenISAIntrinsic::GenISA_storerawvector_indexed ||
            II->getIntrinsicID() == GenISAIntrinsic::GenISA_storeraw_indexed);

    if (etyBytes == 1 || etyBytes == 2 ||
        (etyBytes == 8 && (isa<LdRawIntrinsic>(Inst) || isStoreRaw)))
    {
        IRBuilder<> Builder(Inst);
        if (optionalALI)
        {
            Value* Elt0 = NULL;
            Value* Elt1 = NULL;
            Value* Elt2 = NULL;
            // If alignment is the same as 4-element vector's, it's likely safe
            // to make it 4-element load. (always safe ?)
            if (ALI->getAlignment() >= 4 * etyBytes)
            {
                // Make it 4-element load
                Type* newVTy = FixedVectorType::get(eTy, 4);
                Value* V = ALI->Create(newVTy);

                Elt0 = Builder.CreateExtractElement(V, Builder.getInt32(0), "elt0");
                Elt1 = Builder.CreateExtractElement(V, Builder.getInt32(1), "elt1");
                Elt2 = Builder.CreateExtractElement(V, Builder.getInt32(2), "elt2");
            }
            else
            {
                // One 2-element vector load + one scalar load
                Type* newVTy = FixedVectorType::get(eTy, 2);
                Value* offsetAddr = ALI->CreateConstScalarGEP(eTy, ALI->getPointerOperand(), 2);
                Value* V2 = ALI->Create(newVTy);
                Elt0 = Builder.CreateExtractElement(V2, Builder.getInt32(0), "elt0");
                Elt1 = Builder.CreateExtractElement(V2, Builder.getInt32(1), "elt1");

                uint32_t newAlign = (uint32_t)MinAlign(ALI->getAlignment(), 2 * etyBytes);
                Elt2 = ALI->Create(eTy, offsetAddr, newAlign, ALI->getIsVolatile());
            }

            // A little optimization here
            ExtractElementInst* EEInsts[3];
            for (int i = 0; i < 3; ++i)
            {
                EEInsts[i] = nullptr;
            }
            if (isValueUsedOnlyByEEI(ALI->getInst(), EEInsts))
            {
                if (EEInsts[0] != nullptr)
                {
                    EEInsts[0]->replaceAllUsesWith(Elt0);
                    EEInsts[0]->eraseFromParent();
                }
                if (EEInsts[1] != nullptr)
                {
                    EEInsts[1]->replaceAllUsesWith(Elt1);
                    EEInsts[1]->eraseFromParent();
                }
                if (EEInsts[2] != nullptr)
                {
                    EEInsts[2]->replaceAllUsesWith(Elt2);
                    EEInsts[2]->eraseFromParent();
                }
            }
            else
            {
                Value* V = Builder.CreateInsertElement(UndefValue::get(VTy), Elt0,
                    Builder.getInt32(0));
                V = Builder.CreateInsertElement(V, Elt1, Builder.getInt32(1));
                V = Builder.CreateInsertElement(V, Elt2, Builder.getInt32(2));
                ALI->getInst()->replaceAllUsesWith(V);
            }
            ALI->getInst()->eraseFromParent();
        }
        else
        {
            Value* Ptr = ASI->getPointerOperand();
            // Split 3-element into 2-element + 1 scalar
            Type* newVTy = FixedVectorType::get(eTy, 2);
            Value* StoredVal = ASI->getValueOperand();
            Value* offsetAddr = ASI->CreateConstScalarGEP(StoredVal->getType(), Ptr, 2);
            InsertElementInst* IEInsts[3];
            for (int i = 0; i < 3; ++i)
            {
                IEInsts[i] = nullptr;
            }

            // vec3 = vec2 + scalar,  newAlign is an alignment for scalar store.
            uint32_t newAlign = (uint32_t)MinAlign(ASI->getAlignment(), 2 * etyBytes);
            Value* UDVal = UndefValue::get(eTy);
            if (isValueCreatedOnlyByIEI(ASI->getInst(), IEInsts))
            {
                // This case should be most frequent, and want
                // to generate a better code by removing dead
                // InsertElementInst.

