//===-- SparcISelDAGToDAG.cpp - A dag to dag inst selector for Sparc ------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines an instruction selector for the SPARC target.
//
//===----------------------------------------------------------------------===//

#include "SparcTargetMachine.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

#define DEBUG_TYPE "sparc-isel"
#define PASS_NAME "SPARC DAG->DAG Pattern Instruction Selection"

//===----------------------------------------------------------------------===//
// Instruction Selector Implementation
//===----------------------------------------------------------------------===//

//===--------------------------------------------------------------------===//
/// SparcDAGToDAGISel - SPARC specific code to select SPARC machine
/// instructions for SelectionDAG operations.
///
namespace {
class SparcDAGToDAGISel : public SelectionDAGISel {
  /// Subtarget - Keep a pointer to the Sparc Subtarget around so that we can
  /// make the right decision when generating code for different targets.
  const SparcSubtarget *Subtarget = nullptr;

public:
  SparcDAGToDAGISel() = delete;

  explicit SparcDAGToDAGISel(SparcTargetMachine &tm) : SelectionDAGISel(tm) {}

  bool runOnMachineFunction(MachineFunction &MF) override {
    Subtarget = &MF.getSubtarget<SparcSubtarget>();
    return SelectionDAGISel::runOnMachineFunction(MF);
  }

  void Select(SDNode *N) override;

  // Complex Pattern Selectors.
  bool SelectADDRrr(SDValue N, SDValue &R1, SDValue &R2);
  bool SelectADDRri(SDValue N, SDValue &Base, SDValue &Offset);

  /// SelectInlineAsmMemoryOperand - Implement addressing mode selection for
  /// inline asm expressions.
  bool SelectInlineAsmMemoryOperand(const SDValue &Op,
                                    InlineAsm::ConstraintCode ConstraintID,
                                    std::vector<SDValue> &OutOps) override;

  // Include the pieces autogenerated from the target description.
#include "SparcGenDAGISel.inc"

private:
  SDNode* getGlobalBaseReg();
  bool tryInlineAsm(SDNode *N);
};

class SparcDAGToDAGISelLegacy : public SelectionDAGISelLegacy {
public:
  static char ID;
  explicit SparcDAGToDAGISelLegacy(SparcTargetMachine &tm)
      : SelectionDAGISelLegacy(ID, std::make_unique<SparcDAGToDAGISel>(tm)) {}
};
}  // end anonymous namespace

char SparcDAGToDAGISelLegacy::ID = 0;

INITIALIZE_PASS(SparcDAGToDAGISelLegacy, DEBUG_TYPE, PASS_NAME, false, false)

SDNode* SparcDAGToDAGISel::getGlobalBaseReg() {
  Register GlobalBaseReg = Subtarget->getInstrInfo()->getGlobalBaseReg(MF);
  return CurDAG->getRegister(GlobalBaseReg,
                             TLI->getPointerTy(CurDAG->getDataLayout()))
      .getNode();
}

bool SparcDAGToDAGISel::SelectADDRri(SDValue Addr,
                                     SDValue &Base, SDValue &Offset) {
  if (FrameIndexSDNode *FIN = dyn_cast<FrameIndexSDNode>(Addr)) {
    Base = CurDAG->getTargetFrameIndex(
        FIN->getIndex(), TLI->getPointerTy(CurDAG->getDataLayout()));
    Offset = CurDAG->getTargetConstant(0, SDLoc(Addr), MVT::i32);
    return true;
  }
  if (Addr.getOpcode() == ISD::TargetExternalSymbol ||
      Addr.getOpcode() == ISD::TargetGlobalAddress ||
      Addr.getOpcode() == ISD::TargetGlobalTLSAddress)
    return false;  // direct calls.

