lib/Parse/ParseOpenMP.cpp

//===--- ParseOpenMP.cpp - OpenMP directives parsing ----------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
/// \file
/// This file implements parsing of all OpenMP directives and clauses.
///
//===----------------------------------------------------------------------===//

#include "clang/AST/ASTContext.h"
#include "clang/AST/OpenMPClause.h"
#include "clang/AST/StmtOpenMP.h"
#include "clang/Basic/OpenMPKinds.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/TokenKinds.h"
#include "clang/Parse/ParseDiagnostic.h"
#include "clang/Parse/Parser.h"
#include "clang/Parse/RAIIObjectsForParser.h"
#include "clang/Sema/EnterExpressionEvaluationContext.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/SemaAMDGPU.h"
#include "clang/Sema/SemaCodeCompletion.h"
#include "clang/Sema/SemaOpenMP.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Frontend/OpenMP/OMPAssume.h"
#include "llvm/Frontend/OpenMP/OMPContext.h"
#include <optional>

using namespace clang;
using namespace llvm::omp;

//===----------------------------------------------------------------------===//
// OpenMP declarative directives.
//===----------------------------------------------------------------------===//

namespace {
enum OpenMPDirectiveKindEx {
  OMPD_cancellation = llvm::omp::Directive_enumSize + 1,
  OMPD_data,
  OMPD_declare,
  OMPD_end,
  OMPD_end_declare,
  OMPD_enter,
  OMPD_exit,
  OMPD_point,
  OMPD_reduction,
  OMPD_target_enter,
  OMPD_target_exit,
  OMPD_update,
  OMPD_distribute_parallel,
  OMPD_teams_distribute_parallel,
  OMPD_target_teams_distribute_parallel,
  OMPD_mapper,
  OMPD_variant,
  OMPD_begin,
  OMPD_begin_declare,
};

// Helper to unify the enum class OpenMPDirectiveKind with its extension
// the OpenMPDirectiveKindEx enum which allows to use them together as if they
// are unsigned values.
struct OpenMPDirectiveKindExWrapper {
  OpenMPDirectiveKindExWrapper(unsigned Value) : Value(Value) {}
  OpenMPDirectiveKindExWrapper(OpenMPDirectiveKind DK) : Value(unsigned(DK)) {}
  bool operator==(OpenMPDirectiveKindExWrapper V) const {
    return Value == V.Value;
  }
  bool operator!=(OpenMPDirectiveKindExWrapper V) const {
    return Value != V.Value;
  }
  bool operator==(OpenMPDirectiveKind V) const { return Value == unsigned(V); }
  bool operator!=(OpenMPDirectiveKind V) const { return Value != unsigned(V); }
  bool operator<(OpenMPDirectiveKind V) const { return Value < unsigned(V); }
  operator unsigned() const { return Value; }
  operator OpenMPDirectiveKind() const { return OpenMPDirectiveKind(Value); }
  unsigned Value;
};

class DeclDirectiveListParserHelper final {
  SmallVector<Expr *, 4> Identifiers;
  Parser *P;
  OpenMPDirectiveKind Kind;

public:
  DeclDirectiveListParserHelper(Parser *P, OpenMPDirectiveKind Kind)
      : P(P), Kind(Kind) {}
  void operator()(CXXScopeSpec &SS, DeclarationNameInfo NameInfo) {
    ExprResult Res = P->getActions().OpenMP().ActOnOpenMPIdExpression(
        P->getCurScope(), SS, NameInfo, Kind);
    if (Res.isUsable())
      Identifiers.push_back(Res.get());
  }
  llvm::ArrayRef<Expr *> getIdentifiers() const { return Identifiers; }
};
} // namespace

// Map token string to extended OMP token kind that are
// OpenMPDirectiveKind + OpenMPDirectiveKindEx.
static unsigned getOpenMPDirectiveKindEx(StringRef S) {
  OpenMPDirectiveKindExWrapper DKind = getOpenMPDirectiveKind(S);
  if (DKind != OMPD_unknown)
    return DKind;

  return llvm::StringSwitch<OpenMPDirectiveKindExWrapper>(S)
      .Case("cancellation", OMPD_cancellation)
      .Case("data", OMPD_data)
      .Case("declare", OMPD_declare)
      .Case("end", OMPD_end)
      .Case("enter", OMPD_enter)
      .Case("exit", OMPD_exit)
      .Case("point", OMPD_point)
      .Case("reduction", OMPD_reduction)
      .Case("update", OMPD_update)
      .Case("mapper", OMPD_mapper)
      .Case("variant", OMPD_variant)
      .Case("begin", OMPD_begin)
      .Default(OMPD_unknown);
}

static OpenMPDirectiveKindExWrapper parseOpenMPDirectiveKind(Parser &P) {
  // Array of foldings: F[i][0] F[i][1] ===> F[i][2].
  // E.g.: OMPD_for OMPD_simd ===> OMPD_for_simd
  // TODO: add other combined directives in topological order.
  static const OpenMPDirectiveKindExWrapper F[][3] = {
      {OMPD_begin, OMPD_declare, OMPD_begin_declare},
      {OMPD_begin, OMPD_assumes, OMPD_begin_assumes},
      {OMPD_end, OMPD_declare, OMPD_end_declare},
      {OMPD_end, OMPD_assumes, OMPD_end_assumes},
      {OMPD_cancellation, OMPD_point, OMPD_cancellation_point},
      {OMPD_declare, OMPD_reduction, OMPD_declare_reduction},
      {OMPD_declare, OMPD_mapper, OMPD_declare_mapper},
      {OMPD_declare, OMPD_simd, OMPD_declare_simd},
      {OMPD_declare, OMPD_target, OMPD_declare_target},
      {OMPD_declare, OMPD_variant, OMPD_declare_variant},
      {OMPD_begin_declare, OMPD_target, OMPD_begin_declare_target},
      {OMPD_begin_declare, OMPD_variant, OMPD_begin_declare_variant},
      {OMPD_end_declare, OMPD_variant, OMPD_end_declare_variant},
      {OMPD_distribute, OMPD_parallel, OMPD_distribute_parallel},
      {OMPD_distribute_parallel, OMPD_for, OMPD_distribute_parallel_for},
      {OMPD_distribute_parallel_for, OMPD_simd,
       OMPD_distribute_parallel_for_simd},
      {OMPD_distribute, OMPD_simd, OMPD_distribute_simd},
      {OMPD_end_declare, OMPD_target, OMPD_end_declare_target},
      {OMPD_target, OMPD_data, OMPD_target_data},
      {OMPD_target, OMPD_enter, OMPD_target_enter},
      {OMPD_target, OMPD_exit, OMPD_target_exit},
      {OMPD_target, OMPD_update, OMPD_target_update},
      {OMPD_target_enter, OMPD_data, OMPD_target_enter_data},
      {OMPD_target_exit, OMPD_data, OMPD_target_exit_data},
      {OMPD_for, OMPD_simd, OMPD_for_simd},
      {OMPD_parallel, OMPD_for, OMPD_parallel_for},
      {OMPD_parallel_for, OMPD_simd, OMPD_parallel_for_simd},
      {OMPD_parallel, OMPD_loop, OMPD_parallel_loop},
      {OMPD_parallel, OMPD_sections, OMPD_parallel_sections},
      {OMPD_taskloop, OMPD_simd, OMPD_taskloop_simd},
      {OMPD_target, OMPD_parallel, OMPD_target_parallel},
      {OMPD_target, OMPD_simd, OMPD_target_simd},
      {OMPD_target_parallel, OMPD_loop, OMPD_target_parallel_loop},
      {OMPD_target_parallel, OMPD_for, OMPD_target_parallel_for},
      {OMPD_target_parallel_for, OMPD_simd, OMPD_target_parallel_for_simd},
      {OMPD_teams, OMPD_distribute, OMPD_teams_distribute},
      {OMPD_teams_distribute, OMPD_simd, OMPD_teams_distribute_simd},
      {OMPD_teams_distribute, OMPD_parallel, OMPD_teams_distribute_parallel},
      {OMPD_teams_distribute_parallel, OMPD_for,
       OMPD_teams_distribute_parallel_for},
      {OMPD_teams_distribute_parallel_for, OMPD_simd,
       OMPD_teams_distribute_parallel_for_simd},
      {OMPD_teams, OMPD_loop, OMPD_teams_loop},
      {OMPD_target, OMPD_teams, OMPD_target_teams},
      {OMPD_target_teams, OMPD_distribute, OMPD_target_teams_distribute},
      {OMPD_target_teams, OMPD_loop, OMPD_target_teams_loop},
      {OMPD_target_teams_distribute, OMPD_parallel,
       OMPD_target_teams_distribute_parallel},
      {OMPD_target_teams_distribute, OMPD_simd,
       OMPD_target_teams_distribute_simd},
      {OMPD_target_teams_distribute_parallel, OMPD_for,
       OMPD_target_teams_distribute_parallel_for},
      {OMPD_target_teams_distribute_parallel_for, OMPD_simd,
       OMPD_target_teams_distribute_parallel_for_simd},
      {OMPD_master, OMPD_taskloop, OMPD_master_taskloop},
      {OMPD_masked, OMPD_taskloop, OMPD_masked_taskloop},
      {OMPD_master_taskloop, OMPD_simd, OMPD_master_taskloop_simd},
      {OMPD_masked_taskloop, OMPD_simd, OMPD_masked_taskloop_simd},
      {OMPD_parallel, OMPD_master, OMPD_parallel_master},
      {OMPD_parallel, OMPD_masked, OMPD_parallel_masked},
      {OMPD_parallel_master, OMPD_taskloop, OMPD_parallel_master_taskloop},
      {OMPD_parallel_masked, OMPD_taskloop, OMPD_parallel_masked_taskloop},
      {OMPD_parallel_master_taskloop, OMPD_simd,
       OMPD_parallel_master_taskloop_simd},
      {OMPD_parallel_masked_taskloop, OMPD_simd,
       OMPD_parallel_masked_taskloop_simd}};
  enum { CancellationPoint = 0, DeclareReduction = 1, TargetData = 2 };
  Token Tok = P.getCurToken();
  OpenMPDirectiveKindExWrapper DKind =
      Tok.isAnnotation()
          ? static_cast<unsigned>(OMPD_unknown)
          : getOpenMPDirectiveKindEx(P.getPreprocessor().getSpelling(Tok));
  if (DKind == OMPD_unknown)
    return OMPD_unknown;

  for (const auto &I : F) {
    if (DKind != I[0])
      continue;

    Tok = P.getPreprocessor().LookAhead(0);
    OpenMPDirectiveKindExWrapper SDKind =
        Tok.isAnnotation()
            ? static_cast<unsigned>(OMPD_unknown)
            : getOpenMPDirectiveKindEx(P.getPreprocessor().getSpelling(Tok));
    if (SDKind == OMPD_unknown)
      continue;

    if (SDKind == I[1]) {
      P.ConsumeToken();
      DKind = I[2];
    }
  }
  return unsigned(DKind) < llvm::omp::Directive_enumSize
             ? static_cast<OpenMPDirectiveKind>(DKind)
             : OMPD_unknown;
}

static DeclarationName parseOpenMPReductionId(Parser &P) {
  Token Tok = P.getCurToken();
  Sema &Actions = P.getActions();
  OverloadedOperatorKind OOK = OO_None;
  // Allow to use 'operator' keyword for C++ operators
  bool WithOperator = false;
  if (Tok.is(tok::kw_operator)) {
    P.ConsumeToken();
    Tok = P.getCurToken();
    WithOperator = true;
  }
  switch (Tok.getKind()) {
  case tok::plus: // '+'
    OOK = OO_Plus;
    break;
  case tok::minus: // '-'
    OOK = OO_Minus;
    break;
  case tok::star: // '*'
    OOK = OO_Star;
    break;
  case tok::amp: // '&'
    OOK = OO_Amp;
    break;
  case tok::pipe: // '|'
    OOK = OO_Pipe;
    break;
  case tok::caret: // '^'
    OOK = OO_Caret;
    break;
  case tok::ampamp: // '&&'
    OOK = OO_AmpAmp;
    break;
  case tok::pipepipe: // '||'
    OOK = OO_PipePipe;
    break;
  case tok::identifier: // identifier
    if (!WithOperator)
      break;
    [[fallthrough]];
  default:
    P.Diag(Tok.getLocation(), diag::err_omp_expected_reduction_identifier);
    P.SkipUntil(tok::colon, tok::r_paren, tok::annot_pragma_openmp_end,
                Parser::StopBeforeMatch);
    return DeclarationName();
  }
  P.ConsumeToken();
  auto &DeclNames = Actions.getASTContext().DeclarationNames;
  return OOK == OO_None ? DeclNames.getIdentifier(Tok.getIdentifierInfo())
                        : DeclNames.getCXXOperatorName(OOK);
}

/// Parse 'omp declare reduction' construct.
///
///       declare-reduction-directive:
///        annot_pragma_openmp 'declare' 'reduction'
///        '(' <reduction_id> ':' <type> {',' <type>} ':' <expression> ')'
///        ['initializer' '(' ('omp_priv' '=' <expression>)|<function_call> ')']
///        annot_pragma_openmp_end
/// <reduction_id> is either a base language identifier or one of the following
/// operators: '+', '-', '*', '&', '|', '^', '&&' and '||'.
///
Parser::DeclGroupPtrTy
Parser::ParseOpenMPDeclareReductionDirective(AccessSpecifier AS) {
  // Parse '('.
  BalancedDelimiterTracker T(*this, tok::l_paren, tok::annot_pragma_openmp_end);
  if (T.expectAndConsume(
          diag::err_expected_lparen_after,
          getOpenMPDirectiveName(OMPD_declare_reduction).data())) {
    SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch);
    return DeclGroupPtrTy();
  }

  DeclarationName Name = parseOpenMPReductionId(*this);
  if (Name.isEmpty() && Tok.is(tok::annot_pragma_openmp_end))
    return DeclGroupPtrTy();

  // Consume ':'.
  bool IsCorrect = !ExpectAndConsume(tok::colon);

  if (!IsCorrect && Tok.is(tok::annot_pragma_openmp_end))
    return DeclGroupPtrTy();

  IsCorrect = IsCorrect && !Name.isEmpty();

  if (Tok.is(tok::colon) || Tok.is(tok::annot_pragma_openmp_end)) {
    Diag(Tok.getLocation(), diag::err_expected_type);
    IsCorrect = false;
  }

  if (!IsCorrect && Tok.is(tok::annot_pragma_openmp_end))
    return DeclGroupPtrTy();

