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

Copyright (c) 2017 Intel Corporation

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The above copyright notice and this permission notice shall be included
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======================= end_copyright_notice ==================================*/
//
// AlignmentInfo is a cache of information on the alignment of instruction
// values in a function. Alignment is stored as LogAlign and ExtraBits
// (ExtraBits < 1 << LogAlign) where a value is known to be
// A << LogAlign | ExtraBits.
//
// For a vector value, the alignment information is for element 0.
//
// The alignment of a value is computed as it is required, rather than all
// values in a function being computed in a separate analysis pass.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "GENX_ALIGNMENT_INFO"

#include "IGC/common/StringMacros.hpp"

#include <algorithm>
#include "GenX.h"
#include "GenXAlignmentInfo.h"
#include "GenXBaling.h"
#include "GenXRegion.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/Support/Debug.h"
#include <set>
#include "Probe/Assertion.h"

using namespace llvm;
using namespace genx;

/***********************************************************************
 * AlignmentInfo::get : get the aligmment of a Value
 *
 * Return:  the Alignment
 */
Alignment AlignmentInfo::get(Value *V)
{
  if (auto C = dyn_cast<Constant>(V))
    return Alignment(C);
  auto Inst = dyn_cast<Instruction>(V);

  if (!Inst) {
    // An Argument has unknown alignment.
    // (FIXME: We may need to do better than this, tracing the value of the
    // Argument at call sites, when arg indirection is introduced.)
    return Alignment::getUnknown();
  }
  auto MapEntry = &InstMap[Inst];
  if (!MapEntry->isUncomputed())
    return *MapEntry; // already in cache
  // Need to compute for this instruction.
  LLVM_DEBUG(dbgs() << "AlignmentInfo::get: computing alignment for " << Inst->getName() << "\n");
  // Get the web of instructions related to this one, including going through
  // phi nodes, excluding ones that we already have alignment for.
  std::set<Instruction *> InstWebSet;
  SmallVector<Instruction *, 8> InstWeb;
  InstWebSet.insert(Inst);
  InstWeb.push_back(Inst);
  for (unsigned i = 0; i != InstWeb.size(); ++i) {
    auto WorkInst = InstWeb[i];
    if (auto Phi = dyn_cast<PHINode>(WorkInst)) {
      for (unsigned ii = 0, ie = Phi->getNumIncomingValues(); ii != ie; ++ii)
        if (auto IncomingInst = dyn_cast<Instruction>(Phi->getIncomingValue(ii)))
          if (InstMap.find(IncomingInst) == InstMap.end()
              && InstWebSet.insert(IncomingInst).second)
            InstWeb.push_back(IncomingInst);
    } else if (isa<BinaryOperator>(WorkInst) || isa<CastInst>(WorkInst)) {
      for (unsigned oi = 0, oe = WorkInst->getNumOperands(); oi != oe; ++oi)
        if (auto IncomingInst = dyn_cast<Instruction>(WorkInst->getOperand(oi)))
          if (InstMap.find(IncomingInst) == InstMap.end()
              && InstWebSet.insert(IncomingInst).second)
            InstWeb.push_back(IncomingInst);
    } else if (CastInst *CI = dyn_cast<CastInst>(WorkInst)) {
      if (auto IncomingInst = dyn_cast<Instruction>(WorkInst->getOperand(0)))
        if (InstMap.find(IncomingInst) == InstMap.end()
          && InstWebSet.insert(IncomingInst).second)
          InstWeb.push_back(IncomingInst);
    } else
      switch (GenXIntrinsic::getGenXIntrinsicID(WorkInst)) {
      case GenXIntrinsic::genx_rdregioni:
      case GenXIntrinsic::genx_rdregionf:
      case GenXIntrinsic::genx_convert:
      case GenXIntrinsic::genx_convert_addr:
        if (auto IncomingInst = dyn_cast<Instruction>(WorkInst->getOperand(0)))
          if (InstMap.find(IncomingInst) == InstMap.end()
              && InstWebSet.insert(IncomingInst).second)
            InstWeb.push_back(IncomingInst);
        break;
      case GenXIntrinsic::genx_ssmad:
      case GenXIntrinsic::genx_uumad:
      case GenXIntrinsic::genx_add_addr:
        for (unsigned oi = 0, oe = WorkInst->getNumOperands(); oi != oe; ++oi)
          if (auto IncomingInst = dyn_cast<Instruction>(WorkInst->getOperand(oi)))
            if (InstMap.find(IncomingInst) == InstMap.end()
              && InstWebSet.insert(IncomingInst).second)
              InstWeb.push_back(IncomingInst);
        break;
      default:
        break;
    }
  }
  LLVM_DEBUG(dbgs() << "web:";
        for (unsigned i = 0, e = InstWeb.size(); i != e; ++i)
          dbgs() << " " << InstWeb[i]->getName();
        dbgs() << "\n");
  // Use a worklist algorithm where each instruction in the web is initially on
  // the worklist.
  std::set<Instruction *> WorkSet;
  for (auto i = InstWeb.begin(), e = InstWeb.end(); i != e; ++i)
    WorkSet.insert(*i);
  while (!InstWeb.empty()) {
    Instruction *WorkInst = InstWeb.back();
    InstWeb.pop_back();
    WorkSet.erase(WorkInst);
    LLVM_DEBUG(dbgs() << "  processing " << WorkInst->getName() << "\n");