                // Be ware of partial vector store.
                Value* V = UndefValue::get(newVTy);
                V = Builder.CreateInsertElement(
                    V, (IEInsts[0] != nullptr) ? IEInsts[0]->getOperand(1) : UDVal,
                    Builder.getInt32(0));
                V = Builder.CreateInsertElement(
                    V, (IEInsts[1] != nullptr) ? IEInsts[1]->getOperand(1) : UDVal,
                    Builder.getInt32(1));
                V = ASI->Create(V);

                // If IEInsts[2] is undefined, skip scalar store.
                if (IEInsts[2] != nullptr)
                {
                    (void)ASI->Create(IEInsts[2]->getOperand(1), offsetAddr, newAlign, ASI->getIsVolatile());
                }
                ASI->getInst()->eraseFromParent();

                // Remove all InsertElementInst if possible
                bool change = true;
                while (change)
                {
                    change = false;
                    for (int i = 0; i < 3; ++i)
                    {
                        if (IEInsts[i] && IEInsts[i]->use_empty())
                        {
                            IEInsts[i]->eraseFromParent();
                            IEInsts[i] = nullptr;
                            change = true;
                        }
                    }
                }
            }
            else
            {
                // Get a 2-element vector and a scalar from the
                // 3-element vector and store them respectively.
                // Shuffle isn't handled in Emit, use extract/insert instead
                Value* Elt0 = Builder.CreateExtractElement(StoredVal,
                    Builder.getInt32(0),
                    "Elt0");
                Value* Elt1 = Builder.CreateExtractElement(StoredVal,
                    Builder.getInt32(1),
                    "Elt1");
                Value* Elt2 = Builder.CreateExtractElement(StoredVal,
                    Builder.getInt32(2),
                    "Elt2");
                Value* V = Builder.CreateInsertElement(UndefValue::get(newVTy),
                    Elt0,
                    Builder.getInt32(0));
                V = Builder.CreateInsertElement(V, Elt1, Builder.getInt32(1));
                ASI->Create(V);
                ASI->Create(Elt2, offsetAddr, newAlign, ASI->getIsVolatile());
                ASI->getInst()->eraseFromParent();
            }
        }
        return true;
    }
    return false;
}

// availBeforeInst:
//    Indicate that all scalar values of VecVal are available right before
//    instruction 'availBeforeInst'. If availBeforeInst is null, it means
//    all scalar values are constants.
void VectorPreProcess::getOrGenScalarValues(
    Function& F, Value* VecVal, ValVector& scalars, Instruction*& availBeforeInst)
{
    availBeforeInst = nullptr;

    VectorType* VTy = cast<VectorType>(VecVal->getType());
    if (!VTy)
    {
        scalars[0] = VecVal;
        return;
    }

    uint32_t nelts = int_cast<uint32_t>(VTy->getNumElements());
    Type* ETy = VTy->getElementType();
    if (isa<UndefValue>(VecVal))
    {
        Value* udv = UndefValue::get(ETy);
        for (uint32_t i = 0; i < nelts; ++i)
        {
            scalars[i] = udv;
        }
    }
    else if (ConstantVector * CV = dyn_cast<ConstantVector>(VecVal))
    {
        for (uint32_t i = 0; i < nelts; ++i)
        {
            scalars[i] = CV->getOperand(i);
        }
    }
    else if (ConstantDataVector * CDV = dyn_cast<ConstantDataVector>(VecVal))
    {
        for (uint32_t i = 0; i < nelts; ++i)
        {
            scalars[i] = CDV->getElementAsConstant(i);
        }
    }
    else if (ConstantAggregateZero * CAZ = dyn_cast<ConstantAggregateZero>(VecVal))
    {
        for (uint32_t i = 0; i < nelts; ++i)
        {
            scalars[i] = CAZ->getSequentialElement();
        }
    }
    else
    {
        bool genExtract = false;
        Value* V = VecVal;
        for (uint32_t i = 0; i < nelts; ++i)
        {
            scalars[i] = nullptr;
        }
        while (InsertElementInst * IEI = dyn_cast<InsertElementInst>(V))
        {
            Value* ixVal = IEI->getOperand(2);
            ConstantInt* CI = dyn_cast<ConstantInt>(ixVal);
            if (!CI)
            {
                genExtract = true;
                break;
            }
            uint32_t ix = int_cast<unsigned int>(CI->getZExtValue());
            scalars[ix] = IEI->getOperand(1);
            V = IEI->getOperand(0);
        }
        if (!isa<UndefValue>(V))
        {
            genExtract = true;
        }