  SmallVector<std::pair<QualType, SourceLocation>, 8> ReductionTypes;
  // Parse list of types until ':' token.
  do {
    ColonProtectionRAIIObject ColonRAII(*this);
    SourceRange Range;
    TypeResult TR = ParseTypeName(&Range, DeclaratorContext::Prototype, AS);
    if (TR.isUsable()) {
      QualType ReductionType = Actions.OpenMP().ActOnOpenMPDeclareReductionType(
          Range.getBegin(), TR);
      if (!ReductionType.isNull()) {
        ReductionTypes.push_back(
            std::make_pair(ReductionType, Range.getBegin()));
      }
    } else {
      SkipUntil(tok::comma, tok::colon, tok::annot_pragma_openmp_end,
                StopBeforeMatch);
    }

    if (Tok.is(tok::colon) || Tok.is(tok::annot_pragma_openmp_end))
      break;

    // Consume ','.
    if (ExpectAndConsume(tok::comma)) {
      IsCorrect = false;
      if (Tok.is(tok::annot_pragma_openmp_end)) {
        Diag(Tok.getLocation(), diag::err_expected_type);
        return DeclGroupPtrTy();
      }
    }
  } while (Tok.isNot(tok::annot_pragma_openmp_end));

  if (ReductionTypes.empty()) {
    SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch);
    return DeclGroupPtrTy();
  }

  if (!IsCorrect && Tok.is(tok::annot_pragma_openmp_end))
    return DeclGroupPtrTy();

  // Consume ':'.
  if (ExpectAndConsume(tok::colon))
    IsCorrect = false;

  if (Tok.is(tok::annot_pragma_openmp_end)) {
    Diag(Tok.getLocation(), diag::err_expected_expression);
    return DeclGroupPtrTy();
  }

  DeclGroupPtrTy DRD =
      Actions.OpenMP().ActOnOpenMPDeclareReductionDirectiveStart(
          getCurScope(), Actions.getCurLexicalContext(), Name, ReductionTypes,
          AS);

  // Parse <combiner> expression and then parse initializer if any for each
  // correct type.
  unsigned I = 0, E = ReductionTypes.size();
  for (Decl *D : DRD.get()) {
    TentativeParsingAction TPA(*this);
    ParseScope OMPDRScope(this, Scope::FnScope | Scope::DeclScope |
                                    Scope::CompoundStmtScope |
                                    Scope::OpenMPDirectiveScope);
    // Parse <combiner> expression.
    Actions.OpenMP().ActOnOpenMPDeclareReductionCombinerStart(getCurScope(), D);
    ExprResult CombinerResult = Actions.ActOnFinishFullExpr(
        ParseExpression().get(), D->getLocation(), /*DiscardedValue*/ false);
    Actions.OpenMP().ActOnOpenMPDeclareReductionCombinerEnd(
        D, CombinerResult.get());

    if (CombinerResult.isInvalid() && Tok.isNot(tok::r_paren) &&
        Tok.isNot(tok::annot_pragma_openmp_end)) {
      TPA.Commit();
      IsCorrect = false;
      break;
    }
    IsCorrect = !T.consumeClose() && IsCorrect && CombinerResult.isUsable();
    ExprResult InitializerResult;
    if (Tok.isNot(tok::annot_pragma_openmp_end)) {
      // Parse <initializer> expression.
      if (Tok.is(tok::identifier) &&
          Tok.getIdentifierInfo()->isStr("initializer")) {
        ConsumeToken();
      } else {
        Diag(Tok.getLocation(), diag::err_expected) << "'initializer'";
        TPA.Commit();
        IsCorrect = false;
        break;
      }
      // Parse '('.
      BalancedDelimiterTracker T(*this, tok::l_paren,
                                 tok::annot_pragma_openmp_end);
      IsCorrect =
          !T.expectAndConsume(diag::err_expected_lparen_after, "initializer") &&
          IsCorrect;
      if (Tok.isNot(tok::annot_pragma_openmp_end)) {
        ParseScope OMPDRScope(this, Scope::FnScope | Scope::DeclScope |
                                        Scope::CompoundStmtScope |
                                        Scope::OpenMPDirectiveScope);
        // Parse expression.
        VarDecl *OmpPrivParm =
            Actions.OpenMP().ActOnOpenMPDeclareReductionInitializerStart(
                getCurScope(), D);
        // Check if initializer is omp_priv <init_expr> or something else.
        if (Tok.is(tok::identifier) &&
            Tok.getIdentifierInfo()->isStr("omp_priv")) {
          ConsumeToken();
          ParseOpenMPReductionInitializerForDecl(OmpPrivParm);
        } else {
          InitializerResult = Actions.ActOnFinishFullExpr(
              ParseAssignmentExpression().get(), D->getLocation(),
              /*DiscardedValue*/ false);
        }
        Actions.OpenMP().ActOnOpenMPDeclareReductionInitializerEnd(
            D, InitializerResult.get(), OmpPrivParm);
        if (InitializerResult.isInvalid() && Tok.isNot(tok::r_paren) &&
            Tok.isNot(tok::annot_pragma_openmp_end)) {
          TPA.Commit();
          IsCorrect = false;
          break;
        }
        IsCorrect =
            !T.consumeClose() && IsCorrect && !InitializerResult.isInvalid();
      }
    }

    ++I;
    // Revert parsing if not the last type, otherwise accept it, we're done with
    // parsing.
    if (I != E)
      TPA.Revert();
    else
      TPA.Commit();
  }
  return Actions.OpenMP().ActOnOpenMPDeclareReductionDirectiveEnd(
      getCurScope(), DRD, IsCorrect);
}

void Parser::ParseOpenMPReductionInitializerForDecl(VarDecl *OmpPrivParm) {
  // Parse declarator '=' initializer.
  // If a '==' or '+=' is found, suggest a fixit to '='.
  if (isTokenEqualOrEqualTypo()) {
    ConsumeToken();

    if (Tok.is(tok::code_completion)) {
      cutOffParsing();
      Actions.CodeCompletion().CodeCompleteInitializer(getCurScope(),
                                                       OmpPrivParm);
      Actions.FinalizeDeclaration(OmpPrivParm);
      return;
    }

    PreferredType.enterVariableInit(Tok.getLocation(), OmpPrivParm);
    ExprResult Init = ParseInitializer();

    if (Init.isInvalid()) {
      SkipUntil(tok::r_paren, tok::annot_pragma_openmp_end, StopBeforeMatch);
      Actions.ActOnInitializerError(OmpPrivParm);
    } else {
      Actions.AddInitializerToDecl(OmpPrivParm, Init.get(),
                                   /*DirectInit=*/false);
    }
  } else if (Tok.is(tok::l_paren)) {
    // Parse C++ direct initializer: '(' expression-list ')'
    BalancedDelimiterTracker T(*this, tok::l_paren);
    T.consumeOpen();

    ExprVector Exprs;

    SourceLocation LParLoc = T.getOpenLocation();
    auto RunSignatureHelp = [this, OmpPrivParm, LParLoc, &Exprs]() {
      QualType PreferredType =
          Actions.CodeCompletion().ProduceConstructorSignatureHelp(
              OmpPrivParm->getType()->getCanonicalTypeInternal(),
              OmpPrivParm->getLocation(), Exprs, LParLoc, /*Braced=*/false);
      CalledSignatureHelp = true;
      return PreferredType;
    };
    if (ParseExpressionList(Exprs, [&] {
          PreferredType.enterFunctionArgument(Tok.getLocation(),
                                              RunSignatureHelp);
        })) {
      if (PP.isCodeCompletionReached() && !CalledSignatureHelp)
        RunSignatureHelp();
      Actions.ActOnInitializerError(OmpPrivParm);
      SkipUntil(tok::r_paren, tok::annot_pragma_openmp_end, StopBeforeMatch);
    } else {
      // Match the ')'.
      SourceLocation RLoc = Tok.getLocation();
      if (!T.consumeClose())
        RLoc = T.getCloseLocation();

      ExprResult Initializer =
          Actions.ActOnParenListExpr(T.getOpenLocation(), RLoc, Exprs);
      Actions.AddInitializerToDecl(OmpPrivParm, Initializer.get(),
                                   /*DirectInit=*/true);
    }
  } else if (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace)) {
    // Parse C++0x braced-init-list.
    Diag(Tok, diag::warn_cxx98_compat_generalized_initializer_lists);

    ExprResult Init(ParseBraceInitializer());

    if (Init.isInvalid()) {
      Actions.ActOnInitializerError(OmpPrivParm);
    } else {
      Actions.AddInitializerToDecl(OmpPrivParm, Init.get(),
                                   /*DirectInit=*/true);
    }
  } else {
    Actions.ActOnUninitializedDecl(OmpPrivParm);
  }
}

/// Parses 'omp declare mapper' directive.
///
///       declare-mapper-directive:
///         annot_pragma_openmp 'declare' 'mapper' '(' [<mapper-identifier> ':']
///         <type> <var> ')' [<clause>[[,] <clause>] ... ]
///         annot_pragma_openmp_end
/// <mapper-identifier> and <var> are base language identifiers.
///
Parser::DeclGroupPtrTy
Parser::ParseOpenMPDeclareMapperDirective(AccessSpecifier AS) {
  bool IsCorrect = true;
  // Parse '('
  BalancedDelimiterTracker T(*this, tok::l_paren, tok::annot_pragma_openmp_end);
  if (T.expectAndConsume(diag::err_expected_lparen_after,
                         getOpenMPDirectiveName(OMPD_declare_mapper).data())) {
    SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch);
    return DeclGroupPtrTy();
  }

  // Parse <mapper-identifier>
  auto &DeclNames = Actions.getASTContext().DeclarationNames;
  DeclarationName MapperId;
  if (PP.LookAhead(0).is(tok::colon)) {
    if (Tok.isNot(tok::identifier) && Tok.isNot(tok::kw_default)) {
      Diag(Tok.getLocation(), diag::err_omp_mapper_illegal_identifier);
      IsCorrect = false;
    } else {
      MapperId = DeclNames.getIdentifier(Tok.getIdentifierInfo());
    }
    ConsumeToken();
    // Consume ':'.
    ExpectAndConsume(tok::colon);
  } else {
    // If no mapper identifier is provided, its name is "default" by default
    MapperId =
        DeclNames.getIdentifier(&Actions.getASTContext().Idents.get("default"));
  }

  if (!IsCorrect && Tok.is(tok::annot_pragma_openmp_end))
    return DeclGroupPtrTy();

  // Parse <type> <var>
  DeclarationName VName;
  QualType MapperType;
  SourceRange Range;
  TypeResult ParsedType = parseOpenMPDeclareMapperVarDecl(Range, VName, AS);
  if (ParsedType.isUsable())
    MapperType = Actions.OpenMP().ActOnOpenMPDeclareMapperType(Range.getBegin(),
                                                               ParsedType);
  if (MapperType.isNull())
    IsCorrect = false;
  if (!IsCorrect) {
    SkipUntil(tok::annot_pragma_openmp_end, Parser::StopBeforeMatch);
    return DeclGroupPtrTy();
  }

  // Consume ')'.
  IsCorrect &= !T.consumeClose();
  if (!IsCorrect) {
    SkipUntil(tok::annot_pragma_openmp_end, Parser::StopBeforeMatch);
    return DeclGroupPtrTy();
  }

  // Enter scope.
  DeclarationNameInfo DirName;
  SourceLocation Loc = Tok.getLocation();
  unsigned ScopeFlags = Scope::FnScope | Scope::DeclScope |
                        Scope::CompoundStmtScope | Scope::OpenMPDirectiveScope;
  ParseScope OMPDirectiveScope(this, ScopeFlags);
  Actions.OpenMP().StartOpenMPDSABlock(OMPD_declare_mapper, DirName,
                                       getCurScope(), Loc);

  // Add the mapper variable declaration.
  ExprResult MapperVarRef =
      Actions.OpenMP().ActOnOpenMPDeclareMapperDirectiveVarDecl(
          getCurScope(), MapperType, Range.getBegin(), VName);

  // Parse map clauses.
  SmallVector<OMPClause *, 6> Clauses;
  while (Tok.isNot(tok::annot_pragma_openmp_end)) {
    OpenMPClauseKind CKind = Tok.isAnnotation()
                                 ? OMPC_unknown
                                 : getOpenMPClauseKind(PP.getSpelling(Tok));
    Actions.OpenMP().StartOpenMPClause(CKind);
    OMPClause *Clause =
        ParseOpenMPClause(OMPD_declare_mapper, CKind, Clauses.empty());
    if (Clause)
      Clauses.push_back(Clause);
    else
      IsCorrect = false;
    // Skip ',' if any.
    if (Tok.is(tok::comma))
      ConsumeToken();
    Actions.OpenMP().EndOpenMPClause();
  }
  if (Clauses.empty()) {
    Diag(Tok, diag::err_omp_expected_clause)
        << getOpenMPDirectiveName(OMPD_declare_mapper);
    IsCorrect = false;
  }

  // Exit scope.
  Actions.OpenMP().EndOpenMPDSABlock(nullptr);
  OMPDirectiveScope.Exit();
  DeclGroupPtrTy DG = Actions.OpenMP().ActOnOpenMPDeclareMapperDirective(
      getCurScope(), Actions.getCurLexicalContext(), MapperId, MapperType,
      Range.getBegin(), VName, AS, MapperVarRef.get(), Clauses);
  if (!IsCorrect)
    return DeclGroupPtrTy();

  return DG;
}

TypeResult Parser::parseOpenMPDeclareMapperVarDecl(SourceRange &Range,
                                                   DeclarationName &Name,
                                                   AccessSpecifier AS) {
  // Parse the common declaration-specifiers piece.
  Parser::DeclSpecContext DSC = Parser::DeclSpecContext::DSC_type_specifier;
  DeclSpec DS(AttrFactory);
  ParseSpecifierQualifierList(DS, AS, DSC);

