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

Copyright (c) 2017 Intel Corporation

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
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The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


======================= end_copyright_notice ==================================*/
#include "Compiler/SampleCmpToDiscard.h"
#include "Compiler/CodeGenPublic.h"
#include "GenISAIntrinsics/GenIntrinsicInst.h"
using namespace llvm;
using namespace IGC;
using namespace GenISAIntrinsic;

class SampleCmpToDiscard : public FunctionPass
{
public:
    static char ID;

    SampleCmpToDiscard() : FunctionPass(ID)
    {
    }
    virtual void getAnalysisUsage(llvm::AnalysisUsage& AU) const
    {
        AU.addRequired<CodeGenContextWrapper>();
    }

    virtual bool runOnFunction(Function& F);

    virtual llvm::StringRef getPassName() const
    {
        return "SampleCmpToDiscard";
    }
private:
    bool processBlock(BasicBlock* BB);
    bool canFoldValue(Instruction* inst, std::map<Value*, APFloat>& instToValMap);
};

char SampleCmpToDiscard::ID = 0;

FunctionPass* IGC::CreateSampleCmpToDiscardPass()
{
    return new SampleCmpToDiscard();
}

bool SampleCmpToDiscard::runOnFunction(Function& F)
{
    auto pCtx = getAnalysis<CodeGenContextWrapper>().getCodeGenContext();
    if (pCtx->type != ShaderType::PIXEL_SHADER)
    {
        return false;
    }
    bool changed = false;
    for (auto BI = F.begin(), BE = F.end(); BI != BE;)
    {
        BasicBlock* currentBB = &(*BI);
        ++BI;
        changed |= processBlock(currentBB);
    }
    return changed;
}

bool SampleCmpToDiscard::processBlock(BasicBlock* BB)
{
    auto pCtx = getAnalysis<CodeGenContextWrapper>().getCodeGenContext();
    std::map<Value*, APFloat> instToValMap;
    for (auto II = BB->rbegin(), IE = BB->rend(); II != IE; ++II)
    {
        instToValMap.clear();
        if (GenIntrinsicInst * genIntr = dyn_cast<GenIntrinsicInst>(&(*II)))
        {
            Instruction* valueToFold = nullptr;
            GenISAIntrinsic::ID ID = genIntr->getIntrinsicID();
            // only consider sample_lc
            if (ID == GenISAIntrinsic::GenISA_sampleCptr ||
                ID == GenISAIntrinsic::GenISA_sampleBCptr)
            {
                if (genIntr->hasOneUse())
                {
                    if (ExtractElementInst * ext = dyn_cast<ExtractElementInst>(*genIntr->user_begin()))
                    {
                        if (ConstantInt * index = dyn_cast<ConstantInt>(ext->getIndexOperand()))
                        {
                            if (index->isZero())
                            {
                                valueToFold = ext;
                            }
                        }
                    }
                }
            }
            // if we haven't found the pattern we want to skip to the next instruction
            if (valueToFold == nullptr)
            {
                continue;
            }
            APFloat newAPFloat = cast<ConstantFP>(ConstantFP::get(valueToFold->getType(), 1.0))->getValueAPF();
            instToValMap.emplace(valueToFold, newAPFloat);

            bool foldableInst = canFoldValue(valueToFold, instToValMap);
            if (foldableInst)
            {
                llvm::Value* texOp = cast<SampleIntrinsic>(genIntr)->getTextureValue();
                // set compiler outputs
                if (texOp->getType()->getPointerAddressSpace())
                {
                    uint as = texOp->getType()->getPointerAddressSpace();
                    uint bufferIndex;
                    bool directIndexing;
                    DecodeAS4GFXResource(as, directIndexing, bufferIndex);
                    // set the compiler outputs to indicate sample_Cqa which could write 1.0f to the driver
                    pCtx->m_instrTypes.sampleCmpToDiscardOptimizationPossible = true;
                    pCtx->m_instrTypes.sampleCmpToDiscardOptimizationSlot = bufferIndex;
                    return true;
                }
            }
        }
    }
    instToValMap.clear();
    return false;
}

bool SampleCmpToDiscard::canFoldValue(Instruction* inst, std::map<Value*, APFloat>& instToValMap)
{
    // currently we are handling the following type of cases
    /*
    * %92 = call <4 x half> @llvm.genx.GenISA.sampleCptr.v4f16.f16.p196609v4f32.p524289i32(
        half %91, half %89, half %90, half %91, half %87, half 0xH0000, <4 x float> addrspace(196609)* null,
        i32 addrspace(524289)* null, i32 0, i32 0, i32 0)
    * %93 = extractelement <4 x half> %92, i32 0
    * %94 = fsub half 0xH3C00, %93 // 1 - B
    * %95 = fmul half %94, 0xH3400 // 0.25 * (1-B)
    * %96 = fadd half %95, %93 // 0.25 * ( 1-B) + B
    * call void @llvm.genx.GenISA.OUTPUT.f16(half %96, half %96, half %96, half %96, i32 0, i32 0)
    * ret void
    */