        BasicBlock::iterator inst_b;
        if (Instruction * I = dyn_cast<Instruction>(VecVal))
        {
            inst_b = BasicBlock::iterator(I);
            ++inst_b;
        }
        else
        {
            // VecVal is an argument or constant
            inst_b = F.begin()->getFirstInsertionPt();
        }

        IRBuilder<> Builder(&(*inst_b));
        for (uint32_t i = 0; i < nelts; ++i)
        {
            if (scalars[i] == nullptr)
            {
                Value* S;
                if (genExtract)
                {
                    S = Builder.CreateExtractElement(V, Builder.getInt32(i));
                }
                else
                {
                    S = UndefValue::get(ETy);
                }
                scalars[i] = S;
            }
        }

        availBeforeInst = &(*inst_b);
    }
}

// Perform LoadInst/StoreInst simplification. E.g. The following vector load is
// only used by three extractelements with constants indices, so we can narrow
// the load width to 3.
//
// %34 = load <4 x float> addrspace(1)* %33, align 16
// %scalar35 = extractelement <4 x float> %34, i32 0
// %scalar36 = extractelement <4 x float> %34, i32 1
// %scalar47 = extractelement <4 x float> %34, i32 2
//
// %40 = bitcast <4 x float> addrspace(1)* %33 to <3 x float> addrspace(1)*
// %41 = load <3 x float> addrspace(1)* %40, align 16 (keep alignment!)
// %scalar42 = extractelement <3 x float> %41, i32 0
// %scalar43 = extractelement <3 x float> %41, i32 1
// %scalar44 = extractelement <3 x float> %41, i32 2
//
Instruction* VectorPreProcess::simplifyLoadStore(Instruction* Inst)
{
    if (Optional<AbstractLoadInst> optionalALI = AbstractLoadInst::get(Inst))
    {
        AbstractLoadInst& ALI = optionalALI.getValue();
        if (!Inst->getType()->isVectorTy() || ALI.getAlignment() < 4)
            return Inst;

        unsigned NBits = Inst->getType()->getScalarSizeInBits();
        if (NBits < 32)
            return Inst;

        SmallVector<ExtractElementInst*, 8> ConstEEIUses;
        unsigned MaxIndex = 0;
        for (auto U : Inst->users())
        {
            auto EEI = dyn_cast<ExtractElementInst>(U);
            if (!EEI || !isa<ConstantInt>(EEI->getIndexOperand()))
                return Inst;

            auto CI = cast<ConstantInt>(EEI->getIndexOperand());
            ConstEEIUses.push_back(EEI);
            MaxIndex = std::max(MaxIndex, int_cast<unsigned>(CI->getZExtValue()));
        }

        // All uses are constant EEI.
        IGC_ASSERT_MESSAGE(ConstEEIUses.size() == Inst->getNumUses(), "out of sync");

        // FIXME: this is to WA an issue that splitLoadStore does not split
        // vectors of size 5, 6, 7.
        if (MaxIndex + 1 > 4)
            return Inst;

        // If MaxIndex is smaller than <vector_size - 1>, then narrow the size
        // of this vector load to reduce unnecessary memory load.
        //
        // TODO: further optimize this load into a message with channel masks
        // for cases in which use indices are sparse like {0, 2}.
        unsigned N = (unsigned)cast<VectorType>(Inst->getType())->getNumElements();
        if (N == MaxIndex + 1)
            return Inst;