  // Parse the declarator.
  DeclaratorContext Context = DeclaratorContext::Prototype;
  Declarator DeclaratorInfo(DS, ParsedAttributesView::none(), Context);
  ParseDeclarator(DeclaratorInfo);
  Range = DeclaratorInfo.getSourceRange();
  if (DeclaratorInfo.getIdentifier() == nullptr) {
    Diag(Tok.getLocation(), diag::err_omp_mapper_expected_declarator);
    return true;
  }
  Name = Actions.GetNameForDeclarator(DeclaratorInfo).getName();

  return Actions.OpenMP().ActOnOpenMPDeclareMapperVarDecl(getCurScope(),
                                                          DeclaratorInfo);
}

namespace {
/// RAII that recreates function context for correct parsing of clauses of
/// 'declare simd' construct.
/// OpenMP, 2.8.2 declare simd Construct
/// The expressions appearing in the clauses of this directive are evaluated in
/// the scope of the arguments of the function declaration or definition.
class FNContextRAII final {
  Parser &P;
  Sema::CXXThisScopeRAII *ThisScope;
  Parser::MultiParseScope Scopes;
  bool HasFunScope = false;
  FNContextRAII() = delete;
  FNContextRAII(const FNContextRAII &) = delete;
  FNContextRAII &operator=(const FNContextRAII &) = delete;

public:
  FNContextRAII(Parser &P, Parser::DeclGroupPtrTy Ptr) : P(P), Scopes(P) {
    Decl *D = *Ptr.get().begin();
    NamedDecl *ND = dyn_cast<NamedDecl>(D);
    RecordDecl *RD = dyn_cast_or_null<RecordDecl>(D->getDeclContext());
    Sema &Actions = P.getActions();

    // Allow 'this' within late-parsed attributes.
    ThisScope = new Sema::CXXThisScopeRAII(Actions, RD, Qualifiers(),
                                           ND && ND->isCXXInstanceMember());

    // If the Decl is templatized, add template parameters to scope.
    // FIXME: Track CurTemplateDepth?
    P.ReenterTemplateScopes(Scopes, D);

    // If the Decl is on a function, add function parameters to the scope.
    if (D->isFunctionOrFunctionTemplate()) {
      HasFunScope = true;
      Scopes.Enter(Scope::FnScope | Scope::DeclScope |
                   Scope::CompoundStmtScope);
      Actions.ActOnReenterFunctionContext(Actions.getCurScope(), D);
    }
  }
  ~FNContextRAII() {
    if (HasFunScope)
      P.getActions().ActOnExitFunctionContext();
    delete ThisScope;
  }
};
} // namespace

/// Parses clauses for 'declare simd' directive.
///    clause:
///      'inbranch' | 'notinbranch'
///      'simdlen' '(' <expr> ')'
///      { 'uniform' '(' <argument_list> ')' }
///      { 'aligned '(' <argument_list> [ ':' <alignment> ] ')' }
///      { 'linear '(' <argument_list> [ ':' <step> ] ')' }
static bool parseDeclareSimdClauses(
    Parser &P, OMPDeclareSimdDeclAttr::BranchStateTy &BS, ExprResult &SimdLen,
    SmallVectorImpl<Expr *> &Uniforms, SmallVectorImpl<Expr *> &Aligneds,
    SmallVectorImpl<Expr *> &Alignments, SmallVectorImpl<Expr *> &Linears,
    SmallVectorImpl<unsigned> &LinModifiers, SmallVectorImpl<Expr *> &Steps) {
  SourceRange BSRange;
  const Token &Tok = P.getCurToken();
  bool IsError = false;
  while (Tok.isNot(tok::annot_pragma_openmp_end)) {
    if (Tok.isNot(tok::identifier))
      break;
    OMPDeclareSimdDeclAttr::BranchStateTy Out;
    IdentifierInfo *II = Tok.getIdentifierInfo();
    StringRef ClauseName = II->getName();
    // Parse 'inranch|notinbranch' clauses.
    if (OMPDeclareSimdDeclAttr::ConvertStrToBranchStateTy(ClauseName, Out)) {
      if (BS != OMPDeclareSimdDeclAttr::BS_Undefined && BS != Out) {
        P.Diag(Tok, diag::err_omp_declare_simd_inbranch_notinbranch)
            << ClauseName
            << OMPDeclareSimdDeclAttr::ConvertBranchStateTyToStr(BS) << BSRange;
        IsError = true;
      }
      BS = Out;
      BSRange = SourceRange(Tok.getLocation(), Tok.getEndLoc());
      P.ConsumeToken();
    } else if (ClauseName == "simdlen") {
      if (SimdLen.isUsable()) {
        P.Diag(Tok, diag::err_omp_more_one_clause)
            << getOpenMPDirectiveName(OMPD_declare_simd) << ClauseName << 0;
        IsError = true;
      }
      P.ConsumeToken();
      SourceLocation RLoc;
      SimdLen = P.ParseOpenMPParensExpr(ClauseName, RLoc);
      if (SimdLen.isInvalid())
        IsError = true;
    } else {
      OpenMPClauseKind CKind = getOpenMPClauseKind(ClauseName);
      if (CKind == OMPC_uniform || CKind == OMPC_aligned ||
          CKind == OMPC_linear) {
        SemaOpenMP::OpenMPVarListDataTy Data;
        SmallVectorImpl<Expr *> *Vars = &Uniforms;
        if (CKind == OMPC_aligned) {
          Vars = &Aligneds;
        } else if (CKind == OMPC_linear) {
          Data.ExtraModifier = OMPC_LINEAR_val;
          Vars = &Linears;
        }

        P.ConsumeToken();
        if (P.ParseOpenMPVarList(OMPD_declare_simd,
                                 getOpenMPClauseKind(ClauseName), *Vars, Data))
          IsError = true;
        if (CKind == OMPC_aligned) {
          Alignments.append(Aligneds.size() - Alignments.size(),
                            Data.DepModOrTailExpr);
        } else if (CKind == OMPC_linear) {
          assert(0 <= Data.ExtraModifier &&
                 Data.ExtraModifier <= OMPC_LINEAR_unknown &&
                 "Unexpected linear modifier.");
          if (P.getActions().OpenMP().CheckOpenMPLinearModifier(
                  static_cast<OpenMPLinearClauseKind>(Data.ExtraModifier),
                  Data.ExtraModifierLoc))
            Data.ExtraModifier = OMPC_LINEAR_val;
          LinModifiers.append(Linears.size() - LinModifiers.size(),
                              Data.ExtraModifier);
          Steps.append(Linears.size() - Steps.size(), Data.DepModOrTailExpr);
        }
      } else
        // TODO: add parsing of other clauses.
        break;
    }
    // Skip ',' if any.
    if (Tok.is(tok::comma))
      P.ConsumeToken();
  }
  return IsError;
}

/// Parse clauses for '#pragma omp declare simd'.
Parser::DeclGroupPtrTy
Parser::ParseOMPDeclareSimdClauses(Parser::DeclGroupPtrTy Ptr,
                                   CachedTokens &Toks, SourceLocation Loc) {
  PP.EnterToken(Tok, /*IsReinject*/ true);
  PP.EnterTokenStream(Toks, /*DisableMacroExpansion=*/true,
                      /*IsReinject*/ true);
  // Consume the previously pushed token.
  ConsumeAnyToken(/*ConsumeCodeCompletionTok=*/true);
  ConsumeAnyToken(/*ConsumeCodeCompletionTok=*/true);

  FNContextRAII FnContext(*this, Ptr);
  OMPDeclareSimdDeclAttr::BranchStateTy BS =
      OMPDeclareSimdDeclAttr::BS_Undefined;
  ExprResult Simdlen;
  SmallVector<Expr *, 4> Uniforms;
  SmallVector<Expr *, 4> Aligneds;
  SmallVector<Expr *, 4> Alignments;
  SmallVector<Expr *, 4> Linears;
  SmallVector<unsigned, 4> LinModifiers;
  SmallVector<Expr *, 4> Steps;
  bool IsError =
      parseDeclareSimdClauses(*this, BS, Simdlen, Uniforms, Aligneds,
                              Alignments, Linears, LinModifiers, Steps);
  skipUntilPragmaOpenMPEnd(OMPD_declare_simd);
  // Skip the last annot_pragma_openmp_end.
  SourceLocation EndLoc = ConsumeAnnotationToken();
  if (IsError)
    return Ptr;
  return Actions.OpenMP().ActOnOpenMPDeclareSimdDirective(
      Ptr, BS, Simdlen.get(), Uniforms, Aligneds, Alignments, Linears,
      LinModifiers, Steps, SourceRange(Loc, EndLoc));
}

namespace {
/// Constant used in the diagnostics to distinguish the levels in an OpenMP
/// contexts: selector-set={selector(trait, ...), ...}, ....
enum OMPContextLvl {
  CONTEXT_SELECTOR_SET_LVL = 0,
  CONTEXT_SELECTOR_LVL = 1,
  CONTEXT_TRAIT_LVL = 2,
};

static StringRef stringLiteralParser(Parser &P) {
  ExprResult Res = P.ParseStringLiteralExpression(true);
  return Res.isUsable() ? Res.getAs<StringLiteral>()->getString() : "";
}

static StringRef getNameFromIdOrString(Parser &P, Token &Tok,
                                       OMPContextLvl Lvl) {
  if (Tok.is(tok::identifier) || Tok.is(tok::kw_for)) {
    llvm::SmallString<16> Buffer;
    StringRef Name = P.getPreprocessor().getSpelling(Tok, Buffer);
    (void)P.ConsumeToken();
    return Name;
  }

  if (tok::isStringLiteral(Tok.getKind()))
    return stringLiteralParser(P);

  P.Diag(Tok.getLocation(),
         diag::warn_omp_declare_variant_string_literal_or_identifier)
      << Lvl;
  return "";
}

static bool checkForDuplicates(Parser &P, StringRef Name,
                               SourceLocation NameLoc,
                               llvm::StringMap<SourceLocation> &Seen,
                               OMPContextLvl Lvl) {
  auto Res = Seen.try_emplace(Name, NameLoc);
  if (Res.second)
    return false;

  // Each trait-set-selector-name, trait-selector-name and trait-name can
  // only be specified once.
  P.Diag(NameLoc, diag::warn_omp_declare_variant_ctx_mutiple_use)
      << Lvl << Name;
  P.Diag(Res.first->getValue(), diag::note_omp_declare_variant_ctx_used_here)
      << Lvl << Name;
  return true;
}
} // namespace

void Parser::parseOMPTraitPropertyKind(OMPTraitProperty &TIProperty,
                                       llvm::omp::TraitSet Set,
                                       llvm::omp::TraitSelector Selector,
                                       llvm::StringMap<SourceLocation> &Seen) {
  TIProperty.Kind = TraitProperty::invalid;

  SourceLocation NameLoc = Tok.getLocation();
  StringRef Name = getNameFromIdOrString(*this, Tok, CONTEXT_TRAIT_LVL);
  if (Name.empty()) {
    Diag(Tok.getLocation(), diag::note_omp_declare_variant_ctx_options)
        << CONTEXT_TRAIT_LVL << listOpenMPContextTraitProperties(Set, Selector);
    return;
  }

  TIProperty.RawString = Name;
  TIProperty.Kind = getOpenMPContextTraitPropertyKind(Set, Selector, Name);
  if (TIProperty.Kind != TraitProperty::invalid) {
    if (checkForDuplicates(*this, Name, NameLoc, Seen, CONTEXT_TRAIT_LVL))
      TIProperty.Kind = TraitProperty::invalid;
    return;
  }

  // It follows diagnosis and helping notes.
  // FIXME: We should move the diagnosis string generation into libFrontend.
  Diag(NameLoc, diag::warn_omp_declare_variant_ctx_not_a_property)
      << Name << getOpenMPContextTraitSelectorName(Selector)
      << getOpenMPContextTraitSetName(Set);

  TraitSet SetForName = getOpenMPContextTraitSetKind(Name);
  if (SetForName != TraitSet::invalid) {
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_is_a)
        << Name << CONTEXT_SELECTOR_SET_LVL << CONTEXT_TRAIT_LVL;
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_try)
        << Name << "<selector-name>"
        << "(<property-name>)";
    return;
  }
  TraitSelector SelectorForName = getOpenMPContextTraitSelectorKind(Name);
  if (SelectorForName != TraitSelector::invalid) {
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_is_a)
        << Name << CONTEXT_SELECTOR_LVL << CONTEXT_TRAIT_LVL;
    bool AllowsTraitScore = false;
    bool RequiresProperty = false;
    isValidTraitSelectorForTraitSet(
        SelectorForName, getOpenMPContextTraitSetForSelector(SelectorForName),
        AllowsTraitScore, RequiresProperty);
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_try)
        << getOpenMPContextTraitSetName(
               getOpenMPContextTraitSetForSelector(SelectorForName))
        << Name << (RequiresProperty ? "(<property-name>)" : "");
    return;
  }
  for (const auto &PotentialSet :
       {TraitSet::construct, TraitSet::user, TraitSet::implementation,
        TraitSet::device}) {
    TraitProperty PropertyForName =
        getOpenMPContextTraitPropertyKind(PotentialSet, Selector, Name);
    if (PropertyForName == TraitProperty::invalid)
      continue;
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_try)
        << getOpenMPContextTraitSetName(
               getOpenMPContextTraitSetForProperty(PropertyForName))
        << getOpenMPContextTraitSelectorName(
               getOpenMPContextTraitSelectorForProperty(PropertyForName))
        << ("(" + Name + ")").str();
    return;
  }
  Diag(NameLoc, diag::note_omp_declare_variant_ctx_options)
      << CONTEXT_TRAIT_LVL << listOpenMPContextTraitProperties(Set, Selector);
}

static bool checkExtensionProperty(Parser &P, SourceLocation Loc,
                                   OMPTraitProperty &TIProperty,
                                   OMPTraitSelector &TISelector,
                                   llvm::StringMap<SourceLocation> &Seen) {
  assert(TISelector.Kind ==
             llvm::omp::TraitSelector::implementation_extension &&
         "Only for extension properties, e.g., "
         "`implementation={extension(PROPERTY)}`");
  if (TIProperty.Kind == TraitProperty::invalid)
    return false;

  if (TIProperty.Kind ==
      TraitProperty::implementation_extension_disable_implicit_base)
    return true;

  if (TIProperty.Kind ==
      TraitProperty::implementation_extension_allow_templates)
    return true;

  if (TIProperty.Kind ==
      TraitProperty::implementation_extension_bind_to_declaration)
    return true;

  auto IsMatchExtension = [](OMPTraitProperty &TP) {
    return (TP.Kind ==
                llvm::omp::TraitProperty::implementation_extension_match_all ||
            TP.Kind ==
                llvm::omp::TraitProperty::implementation_extension_match_any ||
            TP.Kind ==
                llvm::omp::TraitProperty::implementation_extension_match_none);
  };

  if (IsMatchExtension(TIProperty)) {
    for (OMPTraitProperty &SeenProp : TISelector.Properties)
      if (IsMatchExtension(SeenProp)) {
        P.Diag(Loc, diag::err_omp_variant_ctx_second_match_extension);
        StringRef SeenName = llvm::omp::getOpenMPContextTraitPropertyName(
            SeenProp.Kind, SeenProp.RawString);
        SourceLocation SeenLoc = Seen[SeenName];
        P.Diag(SeenLoc, diag::note_omp_declare_variant_ctx_used_here)
            << CONTEXT_TRAIT_LVL << SeenName;
        return false;
      }
    return true;
  }

  llvm_unreachable("Unknown extension property!");
}

void Parser::parseOMPContextProperty(OMPTraitSelector &TISelector,
                                     llvm::omp::TraitSet Set,
                                     llvm::StringMap<SourceLocation> &Seen) {
  assert(TISelector.Kind != TraitSelector::user_condition &&
         "User conditions are special properties not handled here!");

