/*===================== 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 ==================================*/

// vim:ts=2:sw=2:et:

#define DEBUG_TYPE "type-legalizer"
#include "TypeLegalizer.h"
#include "InstExpander.h"
#include "common/LLVMWarningsPush.hpp"

#include "llvmWrapper/Support/Debug.h"

#include "llvm/Support/raw_ostream.h"
#include "common/LLVMWarningsPop.hpp"
using namespace llvm;
using namespace IGC::Legalizer;

bool InstExpander::expand(Instruction *I) {
  IRB->SetInsertPoint(&(*std::next(BasicBlock::iterator(I))));
  IRB->SetCurrentDebugLocation(I->getDebugLoc());
  Expanded.clear();

  if (!visit(*I))
    return false;

  if (!Expanded.empty())
    TL->setLegalizedValues(I, Expanded);

  return true;
}

// By default, capture all missing instructions!
bool InstExpander::visitInstruction(Instruction &I) {
  LLVM_DEBUG(dbgs() << "EXPAND: " << I << '\n');
  llvm_unreachable("UNKNOWN INSTRUCTION IS BEING EXPANDED!");
  return false;
}

/// Terminator instructions
///

bool InstExpander::visitTerminatorInst(IGCLLVM::TerminatorInst &I) {
  // All terminators are handled specially.
  return false;
}

/// Standard binary operators
///

// TODO:
// LLVM intrinsic is not good at large integer calculation and lacks of
// intrinsic like:
//
//  %fsum = call {i32, i1} @full.add(i32 %x, i32 %y, i1 %cin);
//  %sum = extractvalue {i32, i1} %fsum, 0
//  %cout = extractvalue {i32, i1} %fsum, 1
//
// we have to use the following sequence to emulate it:
//
//  %cin32 = zext i1 %cin to i32
//  %psum = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %x, i32 %y)
//  %tsum = extractvalue {i32, i1} %psum, 0
//  %cout1 = extractvalue {i32, i1} %psum, 1
//  %fsum = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %tsum, i32 %cin32)
//  %sum = extractvalue {i32, i1} %fsum, 0
//  %cout2 = extractvalue {i32, i1} %fsum, 1
//  %cout = or i1 %cout1, %cout2
//
bool InstExpander::visitAdd(BinaryOperator &I) {
  // FIXME:
  llvm_unreachable("NOT IMPLEMENTED YET!");
  return false;
}

bool InstExpander::visitSub(BinaryOperator &I) {
  // FIXME:
  llvm_unreachable("NOT IMPLEMENTED YET!");
  return false;
}

bool InstExpander::visitMul(BinaryOperator &I) {
  // FIXME:
  llvm_unreachable("NOT IMPLEMENTED YET!");
  return false;
}

bool InstExpander::visitUDiv(BinaryOperator &I) {
  // FIXME:
  llvm_unreachable("NOT IMPLEMENTED YET!");
  return false;
}

bool InstExpander::visitSDiv(BinaryOperator &I) {
  // FIXME:
  llvm_unreachable("NOT IMPLEMENTED YET!");
  return false;
}

bool InstExpander::visitURem(BinaryOperator &I) {
  // FIXME:
  llvm_unreachable("NOT IMPLEMENTED YET!");
  return false;
}

bool InstExpander::visitSRem(BinaryOperator &I) {
  // FIXME:
  llvm_unreachable("NOT IMPLEMENTED YET!");
  return false;
}

bool InstExpander::visitShl(BinaryOperator &I) {
  ValueSeq *Ops0;
  TypeSeq *TySeq;
  std::tie(Ops0, std::ignore) = TL->getLegalizedValues(I.getOperand(0));
  std::tie(TySeq, std::ignore) = TL->getLegalizedTypes(I.getType());
  assert(TySeq->size() == Ops0->size());

  Type *MajorTy = TySeq->front();
  IntegerType *MajorITy = cast<IntegerType>(MajorTy);
  IntegerType *ITy = cast<IntegerType>(I.getType());
  assert(ITy->getBitWidth() < MajorITy->getBitMask() &&
         "YOU HAVE A HUGE INTEGER TO BE SHIFTED! "
         "Shift amount cannot be encoded in legal integer types!");