        //Check if we can turn a ldrawvector into a ldraw
        Instruction* NewLI = nullptr;
        IRBuilder<> Builder(Inst);
        auto ldrawvec = dyn_cast<LdRawIntrinsic>(Inst);
        bool canSimplifyOneUse = ldrawvec && isa<VectorType>(ldrawvec->getType()) &&
            ldrawvec->hasOneUse() &&
            !ConstEEIUses.empty();

        bool canSimplifyOneUseZeroIndex = canSimplifyOneUse &&
            cast<ConstantInt>(ConstEEIUses.front()->getIndexOperand())->getZExtValue() == 0;

        auto simplifyLDVecToLDRaw = [&](bool calc_offset)
        {
            auto EE_user = ConstEEIUses.front();
            auto return_type = cast<VectorType>(ldrawvec->getType())->getElementType();
            auto buffer_ptr = ldrawvec->getResourceValue();
            Value* OffsetVal = ldrawvec->getOffsetValue();
            auto alloc_size = (unsigned)m_DL->getTypeAllocSize(return_type);
            if (calc_offset)
            {
                auto EE_index = (unsigned)cast<ConstantInt>(EE_user->getIndexOperand())->getZExtValue();
                if (isa<ConstantInt>(OffsetVal))
                {
                    // Calculate static offset
                    auto offset = (unsigned)cast<ConstantInt>(OffsetVal)->getZExtValue();
                    auto new_offset = offset + (EE_index * alloc_size);
                    OffsetVal = Builder.getInt32(new_offset);
                }
                else
                {
                    // Calculate runtime offset
                    OffsetVal = Builder.CreateAdd(OffsetVal, Builder.getInt32(EE_index * alloc_size));
                }
            }
            Type* types[2] = { return_type , buffer_ptr->getType() };
            Value* args[4] = { buffer_ptr, OffsetVal,
                Builder.getInt32(alloc_size), Builder.getInt1(ldrawvec->isVolatile()) };
            Function* newLdRawFunction =
                GenISAIntrinsic::getDeclaration(ldrawvec->getModule(), GenISAIntrinsic::GenISA_ldraw_indexed, types);
            NewLI = Builder.CreateCall(newLdRawFunction, args);
            NewLI->setDebugLoc(EE_user->getDebugLoc());
            EE_user->replaceAllUsesWith(NewLI);
            EE_user->eraseFromParent();
        };

        if (canSimplifyOneUseZeroIndex)
        {
            simplifyLDVecToLDRaw(false);
            return NewLI;
        }
        else if (canSimplifyOneUse)
        {
            simplifyLDVecToLDRaw(true);
            return NewLI;
        }
        else
        {
            Type* NewVecTy = FixedVectorType::get(cast<VectorType>(Inst->getType())->getElementType(),
                MaxIndex + 1);
            NewLI = ALI.Create(NewVecTy);

            // Loop and replace all uses.
            SmallVector<Value*, 8> NewEEI(MaxIndex + 1, nullptr);
            for (auto EEI : ConstEEIUses)
            {
                auto CI = cast<ConstantInt>(EEI->getIndexOperand());
                unsigned Idx = int_cast<unsigned>(CI->getZExtValue());
                if (NewEEI[Idx] == nullptr)
                {
                    NewEEI[Idx] = Builder.CreateExtractElement(NewLI, CI);
                }
                dyn_cast<ExtractElementInst>(NewEEI[Idx])->setDebugLoc(EEI->getDebugLoc());
                EEI->replaceAllUsesWith(NewEEI[Idx]);
                EEI->eraseFromParent();
            }
            IGC_ASSERT_MESSAGE(Inst->use_empty(), "out of sync");
            Inst->eraseFromParent();
            return NewLI;
        }
    }

    // %2 = insertelement <4 x float> undef, float 1.000000e+00, i32 0
    // %3 = insertelement <4 x float> %2, float 1.000000e+00, i32 1
    // %4 = insertelement <4 x float> %3, float 1.000000e+00, i32 2
    // store <4 x float> %4, <4 x float>* %1, align 16
    //
    // becomes
    //
    // %5 = bitcast <4 x float>* %1 to <3 x float>*
    // %6 = insertelement <3 x float> undef, float 1.000000e+00, i32 0
    // %7 = insertelement <3 x float> %2, float 1.000000e+00, i32 1
    // %8 = insertelement <3 x float> %3, float 1.000000e+00, i32 2
    // store <3 x float> %8, <3 x float>* %5, align 16
    //
    IGC_ASSERT(isAbstractStoreInst(Inst));
    Optional<AbstractStoreInst> optionalASI = AbstractStoreInst::get(Inst);
    AbstractStoreInst& ASI = optionalASI.getValue();
    Value* Val = ASI.getValueOperand();
    if (isa<UndefValue>(Val))
    {
        Inst->eraseFromParent();
        return nullptr;
    }

