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======================= end_copyright_notice ==================================*/
/**
 * Originated from llvm code-sinking, need add their copyright
 **/
//===-- Sink.cpp - Code Sinking -------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

/***
 * The 1st application of code-sinking is to reduce register pressure:
 * - move input instructions close to its uses
 * - move flag-register definition close to its uses (yet to be done)
 *
 * The 2nd application of code-sinking is to move high-cost operation, 
 * like texture sample, into the control-flow branch that is really used. 
 * However, I think this 2nd goal should only be allowed only if it does 
 * not increase register pressure.
 *
 * step 1. efficient code-sinking limited to inputs and cmps
 * step 2. efficient code-sinking into branch, limited to read-only memory op
 *         and alu operations
 *
 * Two tuning paramters for code-sinking:
 * - General code-sinking, enable code-sinking of step 2
 * - Register-pressure threshold, undo code-sinking when live-out pressure is high 
 */
#include "common/debug/Debug.hpp"
#include "common/debug/Dump.hpp"
#include "common/Stats.hpp"
#include "common/LLVMUtils.h"

#include "common/LLVMWarningsPush.hpp"
#include "llvm/IR/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/CFG.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "common/LLVMWarningsPop.hpp"

#include "Compiler/CodeGenPublic.h"
#include "Compiler/CISACodeGen/CodeSinking.hpp"
#include "Compiler/CISACodeGen/helper.h"
#include "Compiler/CISACodeGen/ShaderCodeGen.hpp"
#include "Compiler/IGCPassSupport.h"

using namespace llvm;
using namespace IGC::Debug;


namespace IGC {

// Register pass to igc-opt
#define PASS_FLAG "code sinking"
#define PASS_DESCRIPTION "code sinking"
#define PASS_CFG_ONLY false
#define PASS_ANALYSIS false
IGC_INITIALIZE_PASS_BEGIN(CodeSinking, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
IGC_INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
IGC_INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
IGC_INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
IGC_INITIALIZE_PASS_END(CodeSinking, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)

CodeSinking::CodeSinking(bool generalSinking) : FunctionPass(ID) {
    generalCodeSinking = generalSinking;
    initializeCodeSinkingPass(*PassRegistry::getPassRegistry());
}

/// AllUsesDominatedByBlock - Return true if all uses of the specified value
/// occur in blocks dominated by the specified block.
bool CodeSinking::AllUsesDominatedByBlock(Instruction *inst,
                                          BasicBlock *blk,
                                          SmallPtrSetImpl<Instruction*> &usesInBlk) const 
{
    usesInBlk.clear();
    // Ignoring debug uses is necessary so debug info doesn't affect the code.
    // This may leave a referencing dbg_value in the original block, before
    // the definition of the vreg.  Dwarf generator handles this although the
    // user might not get the right info at runtime.
    for (Value::user_iterator I = inst->user_begin(), E = inst->user_end(); I != E; ++I) 
    {
        // Determine the block of the use.
        Instruction *useInst = cast<Instruction>(*I);
        BasicBlock *useBlock = useInst->getParent();
        if (useBlock == blk) 
        {
            usesInBlk.insert(useInst);
        }
        if (PHINode *PN = dyn_cast<PHINode>(useInst))
        {
            // PHI nodes use the operand in the predecessor block, 
            // not the block with the PHI.
            Use &U = I.getUse();
            unsigned num = PHINode::getIncomingValueNumForOperand(U.getOperandNo());
            useBlock = PN->getIncomingBlock(num);
        }
        // Check that it dominates.
        if (!DT->dominates(blk, useBlock))
            return false;
    }
    return true;
}