  // Arbitrary integer left-shift is implemented as follows:
  //
  // As left-shift with amount greater than 'width(L)' is always 0, shift
  // amount, 'ShAmt', is canonicalized into
  //
  //  ShAmt := umin(ShAmt, width(L));
  //
  // , where 'width(L)' is defined as the bit width of 'L'.
  //
  // Arbitrary large integer 'L' is expanded into several parts, namely
  // P_0, P_1, ..., P_n, i.e.
  //
  //  L := [P_0, P_1, ..., P_n];
  //
  // and 'P_0' is the rightmost part and 'P_n' is the leftmost part.
  //
  // All P_i have the same type except the tailing one, P_n, which needs
  // extending to have the same type. For simplicity, we assume P_n is already
  // extended.
  //
  // Define 'width(P)' as the bit width of each P_i. If 'ShAmt' is greater
  // than 'width(P)', we need to shift parts left first; otherwise, we need to
  // combine bits from adjacent parts, i.e.
  //
  //  while (ShAmt >= width(P)) {
  //    ShAmt -= width(P);
  //    L := [0, P_0, ..., P_{n-1}];
  //  }
  //
  //  RshAmt := width(P) - shAmt;
  //  L:= [                    | (P_0 << ShAmt),
  //       (P_0     >> RshAmt) | (P_1 << ShAmt),
  //       ...
  //       (P_{n-1) >> RshAmt) | (P_n << ShAmt)]
  //
  // That 'while' loop is unrolled as the maximal iteration is known at
  // compilation time because 'ceil(umin(ShAmt, width(L))/width(P))' is always
  // smaller or equal to 'ceil(width(L)/width(P))'.

  unsigned OrigBW = ITy->getBitWidth();
  unsigned MajorBW = MajorITy->getBitWidth();
  unsigned MaxIters = (OrigBW + MajorBW - 1) / MajorBW;

  Value *MajorBitWidth = TL->getIntN(MajorBW, MajorBW);
  Value *Zero = TL->getIntN(MajorBW, 0);
  Value *ShAmt =
    TL->umin(I.getOperand(1), TL->getIntN(OrigBW, OrigBW), MajorTy);

  // Extend all parts into major type.
  SmallVector<Value *, 8> Parts(Ops0->begin(), Ops0->end());
  Value *TailingPart = Parts.pop_back_val();
  Parts.push_back(
      IRB->CreateZExt(TailingPart, MajorTy,
        Twine(TailingPart->getName(), ".zext")));
  Type *MinorTy = TailingPart->getType();

  for (unsigned i = 0; i != MaxIters; ++i) {
    Value *Cond =
      IRB->CreateICmpUGE(ShAmt, MajorBitWidth,
          Twine(ShAmt->getName(), ".cond"));

    // Skip when the shift amount is known to be smaller than the number of
    // bits of the major type.
    if (Cond == IRB->getFalse())
      break;

    Value *NewShAmt =
      IRB->CreateSub(ShAmt, MajorBitWidth,
          Twine(ShAmt->getName(), ".shamt"));

    // Shift in bits of major type if the shift amount is known to be
    // greater than or equal to the number of bits of the major type.
    if (Cond == IRB->getTrue()) {
      ShAmt = NewShAmt;
      Parts.pop_back();
      Parts.insert(Parts.begin(), Zero);
      continue;
    }

    // Otherwise, create 'select' to shift them in bits of major type.
    ShAmt =
      IRB->CreateSelect(Cond, NewShAmt, ShAmt,
          Twine(ShAmt->getName(), ".shamt.sel"));
    SmallVector<Value *, 8> NewParts;
    for (unsigned j = 0; j != Parts.size(); ++j)
      NewParts.push_back(
          IRB->CreateSelect(
            Cond, (j == 0 ? Zero : Parts[j - 1]), Parts[j],
            Twine(Parts[j]->getName(), ".sel")));
    std::swap(Parts, NewParts);
  }

  // Now, shift amount is smaller than the bits of major type.
  Value *RshAmt =
    IRB->CreateSub(MajorBitWidth, ShAmt,
        Twine(ShAmt->getName(), ".rshAmt"));
  Expanded.push_back(
      IRB->CreateShl(Parts[0], ShAmt,
        Twine(I.getName(), getSuffix()) + Twine(0)));
  for (unsigned i = 1, e = Parts.size(); i != e; ++i) {
    Value *P0 = Parts[i - 1];
    Value *P1 = Parts[i];
    Value *L = IRB->CreateLShr(P0, RshAmt, Twine(P0->getName(), ".rshl"));
    Value *H = IRB->CreateShl(P1, ShAmt, Twine(P1->getName(), ".shl"));
    Expanded.push_back(
        IRB->CreateOr(L, H, Twine(I.getName(), getSuffix()) + Twine(i)));
  }