    if (!Val->getType()->isVectorTy() || ASI.getAlignment() < 4)
        return Inst;

    unsigned NBits = Val->getType()->getScalarSizeInBits();
    if (NBits < 32)
        return Inst;

    unsigned N = (unsigned)cast<VectorType>(Val->getType())->getNumElements();
    if (auto CV = dyn_cast<ConstantVector>(Val))
    {
        unsigned MaxIndex = 0;
        for (unsigned i = N - 1; i != 0; --i)
        {
            Constant* Item = CV->getAggregateElement(i);
            if (!isa<UndefValue>(Item))
            {
                MaxIndex = i;
                break;
            }
        }

        if (MaxIndex + 1 == N)
            return Inst;

        SmallVector<Constant*, 8> Data(MaxIndex + 1, nullptr);
        for (unsigned i = 0; i <= MaxIndex; ++i)
        {
            Data[i] = CV->getAggregateElement(i);
        }
        auto SVal = ConstantVector::get(Data);
        Instruction* NewSI = ASI.Create(SVal);
        ASI.getInst()->eraseFromParent();
        return NewSI;
    }

    SmallVector<InsertElementInst*, 8> ConstIEIs(N, nullptr);
    Value* ChainVal = Val;
    int MaxIndex = -1;
    while (auto IEI = dyn_cast<InsertElementInst>(ChainVal))
    {
        if (MaxIndex + 1 == (int)N || !isa<ConstantInt>(IEI->getOperand(2)))
        {
            return Inst;
        }

        // Make sure the last IEI will be recorded if an element is
        // inserted multiple times.
        auto CI = cast<ConstantInt>(IEI->getOperand(2));
        int Idx = (int)CI->getZExtValue();
        if (ConstIEIs[Idx] == nullptr)
        {
            ConstIEIs[Idx] = IEI;
        }
        MaxIndex = std::max(MaxIndex, Idx);
        ChainVal = IEI->getOperand(0);
    }

    // FIXME: this is to WA an issue that splitLoadStore does not split
    // vectors of size 5, 6, 7.
    if (MaxIndex + 1 > 4)
        return Inst;

    // Inserted less than N values into Undef.
    if (MaxIndex >= 0 && MaxIndex + 1 < (int)N && isa<UndefValue>(ChainVal))
    {
        IRBuilder<> Builder(ASI.getInst());
        Type* NewVecTy = FixedVectorType::get(cast<VectorType>(Val->getType())->getElementType(),
            MaxIndex + 1);
        Value* SVal = UndefValue::get(NewVecTy);
        for (int i = 0; i <= MaxIndex; ++i)
        {
            if (ConstIEIs[i] != nullptr)
            {
                SVal = Builder.CreateInsertElement(SVal,
                    ConstIEIs[i]->getOperand(1),
                    ConstIEIs[i]->getOperand(2));
            }
        }
        Instruction* NewSI = ASI.Create(SVal);
        ASI.getInst()->eraseFromParent();
        return NewSI;
    }

    return Inst;
}

bool VectorPreProcess::runOnFunction(Function& F)
{
    bool changed = false;
    m_DL = &F.getParent()->getDataLayout();
    m_C = &F.getContext();
    m_CGCtx = getAnalysis<CodeGenContextWrapper>().getCodeGenContext();

    for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
    {
        Instruction* inst = &*I;
        if (isAbstractStoreInst(inst) || isAbstractLoadInst(inst))
        {
            m_WorkList.push_back(inst);
        }
    }

    // Simplify loads/stores.
    bool Simplified = false;
    for (unsigned i = 0, n = m_WorkList.size(); i < n; ++i)
    {
        Instruction* Inst = m_WorkList[i];
        Instruction* NewInst = simplifyLoadStore(Inst);
        if (NewInst != Inst)
        {
            m_WorkList[i] = NewInst;
            Simplified = true;
        }
    }

