//===-- RISCVAsmParser.cpp - Parse RISCV assembly to MCInst instructions --===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "MCTargetDesc/RISCVBaseInfo.h"
#include "MCTargetDesc/RISCVMCExpr.h"
#include "MCTargetDesc/RISCVMCTargetDesc.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCParser/MCAsmLexer.h"
#include "llvm/MC/MCParser/MCParsedAsmOperand.h"
#include "llvm/MC/MCParser/MCTargetAsmParser.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/TargetRegistry.h"

using namespace llvm;

namespace {
struct RISCVOperand;

class RISCVAsmParser : public MCTargetAsmParser {
  SMLoc getLoc() const { return getParser().getTok().getLoc(); }

  bool generateImmOutOfRangeError(OperandVector &Operands, uint64_t ErrorInfo,
                                  int Lower, int Upper, Twine Msg);

  bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                               OperandVector &Operands, MCStreamer &Out,
                               uint64_t &ErrorInfo,
                               bool MatchingInlineAsm) override;

  bool ParseRegister(unsigned &RegNo, SMLoc &StartLoc, SMLoc &EndLoc) override;

  bool ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
                        SMLoc NameLoc, OperandVector &Operands) override;

  bool ParseDirective(AsmToken DirectiveID) override;

// Auto-generated instruction matching functions
#define GET_ASSEMBLER_HEADER
#include "RISCVGenAsmMatcher.inc"

  OperandMatchResultTy parseImmediate(OperandVector &Operands);
  OperandMatchResultTy parseRegister(OperandVector &Operands);
  OperandMatchResultTy parseMemOpBaseReg(OperandVector &Operands);
  OperandMatchResultTy parseOperandWithModifier(OperandVector &Operands);

  bool parseOperand(OperandVector &Operands);

public:
  enum RISCVMatchResultTy {
    Match_Dummy = FIRST_TARGET_MATCH_RESULT_TY,
#define GET_OPERAND_DIAGNOSTIC_TYPES
#include "RISCVGenAsmMatcher.inc"
#undef GET_OPERAND_DIAGNOSTIC_TYPES
  };

  static bool classifySymbolRef(const MCExpr *Expr,
                                RISCVMCExpr::VariantKind &Kind,
                                int64_t &Addend);

  RISCVAsmParser(const MCSubtargetInfo &STI, MCAsmParser &Parser,
                 const MCInstrInfo &MII, const MCTargetOptions &Options)
      : MCTargetAsmParser(Options, STI, MII) {
    setAvailableFeatures(ComputeAvailableFeatures(STI.getFeatureBits()));
  }
};

/// RISCVOperand - Instances of this class represent a parsed machine
/// instruction
struct RISCVOperand : public MCParsedAsmOperand {

  enum KindTy {
    Token,
    Register,
    Immediate,
  } Kind;

  struct RegOp {
    unsigned RegNum;
  };

  struct ImmOp {
    const MCExpr *Val;
  };

  SMLoc StartLoc, EndLoc;
  union {
    StringRef Tok;
    RegOp Reg;
    ImmOp Imm;
  };

  RISCVOperand(KindTy K) : MCParsedAsmOperand(), Kind(K) {}

public:
  RISCVOperand(const RISCVOperand &o) : MCParsedAsmOperand() {
    Kind = o.Kind;
    StartLoc = o.StartLoc;
    EndLoc = o.EndLoc;
    switch (Kind) {
    case Register:
      Reg = o.Reg;
      break;
    case Immediate:
      Imm = o.Imm;
      break;
    case Token:
      Tok = o.Tok;
      break;
    }
  }

  bool isToken() const override { return Kind == Token; }
  bool isReg() const override { return Kind == Register; }
  bool isImm() const override { return Kind == Immediate; }
  bool isMem() const override { return false; }

  bool evaluateConstantImm(int64_t &Imm, RISCVMCExpr::VariantKind &VK) const {
    const MCExpr *Val = getImm();
    bool Ret = false;
    if (auto *RE = dyn_cast<RISCVMCExpr>(Val)) {
      Ret = RE->evaluateAsConstant(Imm);
      VK = RE->getKind();
    } else if (auto CE = dyn_cast<MCConstantExpr>(Val)) {
      Ret = true;
      VK = RISCVMCExpr::VK_RISCV_None;
      Imm = CE->getValue();
    }
    return Ret;
  }