  SourceLocation PropertyLoc = Tok.getLocation();
  OMPTraitProperty TIProperty;
  parseOMPTraitPropertyKind(TIProperty, Set, TISelector.Kind, Seen);

  if (TISelector.Kind == llvm::omp::TraitSelector::implementation_extension)
    if (!checkExtensionProperty(*this, Tok.getLocation(), TIProperty,
                                TISelector, Seen))
      TIProperty.Kind = TraitProperty::invalid;

  // If we have an invalid property here we already issued a warning.
  if (TIProperty.Kind == TraitProperty::invalid) {
    if (PropertyLoc != Tok.getLocation())
      Diag(Tok.getLocation(), diag::note_omp_declare_variant_ctx_continue_here)
          << CONTEXT_TRAIT_LVL;
    return;
  }

  if (isValidTraitPropertyForTraitSetAndSelector(TIProperty.Kind,
                                                 TISelector.Kind, Set)) {

    // If we make it here the property, selector, set, score, condition, ... are
    // all valid (or have been corrected). Thus we can record the property.
    TISelector.Properties.push_back(TIProperty);
    return;
  }

  Diag(PropertyLoc, diag::warn_omp_ctx_incompatible_property_for_selector)
      << getOpenMPContextTraitPropertyName(TIProperty.Kind,
                                           TIProperty.RawString)
      << getOpenMPContextTraitSelectorName(TISelector.Kind)
      << getOpenMPContextTraitSetName(Set);
  Diag(PropertyLoc, diag::note_omp_ctx_compatible_set_and_selector_for_property)
      << getOpenMPContextTraitPropertyName(TIProperty.Kind,
                                           TIProperty.RawString)
      << getOpenMPContextTraitSelectorName(
             getOpenMPContextTraitSelectorForProperty(TIProperty.Kind))
      << getOpenMPContextTraitSetName(
             getOpenMPContextTraitSetForProperty(TIProperty.Kind));
  Diag(Tok.getLocation(), diag::note_omp_declare_variant_ctx_continue_here)
      << CONTEXT_TRAIT_LVL;
}

void Parser::parseOMPTraitSelectorKind(OMPTraitSelector &TISelector,
                                       llvm::omp::TraitSet Set,
                                       llvm::StringMap<SourceLocation> &Seen) {
  TISelector.Kind = TraitSelector::invalid;

  SourceLocation NameLoc = Tok.getLocation();
  StringRef Name = getNameFromIdOrString(*this, Tok, CONTEXT_SELECTOR_LVL);
  if (Name.empty()) {
    Diag(Tok.getLocation(), diag::note_omp_declare_variant_ctx_options)
        << CONTEXT_SELECTOR_LVL << listOpenMPContextTraitSelectors(Set);
    return;
  }

  TISelector.Kind = getOpenMPContextTraitSelectorKind(Name);
  if (TISelector.Kind != TraitSelector::invalid) {
    if (checkForDuplicates(*this, Name, NameLoc, Seen, CONTEXT_SELECTOR_LVL))
      TISelector.Kind = TraitSelector::invalid;
    return;
  }

  // It follows diagnosis and helping notes.
  Diag(NameLoc, diag::warn_omp_declare_variant_ctx_not_a_selector)
      << Name << getOpenMPContextTraitSetName(Set);

  TraitSet SetForName = getOpenMPContextTraitSetKind(Name);
  if (SetForName != TraitSet::invalid) {
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_is_a)
        << Name << CONTEXT_SELECTOR_SET_LVL << CONTEXT_SELECTOR_LVL;
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_try)
        << Name << "<selector-name>"
        << "<property-name>";
    return;
  }
  for (const auto &PotentialSet :
       {TraitSet::construct, TraitSet::user, TraitSet::implementation,
        TraitSet::device}) {
    TraitProperty PropertyForName = getOpenMPContextTraitPropertyKind(
        PotentialSet, TraitSelector::invalid, Name);
    if (PropertyForName == TraitProperty::invalid)
      continue;
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_is_a)
        << Name << CONTEXT_TRAIT_LVL << CONTEXT_SELECTOR_LVL;
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_try)
        << getOpenMPContextTraitSetName(
               getOpenMPContextTraitSetForProperty(PropertyForName))
        << getOpenMPContextTraitSelectorName(
               getOpenMPContextTraitSelectorForProperty(PropertyForName))
        << ("(" + Name + ")").str();
    return;
  }
  Diag(NameLoc, diag::note_omp_declare_variant_ctx_options)
      << CONTEXT_SELECTOR_LVL << listOpenMPContextTraitSelectors(Set);
}

/// Parse optional 'score' '(' <expr> ')' ':'.
static ExprResult parseContextScore(Parser &P) {
  ExprResult ScoreExpr;
  llvm::SmallString<16> Buffer;
  StringRef SelectorName =
      P.getPreprocessor().getSpelling(P.getCurToken(), Buffer);
  if (SelectorName != "score")
    return ScoreExpr;
  (void)P.ConsumeToken();
  SourceLocation RLoc;
  ScoreExpr = P.ParseOpenMPParensExpr(SelectorName, RLoc);
  // Parse ':'
  if (P.getCurToken().is(tok::colon))
    (void)P.ConsumeAnyToken();
  else
    P.Diag(P.getCurToken(), diag::warn_omp_declare_variant_expected)
        << "':'"
        << "score expression";
  return ScoreExpr;
}

/// Parses an OpenMP context selector.
///
/// <trait-selector-name> ['('[<trait-score>] <trait-property> [, <t-p>]* ')']
void Parser::parseOMPContextSelector(
    OMPTraitSelector &TISelector, llvm::omp::TraitSet Set,
    llvm::StringMap<SourceLocation> &SeenSelectors) {
  unsigned short OuterPC = ParenCount;

  // If anything went wrong we issue an error or warning and then skip the rest
  // of the selector. However, commas are ambiguous so we look for the nesting
  // of parentheses here as well.
  auto FinishSelector = [OuterPC, this]() -> void {
    bool Done = false;
    while (!Done) {
      while (!SkipUntil({tok::r_brace, tok::r_paren, tok::comma,
                         tok::annot_pragma_openmp_end},
                        StopBeforeMatch))
        ;
      if (Tok.is(tok::r_paren) && OuterPC > ParenCount)
        (void)ConsumeParen();
      if (OuterPC <= ParenCount) {
        Done = true;
        break;
      }
      if (!Tok.is(tok::comma) && !Tok.is(tok::r_paren)) {
        Done = true;
        break;
      }
      (void)ConsumeAnyToken();
    }
    Diag(Tok.getLocation(), diag::note_omp_declare_variant_ctx_continue_here)
        << CONTEXT_SELECTOR_LVL;
  };

  SourceLocation SelectorLoc = Tok.getLocation();
  parseOMPTraitSelectorKind(TISelector, Set, SeenSelectors);
  if (TISelector.Kind == TraitSelector::invalid)
    return FinishSelector();

  bool AllowsTraitScore = false;
  bool RequiresProperty = false;
  if (!isValidTraitSelectorForTraitSet(TISelector.Kind, Set, AllowsTraitScore,
                                       RequiresProperty)) {
    Diag(SelectorLoc, diag::warn_omp_ctx_incompatible_selector_for_set)
        << getOpenMPContextTraitSelectorName(TISelector.Kind)
        << getOpenMPContextTraitSetName(Set);
    Diag(SelectorLoc, diag::note_omp_ctx_compatible_set_for_selector)
        << getOpenMPContextTraitSelectorName(TISelector.Kind)
        << getOpenMPContextTraitSetName(
               getOpenMPContextTraitSetForSelector(TISelector.Kind))
        << RequiresProperty;
    return FinishSelector();
  }

  if (!RequiresProperty) {
    TISelector.Properties.push_back(
        {getOpenMPContextTraitPropertyForSelector(TISelector.Kind),
         getOpenMPContextTraitSelectorName(TISelector.Kind)});
    return;
  }

  if (!Tok.is(tok::l_paren)) {
    Diag(SelectorLoc, diag::warn_omp_ctx_selector_without_properties)
        << getOpenMPContextTraitSelectorName(TISelector.Kind)
        << getOpenMPContextTraitSetName(Set);
    return FinishSelector();
  }

  if (TISelector.Kind == TraitSelector::user_condition) {
    SourceLocation RLoc;
    ExprResult Condition = ParseOpenMPParensExpr("user condition", RLoc);
    if (!Condition.isUsable())
      return FinishSelector();
    TISelector.ScoreOrCondition = Condition.get();
    TISelector.Properties.push_back(
        {TraitProperty::user_condition_unknown, "<condition>"});
    return;
  }

  BalancedDelimiterTracker BDT(*this, tok::l_paren,
                               tok::annot_pragma_openmp_end);
  // Parse '('.
  (void)BDT.consumeOpen();

  SourceLocation ScoreLoc = Tok.getLocation();
  ExprResult Score = parseContextScore(*this);

  if (!AllowsTraitScore && !Score.isUnset()) {
    if (Score.isUsable()) {
      Diag(ScoreLoc, diag::warn_omp_ctx_incompatible_score_for_property)
          << getOpenMPContextTraitSelectorName(TISelector.Kind)
          << getOpenMPContextTraitSetName(Set) << Score.get();
    } else {
      Diag(ScoreLoc, diag::warn_omp_ctx_incompatible_score_for_property)
          << getOpenMPContextTraitSelectorName(TISelector.Kind)
          << getOpenMPContextTraitSetName(Set) << "<invalid>";
    }
    Score = ExprResult();
  }

  if (Score.isUsable())
    TISelector.ScoreOrCondition = Score.get();

  llvm::StringMap<SourceLocation> SeenProperties;
  do {
    parseOMPContextProperty(TISelector, Set, SeenProperties);
  } while (TryConsumeToken(tok::comma));

  // Parse ')'.
  BDT.consumeClose();
}

void Parser::parseOMPTraitSetKind(OMPTraitSet &TISet,
                                  llvm::StringMap<SourceLocation> &Seen) {
  TISet.Kind = TraitSet::invalid;

  SourceLocation NameLoc = Tok.getLocation();
  StringRef Name = getNameFromIdOrString(*this, Tok, CONTEXT_SELECTOR_SET_LVL);
  if (Name.empty()) {
    Diag(Tok.getLocation(), diag::note_omp_declare_variant_ctx_options)
        << CONTEXT_SELECTOR_SET_LVL << listOpenMPContextTraitSets();
    return;
  }

  TISet.Kind = getOpenMPContextTraitSetKind(Name);
  if (TISet.Kind != TraitSet::invalid) {
    if (checkForDuplicates(*this, Name, NameLoc, Seen,
                           CONTEXT_SELECTOR_SET_LVL))
      TISet.Kind = TraitSet::invalid;
    return;
  }

  // It follows diagnosis and helping notes.
  Diag(NameLoc, diag::warn_omp_declare_variant_ctx_not_a_set) << Name;

  TraitSelector SelectorForName = getOpenMPContextTraitSelectorKind(Name);
  if (SelectorForName != TraitSelector::invalid) {
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_is_a)
        << Name << CONTEXT_SELECTOR_LVL << CONTEXT_SELECTOR_SET_LVL;
    bool AllowsTraitScore = false;
    bool RequiresProperty = false;
    isValidTraitSelectorForTraitSet(
        SelectorForName, getOpenMPContextTraitSetForSelector(SelectorForName),
        AllowsTraitScore, RequiresProperty);
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_try)
        << getOpenMPContextTraitSetName(
               getOpenMPContextTraitSetForSelector(SelectorForName))
        << Name << (RequiresProperty ? "(<property-name>)" : "");
    return;
  }
  for (const auto &PotentialSet :
       {TraitSet::construct, TraitSet::user, TraitSet::implementation,
        TraitSet::device}) {
    TraitProperty PropertyForName = getOpenMPContextTraitPropertyKind(
        PotentialSet, TraitSelector::invalid, Name);
    if (PropertyForName == TraitProperty::invalid)
      continue;
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_is_a)
        << Name << CONTEXT_TRAIT_LVL << CONTEXT_SELECTOR_SET_LVL;
    Diag(NameLoc, diag::note_omp_declare_variant_ctx_try)
        << getOpenMPContextTraitSetName(
               getOpenMPContextTraitSetForProperty(PropertyForName))
        << getOpenMPContextTraitSelectorName(
               getOpenMPContextTraitSelectorForProperty(PropertyForName))
        << ("(" + Name + ")").str();
    return;
  }
  Diag(NameLoc, diag::note_omp_declare_variant_ctx_options)
      << CONTEXT_SELECTOR_SET_LVL << listOpenMPContextTraitSets();
}

/// Parses an OpenMP context selector set.
///
/// <trait-set-selector-name> '=' '{' <trait-selector> [, <trait-selector>]* '}'
void Parser::parseOMPContextSelectorSet(
    OMPTraitSet &TISet, llvm::StringMap<SourceLocation> &SeenSets) {
  auto OuterBC = BraceCount;

  // If anything went wrong we issue an error or warning and then skip the rest
  // of the set. However, commas are ambiguous so we look for the nesting
  // of braces here as well.
  auto FinishSelectorSet = [this, OuterBC]() -> void {
    bool Done = false;
    while (!Done) {
      while (!SkipUntil({tok::comma, tok::r_brace, tok::r_paren,
                         tok::annot_pragma_openmp_end},
                        StopBeforeMatch))
        ;
      if (Tok.is(tok::r_brace) && OuterBC > BraceCount)
        (void)ConsumeBrace();
      if (OuterBC <= BraceCount) {
        Done = true;
        break;
      }
      if (!Tok.is(tok::comma) && !Tok.is(tok::r_brace)) {
        Done = true;
        break;
      }
      (void)ConsumeAnyToken();
    }
    Diag(Tok.getLocation(), diag::note_omp_declare_variant_ctx_continue_here)
        << CONTEXT_SELECTOR_SET_LVL;
  };

  parseOMPTraitSetKind(TISet, SeenSets);
  if (TISet.Kind == TraitSet::invalid)
    return FinishSelectorSet();