  if (Addr.getOpcode() == ISD::ADD) {
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Addr.getOperand(1))) {
      if (isInt<13>(CN->getSExtValue())) {
        if (FrameIndexSDNode *FIN =
                dyn_cast<FrameIndexSDNode>(Addr.getOperand(0))) {
          // Constant offset from frame ref.
          Base = CurDAG->getTargetFrameIndex(
              FIN->getIndex(), TLI->getPointerTy(CurDAG->getDataLayout()));
        } else {
          Base = Addr.getOperand(0);
        }
        Offset = CurDAG->getTargetConstant(CN->getZExtValue(), SDLoc(Addr),
                                           MVT::i32);
        return true;
      }
    }
    if (Addr.getOperand(0).getOpcode() == SPISD::Lo) {
      Base = Addr.getOperand(1);
      Offset = Addr.getOperand(0).getOperand(0);
      return true;
    }
    if (Addr.getOperand(1).getOpcode() == SPISD::Lo) {
      Base = Addr.getOperand(0);
      Offset = Addr.getOperand(1).getOperand(0);
      return true;
    }
  }
  Base = Addr;
  Offset = CurDAG->getTargetConstant(0, SDLoc(Addr), MVT::i32);
  return true;
}

bool SparcDAGToDAGISel::SelectADDRrr(SDValue Addr, SDValue &R1, SDValue &R2) {
  if (Addr.getOpcode() == ISD::FrameIndex) return false;
  if (Addr.getOpcode() == ISD::TargetExternalSymbol ||
      Addr.getOpcode() == ISD::TargetGlobalAddress ||
      Addr.getOpcode() == ISD::TargetGlobalTLSAddress)
    return false;  // direct calls.

  if (Addr.getOpcode() == ISD::ADD) {
    if (ConstantSDNode *CN = dyn_cast<ConstantSDNode>(Addr.getOperand(1)))
      if (isInt<13>(CN->getSExtValue()))
        return false;  // Let the reg+imm pattern catch this!
    if (Addr.getOperand(0).getOpcode() == SPISD::Lo ||
        Addr.getOperand(1).getOpcode() == SPISD::Lo)
      return false;  // Let the reg+imm pattern catch this!
    R1 = Addr.getOperand(0);
    R2 = Addr.getOperand(1);
    return true;
  }

  R1 = Addr;
  R2 = CurDAG->getRegister(SP::G0, TLI->getPointerTy(CurDAG->getDataLayout()));
  return true;
}


// Re-assemble i64 arguments split up in SelectionDAGBuilder's
// visitInlineAsm / GetRegistersForValue functions.
//
// Note: This function was copied from, and is essentially identical
// to ARMISelDAGToDAG::SelectInlineAsm. It is very unfortunate that
// such hacking-up is necessary; a rethink of how inline asm operands
// are handled may be in order to make doing this more sane.
//
// TODO: fix inline asm support so I can simply tell it that 'i64'
// inputs to asm need to be allocated to the IntPair register type,
// and have that work. Then, delete this function.
bool SparcDAGToDAGISel::tryInlineAsm(SDNode *N){
  std::vector<SDValue> AsmNodeOperands;
  InlineAsm::Flag Flag;
  bool Changed = false;
  unsigned NumOps = N->getNumOperands();

  // Normally, i64 data is bounded to two arbitrary GPRs for "%r"
  // constraint.  However, some instructions (e.g. ldd/std) require
  // (even/even+1) GPRs.

  // So, here, we check for this case, and mutate the inlineasm to use
  // a single IntPair register instead, which guarantees such even/odd
  // placement.

  SDLoc dl(N);
  SDValue Glue = N->getGluedNode() ? N->getOperand(NumOps - 1) : SDValue();

  SmallVector<bool, 8> OpChanged;
  // Glue node will be appended late.
  for(unsigned i = 0, e = N->getGluedNode() ? NumOps - 1 : NumOps; i < e; ++i) {
    SDValue op = N->getOperand(i);
    AsmNodeOperands.push_back(op);

    if (i < InlineAsm::Op_FirstOperand)
      continue;

    if (const auto *C = dyn_cast<ConstantSDNode>(N->getOperand(i)))
      Flag = InlineAsm::Flag(C->getZExtValue());
    else
      continue;