/// return false if instruction cannot be moved to another block
bool CodeSinking::FindLowestSinkTarget( Instruction *inst,
                                        BasicBlock* &tgtBlk,
                                        SmallPtrSetImpl<Instruction*> &usesInBlk,
                                        bool& outerLoop,
                                        bool doLoopSink)
{
    usesInBlk.clear();
    tgtBlk = 0x0;
    outerLoop = false;
    for (Value::user_iterator I = inst->user_begin(), E = inst->user_end(); I != E; ++I) 
    {
        // Determine the block of the use.
        Instruction *useInst = cast<Instruction>(*I);
        BasicBlock *useBlock = useInst->getParent();
        if (PHINode *PN = dyn_cast<PHINode>(useInst))
        {
            // PHI nodes use the operand in the predecessor block, 
            // not the block with the PHI.
            Use &U = I.getUse();
            unsigned num = PHINode::getIncomingValueNumForOperand(U.getOperandNo());
            useBlock = PN->getIncomingBlock(num);
        }
        else
        {
            if (useBlock == inst->getParent())
            {
                return false;
            }
        }
        if (tgtBlk == 0x0)
        {
            tgtBlk = useBlock;
        }
        else
        {
            tgtBlk = DT->findNearestCommonDominator(tgtBlk, useBlock);
            if (tgtBlk == 0x0)
                break;
        }
    }
    BasicBlock *curBlk = inst->getParent();
    Loop *curLoop = LI->getLoopFor(inst->getParent());
    while (tgtBlk && tgtBlk != curBlk)
    {
        Loop *tgtLoop = LI->getLoopFor(tgtBlk);
        EOPCODE intrinsic_name = GetOpCode(inst);
        // sink the pln instructions in the loop to reduce pressure
        // Sink instruction outside of loop into the loop if doLoopSink is true.
        if (intrinsic_name == llvm_input ||
            (!tgtLoop || tgtLoop->contains(curLoop)) ||
            (doLoopSink && tgtLoop && (!curLoop || curLoop->contains(tgtLoop))))
        {
            for (Value::user_iterator I = inst->user_begin(), E = inst->user_end(); I != E; ++I) 
            {
                // Determine the block of the use.
                Instruction *useInst = cast<Instruction>(*I);
                BasicBlock *useBlock = useInst->getParent();
                if (useBlock == tgtBlk) 
                {
                    usesInBlk.insert(useInst);
                }
            }
            outerLoop = (tgtLoop != curLoop);
            return true;
        }
        else
        {
            tgtBlk = DT->getNode(tgtBlk)->getIDom()->getBlock();
        }
    }

    return false;
}

static unsigned numInsts(const Function &F)
{
    unsigned num = 0;
    for (auto &BB : F)
    {
        num += BB.getInstList().size();
    }
    return num;
}

//diagnosis code: __declspec(thread) int sinkCounter = 0;
//diagnosis code: const int sinkLimit = 19;

bool CodeSinking::runOnFunction(Function &F)
{
    CTX = getAnalysis<CodeGenContextWrapper>().getCodeGenContext();
    // only limited code-sinking to several shader-type
    // vs input has the URB-reuse issue to be resolved. 
    // Also need to understand the performance benefit better.
    if(CTX->type != ShaderType::PIXEL_SHADER &&
       CTX->type != ShaderType::DOMAIN_SHADER &&
       CTX->type != ShaderType::OPENCL_SHADER &&
       CTX->type != ShaderType::COMPUTE_SHADER)
    {
        return false;
    }
    if(IGC_IS_FLAG_ENABLED(DisableCodeSinking) ||
        numInsts(F) < CODE_SINKING_MIN_SIZE)
    {
        return false;
    }

    // Keep track of fat BB. Might need to reverse LICM if
    // the fat BB is inside loop and there are a lot of 
    // loop-invariant insts that have been moved out of the loop.
    m_fatBBPressure = 0;
    m_fatBB = nullptr;

    DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
    PDT = &getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree();
    LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
    DL = &F.getParent()->getDataLayout();

    bool changed = hoistCongruentPhi(F);

    bool madeChange, everMadeChange = false;
    totalGradientMoved = 0;
    // diagnosis code: numChanges = 0;
    // diagnosis code: if (sinkCounter >= 94 && sinkCounter < 95) {
    // even if we limit code-sinking to ps-input instructions, we still need to iterate through
    // all the blocks because llvm-InstCombine may have sinked some ps-input instructions out of entry-block
    do 
    {
        madeChange = false;
        // Process all basic blocks in dominator-tree post-order
        for(po_iterator<DomTreeNode*> domIter = po_begin( DT->getRootNode() ),
            domEnd = po_end( DT->getRootNode() ); domIter != domEnd; ++domIter )
        {
            madeChange |= ProcessBlock(*(domIter->getBlock()));
        }
    } while (madeChange /*diagnosis: && numChanges < sinkLimit*/);

    everMadeChange = madeChange;
    for (SmallPtrSet<BasicBlock*, 8>::iterator BI = localBlkSet.begin(), BE = localBlkSet.end(); BI != BE; BI++)
    {
        madeChange = LocalSink(*BI);
        everMadeChange |= madeChange;
    }
    localBlkSet.clear();
    localInstSet.clear();
    CTX->m_numGradientSinked = totalGradientMoved;


    // diagnosis code: printf("%d:%d:%x\n", sinkCounter, sinkLimit, CTX->hash.getAsmHash());
    //F.viewCFG();
    // } end of diagnosis if 
    // diagnosis code: sinkCounter++;
    return everMadeChange || changed;
}

static uint EstimateLiveOutPressure(BasicBlock *blk, const DataLayout *DL)
{
    // Walk the basic block bottom-up.  Remember if we saw a store.
    uint pressure = 0;
    BasicBlock::iterator I = blk->end();
    --I;
    bool processedBegin = false;
    do {
        Instruction *inst = &(*I);  // The instruction to sink.