  TailingPart = Expanded.back();
  Expanded.pop_back();

  TailingPart =
    IRB->CreateTrunc(TailingPart, MinorTy,
        Twine(TailingPart->getName(), ".trunc"));
  Expanded.push_back(TailingPart);

  return true;
}

bool InstExpander::visitLShr(BinaryOperator &I) {
  ValueSeq *Ops0;
  TypeSeq *TySeq;
  std::tie(Ops0, std::ignore) = TL->getLegalizedValues(I.getOperand(0));
  std::tie(TySeq, std::ignore) = TL->getLegalizedTypes(I.getType());
  assert(TySeq->size() == Ops0->size());

  Type *MajorTy = TySeq->front();
  IntegerType *MajorITy = cast<IntegerType>(MajorTy);
  IntegerType *ITy = cast<IntegerType>(I.getType());
  assert(ITy->getBitWidth() < MajorITy->getBitMask() &&
         "YOU HAVE A HUGE INTEGER TO BE SHIFTED! "
         "Shift amount cannot be encoded in legal integer types!");

  // Arbitrary integer logic-right-shift is implemented similar to
  // arbitrary integer left-shift.

  unsigned OrigBW = ITy->getBitWidth();
  unsigned MajorBW = MajorITy->getBitWidth();
  unsigned MaxIters = (OrigBW + MajorBW - 1) / MajorBW;

  Value *MajorBitWidth = TL->getIntN(MajorBW, MajorBW);
  Value *Zero = TL->getIntN(MajorBW, 0);
  Value *ShAmt =
    TL->umin(I.getOperand(1), TL->getIntN(OrigBW, OrigBW), MajorTy);

  // Extend all parts into major type.
  SmallVector<Value *, 8> Parts(Ops0->begin(), Ops0->end());
  Value *TailingPart = Parts.pop_back_val();
  Parts.push_back(
      IRB->CreateZExt(TailingPart, MajorTy,
        Twine(TailingPart->getName(), ".zext")));
  Type *MinorTy = TailingPart->getType();

  for (unsigned i = 0; i != MaxIters; ++i) {
    Value *Cond =
      IRB->CreateICmpUGE(ShAmt, MajorBitWidth,
          Twine(ShAmt->getName(), ".cond"));

    // Skip when the shift amount is known to be smaller than the number of
    // bits of the major type.
    if (Cond == IRB->getFalse())
      break;

    Value *NewShAmt =
      IRB->CreateSub(ShAmt, MajorBitWidth,
          Twine(ShAmt->getName(), ".shamt"));

    // Shift in bits of major type if the shift amount is known to be
    // greater than or equal to the number of bits of the major type.
    if (Cond == IRB->getTrue()) {
      ShAmt = NewShAmt;
      Parts.erase(Parts.begin());
      Parts.push_back(Zero);
      continue;
    }

    // Otherwise, create 'select' to shift them in bits of major type.
    ShAmt =
      IRB->CreateSelect(Cond, NewShAmt, ShAmt,
          Twine(ShAmt->getName(), ".shamt.sel"));
    SmallVector<Value *, 8> NewParts;
    for (unsigned j = 0, e = Parts.size(); j != e; ++j)
      NewParts.push_back(
          IRB->CreateSelect(
            Cond, ((j == e - 1) ? Zero : Parts[j + 1]), Parts[i],
            Twine(Parts[j]->getName(), ".sel")));
    std::swap(Parts, NewParts);
  }

  // Now, shift amount is smaller than the bits of major type.
  Value *LshAmt =
    IRB->CreateSub(MajorBitWidth, ShAmt,
        Twine(ShAmt->getName(), ".lshAmt"));
  for (unsigned i = 0, e = Parts.size() - 1; i != e; ++i) {
    Value *P0 = Parts[i];
    Value *P1 = Parts[i + 1];
    Value *L = IRB->CreateLShr(P0, ShAmt, Twine(P0->getName(), ".lshr"));
    Value *H = IRB->CreateShl(P1, LshAmt, Twine(P1->getName(), ".shl"));
    Expanded.push_back(
        IRB->CreateOr(L, H, Twine(I.getName(), getSuffix()) + Twine(i)));
  }