  // True if operand is a symbol with no modifiers, or a constant with no
  // modifiers and isShiftedInt<N-1, 1>(Op).
  template <int N> bool isBareSimmNLsb0() const {
    int64_t Imm;
    RISCVMCExpr::VariantKind VK;
    if (!isImm())
      return false;
    bool IsConstantImm = evaluateConstantImm(Imm, VK);
    bool IsValid;
    if (!IsConstantImm)
      IsValid = RISCVAsmParser::classifySymbolRef(getImm(), VK, Imm);
    else
      IsValid = isShiftedInt<N - 1, 1>(Imm);
    return IsValid && VK == RISCVMCExpr::VK_RISCV_None;
  }

  // Predicate methods for AsmOperands defined in RISCVInstrInfo.td

  /// Return true if the operand is a valid for the fence instruction e.g.
  /// ('iorw').
  bool isFenceArg() const {
    if (!isImm())
      return false;
    const MCExpr *Val = getImm();
    auto *SVal = dyn_cast<MCSymbolRefExpr>(Val);
    if (!SVal || SVal->getKind() != MCSymbolRefExpr::VK_None)
      return false;

    StringRef Str = SVal->getSymbol().getName();
    // Letters must be unique, taken from 'iorw', and in ascending order. This
    // holds as long as each individual character is one of 'iorw' and is
    // greater than the previous character.
    char Prev = '\0';
    for (char c : Str) {
      if (c != 'i' && c != 'o' && c != 'r' && c != 'w')
        return false;
      if (c <= Prev)
        return false;
      Prev = c;
    }
    return true;
  }

  bool isUImm5() const {
    int64_t Imm;
    RISCVMCExpr::VariantKind VK;
    if (!isImm())
      return false;
    bool IsConstantImm = evaluateConstantImm(Imm, VK);
    return IsConstantImm && isUInt<5>(Imm) && VK == RISCVMCExpr::VK_RISCV_None;
  }

  bool isSImm12() const {
    RISCVMCExpr::VariantKind VK;
    int64_t Imm;
    bool IsValid;
    if (!isImm())
      return false;
    bool IsConstantImm = evaluateConstantImm(Imm, VK);
    if (!IsConstantImm)
      IsValid = RISCVAsmParser::classifySymbolRef(getImm(), VK, Imm);
    else
      IsValid = isInt<12>(Imm);
    return IsValid &&
           (VK == RISCVMCExpr::VK_RISCV_None || VK == RISCVMCExpr::VK_RISCV_LO);
  }

  bool isUImm12() const {
    int64_t Imm;
    RISCVMCExpr::VariantKind VK;
    if (!isImm())
      return false;
    bool IsConstantImm = evaluateConstantImm(Imm, VK);
    return IsConstantImm && isUInt<12>(Imm) && VK == RISCVMCExpr::VK_RISCV_None;
  }

  bool isSImm13Lsb0() const { return isBareSimmNLsb0<13>(); }

  bool isUImm20() const {
    RISCVMCExpr::VariantKind VK;
    int64_t Imm;
    bool IsValid;
    if (!isImm())
      return false;
    bool IsConstantImm = evaluateConstantImm(Imm, VK);
    if (!IsConstantImm)
      IsValid = RISCVAsmParser::classifySymbolRef(getImm(), VK, Imm);
    else
      IsValid = isUInt<20>(Imm);
    return IsValid && (VK == RISCVMCExpr::VK_RISCV_None ||
                       VK == RISCVMCExpr::VK_RISCV_HI ||
                       VK == RISCVMCExpr::VK_RISCV_PCREL_HI);
  }