        // Predecrement I (if it's not begin) so that it isn't invalidated by sinking.
        processedBegin = (I == blk->begin());
        if (!processedBegin)
            --I;

        if (isa<DbgInfoIntrinsic>(inst))
            continue;
        // intrinsic like discard has no explicit use, get skipped here
        if (inst->use_empty())
            continue;

        bool useOutside = false;
        for (Value::user_iterator useI = inst->user_begin(), useE = inst->user_end(); 
             !useOutside && useI != useE; ++useI) 
        {
            // Determine the block of the use.
            Instruction *useInst = cast<Instruction>(*useI);
            BasicBlock *useBlock = useInst->getParent();
            if (useBlock != blk) 
            {
                if (PHINode *PN = dyn_cast<PHINode>(useInst))
                {
                    // PHI nodes use the operand in the predecessor block, 
                    // not the block with the PHI.
                    Use &U = useI.getUse();
                    unsigned num = PHINode::getIncomingValueNumForOperand(U.getOperandNo());
                    if (PN->getIncomingBlock(num) != blk)
                    {
                        useOutside = true;
                    }
                }
                else
                {
                    useOutside = true;
                }
            }
        }
        
        // estimate register usage by value
        if (useOutside)
        {
            pressure += (uint)(DL->getTypeAllocSize(inst->getType()));
        }
        // If we just processed the first instruction in the block, we're done.
    } while (!processedBegin);
    return pressure;
}

bool CodeSinking::ProcessBlock(BasicBlock &blk) 
{
    if (blk.empty())
        return false;

    uint32_t registerPressureThreshold = CTX->getNumGRFPerThread();

    uint pressure0 = 0;
    if (generalCodeSinking && registerPressureThreshold)
    {
        // estimate live-out register pressure for this blk
        pressure0 = EstimateLiveOutPressure(&blk, DL);

        // Track the highest-pressure BB within a loop
        if (pressure0 > m_fatBBPressure && LI->getLoopFor(&blk)) {
            m_fatBBPressure = pressure0;
            m_fatBB = &blk;
        }
    }

    bool madeChange = false;
    numGradientMovedOutBB = 0;

    // Walk the basic block bottom-up.  Remember if we saw a store.
    BasicBlock::iterator I = blk.end();
    --I;
    bool processedBegin = false;
    SmallPtrSet<Instruction *, 16> stores;
    undoLocas.clear();
    movedInsts.clear();
    Instruction *prevLoca = 0x0;
    do {
        Instruction *inst = &(*I);  // The instruction to sink.

        // Predecrement I (if it's not begin) so that it isn't invalidated by sinking.
        processedBegin = (I == blk.begin());
        if (!processedBegin)
            --I;

        if (inst->mayWriteToMemory())
        {
            stores.insert(inst);
            prevLoca = inst;
        }
        // intrinsic like discard has no explict use, gets skipped here
        else if (isa<DbgInfoIntrinsic>(inst) || inst->isTerminator() || 
                 isa<PHINode>(inst) || inst->use_empty() )
        {
            prevLoca = inst;
        }
        else {
            Instruction *undoLoca = prevLoca;
            prevLoca = inst;
            // diagnosis code: if (numChanges >= sinkLimit)
            // diagnosis code:    continue;
            if (SinkInstruction(inst, stores, false))
            {
                madeChange = true;
                movedInsts.push_back(inst);
                undoLocas.push_back(undoLoca);
                // diagnosis code: numChanges++;
            }
        }
        // If we just processed the first instruction in the block, we're done.
    } while (!processedBegin);

    if (generalCodeSinking && registerPressureThreshold)
    {
        if (madeChange)
        {
            // measure the live-out register pressure again
            uint pressure1 = EstimateLiveOutPressure(&blk, DL);
            if (pressure1 > pressure0 + registerPressureThreshold)
            {
                // undo code motion
                int numChanges = movedInsts.size();
                for (int i = 0; i < numChanges; ++i)
                {
                    Instruction *undoLoca = undoLocas[i];
                    assert(undoLoca);
                    movedInsts[i]->moveBefore(undoLoca);
                }
                madeChange = false;
            }
            else
            {
                totalGradientMoved += numGradientMovedOutBB;
            }
        }
    }

    return madeChange;
}

static bool reduceRP(Instruction *Inst)
{
    // igc specific: to make the flag-register lifetime short
    if (isa<CmpInst>(Inst))
    {
        return true;
    }