    Alignment A(0, 0); // assume unknown
    if (BinaryOperator *BO = dyn_cast<BinaryOperator>(WorkInst)) {
      A = Alignment(); // assume uncomputed
      auto *Op0 = BO->getOperand(0);
      auto *Op1 = BO->getOperand(1);
      Alignment A0 = getFromInstMap(Op0);
      Alignment A1 = getFromInstMap(Op1);
      if (!A0.isUncomputed() && !A1.isUncomputed()) {
        switch (BO->getOpcode()) {
          case Instruction::Add:
            A = A0.add(A1);
            break;
          case Instruction::Sub:
            if (A1.isConstant())
              A = A0.add(-(A1.getConstBits()));
            else
              A = Alignment::getUnknown();
            break;
          case Instruction::Mul:
            A = A0.mul(A1);
            break;
          case Instruction::Shl:
            if (A1.isConstant()) {
              A1 = Alignment(A1.getConstBits(), 0);
              A = A0.mul(A1);
            } else
              A = Alignment::getUnknown();
            break;
          case Instruction::And:
            if (auto *CI0 = dyn_cast<ConstantInt>(Op0)) {
              A = A1.logicalAnd(CI0);
            } else if (auto *CI1 = dyn_cast<ConstantInt>(Op1)) {
              A = A0.logicalAnd(CI1);
            } else
              A = Alignment::getUnknown();
            break;
          default:
            A = Alignment::getUnknown();
            break;
        }
      }
    } else if (CastInst *CI = dyn_cast<CastInst>(WorkInst)) {
      // Handle a bitcast for the same reason as above. This also handles
      // trunc, sext, zext.
      A = getFromInstMap(CI->getOperand(0));
      if (!A.isUncomputed()) {
        unsigned LogAlign = A.getLogAlign(), ExtraBits = A.getExtraBits();
        LogAlign = std::min(
            LogAlign,
            static_cast<unsigned>(
                CI->getType()->getScalarType()->getPrimitiveSizeInBits()));
        if (LogAlign < 32)
          ExtraBits &= (1 << LogAlign) - 1;
        A = Alignment(LogAlign, ExtraBits);
      } else if (!CI->isIntegerCast()) {
        // For no-only-integer cast instructions - FPToUI, FPToSI
        A = Alignment::getUnknown();
      }
    } else if (auto Phi = dyn_cast<PHINode>(WorkInst)) {
      // For a phi node, ignore uncomputed incomings so we have an initial
      // guess at alignment value to propagate round a loop and refine in
      // a later visit to this same phi node.
      A = Alignment(); // initialize to uncomputed
      for (unsigned ii = 0, ie = Phi->getNumIncomingValues(); ii != ie; ++ii) {
        LLVM_DEBUG(dbgs() << "  incoming: " << *Phi->getIncomingValue(ii) << "\n");
        LLVM_DEBUG(dbgs() << "  merging " << A << " and " << getFromInstMap(Phi->getIncomingValue(ii)) << "\n");
        A = A.merge(getFromInstMap(Phi->getIncomingValue(ii)));
        LLVM_DEBUG(dbgs() << "  giving " << A << "\n");
      }
    } else {
      switch (GenXIntrinsic::getGenXIntrinsicID(WorkInst)) {
        case GenXIntrinsic::genx_rdregioni:
        case GenXIntrinsic::genx_rdregionf: {
          // Handle the case of reading a scalar from element of a vector, as
          // a trunc from i32 to i16 is lowered to a bitcast to v2i16 then a
          // rdregion.
          Region R(WorkInst, BaleInfo());
          if (!R.Indirect && (R.NumElements == 1))
            A = getFromInstMap(WorkInst->getOperand(0));
          else
            A = Alignment(0, 0);
          break;
        }
        case GenXIntrinsic::genx_constanti:
          A = Alignment(cast<Constant>(WorkInst->getOperand(0)));
          break;
        case GenXIntrinsic::genx_convert:
        case GenXIntrinsic::genx_convert_addr:
          A = getFromInstMap(WorkInst->getOperand(0));
          break;
        case GenXIntrinsic::genx_add_addr: {
          Alignment AA[2];
          for (unsigned oi = 0, oe = WorkInst->getNumOperands(); oi != oe && oi < 2; ++oi)
            AA[oi] = getFromInstMap(WorkInst->getOperand(oi));
          if (!AA[0].isUncomputed() && !AA[1].isUncomputed())
            A = AA[0].add(AA[1]);
          else
            A = Alignment(0, 0);
          break;
        }
        case GenXIntrinsic::genx_ssmad:
        case GenXIntrinsic::genx_uumad: {
          A = Alignment(); // assume uncomputed
          // every source operand should be computed or constant
          Alignment SA[3];
          for (unsigned oi = 0, oe = WorkInst->getNumOperands(); oi != oe && oi < 3; ++oi)
            SA[oi] = getFromInstMap(WorkInst->getOperand(oi));
          if (!SA[0].isUncomputed() && !SA[1].isUncomputed() && !SA[2].isUncomputed())
            A = SA[0].mul(SA[1]).add(SA[2]);
          else
            A = Alignment(0, 0);
          break;
        }
        default:
          A = Alignment(0, 0); // no alignment info
          break;
      }
    }
    // See if the alignment has changed for WorkInst.
    auto MapEntry = &InstMap[WorkInst];
    if (*MapEntry == A)
      continue; // no change
    *MapEntry = A;
    LLVM_DEBUG(dbgs() << "  " << WorkInst->getName() << " updated to " << A << "\n");
    // Add all users that are in the original web to the worklist, if
    // not already in the worklist.
    for (auto ui = WorkInst->use_begin(), ue = WorkInst->use_end();
        ui != ue; ++ui) {
      auto user = cast<Instruction>(ui->getUser());
      if (InstWebSet.find(user) != InstWebSet.end()
          && WorkSet.insert(user).second)
        InstWeb.push_back(user);
    }
  }
  MapEntry = &InstMap[Inst];
  IGC_ASSERT(!MapEntry->isUncomputed());
  LLVM_DEBUG(dbgs() << "AlignmentInfo::get: returning " << *MapEntry << "\n");
  return *MapEntry;
}