    // Immediate operands to inline asm in the SelectionDAG are modeled with
    // two operands. The first is a constant of value InlineAsm::Kind::Imm, and
    // the second is a constant with the value of the immediate. If we get here
    // and we have a Kind::Imm, skip the next operand, and continue.
    if (Flag.isImmKind()) {
      SDValue op = N->getOperand(++i);
      AsmNodeOperands.push_back(op);
      continue;
    }

    const unsigned NumRegs = Flag.getNumOperandRegisters();
    if (NumRegs)
      OpChanged.push_back(false);

    unsigned DefIdx = 0;
    bool IsTiedToChangedOp = false;
    // If it's a use that is tied with a previous def, it has no
    // reg class constraint.
    if (Changed && Flag.isUseOperandTiedToDef(DefIdx))
      IsTiedToChangedOp = OpChanged[DefIdx];

    if (!Flag.isRegUseKind() && !Flag.isRegDefKind() &&
        !Flag.isRegDefEarlyClobberKind())
      continue;

    unsigned RC;
    const bool HasRC = Flag.hasRegClassConstraint(RC);
    if ((!IsTiedToChangedOp && (!HasRC || RC != SP::IntRegsRegClassID))
        || NumRegs != 2)
      continue;

    assert((i+2 < NumOps) && "Invalid number of operands in inline asm");
    SDValue V0 = N->getOperand(i+1);
    SDValue V1 = N->getOperand(i+2);
    Register Reg0 = cast<RegisterSDNode>(V0)->getReg();
    Register Reg1 = cast<RegisterSDNode>(V1)->getReg();
    SDValue PairedReg;
    MachineRegisterInfo &MRI = MF->getRegInfo();

    if (Flag.isRegDefKind() || Flag.isRegDefEarlyClobberKind()) {
      // Replace the two GPRs with 1 GPRPair and copy values from GPRPair to
      // the original GPRs.

      Register GPVR = MRI.createVirtualRegister(&SP::IntPairRegClass);
      PairedReg = CurDAG->getRegister(GPVR, MVT::v2i32);
      SDValue Chain = SDValue(N,0);

      SDNode *GU = N->getGluedUser();
      SDValue RegCopy = CurDAG->getCopyFromReg(Chain, dl, GPVR, MVT::v2i32,
                                               Chain.getValue(1));

      // Extract values from a GPRPair reg and copy to the original GPR reg.
      SDValue Sub0 = CurDAG->getTargetExtractSubreg(SP::sub_even, dl, MVT::i32,
                                                    RegCopy);
      SDValue Sub1 = CurDAG->getTargetExtractSubreg(SP::sub_odd, dl, MVT::i32,
                                                    RegCopy);
      SDValue T0 = CurDAG->getCopyToReg(Sub0, dl, Reg0, Sub0,
                                        RegCopy.getValue(1));
      SDValue T1 = CurDAG->getCopyToReg(Sub1, dl, Reg1, Sub1, T0.getValue(1));

      // Update the original glue user.
      std::vector<SDValue> Ops(GU->op_begin(), GU->op_end()-1);
      Ops.push_back(T1.getValue(1));
      CurDAG->UpdateNodeOperands(GU, Ops);
    } else {
      // For Kind  == InlineAsm::Kind::RegUse, we first copy two GPRs into a
      // GPRPair and then pass the GPRPair to the inline asm.
      SDValue Chain = AsmNodeOperands[InlineAsm::Op_InputChain];

      // As REG_SEQ doesn't take RegisterSDNode, we copy them first.
      SDValue T0 = CurDAG->getCopyFromReg(Chain, dl, Reg0, MVT::i32,
                                          Chain.getValue(1));
      SDValue T1 = CurDAG->getCopyFromReg(Chain, dl, Reg1, MVT::i32,
                                          T0.getValue(1));
      SDValue Pair = SDValue(
          CurDAG->getMachineNode(
              TargetOpcode::REG_SEQUENCE, dl, MVT::v2i32,
              {
                  CurDAG->getTargetConstant(SP::IntPairRegClassID, dl,
                                            MVT::i32),
                  T0,
                  CurDAG->getTargetConstant(SP::sub_even, dl, MVT::i32),
                  T1,
                  CurDAG->getTargetConstant(SP::sub_odd, dl, MVT::i32),
              }),
          0);

      // Copy REG_SEQ into a GPRPair-typed VR and replace the original two
      // i32 VRs of inline asm with it.
      Register GPVR = MRI.createVirtualRegister(&SP::IntPairRegClass);
      PairedReg = CurDAG->getRegister(GPVR, MVT::v2i32);
      Chain = CurDAG->getCopyToReg(T1, dl, GPVR, Pair, T1.getValue(1));