  bool isSImm21Lsb0() const { return isBareSimmNLsb0<21>(); }

  /// getStartLoc - Gets location of the first token of this operand
  SMLoc getStartLoc() const override { return StartLoc; }
  /// getEndLoc - Gets location of the last token of this operand
  SMLoc getEndLoc() const override { return EndLoc; }

  unsigned getReg() const override {
    assert(Kind == Register && "Invalid type access!");
    return Reg.RegNum;
  }

  const MCExpr *getImm() const {
    assert(Kind == Immediate && "Invalid type access!");
    return Imm.Val;
  }

  StringRef getToken() const {
    assert(Kind == Token && "Invalid type access!");
    return Tok;
  }

  void print(raw_ostream &OS) const override {
    switch (Kind) {
    case Immediate:
      OS << *getImm();
      break;
    case Register:
      OS << "<register x";
      OS << getReg() << ">";
      break;
    case Token:
      OS << "'" << getToken() << "'";
      break;
    }
  }

  static std::unique_ptr<RISCVOperand> createToken(StringRef Str, SMLoc S) {
    auto Op = make_unique<RISCVOperand>(Token);
    Op->Tok = Str;
    Op->StartLoc = S;
    Op->EndLoc = S;
    return Op;
  }

  static std::unique_ptr<RISCVOperand> createReg(unsigned RegNo, SMLoc S,
                                                 SMLoc E) {
    auto Op = make_unique<RISCVOperand>(Register);
    Op->Reg.RegNum = RegNo;
    Op->StartLoc = S;
    Op->EndLoc = E;
    return Op;
  }

  static std::unique_ptr<RISCVOperand> createImm(const MCExpr *Val, SMLoc S,
                                                 SMLoc E) {
    auto Op = make_unique<RISCVOperand>(Immediate);
    Op->Imm.Val = Val;
    Op->StartLoc = S;
    Op->EndLoc = E;
    return Op;
  }

  void addExpr(MCInst &Inst, const MCExpr *Expr) const {
    assert(Expr && "Expr shouldn't be null!");
    int64_t Imm = 0;
    bool IsConstant = false;
    if (auto *RE = dyn_cast<RISCVMCExpr>(Expr)) {
      IsConstant = RE->evaluateAsConstant(Imm);
    } else if (auto *CE = dyn_cast<MCConstantExpr>(Expr)) {
      IsConstant = true;
      Imm = CE->getValue();
    }

    if (IsConstant)
      Inst.addOperand(MCOperand::createImm(Imm));
    else
      Inst.addOperand(MCOperand::createExpr(Expr));
  }

  // Used by the TableGen Code
  void addRegOperands(MCInst &Inst, unsigned N) const {
    assert(N == 1 && "Invalid number of operands!");
    Inst.addOperand(MCOperand::createReg(getReg()));
  }

  void addImmOperands(MCInst &Inst, unsigned N) const {
    assert(N == 1 && "Invalid number of operands!");
    addExpr(Inst, getImm());
  }

  void addFenceArgOperands(MCInst &Inst, unsigned N) const {
    assert(N == 1 && "Invalid number of operands!");
    // isFenceArg has validated the operand, meaning this cast is safe
    auto SE = cast<MCSymbolRefExpr>(getImm());

    unsigned Imm = 0;
    for (char c : SE->getSymbol().getName()) {
      switch (c) {
        default: llvm_unreachable("FenceArg must contain only [iorw]");
        case 'i': Imm |= RISCVFenceField::I; break;
        case 'o': Imm |= RISCVFenceField::O; break;
        case 'r': Imm |= RISCVFenceField::R; break;
        case 'w': Imm |= RISCVFenceField::W; break;
      }
    }
    Inst.addOperand(MCOperand::createImm(Imm));
  }
};
} // end anonymous namespace.

