// vim:ts=2:sw=2:et:
/*===================== 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
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

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
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


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

#define DEBUG_TYPE "type-demote"
#include "Compiler/CISACodeGen/TypeDemote.h"
#include "Compiler/CISACodeGen/ShaderCodeGen.hpp"
#include "Compiler/CodeGenContextWrapper.hpp"
#include "Compiler/MetaDataUtilsWrapper.h"
#include "Compiler/IGCPassSupport.h"

#include "common/LLVMWarningsPush.hpp"
#include <llvm/ADT/PostOrderIterator.h>
#include <llvm/IR/IRBuilder.h>
#include <llvm/Pass.h>
#include "common/LLVMWarningsPop.hpp"

#include "GenISAIntrinsics/GenIntrinsics.h"

using namespace llvm;
using namespace IGC;
using namespace IGC::IGCMD;

namespace {

  typedef IRBuilder<> BuilderType;

  class TypeDemote : public FunctionPass {
    BuilderType *IRB;

  public:
    static char ID;

    TypeDemote() : FunctionPass(ID), IRB(nullptr) {
      initializeTypeDemotePass(*PassRegistry::getPassRegistry());
    }

    bool runOnFunction(Function &) override;

    void getAnalysisUsage(AnalysisUsage &AU) const override {
      AU.setPreservesCFG();
    }

  private:
    bool demoteOnFunction(Function *) const;
    bool demoteOnBasicBlock(BasicBlock *) const;

    Value *getDemotedValue(Value *V, Type *DemotedTy, bool Unsigned) const;
  };

} // End anonymous namespace

FunctionPass *IGC::createTypeDemotePass() {
  return new TypeDemote();
}

char TypeDemote::ID = 0;

#define PASS_FLAG     "igc-type-demote"
#define PASS_DESC     "Demote type safely"
#define PASS_CFG_ONLY false
#define PASS_ANALYSIS false
namespace IGC {
IGC_INITIALIZE_PASS_BEGIN(TypeDemote, PASS_FLAG, PASS_DESC, PASS_CFG_ONLY, PASS_ANALYSIS)
IGC_INITIALIZE_PASS_END(TypeDemote, PASS_FLAG, PASS_DESC, PASS_CFG_ONLY, PASS_ANALYSIS)
}

bool TypeDemote::runOnFunction(Function &F) {
  BuilderType TheBuilder(F.getContext());
  IRB = &TheBuilder;

  bool Changed = false;
  bool LocalChanged = false;
  do {
    LocalChanged = demoteOnFunction(&F);
    Changed |= LocalChanged;
  } while (LocalChanged);

  return Changed;
}

bool TypeDemote::demoteOnFunction(Function *F) const {
  bool Changed = false;

  ReversePostOrderTraversal<Function *> RPOT(F);
  for (auto &BB : RPOT)
    Changed |= demoteOnBasicBlock(BB);

  return Changed;
}

bool TypeDemote::demoteOnBasicBlock(BasicBlock *BB) const {
  bool Changed = false;

  Type *DemotedTy = IRB->getInt8Ty();
  for (auto BI = BB->begin(), BE = BB->end(); BI != BE; /* EMPTY */) {
    Instruction *I = &(*BI++);
    // So far, we only demote unsigned i32 to i8.
    // TODO: Consider demote to i16 as well as i8 may not be supported natively
    // on future Gen.
    if (PHINode *PN = dyn_cast<PHINode>(I)) {
      // Skip non-i32 so far.
      if (!PN->getType()->isIntegerTy(32))
        continue;

      unsigned N = PN->getNumIncomingValues();
      SmallVector<Value *, 8> DemotedValues(N, nullptr);
      bool SafeToDemote = true;
      for (unsigned i = 0; i != N; ++i) {
        Value *DemotedVal = getDemotedValue(PN->getIncomingValue(i), DemotedTy, true);
        if (!DemotedVal) {
          SafeToDemote = false;
          break;
        }
        DemotedValues[i] = DemotedVal;
      }
      if (!SafeToDemote)
        continue;

      Type *OriginTy = PN->getType();
      // Demote the original `phi` to i8 one followed a `zext`.
      PN->mutateType(DemotedTy);
      for (unsigned i = 0; i != N; ++i)
        PN->setIncomingValue(i, DemotedValues[i]);
      // Create the unsigned extension.
      BuilderType::InsertPointGuard Guard(*IRB);
      IRB->SetInsertPoint(BB->getFirstNonPHI());
      Value *V = IRB->CreateZExt(PN, OriginTy, ".demoted.zext");
      for (auto UI = PN->use_begin(), UE = PN->use_end(); UI != UE; /* EMPTY */) {
        Use &U = *UI++;
        if (U.getUser() == V)
          continue;
        U.set(V);
      }
      Changed = true;
      BI = std::next(BasicBlock::iterator(PN));
      continue;
    }

    if (ICmpInst *Cmp = dyn_cast<ICmpInst>(I)) {
      if (!Cmp->getOperand(0)->getType()->isIntegerTy(32))
        continue;
      if (!Cmp->isUnsigned())
        continue;
      Value *DemotedLHS = getDemotedValue(Cmp->getOperand(0), DemotedTy, true);
      if (!DemotedLHS)
        continue;
      Value *DemotedRHS = getDemotedValue(Cmp->getOperand(1), DemotedTy, true);
      if (!DemotedRHS)
        continue;
      Cmp->setOperand(0, DemotedLHS);
      Cmp->setOperand(1, DemotedRHS);
      Changed = true;
      continue;
    }

    if (SelectInst *SI = dyn_cast<SelectInst>(I)) {
      // Check for min or max before doing this
      if (ICmpInst *cmp = dyn_cast<ICmpInst>(SI->getOperand(0)))
      {
        if ((cmp->getOperand(0) == SI->getOperand(1) && cmp->getOperand(1) == SI->getOperand(2)) ||
            (cmp->getOperand(0) == SI->getOperand(2) && cmp->getOperand(1) == SI->getOperand(1)))
          {
            continue;
          }
      }
      if (!SI->getType()->isIntegerTy(32))
        continue;
      Value *DemotedTrueVal = getDemotedValue(SI->getTrueValue(), DemotedTy, true);
      if (!DemotedTrueVal)
        continue;
      Value *DemotedFalseVal = getDemotedValue(SI->getFalseValue(), DemotedTy, true);
      if (!DemotedFalseVal)
        continue;