    if (auto CI = dyn_cast<CastInst>(Inst))
    {
        unsigned SrcSize = CI->getSrcTy()->getPrimitiveSizeInBits();
        unsigned DstSize = CI->getDestTy()->getPrimitiveSizeInBits();
        if (SrcSize == 0 || DstSize == 0)
        {
            // Non-primitive types.
            return false;
        }
        if (SrcSize == 1)
        {
            // i1 -> i32, reduces GRF pressure but increases flag pressure.
            // Do not consider it as reduce.
            return false;
        }
        else if (DstSize == 1)
        {
            // i32 -> i1, reduces flag pressure but increases grf pressure.
            // Consider it as reduce.
            return true;
        }
        else if (SrcSize < DstSize)
        {
            // sext i32 to i64.
            return true;
        }
    }

    return false;
}

bool CodeSinking::isSafeToMove(Instruction *inst
                         , bool &reducePressure
                         , bool &hasAliasConcern
                         , SmallPtrSetImpl<Instruction *> &Stores)
{
    if (isa<AllocaInst>(inst) || isa<ExtractValueInst>(inst))
    {
        return false;
    }
    if (isa<CallInst>(inst) && cast<CallInst>(inst)->isConvergent())
    {
        return false;
    }
    hasAliasConcern = true;
    reducePressure = false;
    if (generalCodeSinking)
    {
        if (isa<GetElementPtrInst>(inst) ||
            isa<ExtractElementInst>(inst) ||
            isa<InsertElementInst>(inst) ||
            isa<InsertValueInst>(inst) ||
            (isa<UnaryInstruction>(inst) && !isa<LoadInst>(inst)) ||
            isa<BinaryOperator>(inst))
        {
            hasAliasConcern = false;
            reducePressure = reduceRP(inst);
            return true;
        }
    }
    if (isa<CmpInst>(inst))
    {
        hasAliasConcern = false;
        reducePressure = true;
        return true;
    }
    EOPCODE intrinsic_name = GetOpCode(inst);
    if (intrinsic_name == llvm_input ||
        intrinsic_name == llvm_shaderinputvec)
    {
        hasAliasConcern = false;
        reducePressure = true;
        return true;
    }
    if (generalCodeSinking)
    {
        if (IsMathIntrinsic(intrinsic_name) || IsGradientIntrinsic(intrinsic_name))
        {
            hasAliasConcern = false;
            reducePressure = false;
            return true;
        }
        if (isSampleInstruction(inst) || isGather4Instruction(inst) ||
            isInfoInstruction(inst) || isLdInstruction(inst))
        {
            if(!inst->mayReadFromMemory())
            {
                hasAliasConcern = false;
                return true;
            }
        }
        if (isSubGroupIntrinsic(inst))
        {
            return false;
        }

        if (LoadInst *load = dyn_cast<LoadInst>(inst))
        {
            if (load->isVolatile())
                return false;

            BufferType bufType = GetBufferType(load->getPointerAddressSpace());
            if (bufType == CONSTANT_BUFFER || bufType == RESOURCE)
            {
                hasAliasConcern = false;
                return true;
            }
            if (!Stores.empty())
            {
                return false;
            }
        }
        else
        if (SamplerLoadIntrinsic* intrin = dyn_cast<SamplerLoadIntrinsic>(inst))
        {
            Value* texture = intrin->getTextureValue();
            if (texture->getType()->isPointerTy())
            {
                unsigned as = texture->getType()->getPointerAddressSpace();
                BufferType bufType = GetBufferType(as);
                if (bufType == CONSTANT_BUFFER || bufType == RESOURCE)
                {
                    hasAliasConcern = false;
                    return true;
                }
                else
                {
                    return (Stores.empty());
                }
            }
            else
            {
                hasAliasConcern = false;
                return true;
            }
        }
        else if (inst->mayReadFromMemory())
        {
            return (Stores.empty());
        }

        return true;
    }
    return false;
}

/// SinkInstruction - Determine whether it is safe to sink the specified machine
/// instruction out of its current block into a successor.
bool CodeSinking::SinkInstruction(
    Instruction *inst,
    SmallPtrSetImpl<Instruction *> &Stores,
    bool ForceToReducePressure)
{
    // Check if it's safe to move the instruction.
    bool hasAliasConcern;
    bool reducePressure;
    if (!isSafeToMove(inst, reducePressure, hasAliasConcern, Stores/*, AA*/))
        return false;
    if (ForceToReducePressure) {
        reducePressure = true;
    }