#define GET_REGISTER_MATCHER
#define GET_MATCHER_IMPLEMENTATION
#include "RISCVGenAsmMatcher.inc"

bool RISCVAsmParser::generateImmOutOfRangeError(
    OperandVector &Operands, uint64_t ErrorInfo, int Lower, int Upper,
    Twine Msg = "immediate must be an integer in the range") {
  SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
  return Error(ErrorLoc, Msg + " [" + Twine(Lower) + ", " + Twine(Upper) + "]");
}

bool RISCVAsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
                                             OperandVector &Operands,
                                             MCStreamer &Out,
                                             uint64_t &ErrorInfo,
                                             bool MatchingInlineAsm) {
  MCInst Inst;

  switch (MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm)) {
  default:
    break;
  case Match_Success:
    Inst.setLoc(IDLoc);
    Out.EmitInstruction(Inst, getSTI());
    return false;
  case Match_MissingFeature:
    return Error(IDLoc, "instruction use requires an option to be enabled");
  case Match_MnemonicFail:
    return Error(IDLoc, "unrecognized instruction mnemonic");
  case Match_InvalidOperand: {
    SMLoc ErrorLoc = IDLoc;
    if (ErrorInfo != ~0U) {
      if (ErrorInfo >= Operands.size())
        return Error(ErrorLoc, "too few operands for instruction");

      ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
      if (ErrorLoc == SMLoc())
        ErrorLoc = IDLoc;
    }
    return Error(ErrorLoc, "invalid operand for instruction");
  }
  case Match_InvalidUImm5:
    return generateImmOutOfRangeError(Operands, ErrorInfo, 0, (1 << 5) - 1);
  case Match_InvalidSImm12:
    return generateImmOutOfRangeError(Operands, ErrorInfo, -(1 << 11),
                                      (1 << 11) - 1);
  case Match_InvalidUImm12:
    return generateImmOutOfRangeError(Operands, ErrorInfo, 0, (1 << 12) - 1);
  case Match_InvalidSImm13Lsb0:
    return generateImmOutOfRangeError(
        Operands, ErrorInfo, -(1 << 12), (1 << 12) - 2,
        "immediate must be a multiple of 2 bytes in the range");
  case Match_InvalidUImm20:
    return generateImmOutOfRangeError(Operands, ErrorInfo, 0, (1 << 20) - 1);
  case Match_InvalidSImm21Lsb0:
    return generateImmOutOfRangeError(
        Operands, ErrorInfo, -(1 << 20), (1 << 20) - 2,
        "immediate must be a multiple of 2 bytes in the range");
  case Match_InvalidFenceArg: {
    SMLoc ErrorLoc = ((RISCVOperand &)*Operands[ErrorInfo]).getStartLoc();
    return Error(
        ErrorLoc,
        "operand must be formed of letters selected in-order from 'iorw'");
  }
  }

  llvm_unreachable("Unknown match type detected!");
}

bool RISCVAsmParser::ParseRegister(unsigned &RegNo, SMLoc &StartLoc,
                                   SMLoc &EndLoc) {
  const AsmToken &Tok = getParser().getTok();
  StartLoc = Tok.getLoc();
  EndLoc = Tok.getEndLoc();
  RegNo = 0;
  StringRef Name = getLexer().getTok().getIdentifier();

  if (!MatchRegisterName(Name) || !MatchRegisterAltName(Name)) {
    getParser().Lex(); // Eat identifier token.
    return false;
  }

  return Error(StartLoc, "invalid register name");
}

OperandMatchResultTy RISCVAsmParser::parseRegister(OperandVector &Operands) {
  SMLoc S = getLoc();
  SMLoc E = SMLoc::getFromPointer(S.getPointer() - 1);

  switch (getLexer().getKind()) {
  default:
    return MatchOperand_NoMatch;
  case AsmToken::Identifier:
    StringRef Name = getLexer().getTok().getIdentifier();
    unsigned RegNo = MatchRegisterName(Name);
    if (RegNo == 0) {
      RegNo = MatchRegisterAltName(Name);
      if (RegNo == 0)
        return MatchOperand_NoMatch;
    }
    getLexer().Lex();
    Operands.push_back(RISCVOperand::createReg(RegNo, S, E));
  }
  return MatchOperand_Success;
}