/***********************************************************************
 * Alignment constructor given literal value
 */
Alignment::Alignment(unsigned C)
{
  LogAlign = countTrailingZeros(C);
  ExtraBits = 0;
  ConstBits = (C < MaskForUnknown) ? C : MaskForUnknown;
}

Alignment Alignment::getAlignmentForConstant(Constant *C) {
  IGC_ASSERT(!isa<VectorType>(C->getType()));
  Alignment A;
  A.setUncomputed();
  if (isa<UndefValue>(C)) {
    A.LogAlign = 31;
    A.ExtraBits = 0;
    A.ConstBits = MaskForUnknown;
  } else if (auto CI = dyn_cast<ConstantInt>(C)) {
    int64_t SVal = CI->getSExtValue();
    // Get least significant bits to count LogAlign
    unsigned LSBBits = SVal & UnsignedAllOnes;
    A.LogAlign = countTrailingZeros(LSBBits);

    A.ExtraBits = 0;
    A.ConstBits = MaskForUnknown;
    if (SVal < MaskForUnknown && SVal >= 0 &&
        SVal <= std::numeric_limits<unsigned>::max())
      A.ConstBits = static_cast<unsigned>(SVal);
  }
  return A;
}

/***********************************************************************
 * Alignment constructor given Constant
 */
Alignment::Alignment(Constant *C)
{
  setUncomputed();
  if (auto *VT = dyn_cast<VectorType>(C->getType())) {
    // Take splat if exists
    if (auto *SplatVal = C->getSplatValue())
      C = SplatVal;
    else {
      // Otherwise be conservative and pretend alignment
      // unknown for non-splat vectors
      *this = Alignment::getUnknown();
      return;
    }
  }
  *this = getAlignmentForConstant(C);
}