  // Parse '='.
  if (!TryConsumeToken(tok::equal))
    Diag(Tok.getLocation(), diag::warn_omp_declare_variant_expected)
        << "="
        << ("context set name \"" + getOpenMPContextTraitSetName(TISet.Kind) +
            "\"")
               .str();

  // Parse '{'.
  if (Tok.is(tok::l_brace)) {
    (void)ConsumeBrace();
  } else {
    Diag(Tok.getLocation(), diag::warn_omp_declare_variant_expected)
        << "{"
        << ("'=' that follows the context set name \"" +
            getOpenMPContextTraitSetName(TISet.Kind) + "\"")
               .str();
  }

  llvm::StringMap<SourceLocation> SeenSelectors;
  do {
    OMPTraitSelector TISelector;
    parseOMPContextSelector(TISelector, TISet.Kind, SeenSelectors);
    if (TISelector.Kind != TraitSelector::invalid &&
        !TISelector.Properties.empty())
      TISet.Selectors.push_back(TISelector);
  } while (TryConsumeToken(tok::comma));

  // Parse '}'.
  if (Tok.is(tok::r_brace)) {
    (void)ConsumeBrace();
  } else {
    Diag(Tok.getLocation(), diag::warn_omp_declare_variant_expected)
        << "}"
        << ("context selectors for the context set \"" +
            getOpenMPContextTraitSetName(TISet.Kind) + "\"")
               .str();
  }
}

/// Parse OpenMP context selectors:
///
/// <trait-set-selector> [, <trait-set-selector>]*
bool Parser::parseOMPContextSelectors(SourceLocation Loc, OMPTraitInfo &TI) {
  llvm::StringMap<SourceLocation> SeenSets;
  do {
    OMPTraitSet TISet;
    parseOMPContextSelectorSet(TISet, SeenSets);
    if (TISet.Kind != TraitSet::invalid && !TISet.Selectors.empty())
      TI.Sets.push_back(TISet);
  } while (TryConsumeToken(tok::comma));

  return false;
}

/// Parse clauses for '#pragma omp declare variant ( variant-func-id ) clause'.
void Parser::ParseOMPDeclareVariantClauses(Parser::DeclGroupPtrTy Ptr,
                                           CachedTokens &Toks,
                                           SourceLocation Loc) {
  PP.EnterToken(Tok, /*IsReinject*/ true);
  PP.EnterTokenStream(Toks, /*DisableMacroExpansion=*/true,
                      /*IsReinject*/ true);
  // Consume the previously pushed token.
  ConsumeAnyToken(/*ConsumeCodeCompletionTok=*/true);
  ConsumeAnyToken(/*ConsumeCodeCompletionTok=*/true);

  FNContextRAII FnContext(*this, Ptr);
  // Parse function declaration id.
  SourceLocation RLoc;
  // Parse with IsAddressOfOperand set to true to parse methods as DeclRefExprs
  // instead of MemberExprs.
  ExprResult AssociatedFunction;
  {
    // Do not mark function as is used to prevent its emission if this is the
    // only place where it is used.
    EnterExpressionEvaluationContext Unevaluated(
        Actions, Sema::ExpressionEvaluationContext::Unevaluated);
    AssociatedFunction = ParseOpenMPParensExpr(
        getOpenMPDirectiveName(OMPD_declare_variant), RLoc,
        /*IsAddressOfOperand=*/true);
  }
  if (!AssociatedFunction.isUsable()) {
    if (!Tok.is(tok::annot_pragma_openmp_end))
      while (!SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch))
        ;
    // Skip the last annot_pragma_openmp_end.
    (void)ConsumeAnnotationToken();
    return;
  }

  OMPTraitInfo *ParentTI =
      Actions.OpenMP().getOMPTraitInfoForSurroundingScope();
  ASTContext &ASTCtx = Actions.getASTContext();
  OMPTraitInfo &TI = ASTCtx.getNewOMPTraitInfo();
  SmallVector<Expr *, 6> AdjustNothing;
  SmallVector<Expr *, 6> AdjustNeedDevicePtr;
  SmallVector<OMPInteropInfo, 3> AppendArgs;
  SourceLocation AdjustArgsLoc, AppendArgsLoc;

  // At least one clause is required.
  if (Tok.is(tok::annot_pragma_openmp_end)) {
    Diag(Tok.getLocation(), diag::err_omp_declare_variant_wrong_clause)
        << (getLangOpts().OpenMP < 51 ? 0 : 1);
  }

  bool IsError = false;
  while (Tok.isNot(tok::annot_pragma_openmp_end)) {
    OpenMPClauseKind CKind = Tok.isAnnotation()
                                 ? OMPC_unknown
                                 : getOpenMPClauseKind(PP.getSpelling(Tok));
    if (!isAllowedClauseForDirective(OMPD_declare_variant, CKind,
                                     getLangOpts().OpenMP)) {
      Diag(Tok.getLocation(), diag::err_omp_declare_variant_wrong_clause)
          << (getLangOpts().OpenMP < 51 ? 0 : 1);
      IsError = true;
    }
    if (!IsError) {
      switch (CKind) {
      case OMPC_match:
        IsError = parseOMPDeclareVariantMatchClause(Loc, TI, ParentTI);
        break;
      case OMPC_adjust_args: {
        AdjustArgsLoc = Tok.getLocation();
        ConsumeToken();
        SemaOpenMP::OpenMPVarListDataTy Data;
        SmallVector<Expr *> Vars;
        IsError = ParseOpenMPVarList(OMPD_declare_variant, OMPC_adjust_args,
                                     Vars, Data);
        if (!IsError)
          llvm::append_range(Data.ExtraModifier == OMPC_ADJUST_ARGS_nothing
                                 ? AdjustNothing
                                 : AdjustNeedDevicePtr,
                             Vars);
        break;
      }
      case OMPC_append_args:
        if (!AppendArgs.empty()) {
          Diag(AppendArgsLoc, diag::err_omp_more_one_clause)
              << getOpenMPDirectiveName(OMPD_declare_variant)
              << getOpenMPClauseName(CKind) << 0;
          IsError = true;
        }
        if (!IsError) {
          AppendArgsLoc = Tok.getLocation();
          ConsumeToken();
          IsError = parseOpenMPAppendArgs(AppendArgs);
        }
        break;
      default:
        llvm_unreachable("Unexpected clause for declare variant.");
      }
    }
    if (IsError) {
      while (!SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch))
        ;
      // Skip the last annot_pragma_openmp_end.
      (void)ConsumeAnnotationToken();
      return;
    }
    // Skip ',' if any.
    if (Tok.is(tok::comma))
      ConsumeToken();
  }

  std::optional<std::pair<FunctionDecl *, Expr *>> DeclVarData =
      Actions.OpenMP().checkOpenMPDeclareVariantFunction(
          Ptr, AssociatedFunction.get(), TI, AppendArgs.size(),
          SourceRange(Loc, Tok.getLocation()));

  if (DeclVarData && !TI.Sets.empty())
    Actions.OpenMP().ActOnOpenMPDeclareVariantDirective(
        DeclVarData->first, DeclVarData->second, TI, AdjustNothing,
        AdjustNeedDevicePtr, AppendArgs, AdjustArgsLoc, AppendArgsLoc,
        SourceRange(Loc, Tok.getLocation()));

  // Skip the last annot_pragma_openmp_end.
  (void)ConsumeAnnotationToken();
}

bool Parser::parseOpenMPAppendArgs(
    SmallVectorImpl<OMPInteropInfo> &InteropInfos) {
  bool HasError = false;
  // Parse '('.
  BalancedDelimiterTracker T(*this, tok::l_paren, tok::annot_pragma_openmp_end);
  if (T.expectAndConsume(diag::err_expected_lparen_after,
                         getOpenMPClauseName(OMPC_append_args).data()))
    return true;

  // Parse the list of append-ops, each is;
  // interop(interop-type[,interop-type]...)
  while (Tok.is(tok::identifier) && Tok.getIdentifierInfo()->isStr("interop")) {
    ConsumeToken();
    BalancedDelimiterTracker IT(*this, tok::l_paren,
                                tok::annot_pragma_openmp_end);
    if (IT.expectAndConsume(diag::err_expected_lparen_after, "interop"))
      return true;

    OMPInteropInfo InteropInfo;
    if (ParseOMPInteropInfo(InteropInfo, OMPC_append_args))
      HasError = true;
    else
      InteropInfos.push_back(InteropInfo);

    IT.consumeClose();
    if (Tok.is(tok::comma))
      ConsumeToken();
  }
  if (!HasError && InteropInfos.empty()) {
    HasError = true;
    Diag(Tok.getLocation(), diag::err_omp_unexpected_append_op);
    SkipUntil(tok::comma, tok::r_paren, tok::annot_pragma_openmp_end,
              StopBeforeMatch);
  }
  HasError = T.consumeClose() || HasError;
  return HasError;
}

bool Parser::parseOMPDeclareVariantMatchClause(SourceLocation Loc,
                                               OMPTraitInfo &TI,
                                               OMPTraitInfo *ParentTI) {
  // Parse 'match'.
  OpenMPClauseKind CKind = Tok.isAnnotation()
                               ? OMPC_unknown
                               : getOpenMPClauseKind(PP.getSpelling(Tok));
  if (CKind != OMPC_match) {
    Diag(Tok.getLocation(), diag::err_omp_declare_variant_wrong_clause)
        << (getLangOpts().OpenMP < 51 ? 0 : 1);
    return true;
  }
  (void)ConsumeToken();
  // Parse '('.
  BalancedDelimiterTracker T(*this, tok::l_paren, tok::annot_pragma_openmp_end);
  if (T.expectAndConsume(diag::err_expected_lparen_after,
                         getOpenMPClauseName(OMPC_match).data()))
    return true;

  // Parse inner context selectors.
  parseOMPContextSelectors(Loc, TI);

  // Parse ')'
  (void)T.consumeClose();

  if (!ParentTI)
    return false;

  // Merge the parent/outer trait info into the one we just parsed and diagnose
  // problems.
  // TODO: Keep some source location in the TI to provide better diagnostics.
  // TODO: Perform some kind of equivalence check on the condition and score
  //       expressions.
  for (const OMPTraitSet &ParentSet : ParentTI->Sets) {
    bool MergedSet = false;
    for (OMPTraitSet &Set : TI.Sets) {
      if (Set.Kind != ParentSet.Kind)
        continue;
      MergedSet = true;
      for (const OMPTraitSelector &ParentSelector : ParentSet.Selectors) {
        bool MergedSelector = false;
        for (OMPTraitSelector &Selector : Set.Selectors) {
          if (Selector.Kind != ParentSelector.Kind)
            continue;
          MergedSelector = true;
          for (const OMPTraitProperty &ParentProperty :
               ParentSelector.Properties) {
            bool MergedProperty = false;
            for (OMPTraitProperty &Property : Selector.Properties) {
              // Ignore "equivalent" properties.
              if (Property.Kind != ParentProperty.Kind)
                continue;

              // If the kind is the same but the raw string not, we don't want
              // to skip out on the property.
              MergedProperty |= Property.RawString == ParentProperty.RawString;

              if (Property.RawString == ParentProperty.RawString &&
                  Selector.ScoreOrCondition == ParentSelector.ScoreOrCondition)
                continue;

              if (Selector.Kind == llvm::omp::TraitSelector::user_condition) {
                Diag(Loc, diag::err_omp_declare_variant_nested_user_condition);
              } else if (Selector.ScoreOrCondition !=
                         ParentSelector.ScoreOrCondition) {
                Diag(Loc, diag::err_omp_declare_variant_duplicate_nested_trait)
                    << getOpenMPContextTraitPropertyName(
                           ParentProperty.Kind, ParentProperty.RawString)
                    << getOpenMPContextTraitSelectorName(ParentSelector.Kind)
                    << getOpenMPContextTraitSetName(ParentSet.Kind);
              }
            }
            if (!MergedProperty)
              Selector.Properties.push_back(ParentProperty);
          }
        }
        if (!MergedSelector)
          Set.Selectors.push_back(ParentSelector);
      }
    }
    if (!MergedSet)
      TI.Sets.push_back(ParentSet);
  }

  return false;
}

/// <clause> [clause[ [,] clause] ... ]
///
///  clauses: for error directive
///     'at' '(' compilation | execution ')'
///     'severity' '(' fatal | warning ')'
///     'message' '(' msg-string ')'
/// ....
void Parser::ParseOpenMPClauses(OpenMPDirectiveKind DKind,
                                SmallVectorImpl<OMPClause *> &Clauses,
                                SourceLocation Loc) {
  std::bitset<llvm::omp::Clause_enumSize + 1> SeenClauses;
  while (Tok.isNot(tok::annot_pragma_openmp_end)) {
    OpenMPClauseKind CKind = Tok.isAnnotation()
                                 ? OMPC_unknown
                                 : getOpenMPClauseKind(PP.getSpelling(Tok));
    Actions.OpenMP().StartOpenMPClause(CKind);
    OMPClause *Clause =
        ParseOpenMPClause(DKind, CKind, !SeenClauses[unsigned(CKind)]);
    SkipUntil(tok::comma, tok::identifier, tok::annot_pragma_openmp_end,
              StopBeforeMatch);
    SeenClauses[unsigned(CKind)] = true;
    if (Clause != nullptr)
      Clauses.push_back(Clause);
    if (Tok.is(tok::annot_pragma_openmp_end)) {
      Actions.OpenMP().EndOpenMPClause();
      break;
    }
    // Skip ',' if any.
    if (Tok.is(tok::comma))
      ConsumeToken();
    Actions.OpenMP().EndOpenMPClause();
  }
}

/// `omp assumes` or `omp begin/end assumes` <clause> [[,]<clause>]...
/// where
///
///   clause:
///     'ext_IMPL_DEFINED'
///     'absent' '(' directive-name [, directive-name]* ')'
///     'contains' '(' directive-name [, directive-name]* ')'
///     'holds' '(' scalar-expression ')'
///     'no_openmp'
///     'no_openmp_routines'
///     'no_parallelism'
///
void Parser::ParseOpenMPAssumesDirective(OpenMPDirectiveKind DKind,
                                         SourceLocation Loc) {
  SmallVector<std::string, 4> Assumptions;
  bool SkippedClauses = false;

  auto SkipBraces = [&](llvm::StringRef Spelling, bool IssueNote) {
    BalancedDelimiterTracker T(*this, tok::l_paren,
                               tok::annot_pragma_openmp_end);
    if (T.expectAndConsume(diag::err_expected_lparen_after, Spelling.data()))
      return;
    T.skipToEnd();
    if (IssueNote && T.getCloseLocation().isValid())
      Diag(T.getCloseLocation(),
           diag::note_omp_assumption_clause_continue_here);
  };