OperandMatchResultTy RISCVAsmParser::parseImmediate(OperandVector &Operands) {
  SMLoc S = getLoc();
  SMLoc E = SMLoc::getFromPointer(S.getPointer() - 1);
  const MCExpr *Res;

  switch (getLexer().getKind()) {
  default:
    return MatchOperand_NoMatch;
  case AsmToken::LParen:
  case AsmToken::Minus:
  case AsmToken::Plus:
  case AsmToken::Integer:
  case AsmToken::String:
    if (getParser().parseExpression(Res))
      return MatchOperand_ParseFail;
    break;
  case AsmToken::Identifier: {
    StringRef Identifier;
    if (getParser().parseIdentifier(Identifier))
      return MatchOperand_ParseFail;
    MCSymbol *Sym = getContext().getOrCreateSymbol(Identifier);
    Res = MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_None, getContext());
    break;
  }
  case AsmToken::Percent:
    return parseOperandWithModifier(Operands);
  }

  Operands.push_back(RISCVOperand::createImm(Res, S, E));
  return MatchOperand_Success;
}

OperandMatchResultTy
RISCVAsmParser::parseOperandWithModifier(OperandVector &Operands) {
  SMLoc S = getLoc();
  SMLoc E = SMLoc::getFromPointer(S.getPointer() - 1);

  if (getLexer().getKind() != AsmToken::Percent) {
    Error(getLoc(), "expected '%' for operand modifier");
    return MatchOperand_ParseFail;
  }

  getParser().Lex(); // Eat '%'

  if (getLexer().getKind() != AsmToken::Identifier) {
    Error(getLoc(), "expected valid identifier for operand modifier");
    return MatchOperand_ParseFail;
  }
  StringRef Identifier = getParser().getTok().getIdentifier();
  RISCVMCExpr::VariantKind VK = RISCVMCExpr::getVariantKindForName(Identifier);
  if (VK == RISCVMCExpr::VK_RISCV_Invalid) {
    Error(getLoc(), "unrecognized operand modifier");
    return MatchOperand_ParseFail;
  }

  getParser().Lex(); // Eat the identifier
  if (getLexer().getKind() != AsmToken::LParen) {
    Error(getLoc(), "expected '('");
    return MatchOperand_ParseFail;
  }
  getParser().Lex(); // Eat '('

  const MCExpr *SubExpr;
  if (getParser().parseParenExpression(SubExpr, E)) {
    return MatchOperand_ParseFail;
  }

  const MCExpr *ModExpr = RISCVMCExpr::create(SubExpr, VK, getContext());
  Operands.push_back(RISCVOperand::createImm(ModExpr, S, E));
  return MatchOperand_Success;
}

OperandMatchResultTy
RISCVAsmParser::parseMemOpBaseReg(OperandVector &Operands) {
  if (getLexer().isNot(AsmToken::LParen)) {
    Error(getLoc(), "expected '('");
    return MatchOperand_ParseFail;
  }

  getParser().Lex(); // Eat '('
  Operands.push_back(RISCVOperand::createToken("(", getLoc()));

  if (parseRegister(Operands) != MatchOperand_Success) {
    Error(getLoc(), "expected register");
    return MatchOperand_ParseFail;
  }

  if (getLexer().isNot(AsmToken::RParen)) {
    Error(getLoc(), "expected ')'");
    return MatchOperand_ParseFail;
  }

  getParser().Lex(); // Eat ')'
  Operands.push_back(RISCVOperand::createToken(")", getLoc()));

  return MatchOperand_Success;
}

/// Looks at a token type and creates the relevant operand
/// from this information, adding to Operands.
/// If operand was parsed, returns false, else true.
bool RISCVAsmParser::parseOperand(OperandVector &Operands) {
  // Attempt to parse token as register
  if (parseRegister(Operands) == MatchOperand_Success)
    return false;