/***********************************************************************
 * merge : merge two alignments
 */
Alignment Alignment::merge(Alignment Other) const
{
  // If either is uncomputed, result is the other one.
  if (isUncomputed())
    return Other;
  if (Other.isUncomputed())
    return *this;
  // Take the minimum of the two logaligns, then chop off some more for
  // disagreeing extrabits.
  unsigned MinLogAlign = std::min(LogAlign, Other.LogAlign);
  if (MinLogAlign) {
    unsigned DisagreeExtraBits = (ExtraBits ^ Other.ExtraBits)
      & ((1 << MinLogAlign) - 1);
    MinLogAlign = std::min(MinLogAlign,
      (unsigned)countTrailingZeros(DisagreeExtraBits, ZB_Width));
  }
  return Alignment(MinLogAlign, ExtraBits & ((1 << MinLogAlign) - 1));
}

/***********************************************************************
 * merge : add two alignments
 */
Alignment Alignment::add(Alignment Other) const
{
  IGC_ASSERT(!isUncomputed() && !Other.isUncomputed());
  // Take the minimum of the two logaligns, then chop off some more for
  // disagreeing extrabits.
  unsigned MinLogAlign = std::min(LogAlign, Other.LogAlign);
  unsigned ExtraBits2 = 0;
  if (MinLogAlign) {
    ExtraBits2 = (ExtraBits + Other.ExtraBits)
      & ((1 << MinLogAlign) - 1);
    MinLogAlign = std::min(MinLogAlign,
      (unsigned)countTrailingZeros(ExtraBits2, ZB_Width));
  }
  return Alignment(MinLogAlign, ExtraBits2 & ((1 << MinLogAlign) - 1));
}

/***********************************************************************
* merge : mul two alignments
*/
Alignment Alignment::mul(Alignment Other) const
{
  IGC_ASSERT(!isUncomputed() && !Other.isUncomputed());
  // Take the minimum of the two logaligns, then chop off some more for
  // disagreeing extrabits.
  unsigned MinLogAlign = std::min(LogAlign, Other.LogAlign);
  if (ExtraBits == 0 && Other.ExtraBits == 0)
    MinLogAlign = LogAlign + Other.LogAlign;
  else if (ExtraBits == 0)
    MinLogAlign = LogAlign;
  else if (Other.ExtraBits == 0)
    MinLogAlign = Other.LogAlign;
  unsigned ExtraBits2 = 0;
  if (MinLogAlign) {
    ExtraBits2 = (ExtraBits * Other.ExtraBits)
      & ((1 << MinLogAlign) - 1);
    MinLogAlign = std::min(MinLogAlign,
      (unsigned)countTrailingZeros(ExtraBits2, ZB_Width));
  }
  return Alignment(MinLogAlign, ExtraBits2 & ((1 << MinLogAlign) - 1));
}

/***********************************************************************
 * logicalAnd : logical and two alignments. Only constant int supported.
 */
Alignment Alignment::logicalAnd(ConstantInt *CI) const {
  IGC_ASSERT(!isUncomputed() && CI);
  // If value doesn't fit into unsigned then be conservative and pretend
  // that alignement is unknown
  int64_t Val = CI->getSExtValue();
  if (Val < std::numeric_limits<int>::min() ||
      Val > std::numeric_limits<int>::max())
    return Alignment::getUnknown();
  unsigned UVal = static_cast<unsigned>(std::abs(Val));
  unsigned ValLSB = countTrailingZeros(UVal, ZB_Width);
  // Chop off constant bits according to maximum log align
  unsigned NewLogAlign = std::max(ValLSB, LogAlign);
  return Alignment(NewLogAlign, UVal & ((1 << NewLogAlign) - 1));
}

/***********************************************************************
 * getFromInstMap : get the alignment of a value, direct from InstMap if
 * found else return Unknown, Alignment(0, 0)
 */
Alignment AlignmentInfo::getFromInstMap(Value *V)
{
  if (auto C = dyn_cast<Constant>(V))
    return Alignment(C);
  if (auto Inst = dyn_cast<Instruction>(V)) {
    return InstMap[V];
  }
  return Alignment::getUnknown();
}

/***********************************************************************
 * Alignment debug dump/print
 */
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void Alignment::dump() const
{
  errs() << *this << "\n";
}
#endif

void Alignment::print(raw_ostream &OS) const
{
  if (isUncomputed())
    OS << "uncomputed";
  else if (isUnknown())
    OS << "unknown";
  else if (isConstant())
    OS << "const=" << ConstBits;
  else
    OS << "n<<" << LogAlign << "+" << ExtraBits;
}