  /// Helper to determine which AssumptionClauseMapping (ACM) in the
  /// AssumptionClauseMappings table matches \p RawString. The return value is
  /// the index of the matching ACM into the table or -1 if there was no match.
  auto MatchACMClause = [&](StringRef RawString) {
    llvm::StringSwitch<int> SS(RawString);
    unsigned ACMIdx = 0;
    for (const AssumptionClauseMappingInfo &ACMI : AssumptionClauseMappings) {
      if (ACMI.StartsWith)
        SS.StartsWith(ACMI.Identifier, ACMIdx++);
      else
        SS.Case(ACMI.Identifier, ACMIdx++);
    }
    return SS.Default(-1);
  };

  while (Tok.isNot(tok::annot_pragma_openmp_end)) {
    IdentifierInfo *II = nullptr;
    SourceLocation StartLoc = Tok.getLocation();
    int Idx = -1;
    if (Tok.isAnyIdentifier()) {
      II = Tok.getIdentifierInfo();
      Idx = MatchACMClause(II->getName());
    }
    ConsumeAnyToken();

    bool NextIsLPar = Tok.is(tok::l_paren);
    // Handle unknown clauses by skipping them.
    if (Idx == -1) {
      Diag(StartLoc, diag::warn_omp_unknown_assumption_clause_missing_id)
          << llvm::omp::getOpenMPDirectiveName(DKind)
          << llvm::omp::getAllAssumeClauseOptions() << NextIsLPar;
      if (NextIsLPar)
        SkipBraces(II ? II->getName() : "", /* IssueNote */ true);
      SkippedClauses = true;
      continue;
    }
    const AssumptionClauseMappingInfo &ACMI = AssumptionClauseMappings[Idx];
    if (ACMI.HasDirectiveList || ACMI.HasExpression) {
      // TODO: We ignore absent, contains, and holds assumptions for now. We
      //       also do not verify the content in the parenthesis at all.
      SkippedClauses = true;
      SkipBraces(II->getName(), /* IssueNote */ false);
      continue;
    }

    if (NextIsLPar) {
      Diag(Tok.getLocation(),
           diag::warn_omp_unknown_assumption_clause_without_args)
          << II;
      SkipBraces(II->getName(), /* IssueNote */ true);
    }

    assert(II && "Expected an identifier clause!");
    std::string Assumption = II->getName().str();
    if (ACMI.StartsWith)
      Assumption = "ompx_" + Assumption.substr(ACMI.Identifier.size());
    else
      Assumption = "omp_" + Assumption;
    Assumptions.push_back(Assumption);
  }

  Actions.OpenMP().ActOnOpenMPAssumesDirective(Loc, DKind, Assumptions,
                                               SkippedClauses);
}

void Parser::ParseOpenMPEndAssumesDirective(SourceLocation Loc) {
  if (Actions.OpenMP().isInOpenMPAssumeScope())
    Actions.OpenMP().ActOnOpenMPEndAssumesDirective();
  else
    Diag(Loc, diag::err_expected_begin_assumes);
}

/// Parsing of simple OpenMP clauses like 'default' or 'proc_bind'.
///
///    default-clause:
///         'default' '(' 'none' | 'shared'  | 'private' | 'firstprivate' ')
///
///    proc_bind-clause:
///         'proc_bind' '(' 'master' | 'close' | 'spread' ')
///
///    device_type-clause:
///         'device_type' '(' 'host' | 'nohost' | 'any' )'
namespace {
struct SimpleClauseData {
  unsigned Type;
  SourceLocation Loc;
  SourceLocation LOpen;
  SourceLocation TypeLoc;
  SourceLocation RLoc;
  SimpleClauseData(unsigned Type, SourceLocation Loc, SourceLocation LOpen,
                   SourceLocation TypeLoc, SourceLocation RLoc)
      : Type(Type), Loc(Loc), LOpen(LOpen), TypeLoc(TypeLoc), RLoc(RLoc) {}
};
} // anonymous namespace

static std::optional<SimpleClauseData>
parseOpenMPSimpleClause(Parser &P, OpenMPClauseKind Kind) {
  const Token &Tok = P.getCurToken();
  SourceLocation Loc = Tok.getLocation();
  SourceLocation LOpen = P.ConsumeToken();
  // Parse '('.
  BalancedDelimiterTracker T(P, tok::l_paren, tok::annot_pragma_openmp_end);
  if (T.expectAndConsume(diag::err_expected_lparen_after,
                         getOpenMPClauseName(Kind).data()))
    return std::nullopt;

  unsigned Type = getOpenMPSimpleClauseType(
      Kind, Tok.isAnnotation() ? "" : P.getPreprocessor().getSpelling(Tok),
      P.getLangOpts());
  SourceLocation TypeLoc = Tok.getLocation();
  if (Tok.isNot(tok::r_paren) && Tok.isNot(tok::comma) &&
      Tok.isNot(tok::annot_pragma_openmp_end))
    P.ConsumeAnyToken();

  // Parse ')'.
  SourceLocation RLoc = Tok.getLocation();
  if (!T.consumeClose())
    RLoc = T.getCloseLocation();

  return SimpleClauseData(Type, Loc, LOpen, TypeLoc, RLoc);
}

void Parser::ParseOMPDeclareTargetClauses(
    SemaOpenMP::DeclareTargetContextInfo &DTCI) {
  SourceLocation DeviceTypeLoc;
  bool RequiresToOrLinkOrIndirectClause = false;
  bool HasToOrLinkOrIndirectClause = false;
  while (Tok.isNot(tok::annot_pragma_openmp_end)) {
    OMPDeclareTargetDeclAttr::MapTypeTy MT = OMPDeclareTargetDeclAttr::MT_To;
    bool HasIdentifier = Tok.is(tok::identifier);
    if (HasIdentifier) {
      // If we see any clause we need a to or link clause.
      RequiresToOrLinkOrIndirectClause = true;
      IdentifierInfo *II = Tok.getIdentifierInfo();
      StringRef ClauseName = II->getName();
      bool IsDeviceTypeClause =
          getLangOpts().OpenMP >= 50 &&
          getOpenMPClauseKind(ClauseName) == OMPC_device_type;

      bool IsIndirectClause = getLangOpts().OpenMP >= 51 &&
                              getOpenMPClauseKind(ClauseName) == OMPC_indirect;
      if (DTCI.Indirect && IsIndirectClause) {
        Diag(Tok, diag::err_omp_more_one_clause)
            << getOpenMPDirectiveName(OMPD_declare_target)
            << getOpenMPClauseName(OMPC_indirect) << 0;
        break;
      }
      bool IsToEnterOrLinkClause =
          OMPDeclareTargetDeclAttr::ConvertStrToMapTypeTy(ClauseName, MT);
      assert((!IsDeviceTypeClause || !IsToEnterOrLinkClause) &&
             "Cannot be both!");

      // Starting with OpenMP 5.2 the `to` clause has been replaced by the
      // `enter` clause.
      if (getLangOpts().OpenMP >= 52 && ClauseName == "to") {
        Diag(Tok, diag::err_omp_declare_target_unexpected_to_clause);
        break;
      }
      if (getLangOpts().OpenMP <= 51 && ClauseName == "enter") {
        Diag(Tok, diag::err_omp_declare_target_unexpected_enter_clause);
        break;
      }

      if (!IsDeviceTypeClause && !IsIndirectClause &&
          DTCI.Kind == OMPD_begin_declare_target) {
        Diag(Tok, diag::err_omp_declare_target_unexpected_clause)
            << ClauseName << (getLangOpts().OpenMP >= 51 ? 3 : 0);
        break;
      }
      if (!IsDeviceTypeClause && !IsToEnterOrLinkClause && !IsIndirectClause) {
        Diag(Tok, getLangOpts().OpenMP >= 52
                      ? diag::err_omp_declare_target_unexpected_clause_52
                      : diag::err_omp_declare_target_unexpected_clause)
            << ClauseName
            << (getLangOpts().OpenMP >= 51
                    ? 4
                    : getLangOpts().OpenMP >= 50 ? 2 : 1);
        break;
      }

      if (IsToEnterOrLinkClause || IsIndirectClause)
        HasToOrLinkOrIndirectClause = true;

      if (IsIndirectClause) {
        if (!ParseOpenMPIndirectClause(DTCI, /*ParseOnly*/ false))
          break;
        continue;
      }
      // Parse 'device_type' clause and go to next clause if any.
      if (IsDeviceTypeClause) {
        std::optional<SimpleClauseData> DevTypeData =
            parseOpenMPSimpleClause(*this, OMPC_device_type);
        if (DevTypeData) {
          if (DeviceTypeLoc.isValid()) {
            // We already saw another device_type clause, diagnose it.
            Diag(DevTypeData->Loc,
                 diag::warn_omp_more_one_device_type_clause);
            break;
          }
          switch (static_cast<OpenMPDeviceType>(DevTypeData->Type)) {
          case OMPC_DEVICE_TYPE_any:
            DTCI.DT = OMPDeclareTargetDeclAttr::DT_Any;
            break;
          case OMPC_DEVICE_TYPE_host:
            DTCI.DT = OMPDeclareTargetDeclAttr::DT_Host;
            break;
          case OMPC_DEVICE_TYPE_nohost:
            DTCI.DT = OMPDeclareTargetDeclAttr::DT_NoHost;
            break;
          case OMPC_DEVICE_TYPE_unknown:
            llvm_unreachable("Unexpected device_type");
          }
          DeviceTypeLoc = DevTypeData->Loc;
        }
        continue;
      }
      ConsumeToken();
    }

    if (DTCI.Kind == OMPD_declare_target || HasIdentifier) {
      auto &&Callback = [this, MT, &DTCI](CXXScopeSpec &SS,
                                          DeclarationNameInfo NameInfo) {
        NamedDecl *ND = Actions.OpenMP().lookupOpenMPDeclareTargetName(
            getCurScope(), SS, NameInfo);
        if (!ND)
          return;
        SemaOpenMP::DeclareTargetContextInfo::MapInfo MI{MT, NameInfo.getLoc()};
        bool FirstMapping = DTCI.ExplicitlyMapped.try_emplace(ND, MI).second;
        if (!FirstMapping)
          Diag(NameInfo.getLoc(), diag::err_omp_declare_target_multiple)
              << NameInfo.getName();
      };
      if (ParseOpenMPSimpleVarList(OMPD_declare_target, Callback,
                                   /*AllowScopeSpecifier=*/true))
        break;
    }

    if (Tok.is(tok::l_paren)) {
      Diag(Tok,
           diag::err_omp_begin_declare_target_unexpected_implicit_to_clause);
      break;
    }
    if (!HasIdentifier && Tok.isNot(tok::annot_pragma_openmp_end)) {
      Diag(Tok,
           getLangOpts().OpenMP >= 52
               ? diag::err_omp_declare_target_wrong_clause_after_implicit_enter
               : diag::err_omp_declare_target_wrong_clause_after_implicit_to);
      break;
    }

    // Consume optional ','.
    if (Tok.is(tok::comma))
      ConsumeToken();
  }

  if (DTCI.Indirect && DTCI.DT != OMPDeclareTargetDeclAttr::DT_Any)
    Diag(DeviceTypeLoc, diag::err_omp_declare_target_indirect_device_type);

  // For declare target require at least 'to' or 'link' to be present.
  if (DTCI.Kind == OMPD_declare_target && RequiresToOrLinkOrIndirectClause &&
      !HasToOrLinkOrIndirectClause)
    Diag(DTCI.Loc,
         getLangOpts().OpenMP >= 52
             ? diag::err_omp_declare_target_missing_enter_or_link_clause
             : diag::err_omp_declare_target_missing_to_or_link_clause)
        << (getLangOpts().OpenMP >= 51 ? 1 : 0);

  SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch);
}

void Parser::skipUntilPragmaOpenMPEnd(OpenMPDirectiveKind DKind) {
  // The last seen token is annot_pragma_openmp_end - need to check for
  // extra tokens.
  if (Tok.is(tok::annot_pragma_openmp_end))
    return;

  Diag(Tok, diag::warn_omp_extra_tokens_at_eol)
      << getOpenMPDirectiveName(DKind);
  while (Tok.isNot(tok::annot_pragma_openmp_end))
    ConsumeAnyToken();
}

void Parser::parseOMPEndDirective(OpenMPDirectiveKind BeginKind,
                                  OpenMPDirectiveKind ExpectedKind,
                                  OpenMPDirectiveKind FoundKind,
                                  SourceLocation BeginLoc,
                                  SourceLocation FoundLoc,
                                  bool SkipUntilOpenMPEnd) {
  int DiagSelection = ExpectedKind == OMPD_end_declare_target ? 0 : 1;

  if (FoundKind == ExpectedKind) {
    ConsumeAnyToken();
    skipUntilPragmaOpenMPEnd(ExpectedKind);
    return;
  }

  Diag(FoundLoc, diag::err_expected_end_declare_target_or_variant)
      << DiagSelection;
  Diag(BeginLoc, diag::note_matching)
      << ("'#pragma omp " + getOpenMPDirectiveName(BeginKind) + "'").str();
  if (SkipUntilOpenMPEnd)
    SkipUntil(tok::annot_pragma_openmp_end, StopBeforeMatch);
}

void Parser::ParseOMPEndDeclareTargetDirective(OpenMPDirectiveKind BeginDKind,
                                               OpenMPDirectiveKind EndDKind,
                                               SourceLocation DKLoc) {
  parseOMPEndDirective(BeginDKind, OMPD_end_declare_target, EndDKind, DKLoc,
                       Tok.getLocation(),
                       /* SkipUntilOpenMPEnd */ false);
  // Skip the last annot_pragma_openmp_end.
  if (Tok.is(tok::annot_pragma_openmp_end))
    ConsumeAnnotationToken();
}