    // SuccToSinkTo - This is the successor to sink this instruction to, once we
    // decide.
    BasicBlock *succToSinkTo = 0;
    SmallPtrSet<Instruction*, 16> usesInBlk;
    if (!hasAliasConcern)
    {
        // find the lowest common dominator of all uses
        BasicBlock *tgtBlk = 0x0;
        bool outerLoop;
        if (FindLowestSinkTarget(inst, tgtBlk, usesInBlk, outerLoop, ForceToReducePressure))
        {
            // heuristic, avoid code-motion that does not reduce execution frequency but may increase register usage
            if (reducePressure || 
                (tgtBlk && (outerLoop || !PDT->dominates(tgtBlk, inst->getParent()))))
            {
                succToSinkTo = tgtBlk;
            }
        }
        else
        {
            // local code motion for cases like cmp and pln
            if (reducePressure)
            {
                localBlkSet.insert(inst->getParent());
                localInstSet.insert(inst);
            }
            return false;
        }
    }
    else 
    {
        // when aliasing is a concern, only look at all the immed successors and
        // decide which one we should sink to, if any.
        BasicBlock *curBlk = inst->getParent();
        for (succ_iterator I = succ_begin(inst->getParent()),
             E = succ_end(inst->getParent()); I != E && succToSinkTo == 0; ++I)
        {
            // avoid sinking an instruction into its own block.  This can
            // happen with loops.
            if ( (*I) == curBlk )
                continue;
            // punt on it because of alias concern
            if ( (*I)->getUniquePredecessor() != curBlk )
                continue;
            // Don't move instruction across a loop.
            Loop *succLoop = LI->getLoopFor((*I));
            Loop *currLoop = LI->getLoopFor(curBlk);
            if (succLoop != currLoop)
                continue;
            if (AllUsesDominatedByBlock(inst, (*I), usesInBlk))
                succToSinkTo = *I;
        }
    }

    // If we couldn't find a block to sink to, ignore this instruction.
    if (succToSinkTo == 0)
    {
        return false;
    }

    if (ComputesGradient(inst))
    {
        numGradientMovedOutBB++;
    }

    if (!reducePressure || hasAliasConcern)
    {
        inst->moveBefore(&(*succToSinkTo->getFirstInsertionPt()));
    }
    // when alasing is not an issue and reg-pressure is not an issue
    // move it as close to the uses as possible
    else if (usesInBlk.empty())
    {
        inst->moveBefore(succToSinkTo->getTerminator());
    }
    else if (usesInBlk.size()==1)
    {
        Instruction *use = *(usesInBlk.begin());
        inst->moveBefore(use);
    }
    else
    {
        // first move to the beginning of the target block
        inst->moveBefore(&(*succToSinkTo->getFirstInsertionPt()));
        // later on, move it close to the use
        localBlkSet.insert(succToSinkTo);
        localInstSet.insert(inst);
    }
    return true;
}

bool CodeSinking::LocalSink(BasicBlock *blk)
{
    bool madeChange = false;
    for (BasicBlock::iterator I = blk->begin(), E = blk->end(); I != E; ++I)
    {
        Instruction *use = &(*I);
        for (unsigned i = 0; i < use->getNumOperands(); ++i)
        {
            Instruction *def = dyn_cast<Instruction>(use->getOperand(i));
            if (def && def->getParent() == blk && localInstSet.count(def))
            {
                // "use" can be a phi-node for a single-block loop, 
                // which is not really a local-code-motion
                if (def->getNextNode() != use && !isa<PHINode>(use))
                {
                    def->moveBefore(use);
                    madeChange = true;
                }
                localInstSet.erase(def);
            }
        }
    }
    return madeChange;
}

///////////////////////////////////////////////////////////////////////////
bool CodeSinking::checkCongruent(const InstPair& values, InstVec& leaves, unsigned depth)
{
    Instruction* src0 = values.first;
    Instruction* src1 = values.second;

    if (depth > 32 ||
        src0->getOpcode() != src1->getOpcode() ||
        src0->getNumOperands() != src1->getNumOperands() ||
        src0->getType() != src1->getType() ||
        isa<PHINode>(src0) ||
        isa<CmpInst>(src0) ||
        !(src0->getNumOperands() == 1 ||
          src0->getNumOperands() == 2)||
        (isa<AllocaInst>(src0) && src0 != src1))
        return false;

    if (CallInst* call0 = dyn_cast<CallInst>(src0))
    {
        CallInst* call1 = dyn_cast<CallInst>(src1);
        assert(call1 != nullptr);
        if (call0->getCalledFunction() != call1->getCalledFunction() ||
            !call0->getCalledFunction()->doesNotReadMemory() ||
            call0->isConvergent())
        {
            return false;
        }
    }
    else
    if (LoadInst* ld0 = dyn_cast<LoadInst>(src0))
    {
        LoadInst* ld1 = dyn_cast<LoadInst>(src1);
        assert(ld1 != nullptr);
        if (ld0->getPointerAddressSpace() != ld1->getPointerAddressSpace())
        {
            return false;
        }
        unsigned as = ld0->getPointerAddressSpace();
        unsigned bufId = 0;
        bool directBuf = false;
        BufferType bufType = IGC::DecodeAS4GFXResource(as, directBuf, bufId);
        if (bufType != CONSTANT_BUFFER)
        {
            return false;
        }
    }