  // Attempt to parse token as an immediate
  if (parseImmediate(Operands) == MatchOperand_Success) {
    // Parse memory base register if present
    if (getLexer().is(AsmToken::LParen))
      return parseMemOpBaseReg(Operands) != MatchOperand_Success;
    return false;
  }

  // Finally we have exhausted all options and must declare defeat.
  Error(getLoc(), "unknown operand");
  return true;
}

bool RISCVAsmParser::ParseInstruction(ParseInstructionInfo &Info,
                                      StringRef Name, SMLoc NameLoc,
                                      OperandVector &Operands) {
  // First operand is token for instruction
  Operands.push_back(RISCVOperand::createToken(Name, NameLoc));

  // If there are no more operands, then finish
  if (getLexer().is(AsmToken::EndOfStatement))
    return false;

  // Parse first operand
  if (parseOperand(Operands))
    return true;

  // Parse until end of statement, consuming commas between operands
  while (getLexer().is(AsmToken::Comma)) {
    // Consume comma token
    getLexer().Lex();

    // Parse next operand
    if (parseOperand(Operands))
      return true;
  }

  if (getLexer().isNot(AsmToken::EndOfStatement)) {
    SMLoc Loc = getLexer().getLoc();
    getParser().eatToEndOfStatement();
    return Error(Loc, "unexpected token");
  }

  getParser().Lex(); // Consume the EndOfStatement.
  return false;
}

bool RISCVAsmParser::classifySymbolRef(const MCExpr *Expr,
                                       RISCVMCExpr::VariantKind &Kind,
                                       int64_t &Addend) {
  Kind = RISCVMCExpr::VK_RISCV_None;
  Addend = 0;

  if (const RISCVMCExpr *RE = dyn_cast<RISCVMCExpr>(Expr)) {
    Kind = RE->getKind();
    Expr = RE->getSubExpr();
  }

  // It's a simple symbol reference or constant with no addend.
  if (isa<MCConstantExpr>(Expr) || isa<MCSymbolRefExpr>(Expr))
    return true;

  const MCBinaryExpr *BE = dyn_cast<MCBinaryExpr>(Expr);
  if (!BE)
    return false;

  if (!isa<MCSymbolRefExpr>(BE->getLHS()))
    return false;

  if (BE->getOpcode() != MCBinaryExpr::Add &&
      BE->getOpcode() != MCBinaryExpr::Sub)
    return false;

  // We are able to support the subtraction of two symbol references
  if (BE->getOpcode() == MCBinaryExpr::Sub &&
      isa<MCSymbolRefExpr>(BE->getRHS()))
    return true;

  // See if the addend is is a constant, otherwise there's more going
  // on here than we can deal with.
  auto AddendExpr = dyn_cast<MCConstantExpr>(BE->getRHS());
  if (!AddendExpr)
    return false;

  Addend = AddendExpr->getValue();
  if (BE->getOpcode() == MCBinaryExpr::Sub)
    Addend = -Addend;

  // It's some symbol reference + a constant addend
  return Kind != RISCVMCExpr::VK_RISCV_Invalid;
}

bool RISCVAsmParser::ParseDirective(AsmToken DirectiveID) { return true; }

extern "C" void LLVMInitializeRISCVAsmParser() {
  RegisterMCAsmParser<RISCVAsmParser> X(getTheRISCV32Target());
  RegisterMCAsmParser<RISCVAsmParser> Y(getTheRISCV64Target());
}