      Type *OriginTy = SI->getType();
      SI->setOperand(1, DemotedTrueVal);
      SI->setOperand(2, DemotedFalseVal);
      SI->mutateType(DemotedTy);
      // Create the unsigned extension.
      BuilderType::InsertPointGuard Guard(*IRB);
      IRB->SetInsertPoint(&(*std::next(BasicBlock::iterator(I))));
      Value *V = IRB->CreateZExt(SI, OriginTy, ".demoted.zext");
      for (auto UI = SI->use_begin(), UE = SI->use_end(); UI != UE; /* EMPTY */) {
        Use &U = *UI++;
        if (U.getUser() == V)
          continue;
        U.set(V);
      }
      Changed = true;
      BI = std::next(BasicBlock::iterator(SI));
      continue;
    }

    if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
      // Skip if it's already demoted.
      if (BO->getType() == DemotedTy)
        continue;
      switch (BO->getOpcode()) {
      default:
        continue;
      // TODO: Only handle 'and', 'or', 'xor' so far.
      case Instruction::And:
      case Instruction::Or:
      case Instruction::Xor:
        break;
      }
      Value *DemotedLHS = getDemotedValue(BO->getOperand(0), DemotedTy, true);
      if (!DemotedLHS)
        continue;
      Value *DemotedRHS = getDemotedValue(BO->getOperand(1), DemotedTy, true);
      if (!DemotedRHS)
        continue;

      Type *OriginTy = BO->getType();
      BO->setOperand(0, DemotedLHS);
      BO->setOperand(1, DemotedRHS);
      BO->mutateType(DemotedTy);
      // Create the unsigned extension.
      BuilderType::InsertPointGuard Guard(*IRB);
      IRB->SetInsertPoint(&(*std::next(BasicBlock::iterator(I))));
      Value *V = IRB->CreateZExt(BO, OriginTy, ".demoted.zext");
      for (auto UI = BO->use_begin(), UE = BO->use_end(); UI != UE; /* EMPTY */) {
        Use &U = *UI++;
        if (U.getUser() == V)
          continue;
        U.set(V);
      }
      BI = std::next(BasicBlock::iterator(BO));
      if (BO->getOpcode() == Instruction::And) {
        if (ConstantInt *CI = dyn_cast<ConstantInt>(DemotedRHS))
          if (CI->isAllOnesValue()) {
            BO->replaceAllUsesWith(DemotedLHS);
            BO->eraseFromParent();
          }
      }
      Changed = true;
      continue;
    }

    if (TruncInst *TI = dyn_cast<TruncInst>(I)) {
      if (!TI->getType()->isIntegerTy(8))
        continue;
      if (!TI->getSrcTy()->isIntegerTy(32))
        continue;
      Value *DemotedVal = getDemotedValue(TI->getOperand(0), DemotedTy, true);
      if (!DemotedVal)
        continue;

      TI->replaceAllUsesWith(DemotedVal);
      TI->eraseFromParent();

      Changed = true;
      continue;
    }

    if (ZExtInst *ZEI = dyn_cast<ZExtInst>(I)) {
      if (!ZEI->getSrcTy()->isIntegerTy(8))
        continue;
      // TODO
    }
    
    // j.0163 = phi i16 [ 0, %._crit_edge155 ], [ %337, %..lr.ph_crit_edge ]
    // %57 = zext i16 %j.0163 to i64
    // %58 = extractelement <32 x i16> <i16 3, ..., i16 44, i16 50>, i64 %57
    // 
    if (auto EEI = dyn_cast<ExtractElementInst>(I)) {
      Value *Index = EEI->getIndexOperand();
      CastInst *CI = dyn_cast<CastInst>(Index);
      if (CI && (CI->getOpcode() == Instruction::ZExt ||
                 CI->getOpcode() == Instruction::SExt)) {
        unsigned VS = EEI->getVectorOperandType()->getVectorNumElements();
        unsigned N = CI->getSrcTy()->getPrimitiveSizeInBits();
        unsigned Bound = (N < 32) ? (1U << N) : UINT32_MAX; 
        if (VS <= Bound) {
          EEI->setOperand(1, CI->getOperand(0));
          if (CI->use_empty())
            CI->eraseFromParent();
          Changed = true;
        }
      }
      continue;
    }
  }

  return Changed;
}

Value *TypeDemote::getDemotedValue(Value *V, Type *DemotedTy, bool Unsigned) const {
  assert(DemotedTy->isIntegerTy(8) && Unsigned && "Only support demotion to i8!");

  if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
    if (!CI->getValue().isIntN(8))
      return nullptr;
    V = IRB->CreateTrunc(V, DemotedTy);
    assert(isa<ConstantInt>(V) && "Constant folding is failed!");
    return V;
  }

  if (ZExtInst *ZEI = dyn_cast<ZExtInst>(V)) {
    if (!ZEI->getSrcTy()->isIntegerTy(8))
      return nullptr;
    return ZEI->getOperand(0);
  }

  return nullptr;
}