    bool equals = true;
    InstVec tmpVec;

    unsigned nopnds = src0->getNumOperands();

    if (nopnds == 2 && src0->getOperand(0) == src0->getOperand(1))
    {
        if (src1->getOperand(0) == src1->getOperand(1))
        {
            nopnds = 1;
        }
        else
        {
            return false;
        }
    }

    for (unsigned i = 0; i < nopnds; i++)
    {
        Value *v0, *v1;
        Instruction *iv0, *iv1;
        v0 = src0->getOperand(i);
        v1 = src1->getOperand(i);
        iv0 = dyn_cast<Instruction>(v0);
        iv1 = dyn_cast<Instruction>(v1);

        if (v0 == v1)
        {
            if (iv0)
            {
                if (DT->dominates(iv0->getParent(), src0->getParent()) &&
                    DT->dominates(iv0->getParent(), src1->getParent()))
                {
                    appendIfNotExist(tmpVec, iv0);
                    continue;
                }
                else
                {
                    return false;
                }
            }
            else
            if (!(isa<Argument>(v0) || isa<Constant>(v0) || isa<GlobalValue>(v0)))
            {
                return false;
            }
            continue;
        }
        if (iv0 && iv0->getParent() == src0->getParent() &&
            iv1 && iv1->getParent() == src1->getParent())
        {
            if (!checkCongruent(std::make_pair(iv0, iv1), tmpVec, depth+1))
            {
                equals = false;
                break;
            }
        }
        else
        {
            equals = false;
            break;
        }
    }
    if (equals)
    {
        appendIfNotExist(std::make_pair(src0, src1));
        appendIfNotExist(leaves, tmpVec);
        return equals;
    }

    if (!src0->isCommutative() ||
        (src0->isCommutative() && src0->getOperand(0) == src0->getOperand(1)))
        return equals;

    equals = true;
    tmpVec.clear();
    for (unsigned i = 0; i < src0->getNumOperands(); i++)
    {
        Value *v0, *v1;
        Instruction *iv0, *iv1;
        v0 = src0->getOperand(i);
        v1 = src1->getOperand(1-i);
        iv0 = dyn_cast<Instruction>(v0);
        iv1 = dyn_cast<Instruction>(v1);

        if (v0 == v1)
        {
            if (iv0)
            {
                if (DT->dominates(iv0->getParent(), src0->getParent()) &&
                    DT->dominates(iv0->getParent(), src1->getParent()))
                {
                    appendIfNotExist(tmpVec, iv0);
                    continue;
                }
                else
                {
                    return false;
                }
            }
            else
            if (!(isa<Argument>(v0) || isa<Constant>(v0) || isa<GlobalValue>(v0)))
            {
                return false;
            }
            continue;
        }

        if (iv0 && iv0->getParent() == src0->getParent() &&
            iv1 && iv1->getParent() == src1->getParent())
        {
            if (!checkCongruent(std::make_pair(iv0, iv1), leaves, depth+1))
            {
                equals = false;
                break;
            }
        }
        else
        {
            equals = false;
            break;
        }
    }
    if (equals)
    {
        appendIfNotExist(std::make_pair(src0, src1));
        appendIfNotExist(leaves, tmpVec);
    }
    return equals;
}

bool CodeSinking::hoistCongruentPhi(PHINode* phi)
{
    if (phi->getNumIncomingValues() != 2)
        return false;

    bool changed = false;
    InstVec leaves;

    Instruction *src0, *src1;
    src0 = dyn_cast<Instruction>(phi->getIncomingValue(0));
    src1 = dyn_cast<Instruction>(phi->getIncomingValue(1));
    if (src0 && src1 && src0 != src1)
    {
        if (checkCongruent(std::make_pair(src0, src1), leaves, 0))
        {
            BasicBlock* predBB = nullptr;
            Instruction* insertPos = nullptr;
            bool apply = true;

            if (leaves.size() == 0)
            {
                if (DT->dominates(src0, phi->getParent()))
                {
                    phi->replaceAllUsesWith(src0);
                    return true;
                }
                else
                if (DT->dominates(src1, phi->getParent()))
                {
                    phi->replaceAllUsesWith(src1);
                    return true;
                }
                else
                {
                    predBB = DT->findNearestCommonDominator(
                        src0->getParent(), src1->getParent());
                    insertPos = predBB->getTerminator();
                }
            }
            else
            {
                Instruction* last;
                for (auto* I : leaves)
                {
                    if (!predBB)
                    {
                        predBB = I->getParent();
                        last = I;
                    }
                    else
                    if (predBB != I->getParent() ||
                        !DT->dominates(predBB, src0->getParent()) ||
                        !DT->dominates(predBB, src1->getParent()))
                    {
                        apply = false;
                        break;
                    }
                    else
                    if (!isInstPrecede(I, last))
                    {
                        last = I;
                    }
                }
                if (isa<PHINode>(last))
                {
                    insertPos = predBB->getFirstNonPHI();
                }
                else
                {
                    insertPos = last->getNextNode();
                }
            }