/// Parsing of declarative OpenMP directives.
///
///       threadprivate-directive:
///         annot_pragma_openmp 'threadprivate' simple-variable-list
///         annot_pragma_openmp_end
///
///       allocate-directive:
///         annot_pragma_openmp 'allocate' simple-variable-list [<clause>]
///         annot_pragma_openmp_end
///
///       declare-reduction-directive:
///        annot_pragma_openmp 'declare' 'reduction' [...]
///        annot_pragma_openmp_end
///
///       declare-mapper-directive:
///         annot_pragma_openmp 'declare' 'mapper' '(' [<mapper-identifer> ':']
///         <type> <var> ')' [<clause>[[,] <clause>] ... ]
///         annot_pragma_openmp_end
///
///       declare-simd-directive:
///         annot_pragma_openmp 'declare simd' {<clause> [,]}
///         annot_pragma_openmp_end
///         <function declaration/definition>
///
///       requires directive:
///         annot_pragma_openmp 'requires' <clause> [[[,] <clause>] ... ]
///         annot_pragma_openmp_end
///
///       assumes directive:
///         annot_pragma_openmp 'assumes' <clause> [[[,] <clause>] ... ]
///         annot_pragma_openmp_end
///       or
///         annot_pragma_openmp 'begin assumes' <clause> [[[,] <clause>] ... ]
///         annot_pragma_openmp 'end assumes'
///         annot_pragma_openmp_end
///
Parser::DeclGroupPtrTy Parser::ParseOpenMPDeclarativeDirectiveWithExtDecl(
    AccessSpecifier &AS, ParsedAttributes &Attrs, bool Delayed,
    DeclSpec::TST TagType, Decl *Tag) {
  assert(Tok.isOneOf(tok::annot_pragma_openmp, tok::annot_attr_openmp) &&
         "Not an OpenMP directive!");
  ParsingOpenMPDirectiveRAII DirScope(*this);
  ParenBraceBracketBalancer BalancerRAIIObj(*this);

  SourceLocation Loc;
  OpenMPDirectiveKind DKind;
  if (Delayed) {
    TentativeParsingAction TPA(*this);
    Loc = ConsumeAnnotationToken();
    DKind = parseOpenMPDirectiveKind(*this);
    if (DKind == OMPD_declare_reduction || DKind == OMPD_declare_mapper) {
      // Need to delay parsing until completion of the parent class.
      TPA.Revert();
      CachedTokens Toks;
      unsigned Cnt = 1;
      Toks.push_back(Tok);
      while (Cnt && Tok.isNot(tok::eof)) {
        (void)ConsumeAnyToken();
        if (Tok.isOneOf(tok::annot_pragma_openmp, tok::annot_attr_openmp))
          ++Cnt;
        else if (Tok.is(tok::annot_pragma_openmp_end))
          --Cnt;
        Toks.push_back(Tok);
      }
      // Skip last annot_pragma_openmp_end.
      if (Cnt == 0)
        (void)ConsumeAnyToken();
      auto *LP = new LateParsedPragma(this, AS);
      LP->takeToks(Toks);
      getCurrentClass().LateParsedDeclarations.push_back(LP);
      return nullptr;
    }
    TPA.Commit();
  } else {
    Loc = ConsumeAnnotationToken();
    DKind = parseOpenMPDirectiveKind(*this);
  }

  switch (DKind) {
  case OMPD_threadprivate: {
    ConsumeToken();
    DeclDirectiveListParserHelper Helper(this, DKind);
    if (!ParseOpenMPSimpleVarList(DKind, Helper,
                                  /*AllowScopeSpecifier=*/true)) {
      skipUntilPragmaOpenMPEnd(DKind);
      // Skip the last annot_pragma_openmp_end.
      ConsumeAnnotationToken();
      return Actions.OpenMP().ActOnOpenMPThreadprivateDirective(
          Loc, Helper.getIdentifiers());
    }
    break;
  }
  case OMPD_allocate: {
    ConsumeToken();
    DeclDirectiveListParserHelper Helper(this, DKind);
    if (!ParseOpenMPSimpleVarList(DKind, Helper,
                                  /*AllowScopeSpecifier=*/true)) {
      SmallVector<OMPClause *, 1> Clauses;
      if (Tok.isNot(tok::annot_pragma_openmp_end)) {
        std::bitset<llvm::omp::Clause_enumSize + 1> SeenClauses;
        while (Tok.isNot(tok::annot_pragma_openmp_end)) {
          OpenMPClauseKind CKind =
              Tok.isAnnotation() ? OMPC_unknown
                                 : getOpenMPClauseKind(PP.getSpelling(Tok));
          Actions.OpenMP().StartOpenMPClause(CKind);
          OMPClause *Clause = ParseOpenMPClause(OMPD_allocate, CKind,
                                                !SeenClauses[unsigned(CKind)]);
          SkipUntil(tok::comma, tok::identifier, tok::annot_pragma_openmp_end,
                    StopBeforeMatch);
          SeenClauses[unsigned(CKind)] = true;
          if (Clause != nullptr)
            Clauses.push_back(Clause);
          if (Tok.is(tok::annot_pragma_openmp_end)) {
            Actions.OpenMP().EndOpenMPClause();
            break;
          }
          // Skip ',' if any.
          if (Tok.is(tok::comma))
            ConsumeToken();
          Actions.OpenMP().EndOpenMPClause();
        }
        skipUntilPragmaOpenMPEnd(DKind);
      }
      // Skip the last annot_pragma_openmp_end.
      ConsumeAnnotationToken();
      return Actions.OpenMP().ActOnOpenMPAllocateDirective(
          Loc, Helper.getIdentifiers(), Clauses);
    }
    break;
  }
  case OMPD_requires: {
    SourceLocation StartLoc = ConsumeToken();
    SmallVector<OMPClause *, 5> Clauses;
    llvm::SmallBitVector SeenClauses(llvm::omp::Clause_enumSize + 1);
    if (Tok.is(tok::annot_pragma_openmp_end)) {
      Diag(Tok, diag::err_omp_expected_clause)
          << getOpenMPDirectiveName(OMPD_requires);
      break;
    }
    while (Tok.isNot(tok::annot_pragma_openmp_end)) {
      OpenMPClauseKind CKind = Tok.isAnnotation()
                                   ? OMPC_unknown
                                   : getOpenMPClauseKind(PP.getSpelling(Tok));
      Actions.OpenMP().StartOpenMPClause(CKind);
      OMPClause *Clause = ParseOpenMPClause(OMPD_requires, CKind,
                                            !SeenClauses[unsigned(CKind)]);
      SkipUntil(tok::comma, tok::identifier, tok::annot_pragma_openmp_end,
                StopBeforeMatch);
      SeenClauses[unsigned(CKind)] = true;
      if (Clause != nullptr)
        Clauses.push_back(Clause);
      if (Tok.is(tok::annot_pragma_openmp_end)) {
        Actions.OpenMP().EndOpenMPClause();
        break;
      }
      // Skip ',' if any.
      if (Tok.is(tok::comma))
        ConsumeToken();
      Actions.OpenMP().EndOpenMPClause();
    }
    // Consume final annot_pragma_openmp_end
    if (Clauses.empty()) {
      Diag(Tok, diag::err_omp_expected_clause)
          << getOpenMPDirectiveName(OMPD_requires);
      ConsumeAnnotationToken();
      return nullptr;
    }
    ConsumeAnnotationToken();
    return Actions.OpenMP().ActOnOpenMPRequiresDirective(StartLoc, Clauses);
  }
  case OMPD_error: {
    SmallVector<OMPClause *, 1> Clauses;
    SourceLocation StartLoc = ConsumeToken();
    ParseOpenMPClauses(DKind, Clauses, StartLoc);
    Actions.OpenMP().ActOnOpenMPErrorDirective(Clauses, StartLoc,
                                               SourceLocation(),
                                               /*InExContext = */ false);
    break;
  }
  case OMPD_assumes:
  case OMPD_begin_assumes:
    ParseOpenMPAssumesDirective(DKind, ConsumeToken());
    break;
  case OMPD_end_assumes:
    ParseOpenMPEndAssumesDirective(ConsumeToken());
    break;
  case OMPD_declare_reduction:
    ConsumeToken();
    if (DeclGroupPtrTy Res = ParseOpenMPDeclareReductionDirective(AS)) {
      skipUntilPragmaOpenMPEnd(OMPD_declare_reduction);
      // Skip the last annot_pragma_openmp_end.
      ConsumeAnnotationToken();
      return Res;
    }
    break;
  case OMPD_declare_mapper: {
    ConsumeToken();
    if (DeclGroupPtrTy Res = ParseOpenMPDeclareMapperDirective(AS)) {
      // Skip the last annot_pragma_openmp_end.
      ConsumeAnnotationToken();
      return Res;
    }
    break;
  }
  case OMPD_begin_declare_variant: {
    // The syntax is:
    // { #pragma omp begin declare variant clause }
    // <function-declaration-or-definition-sequence>
    // { #pragma omp end declare variant }
    //
    ConsumeToken();
    OMPTraitInfo *ParentTI =
        Actions.OpenMP().getOMPTraitInfoForSurroundingScope();
    ASTContext &ASTCtx = Actions.getASTContext();
    OMPTraitInfo &TI = ASTCtx.getNewOMPTraitInfo();
    if (parseOMPDeclareVariantMatchClause(Loc, TI, ParentTI)) {
      while (!SkipUntil(tok::annot_pragma_openmp_end, Parser::StopBeforeMatch))
        ;
      // Skip the last annot_pragma_openmp_end.
      (void)ConsumeAnnotationToken();
      break;
    }

    // Skip last tokens.
    skipUntilPragmaOpenMPEnd(OMPD_begin_declare_variant);

    ParsingOpenMPDirectiveRAII NormalScope(*this, /*Value=*/false);

    VariantMatchInfo VMI;
    TI.getAsVariantMatchInfo(ASTCtx, VMI);

    std::function<void(StringRef)> DiagUnknownTrait =
        [this, Loc](StringRef ISATrait) {
          // TODO Track the selector locations in a way that is accessible here
          // to improve the diagnostic location.
          Diag(Loc, diag::warn_unknown_declare_variant_isa_trait) << ISATrait;
        };
    TargetOMPContext OMPCtx(
        ASTCtx, std::move(DiagUnknownTrait),
        /* CurrentFunctionDecl */ nullptr,
        /* ConstructTraits */ ArrayRef<llvm::omp::TraitProperty>());

    if (isVariantApplicableInContext(VMI, OMPCtx, /* DeviceSetOnly */ true)) {
      Actions.OpenMP().ActOnOpenMPBeginDeclareVariant(Loc, TI);
      break;
    }

    // Elide all the code till the matching end declare variant was found.
    unsigned Nesting = 1;
    SourceLocation DKLoc;
    OpenMPDirectiveKind DK = OMPD_unknown;
    do {
      DKLoc = Tok.getLocation();
      DK = parseOpenMPDirectiveKind(*this);
      if (DK == OMPD_end_declare_variant)
        --Nesting;
      else if (DK == OMPD_begin_declare_variant)
        ++Nesting;
      if (!Nesting || isEofOrEom())
        break;
      ConsumeAnyToken();
    } while (true);

    parseOMPEndDirective(OMPD_begin_declare_variant, OMPD_end_declare_variant,
                         DK, Loc, DKLoc, /* SkipUntilOpenMPEnd */ true);
    if (isEofOrEom())
      return nullptr;
    break;
  }
  case OMPD_end_declare_variant: {
    if (Actions.OpenMP().isInOpenMPDeclareVariantScope())
      Actions.OpenMP().ActOnOpenMPEndDeclareVariant();
    else
      Diag(Loc, diag::err_expected_begin_declare_variant);
    ConsumeToken();
    break;
  }
  case OMPD_declare_variant:
  case OMPD_declare_simd: {
    // The syntax is:
    // { #pragma omp declare {simd|variant} }
    // <function-declaration-or-definition>
    //
    CachedTokens Toks;
    Toks.push_back(Tok);
    ConsumeToken();
    while (Tok.isNot(tok::annot_pragma_openmp_end)) {
      Toks.push_back(Tok);
      ConsumeAnyToken();
    }
    Toks.push_back(Tok);
    ConsumeAnyToken();

    DeclGroupPtrTy Ptr;
    if (Tok.isOneOf(tok::annot_pragma_openmp, tok::annot_attr_openmp)) {
      Ptr = ParseOpenMPDeclarativeDirectiveWithExtDecl(AS, Attrs, Delayed,
                                                       TagType, Tag);
    } else if (Tok.isNot(tok::r_brace) && !isEofOrEom()) {
      // Here we expect to see some function declaration.
      if (AS == AS_none) {
        assert(TagType == DeclSpec::TST_unspecified);
        ParsedAttributes EmptyDeclSpecAttrs(AttrFactory);
        MaybeParseCXX11Attributes(Attrs);
        ParsingDeclSpec PDS(*this);
        Ptr = ParseExternalDeclaration(Attrs, EmptyDeclSpecAttrs, &PDS);
      } else {
        Ptr =
            ParseCXXClassMemberDeclarationWithPragmas(AS, Attrs, TagType, Tag);
      }
    }
    if (!Ptr) {
      Diag(Loc, diag::err_omp_decl_in_declare_simd_variant)
          << (DKind == OMPD_declare_simd ? 0 : 1);
      return DeclGroupPtrTy();
    }
    if (DKind == OMPD_declare_simd)
      return ParseOMPDeclareSimdClauses(Ptr, Toks, Loc);
    assert(DKind == OMPD_declare_variant &&
           "Expected declare variant directive only");
    ParseOMPDeclareVariantClauses(Ptr, Toks, Loc);
    return Ptr;
  }
  case OMPD_begin_declare_target:
  case OMPD_declare_target: {
    SourceLocation DTLoc = ConsumeAnyToken();
    bool HasClauses = Tok.isNot(tok::annot_pragma_openmp_end);
    SemaOpenMP::DeclareTargetContextInfo DTCI(DKind, DTLoc);
    if (HasClauses)
      ParseOMPDeclareTargetClauses(DTCI);
    bool HasImplicitMappings = DKind == OMPD_begin_declare_target ||
                               !HasClauses ||
                               (DTCI.ExplicitlyMapped.empty() && DTCI.Indirect);

    // Skip the last annot_pragma_openmp_end.
    ConsumeAnyToken();

    if (HasImplicitMappings) {
      Actions.OpenMP().ActOnStartOpenMPDeclareTargetContext(DTCI);
      return nullptr;
    }