    // Cleanup work items, only keep load and store instructions.
    if (Simplified)
    {
        changed = true;
        auto new_end = std::remove_if(m_WorkList.begin(), m_WorkList.end(),
            [](Value* V) -> bool {
            return !V || (!isAbstractStoreInst(V) && !isAbstractLoadInst(V));
        });
        m_WorkList.erase(new_end, m_WorkList.end());
    }

    // Split vectors
    if (m_WorkList.size() > 0)
    {
        V2SMap vecToSubVec;

        // m_Temps is used to keep loads that needs post-processing.
        m_Temps.clear();

        {
            auto* MDUtils =
                getAnalysis<MetaDataUtilsWrapper>().getMetaDataUtils();
            auto* DT =
                &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
            auto* PDT =
                &getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree();
            auto* ModMD =
                getAnalysis<MetaDataUtilsWrapper>().getModuleMetaData();

            TranslationTable TT;
            TT.run(F);
            WIAnalysisRunner WI(&F, DT, PDT, MDUtils, m_CGCtx, ModMD, &TT);
            WI.run();

            for (uint32_t i = 0; i < m_WorkList.size(); ++i)
            {
                if (splitLoadStore(m_WorkList[i], vecToSubVec, WI))
                {
                    changed = true;
                }
            }
        }

        // Now, do post-processing for the splitted loads
        for (uint32_t i = 0; i < m_Temps.size(); ++i)
        {
            Value* V = m_Temps[i];
            Optional<AbstractLoadInst> ALI = AbstractLoadInst::get(V);
            if (!ALI)
            {
                continue;
            }
            Instruction* LI = ALI.getValue().getInst();
            ValVector& svals = vecToSubVec[V];
            if (!LI->use_empty())
            {
                ValVector Scalars;
                IRBuilder<> Builder(LI);
                for (uint32_t j = 0; j < svals.size(); ++j)
                {
                    Type* Ty1 = svals[j]->getType();
                    VectorType* VTy1 = dyn_cast<VectorType>(Ty1);
                    if (VTy1) {
                        for (uint32_t k = 0; k < VTy1->getNumElements(); ++k)
                        {
                            Value* S = Builder.CreateExtractElement(
                                svals[j], Builder.getInt32(k), "split");
                            Scalars.push_back(S);
                        }
                    }
                    else
                    {
                        Scalars.push_back(svals[j]);

                        // svals[j] will be no long needed, set it to null
                        // to prevent double-deleting later
                        svals[j] = nullptr;
                    }
                }
                // Replace LI and erase LI.
                replaceAllVectorUsesWithScalars(LI, Scalars);

                // Remove any dead scalars
                for (uint32_t j = 0; j < Scalars.size(); ++j)
                {
                    if (Scalars[j]->use_empty())
                    {
                        Instruction* tInst = cast<Instruction>(Scalars[j]);
                        tInst->eraseFromParent();
                    }
                }
            }
            else
            {
                LI->eraseFromParent();
            }

            // Remove any dead sub vectors
            for (uint32_t j = 0; j < svals.size(); ++j)
            {
                if (svals[j] == nullptr)
                {
                    continue;
                }
                Instruction* tInst = cast<Instruction>(svals[j]);
                if (tInst->use_empty())
                {
                    // If this is a 3-element vector load, remove it
                    // from m_Vector3List as well.
                    if (isAbstractLoadInst(tInst) && tInst->getType()->isVectorTy() &&
                        cast<VectorType>(tInst->getType())->getNumElements() == 3)
                    {
                        InstWorkVector::iterator
                            tI = m_Vector3List.begin(),
                            tE = m_Vector3List.end();
                        for (; tI != tE; ++tI)
                        {
                            Instruction* tmp = *tI;
                            if (tmp == tInst)
                            {
                                break;
                            }
                        }
                        if (tI != m_Vector3List.end())
                        {
                            m_Vector3List.erase(tI);
                        }
                    }

                    tInst->eraseFromParent();
                }
            }
        }

        // Last, split 3-element vector if necessary
        for (uint32_t i = 0; i < m_Vector3List.size(); ++i)
        {
            if (splitVector3LoadStore(m_Vector3List[i]))
            {
                changed = true;
            }
        }

        vecToSubVec.clear();
        m_Vector3List.clear();
        m_WorkList.clear();
    }
    return changed;
}