            if (apply)
            {
                auto compareFunc = [](const InstPair& a, const InstPair& b) {
                    return isInstPrecede(a.first, b.first);
                };
                std::sort(instMap.begin(), instMap.end(), compareFunc);

                for (auto& insts : instMap)
                {
                    Instruction* I = insts.first;
                    Instruction* ni = I->clone();
                    ni->insertBefore(insertPos);
                    ni->setName(ni->getName() + ".hoist");

                    if (phi->getIncomingValue(0) == I)
                    {
                        // replace phi also
                        phi->replaceAllUsesWith(ni);
                    }
                    I->replaceAllUsesWith(ni);
                    insts.second->replaceAllUsesWith(ni);
                }
                changed = true;
            }
        }
    }
    instMap.clear();
    return changed;
}

bool CodeSinking::hoistCongruentPhi(Function& F)
{
    bool changed = false;
    for (auto& BB : F)
    {
        for (auto II = BB.begin(), IE = BB.end(); II != IE; )
        {
            PHINode* phi = dyn_cast<PHINode>(II);

            if (!phi)
                break;

            if (hoistCongruentPhi(phi))
            {
                changed = true;
                II = phi->eraseFromParent();
            }
            else
            {
                ++II;
            }
        }
    }
    return changed;
}

bool CodeSinking::loopSink(BasicBlock* BBWithPressure, bool SinkMultipleLevel)
{
    // Sink loop invariants back into the loop body if register
    // pressure can be reduced.

    // L0 is inner loop
    Loop* L0 = LI->getLoopFor(BBWithPressure);
    if (!L0)
        return false;

    // L1 is parent loop
    Loop* L1 = nullptr;
    if (SinkMultipleLevel) {
        L1 = L0->getParentLoop();
    }

    // At most, do two-level loop sink
    //     x = ...
    //   ParentLoop
    //     y = ...
    //     Loop:
    //          = x 
    //          = y
    // Normally, only y can be sinked. When multiLevel is true,
    // x can be sinked into Loop (inner) as well.
    bool changed = false;
    for (int i = 0; i < 2; ++i)
    {
        Loop* L = (i == 0) ? L0 : L1;
        if (!L) {
            break;
        }
        // No Preheader, stop!
        BasicBlock *Preheader = L->getLoopPreheader();
        if (!Preheader)
            break;

        // Find LIs in preheader that would definitely reduce
        // register pressure after moving those LIs inside the loop
        SmallPtrSet<Instruction *, 16> stores;
        SmallVector<Instruction*, 64> sinkCandidates;

        // Moving LI back to the loop. Here we only consider to move LIs into
        // the single BB (BBWithPressure).
        //
        // Go over instructions in reverse order and sink the noOp instructions
        // on-the-fly first, so that their dependent instructions can be added
        // into candidate lists for further sinking.
        for (auto II = Preheader->rbegin(), IE = Preheader->rend(); II != IE;)
        {
            Instruction *I = &*II++;

            if (I->mayWriteToMemory()) {
                stores.insert(I);
            }
            if (!canLoopSink(I, L, BBWithPressure))
                continue;

            // Sink noOp instruction.
            if (isNoOpInst(I, CTX)) {
                if (SinkInstruction(I, stores, true)) {
                    changed = true;
                }
                continue;
            }

            sinkCandidates.push_back(I);
        }

        bool t = LoopSinkInstructions(sinkCandidates, L);
        changed |= t;
    }

    // Invoke LocalSink() to move def to its first use
    // (Currently, it should be no opt as LoopSink only
    // sinks singleUse instructions, which should be done
    // completely within sinkInstruction.
    if (localBlkSet.size() > 0)
    {
        for (auto BI = localBlkSet.begin(), BE = localBlkSet.end(); BI != BE; BI++)
        {
            BasicBlock *BB = *BI;
            bool t = LocalSink(BB);
            changed |= t;
        }
        localBlkSet.clear();
        localInstSet.clear();
    }

    return changed;
}

bool CodeSinking::canLoopSink(Instruction *I, Loop* L, BasicBlock* FatBB)
{
    // Limit sinking for the following case for now.
    if (!isNoOpInst(I, CTX) && !isa<BinaryOperator>(I))
        return false;

    if (!I->hasOneUse())
        return false;
    Instruction *UserInst = I->user_back();
    if (!L->contains(UserInst))
        return false;
    return true;
};