      AsmNodeOperands[InlineAsm::Op_InputChain] = Chain;
      Glue = Chain.getValue(1);
    }

    Changed = true;

    if(PairedReg.getNode()) {
      OpChanged[OpChanged.size() -1 ] = true;
      Flag = InlineAsm::Flag(Flag.getKind(), 1 /* RegNum*/);
      if (IsTiedToChangedOp)
        Flag.setMatchingOp(DefIdx);
      else
        Flag.setRegClass(SP::IntPairRegClassID);
      // Replace the current flag.
      AsmNodeOperands[AsmNodeOperands.size() -1] = CurDAG->getTargetConstant(
          Flag, dl, MVT::i32);
      // Add the new register node and skip the original two GPRs.
      AsmNodeOperands.push_back(PairedReg);
      // Skip the next two GPRs.
      i += 2;
    }
  }

  if (Glue.getNode())
    AsmNodeOperands.push_back(Glue);
  if (!Changed)
    return false;

  SelectInlineAsmMemoryOperands(AsmNodeOperands, SDLoc(N));

  SDValue New = CurDAG->getNode(N->getOpcode(), SDLoc(N),
      CurDAG->getVTList(MVT::Other, MVT::Glue), AsmNodeOperands);
  New->setNodeId(-1);
  ReplaceNode(N, New.getNode());
  return true;
}

void SparcDAGToDAGISel::Select(SDNode *N) {
  SDLoc dl(N);
  if (N->isMachineOpcode()) {
    N->setNodeId(-1);
    return;   // Already selected.
  }

  switch (N->getOpcode()) {
  default: break;
  case ISD::INLINEASM:
  case ISD::INLINEASM_BR: {
    if (tryInlineAsm(N))
      return;
    break;
  }
  case SPISD::GLOBAL_BASE_REG:
    ReplaceNode(N, getGlobalBaseReg());
    return;

  case ISD::SDIV:
  case ISD::UDIV: {
    // sdivx / udivx handle 64-bit divides.
    if (N->getValueType(0) == MVT::i64)
      break;
    // FIXME: should use a custom expander to expose the SRA to the dag.
    SDValue DivLHS = N->getOperand(0);
    SDValue DivRHS = N->getOperand(1);

    // Set the Y register to the high-part.
    SDValue TopPart;
    if (N->getOpcode() == ISD::SDIV) {
      TopPart = SDValue(CurDAG->getMachineNode(SP::SRAri, dl, MVT::i32, DivLHS,
                                   CurDAG->getTargetConstant(31, dl, MVT::i32)),
                        0);
    } else {
      TopPart = CurDAG->getRegister(SP::G0, MVT::i32);
    }
    TopPart = CurDAG->getCopyToReg(CurDAG->getEntryNode(), dl, SP::Y, TopPart,
                                   SDValue())
                  .getValue(1);

    // FIXME: Handle div by immediate.
    unsigned Opcode = N->getOpcode() == ISD::SDIV ? SP::SDIVrr : SP::UDIVrr;
    CurDAG->SelectNodeTo(N, Opcode, MVT::i32, DivLHS, DivRHS, TopPart);
    return;
  }
  }

  SelectCode(N);
}


/// SelectInlineAsmMemoryOperand - Implement addressing mode selection for
/// inline asm expressions.
bool SparcDAGToDAGISel::SelectInlineAsmMemoryOperand(
    const SDValue &Op, InlineAsm::ConstraintCode ConstraintID,
    std::vector<SDValue> &OutOps) {
  SDValue Op0, Op1;
  switch (ConstraintID) {
  default: return true;
  case InlineAsm::ConstraintCode::o:
  case InlineAsm::ConstraintCode::m: // memory
    if (!SelectADDRrr(Op, Op0, Op1))
      SelectADDRri(Op, Op0, Op1);
    break;
  }

  OutOps.push_back(Op0);
  OutOps.push_back(Op1);
  return false;
}

/// createSparcISelDag - This pass converts a legalized DAG into a
/// SPARC-specific DAG, ready for instruction scheduling.
///
FunctionPass *llvm::createSparcISelDag(SparcTargetMachine &TM) {
  return new SparcDAGToDAGISelLegacy(TM);
}