  TailingPart = Parts.back();
  TailingPart =
    IRB->CreateLShr(TailingPart, ShAmt,
        Twine(TailingPart->getName(), ".lshr"));
  Expanded.push_back(
      IRB->CreateTrunc(TailingPart, MinorTy,
        Twine(I.getName(), getSuffix()) + Twine(Parts.size() - 1)));

  return true;
}

bool InstExpander::visitAShr(BinaryOperator &I) {
  // FIXME:
  llvm_unreachable("NOT IMPLEMENTED YET!");
  return false;
}

bool InstExpander::visitBinaryOperator(BinaryOperator &I) {
  ValueSeq *Ops0, *Ops1;
  std::tie(Ops0, std::ignore) = TL->getLegalizedValues(I.getOperand(0));
  // we should get copy of Ops0 here, as next getLegalizedValues call may grow ValueMap object 
  // when inserting new pair with ValueMap.insert(e.g.when ValueMap.NumBuckets grows from 64 to 128) 
  // and previously received ValueSeq objects will become invalid.
  ValueSeq Ops0Copy(*Ops0);

  std::tie(Ops1, std::ignore) = TL->getLegalizedValues(I.getOperand(1));
  assert(Ops0Copy.size() == Ops1->size());

  switch (I.getOpcode()) {
  case Instruction::And:
  case Instruction::Or:
  case Instruction::Xor: {
    StringRef Name = I.getName();
    for (unsigned i = 0, e = Ops0Copy.size(); i != e; ++i) {
      Value *LHS = (Ops0Copy)[i];
      Value *RHS = (*Ops1)[i];
      Expanded.push_back(
          TL->createBinOpAsGiven(&I, LHS, RHS,
            Twine(Name, getSuffix()) + Twine(i)));
    }
    break;
  }
  default:
    llvm_unreachable("UNKNOWN BINARY OPERATOR IS BEING EXPANDED!");
  }
  return true;
}

/// Memory operators
///

bool InstExpander::visitLoadInst(LoadInst &I) {
  Type *OrigTy = I.getType();

  TypeSeq *TySeq;
  std::tie(TySeq, std::ignore) = TL->getLegalizedTypes(OrigTy);

  unsigned AS = I.getPointerAddressSpace();
  // After expanding, illegal types are represented in a sequence of types
  // of the major type except the last one, which may be a different type.
  Type *MajorTy = TySeq->front();
  Type *MajorPtrTy = PointerType::get(MajorTy, AS);

  Value *OldPtr = I.getPointerOperand();
  Value *NewBasePtr =
    IRB->CreatePointerCast(OldPtr, MajorPtrTy,
        Twine(OldPtr->getName(), getSuffix()) + Twine(0));

  unsigned Part = 0;
  unsigned Off = 0;
  for (auto *Ty : *TySeq) {
    Value *NewPtr =
      TL->getPointerToElt(NewBasePtr, Part, PointerType::get(Ty, AS),
          Twine(OldPtr->getName(), getSuffix()) + Twine(Part));
    LoadInst *NewLd =
      IRB->CreateLoad(NewPtr, Twine(I.getName(), getSuffix()) + Twine(Part));
    TL->dupMemoryAttribute(NewLd, &I, Off);

    Expanded.push_back(NewLd);
    Off += TL->getTypeStoreSize(Ty);
    ++Part;
  }

  return true;
}

bool InstExpander::visitStoreInst(StoreInst &I) {
  Value *OrigVal = I.getValueOperand();
  Type *OrigTy = OrigVal->getType();

  ValueSeq *ValSeq;
  TypeSeq *TySeq;
  std::tie(ValSeq, std::ignore) = TL->getLegalizedValues(OrigVal);
  std::tie(TySeq, std::ignore) = TL->getLegalizedTypes(OrigTy);
  assert(ValSeq->size() == TySeq->size());

  unsigned AS = I.getPointerAddressSpace();

  // After expanding, illegal types are represented in a sequence of types
  // of the major type except the last one, which may be a different type.
  Type *MajorTy = TySeq->front();
  Type *MajorPtrTy = PointerType::get(MajorTy, AS);