bool CodeSinking::LoopSinkInstructions(
    SmallVector<Instruction*, 64> sinkCandidates,
    Loop* L)
{
    auto IsUsedInLoop = [](Value* V, Loop* L) -> bool {
        if (isa<Constant>(V)) {
            // Ignore constant
            return false;
        }
        for (auto UI : V->users()) {
            if (Instruction* User = dyn_cast<Instruction>(UI))
            {
                if (L->contains(User))
                    return true;
            }
        }
        return false;
    };

    auto IsSameSet = [](SmallPtrSet <Value*, 4>& S0, SmallPtrSet <Value*, 4>& S1)-> bool {
        if (S0.size() == S1.size()) {
            for (auto I : S1) {
                Value* V = I;
                if (!S0.count(V)) {
                    return false;
                }
            }
            return true;
        }
        return false;
    };

    // For each candidate like the following:
    //   preheader:
    //            x = add y, z
    //   loop:
    //         ...
    //      BB: 
    //           = x
    //
    // Afer sinking, x changes from global to local, and thus reduce pressure.
    // But y and z could change to global to local (if y and z are local).
    // Thus, we reduce pressure by 1 (x), but increase by the number of its
    // operands (y and z). If there are more candidates share the same operands, 
    // we will reduce the pressure.  For example:
    //   preheader:
    //        x0 = add y, 10
    //        x1 = add y, 20
    //        x2 = add y, 100
    //        x3 = add y, 150
    //   loop:
    //         = x0
    //         = x1
    //         = x2
    //         = x3
    //
    // After sinking x0-x3 into loop, we make x0-x3 be local and make y be global,
    // which results in 3 (4 - 1) pressure reduction.
    //
    // Here we group all candidates based on its operands and select ones that definitely
    // reduce the pressure.
    //
    struct OperandUseGroup {
        SmallPtrSet <Value*, 4> Operands;
        SmallVector<Instruction*, 16> Users;
    };
    OperandUseGroup* allGroups = new OperandUseGroup[sinkCandidates.size()];
    SmallVector<OperandUseGroup*, 16> InstUseInfo;
    for (uint32_t i = 0, e = (uint32_t)sinkCandidates.size(); i < e; ++i)
    {
        Instruction* I = sinkCandidates[i];
        SmallPtrSet<Value*, 4> theUses;
        for (Use& U : I->operands())
        {
            Value* V = U;
            if (isa<Constant>(V) || IsUsedInLoop(V, L))
                continue;

            theUses.insert(V);
        }
        // If this set of uses have been referenced by other instructions,
        // put this inst in the same group. Note that we don't union sets
        // that intersect each other.
        uint32_t j, je = (uint32_t)InstUseInfo.size();
        for (j = 0; j < je; ++j)
        {
            OperandUseGroup* OUG = InstUseInfo[j];
            if (IsSameSet(OUG->Operands, theUses)) {
                OUG->Users.push_back(I);
                break;
            }
        }


        if (j == je) {
            // No match found, create the new one.
            OperandUseGroup& OUG = allGroups[i];
            OUG.Operands = theUses;
            OUG.Users.push_back(I);
            InstUseInfo.push_back(&OUG);
        }
    }

    bool changed = false;
    // Just a placeholder, all LIs considered here are ALUs.
    SmallPtrSet<Instruction *, 16> stores;
    const int SaveThreshold = IGC_GET_FLAG_VALUE(LoopSinkMinSave);
    bool keepLooping;
    uint32_t N = (uint32_t)InstUseInfo.size();
    do {
        keepLooping = false;
        for (uint32_t i = 0; i < N; ++i)
        {
            OperandUseGroup* OUG = InstUseInfo[i];
            if (!OUG)
                continue;

            int sz1 = (int)OUG->Users.size();
            int save = sz1 - (int)(OUG->Operands.size());
            if (save >= SaveThreshold)
            {
                // Sink
                bool t = false;
                for (int j = 0; j < sz1; ++j)
                {
                    Instruction* I = OUG->Users[j];
                    bool t1 = SinkInstruction(I, stores, true);
                    t |= t1;
                }
                if (t) {
                    changed = true;
                    keepLooping = true;

                    // Since those operands become global already, remove
                    // them from the sets in the vector.
                    for (uint32_t k = 0; k < N; ++k)
                    {
                        OperandUseGroup* OUG1 = InstUseInfo[k];
                        if (k == i || !OUG1)
                            continue;

                        for (auto I : OUG->Operands) {
                            Value* V = I;
                            OUG1->Operands.erase(V);
                        }
                    }
                }

                // Just set it to nullptr (erasing it would be more expensive).
                InstUseInfo[i] = nullptr;
            }
        }
    } while (keepLooping);

    delete[] allGroups;

    return changed;
}

char CodeSinking::ID = 0;
}