    /*
    * %62 = call <4 x float> @llvm.genx.GenISA.sampleBCptr.v4f32.f32.p196609i8.p524293i8(
    * float %61, float 0.000000e+00, float %57, float %58, float 0.000000e+00,
    * float 0.000000e+00, i8 addrspace(196609)* null,
    * i8 addrspace(524293)* inttoptr (i64 5 to i8 addrspace(524293)*), i32 0, i32 0, i32 0)
    * %scalar40 = extractelement <4 x float> %62, i32 0
    * %phitmp = fmul float %scalar40, 7.500000e-01
    * %63 = fadd float %phitmp, 2.500000e-01
    * call void @llvm.genx.GenISA.OUTPUT.f32(float %63, float %63, float %63, float %63, i32 0, i32 0)
    */
    bool foldInst = false;
    APFloat newConstantFloat = cast<ConstantFP>(ConstantFP::get(inst->getType(), 1.0))->getValueAPF();
    auto mapFind = instToValMap.find(inst);
    if (mapFind == instToValMap.end())
    {
        return false;
    }

    for (auto UI = inst->user_begin(), UE = inst->user_end(); UI != UE; ++UI)
    {
        // assume the value of inst returns value 1;
        BinaryOperator* bin = dyn_cast<BinaryOperator>(*UI);
        if (bin && bin->getOpcode() == Instruction::FSub)
        {
            auto itOtherOp = (bin->getOperand(0) == inst) ? instToValMap.find(bin->getOperand(1)) : instToValMap.find(bin->getOperand(0));
            if (isa<ConstantFP>(bin->getOperand(0)))
            {
                ConstantFP* C0 = dyn_cast<ConstantFP>(bin->getOperand(0));
                newConstantFloat = C0->getValueAPF();
                newConstantFloat.subtract(mapFind->second, llvm::APFloat::rmNearestTiesToEven);
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
            else if (isa<ConstantFP>(bin->getOperand(1)))
            {
                ConstantFP* C0 = dyn_cast<ConstantFP>(bin->getOperand(1));
                newConstantFloat = mapFind->second;
                newConstantFloat.subtract(C0->getValueAPF(), llvm::APFloat::rmNearestTiesToEven);
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
            else if (itOtherOp != instToValMap.end())
            {
                if (bin->getOperand(0) == inst)
                {
                    newConstantFloat = mapFind->second;
                    newConstantFloat.subtract(itOtherOp->second, llvm::APFloat::rmNearestTiesToEven);
                }
                else
                {
                    newConstantFloat = itOtherOp->second;
                    newConstantFloat.subtract(mapFind->second, llvm::APFloat::rmNearestTiesToEven);
                }
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
        }

        else if (bin && bin->getOpcode() == Instruction::FAdd)
        {
            auto itOtherOp = (bin->getOperand(0) == inst) ? instToValMap.find(bin->getOperand(1)) : instToValMap.find(bin->getOperand(0));
            if (isa<ConstantFP>(bin->getOperand(0)))
            {
                ConstantFP* C0 = dyn_cast<ConstantFP>(bin->getOperand(0));
                newConstantFloat = mapFind->second;
                newConstantFloat.add(C0->getValueAPF(), llvm::APFloat::rmNearestTiesToEven);
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
            else if (isa<ConstantFP>(bin->getOperand(1)))
            {
                ConstantFP* C0 = dyn_cast<ConstantFP>(bin->getOperand(1));
                newConstantFloat = mapFind->second;
                newConstantFloat.add(C0->getValueAPF(), llvm::APFloat::rmNearestTiesToEven);
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
            else if (itOtherOp != instToValMap.end())
            {
                newConstantFloat = mapFind->second;
                newConstantFloat.add(itOtherOp->second, llvm::APFloat::rmNearestTiesToEven);
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
        }

        else if (bin && bin->getOpcode() == Instruction::FMul)
        {
            auto itOtherOp = (bin->getOperand(0) == inst) ? instToValMap.find(bin->getOperand(1)) : instToValMap.find(bin->getOperand(0));
            if (isa<ConstantFP>(bin->getOperand(0)))
            {
                ConstantFP* C0 = dyn_cast<ConstantFP>(bin->getOperand(0));
                newConstantFloat = mapFind->second;
                newConstantFloat.multiply(C0->getValueAPF(), llvm::APFloat::rmNearestTiesToEven);
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
            else if (isa<ConstantFP>(bin->getOperand(1)))
            {
                ConstantFP* C0 = dyn_cast<ConstantFP>(bin->getOperand(1));
                newConstantFloat = mapFind->second;
                newConstantFloat.multiply(C0->getValueAPF(), llvm::APFloat::rmNearestTiesToEven);
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
            else if (itOtherOp != instToValMap.end())
            {
                newConstantFloat = mapFind->second;
                newConstantFloat.multiply(itOtherOp->second, llvm::APFloat::rmNearestTiesToEven);
                instToValMap.emplace(bin, newConstantFloat);
                foldInst = canFoldValue(bin, instToValMap);
            }
        }

        else if (isa<GenIntrinsicInst>(*UI) && ((mapFind->second).compare(newConstantFloat) == APFloat::cmpEqual))
        {
            GenIntrinsicInst* CI = dyn_cast<GenIntrinsicInst>(*UI);
            if ((CI->getIntrinsicID() == GenISA_RTWrite) && (llvm::isa<llvm::ReturnInst>(CI->getNextNode())))
            {
                return true;
            }
        }
    }

    return foldInst;
}