  Value *OldPtr = I.getPointerOperand();
  Value *NewBasePtr =
    IRB->CreatePointerCast(OldPtr, MajorPtrTy,
        Twine(OldPtr->getName(), getSuffix()) + Twine(0));

  unsigned Part = 0;
  unsigned Off = 0;
  for (auto *Ty : *TySeq) {
    Value *NewPtr =
      TL->getPointerToElt(NewBasePtr, Part, PointerType::get(Ty, AS),
          Twine(OldPtr->getName(), getSuffix()) + Twine(Part));
    StoreInst *NewSt = IRB->CreateStore((*ValSeq)[Part], NewPtr);
    TL->dupMemoryAttribute(NewSt, &I, Off);

    Off += TL->getTypeStoreSize(Ty);
    ++Part;
  }

  return true;
}

/// Cast operators
///

bool InstExpander::visitTruncInst(TruncInst &I) {
  ValueSeq *ValSeq;
  std::tie(ValSeq, std::ignore) = TL->getLegalizedValues(I.getOperand(0));
  assert(ValSeq->size() > 1);

  TypeSeq *TySeq; LegalizeAction Act;
  std::tie(TySeq, Act) = TL->getLegalizedTypes(I.getDestTy());

  if (Act == Legal) {
    Value *Val = ValSeq->front();

    if (Val->getType() == I.getType())
      I.replaceAllUsesWith(Val);
    else
      I.setOperand(0, Val);

    return true;
  }

  assert(TySeq->size() <= ValSeq->size());

  unsigned Part = 0;
  for (auto *Ty : *TySeq) {
    Value *Val = (*ValSeq)[Part];
    assert(isa<IntegerType>(Ty) && isa<IntegerType>(Val->getType()));
    assert(cast<IntegerType>(Val->getType())->getBitWidth() >=
           cast<IntegerType>(Ty)->getBitWidth());

    Expanded.push_back(
        IRB->CreateTrunc(Val, Ty,
          Twine(I.getName(), getSuffix()) + Twine(Part)));
    ++Part;
  }

  return true;
}

bool InstExpander::visitZExtInst(ZExtInst &I) {
  ValueSeq *ValSeq; LegalizeAction Act;
  std::tie(ValSeq, Act) = TL->getLegalizedValues(I.getOperand(0));

  ValueSeq LegalVal;
  switch (Act) {
  case Legal:
    LegalVal.push_back(I.getOperand(0));
    ValSeq = &LegalVal;
    break;
  case Promote:
    LegalVal.push_back(TL->zext(ValSeq->front(), I.getSrcTy()));
    ValSeq = &LegalVal;
    break;
  default:
    break;
  }

  TypeSeq *TySeq;
  std::tie(TySeq, std::ignore) = TL->getLegalizedTypes(I.getDestTy());

  assert(TySeq->size() >= ValSeq->size());

  unsigned Part = 0;
  for (auto *Ty : *TySeq) {
    Value *Val =
      Part < ValSeq->size() ? (*ValSeq)[Part] : Constant::getNullValue(Ty);
    assert(isa<IntegerType>(Ty) && isa<IntegerType>(Val->getType()));
    assert(cast<IntegerType>(Val->getType())->getBitWidth() <=
           cast<IntegerType>(Ty)->getBitWidth());

    if (Ty != Val->getType())
      Expanded.push_back(IRB->CreateZExt(Val, Ty, Twine(Val->getName(), ".zext")));
    else
      Expanded.push_back(Val);
    ++Part;
  }

  return true;
}

bool InstExpander::visitBitCastInst(BitCastInst &I) {
  ValueSeq *ValSeq; LegalizeAction ValAct;
  std::tie(ValSeq, ValAct) = TL->getLegalizedValues(I.getOperand(0));

  ValueSeq LegalVal;
  if (ValAct == Legal) {
    LegalVal.push_back(I.getOperand(0));
    ValSeq = &LegalVal;
  }

  TypeSeq *TySeq; LegalizeAction Act;
  std::tie(TySeq, Act) = TL->getLegalizedTypes(I.getDestTy());

  TypeSeq LegalTy;
  if (Act == Legal) {
    LegalTy.push_back(I.getDestTy());
    TySeq = &LegalTy;
  }

  ValueSeq Repacked;
  TL->repack(&Repacked, *TySeq, *ValSeq, I.getName() + getSuffix());

  if (Act == Legal) {
    assert(Repacked.size() == 1);

    I.replaceAllUsesWith(Repacked.front());
    return true;
  }

  std::swap(Expanded, Repacked);

  return true;
}