    Actions.OpenMP().ActOnFinishedOpenMPDeclareTargetContext(DTCI);
    llvm::SmallVector<Decl *, 4> Decls;
    for (auto &It : DTCI.ExplicitlyMapped)
      Decls.push_back(It.first);
    return Actions.BuildDeclaratorGroup(Decls);
  }
  case OMPD_end_declare_target: {
    if (!Actions.OpenMP().isInOpenMPDeclareTargetContext()) {
      Diag(Tok, diag::err_omp_unexpected_directive)
          << 1 << getOpenMPDirectiveName(DKind);
      break;
    }
    const SemaOpenMP::DeclareTargetContextInfo &DTCI =
        Actions.OpenMP().ActOnOpenMPEndDeclareTargetDirective();
    ParseOMPEndDeclareTargetDirective(DTCI.Kind, DKind, DTCI.Loc);
    return nullptr;
  }
  case OMPD_assume: {
    Diag(Tok, diag::err_omp_unexpected_directive)
        << 1 << getOpenMPDirectiveName(DKind);
    break;
  }
  case OMPD_unknown:
    Diag(Tok, diag::err_omp_unknown_directive);
    break;
  default:
    switch (getDirectiveCategory(DKind)) {
    case Category::Executable:
    case Category::Meta:
    case Category::Subsidiary:
    case Category::Utility:
      Diag(Tok, diag::err_omp_unexpected_directive)
          << 1 << getOpenMPDirectiveName(DKind);
      break;
    case Category::Declarative:
    case Category::Informational:
      break;
    }
  }
  while (Tok.isNot(tok::annot_pragma_openmp_end))
    ConsumeAnyToken();
  ConsumeAnyToken();
  return nullptr;
}

StmtResult Parser::ParseOpenMPExecutableDirective(
    ParsedStmtContext StmtCtx, OpenMPDirectiveKind DKind, SourceLocation Loc,
    bool ReadDirectiveWithinMetadirective) {
  assert(isOpenMPExecutableDirective(DKind) && "Unexpected directive category");

  bool HasAssociatedStatement = true;
  Association Assoc = getDirectiveAssociation(DKind);

  // OMPD_ordered has None as association, but it comes in two variants,
  // the second of which is associated with a block.
  // OMPD_scan and OMPD_section are both "separating", but section is treated
  // as if it was associated with a statement, while scan is not.
  if (DKind != OMPD_ordered && DKind != OMPD_section &&
      (Assoc == Association::None || Assoc == Association::Separating)) {
    if ((StmtCtx & ParsedStmtContext::AllowStandaloneOpenMPDirectives) ==
        ParsedStmtContext()) {
      Diag(Tok, diag::err_omp_immediate_directive)
          << getOpenMPDirectiveName(DKind) << 0;
      if (DKind == OMPD_error) {
        SkipUntil(tok::annot_pragma_openmp_end);
        return StmtError();
      }
    }
    HasAssociatedStatement = false;
  }

  SourceLocation EndLoc;
  SmallVector<OMPClause *, 5> Clauses;
  llvm::SmallBitVector SeenClauses(llvm::omp::Clause_enumSize + 1);
  DeclarationNameInfo DirName;
  OpenMPDirectiveKind CancelRegion = OMPD_unknown;
  unsigned ScopeFlags = Scope::FnScope | Scope::DeclScope |
                        Scope::CompoundStmtScope | Scope::OpenMPDirectiveScope;

  // Special processing for flush and depobj clauses.
  Token ImplicitTok;
  bool ImplicitClauseAllowed = false;
  if (DKind == OMPD_flush || DKind == OMPD_depobj) {
    ImplicitTok = Tok;
    ImplicitClauseAllowed = true;
  }
  ConsumeToken();
  // Parse directive name of the 'critical' directive if any.
  if (DKind == OMPD_critical) {
    BalancedDelimiterTracker T(*this, tok::l_paren,
                               tok::annot_pragma_openmp_end);
    if (!T.consumeOpen()) {
      if (Tok.isAnyIdentifier()) {
        DirName =
            DeclarationNameInfo(Tok.getIdentifierInfo(), Tok.getLocation());
        ConsumeAnyToken();
      } else {
        Diag(Tok, diag::err_omp_expected_identifier_for_critical);
      }
      T.consumeClose();
    }
  } else if (DKind == OMPD_cancellation_point || DKind == OMPD_cancel) {
    CancelRegion = parseOpenMPDirectiveKind(*this);
    if (Tok.isNot(tok::annot_pragma_openmp_end))
      ConsumeToken();
  }

  if (isOpenMPLoopDirective(DKind))
    ScopeFlags |= Scope::OpenMPLoopDirectiveScope;
  if (isOpenMPSimdDirective(DKind))
    ScopeFlags |= Scope::OpenMPSimdDirectiveScope;
  ParseScope OMPDirectiveScope(this, ScopeFlags);
  Actions.OpenMP().StartOpenMPDSABlock(DKind, DirName, Actions.getCurScope(),
                                       Loc);

  while (Tok.isNot(tok::annot_pragma_openmp_end)) {
    // If we are parsing for a directive within a metadirective, the directive
    // ends with a ')'.
    if (ReadDirectiveWithinMetadirective && Tok.is(tok::r_paren)) {
      while (Tok.isNot(tok::annot_pragma_openmp_end))
        ConsumeAnyToken();
      break;
    }
    bool HasImplicitClause = false;
    if (ImplicitClauseAllowed && Tok.is(tok::l_paren)) {
      HasImplicitClause = true;
      // Push copy of the current token back to stream to properly parse
      // pseudo-clause OMPFlushClause or OMPDepobjClause.
      PP.EnterToken(Tok, /*IsReinject*/ true);
      PP.EnterToken(ImplicitTok, /*IsReinject*/ true);
      ConsumeAnyToken();
    }
    OpenMPClauseKind CKind = Tok.isAnnotation()
                                 ? OMPC_unknown
                                 : getOpenMPClauseKind(PP.getSpelling(Tok));
    if (HasImplicitClause) {
      assert(CKind == OMPC_unknown && "Must be unknown implicit clause.");
      if (DKind == OMPD_flush) {
        CKind = OMPC_flush;
      } else {
        assert(DKind == OMPD_depobj && "Expected flush or depobj directives.");
        CKind = OMPC_depobj;
      }
    }
    // No more implicit clauses allowed.
    ImplicitClauseAllowed = false;
    Actions.OpenMP().StartOpenMPClause(CKind);
    HasImplicitClause = false;
    OMPClause *Clause =
        ParseOpenMPClause(DKind, CKind, !SeenClauses[unsigned(CKind)]);
    SeenClauses[unsigned(CKind)] = true;
    if (Clause)
      Clauses.push_back(Clause);

    // Skip ',' if any.
    if (Tok.is(tok::comma))
      ConsumeToken();
    Actions.OpenMP().EndOpenMPClause();
  }
  // End location of the directive.
  EndLoc = Tok.getLocation();
  // Consume final annot_pragma_openmp_end.
  ConsumeAnnotationToken();

  if (DKind == OMPD_ordered) {
    // If the depend or doacross clause is specified, the ordered construct
    // is a stand-alone directive.
    for (auto CK : {OMPC_depend, OMPC_doacross}) {
      if (SeenClauses[unsigned(CK)]) {
        if ((StmtCtx & ParsedStmtContext::AllowStandaloneOpenMPDirectives) ==
            ParsedStmtContext()) {
          Diag(Loc, diag::err_omp_immediate_directive)
              << getOpenMPDirectiveName(DKind) << 1 << getOpenMPClauseName(CK);
        }
        HasAssociatedStatement = false;
      }
    }
  }

  if (DKind == OMPD_tile && !SeenClauses[unsigned(OMPC_sizes)]) {
    Diag(Loc, diag::err_omp_required_clause)
        << getOpenMPDirectiveName(OMPD_tile) << "sizes";
  }

  StmtResult AssociatedStmt;
  if (HasAssociatedStatement) {
    // The body is a block scope like in Lambdas and Blocks.
    Actions.OpenMP().ActOnOpenMPRegionStart(DKind, getCurScope());
    // FIXME: We create a bogus CompoundStmt scope to hold the contents of
    // the captured region. Code elsewhere assumes that any FunctionScopeInfo
    // should have at least one compound statement scope within it.
    ParsingOpenMPDirectiveRAII NormalScope(*this, /*Value=*/false);
    {
      Sema::CompoundScopeRAII Scope(Actions);
      AssociatedStmt = ParseStatement();

      if (AssociatedStmt.isUsable() && isOpenMPLoopDirective(DKind) &&
          getLangOpts().OpenMPIRBuilder)
        AssociatedStmt =
            Actions.OpenMP().ActOnOpenMPLoopnest(AssociatedStmt.get());
    }
    AssociatedStmt =
        Actions.OpenMP().ActOnOpenMPRegionEnd(AssociatedStmt, Clauses);
  } else if (DKind == OMPD_target_update || DKind == OMPD_target_enter_data ||
             DKind == OMPD_target_exit_data) {
    Actions.OpenMP().ActOnOpenMPRegionStart(DKind, getCurScope());
    AssociatedStmt = (Sema::CompoundScopeRAII(Actions),
                      Actions.ActOnCompoundStmt(Loc, Loc, std::nullopt,
                                                /*isStmtExpr=*/false));
    AssociatedStmt =
        Actions.OpenMP().ActOnOpenMPRegionEnd(AssociatedStmt, Clauses);
  }

  StmtResult Directive = Actions.OpenMP().ActOnOpenMPExecutableDirective(
      DKind, DirName, CancelRegion, Clauses, AssociatedStmt.get(), Loc, EndLoc);

  // Exit scope.
  Actions.OpenMP().EndOpenMPDSABlock(Directive.get());
  OMPDirectiveScope.Exit();

  return Directive;
}

StmtResult Parser::ParseOpenMPInformationalDirective(
    ParsedStmtContext StmtCtx, OpenMPDirectiveKind DKind, SourceLocation Loc,
    bool ReadDirectiveWithinMetadirective) {
  assert(isOpenMPInformationalDirective(DKind) &&
         "Unexpected directive category");

  bool HasAssociatedStatement = true;

  SmallVector<OMPClause *, 5> Clauses;
  llvm::SmallBitVector SeenClauses(llvm::omp::Clause_enumSize + 1);
  DeclarationNameInfo DirName;
  unsigned ScopeFlags = Scope::FnScope | Scope::DeclScope |
                        Scope::CompoundStmtScope | Scope::OpenMPDirectiveScope;
  ParseScope OMPDirectiveScope(this, ScopeFlags);

  Actions.OpenMP().StartOpenMPDSABlock(DKind, DirName, Actions.getCurScope(),
                                       Loc);

  while (Tok.isNot(tok::annot_pragma_openmp_end)) {
    if (ReadDirectiveWithinMetadirective && Tok.is(tok::r_paren)) {
      while (Tok.isNot(tok::annot_pragma_openmp_end))
        ConsumeAnyToken();
      break;
    }

    OpenMPClauseKind CKind = Tok.isAnnotation()
                                 ? OMPC_unknown
                                 : getOpenMPClauseKind(PP.getSpelling(Tok));
    Actions.OpenMP().StartOpenMPClause(CKind);
    OMPClause *Clause =
        ParseOpenMPClause(DKind, CKind, !SeenClauses[unsigned(CKind)]);
    SeenClauses[unsigned(CKind)] = true;
    if (Clause)
      Clauses.push_back(Clause);

    if (Tok.is(tok::comma))
      ConsumeToken();
    Actions.OpenMP().EndOpenMPClause();
  }

  SourceLocation EndLoc = Tok.getLocation();
  ConsumeAnnotationToken();

  StmtResult AssociatedStmt;
  if (HasAssociatedStatement) {
    Actions.OpenMP().ActOnOpenMPRegionStart(DKind, getCurScope());
    ParsingOpenMPDirectiveRAII NormalScope(*this, /*Value=*/false);
    {
      Sema::CompoundScopeRAII Scope(Actions);
      AssociatedStmt = ParseStatement();
    }
    AssociatedStmt =
        Actions.OpenMP().ActOnOpenMPRegionEnd(AssociatedStmt, Clauses);
  }

  StmtResult Directive = Actions.OpenMP().ActOnOpenMPInformationalDirective(
      DKind, DirName, Clauses, AssociatedStmt.get(), Loc, EndLoc);

  Actions.OpenMP().EndOpenMPDSABlock(Directive.get());
  OMPDirectiveScope.Exit();

  return Directive;
}

/// Parsing of declarative or executable OpenMP directives.
///
///       threadprivate-directive:
///         annot_pragma_openmp 'threadprivate' simple-variable-list
///         annot_pragma_openmp_end
///
///       allocate-directive:
///         annot_pragma_openmp 'allocate' simple-variable-list
///         annot_pragma_openmp_end
///
///       declare-reduction-directive:
///         annot_pragma_openmp 'declare' 'reduction' '(' <reduction_id> ':'
///         <type> {',' <type>} ':' <expression> ')' ['initializer' '('
///         ('omp_priv' '=' <expression>|<function_call>) ')']
///         annot_pragma_openmp_end
///
///       declare-mapper-directive:
///         annot_pragma_openmp 'declare' 'mapper' '(' [<mapper-identifer> ':']
///         <type> <var> ')' [<clause>[[,] <clause>] ... ]
///         annot_pragma_openmp_end
///
///       executable-directive:
///         annot_pragma_openmp 'parallel' | 'simd' | 'for' | 'sections' |
///         'section' | 'single' | 'master' | 'critical' [ '(' <name> ')' ] |
///         'parallel for' | 'parallel sections' | 'parallel master' | 'task' |
///         'taskyield' | 'barrier' | 'taskwait' | 'flush' | 'ordered' | 'error'
///         | 'atomic' | 'for simd' | 'parallel for simd' | 'target' | 'target
///         data' | 'taskgroup' | 'teams' | 'taskloop' | 'taskloop simd' |
///         'master taskloop' | 'master taskloop simd' | 'parallel master
///         taskloop' | 'parallel master taskloop simd' | 'distribute' | 'target
///         enter data' | 'target exit data' | 'target parallel' | 'target
///         parallel for' | 'target update' | 'distribute parallel for' |
///         'distribute paralle for simd' | 'distribute simd' | 'target parallel
///         for simd' | 'target simd' | 'teams distribute' | 'teams distribute
///         simd' | 'teams distribute parallel for simd' | 'teams distribute
///         parallel for' | 'target teams' | 'target teams distribute' | 'target
///         teams distribute parallel for' | 'target teams distribute parallel
///         for simd' | 'target teams distribute simd' | 'masked' |
///         'parallel masked' {clause} annot_pragma_openmp_end
///
StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective(
    ParsedStmtContext StmtCtx, bool ReadDirectiveWithinMetadirective) {
  if (!ReadDirectiveWithinMetadirective)
    assert(Tok.isOneOf(tok::annot_pragma_openmp, tok::annot_attr_openmp) &&
           "Not an OpenMP directive!");
  ParsingOpenMPDirectiveRAII DirScope(*this);
  ParenBraceBracketBalancer BalancerRAIIObj(*this);