text: //===--- SemaStmtAttr.cpp - Statement Attribute Handling ------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file implements stmt-related attribute processing.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Sema/SemaInternal.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Sema/DelayedDiagnostic.h"
  #include "clang/Sema/Lookup.h"
  #include "clang/Sema/ScopeInfo.h"
  #include "llvm/ADT/StringExtras.h"
  
  using namespace clang;
  using namespace sema;
  
  static Attr *handleFallThroughAttr(Sema &S, Stmt *St, const ParsedAttr &A,
                                     SourceRange Range) {
    FallThroughAttr Attr(A.getRange(), S.Context,
                         A.getAttributeSpellingListIndex());
    if (!isa<NullStmt>(St)) {
      S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
          << Attr.getSpelling() << St->getBeginLoc();
      if (isa<SwitchCase>(St)) {
        SourceLocation L = S.getLocForEndOfToken(Range.getEnd());
        S.Diag(L, diag::note_fallthrough_insert_semi_fixit)
            << FixItHint::CreateInsertion(L, ";");
      }
      return nullptr;
    }
    auto *FnScope = S.getCurFunction();
    if (FnScope->SwitchStack.empty()) {
      S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch);
      return nullptr;
    }
  
    // If this is spelled as the standard C++17 attribute, but not in C++17, warn
    // about using it as an extension.
    if (!S.getLangOpts().CPlusPlus17 && A.isCXX11Attribute() &&
        !A.getScopeName())
      S.Diag(A.getLoc(), diag::ext_cxx17_attr) << A.getName();
  
    FnScope->setHasFallthroughStmt();
    return ::new (S.Context) auto(Attr);
  }
  
  static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A,
                                  SourceRange Range) {
    if (A.getNumArgs() < 1) {
      S.Diag(A.getLoc(), diag::err_attribute_too_few_arguments) << A << 1;
      return nullptr;
    }
  
    std::vector<StringRef> DiagnosticIdentifiers;
    for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) {
      StringRef RuleName;
  
      if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr))
        return nullptr;
  
      // FIXME: Warn if the rule name is unknown. This is tricky because only
      // clang-tidy knows about available rules.
      DiagnosticIdentifiers.push_back(RuleName);
    }
  
    return ::new (S.Context) SuppressAttr(
        A.getRange(), S.Context, DiagnosticIdentifiers.data(),
        DiagnosticIdentifiers.size(), A.getAttributeSpellingListIndex());
  }
  
  static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A,
                                  SourceRange) {
    IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
    IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
    IdentifierLoc *StateLoc = A.getArgAsIdent(2);
    Expr *ValueExpr = A.getArgAsExpr(3);
  
    StringRef PragmaName =
        llvm::StringSwitch<StringRef>(PragmaNameLoc->Ident->getName())
            .Cases("unroll", "nounroll", "unroll_and_jam", "nounroll_and_jam",
                   "cilk", PragmaNameLoc->Ident->getName())
            .Default("clang loop");
  
    if ((PragmaName == "cilk") &&
        (St->getStmtClass() != Stmt::CilkForStmtClass)) {
      S.Diag(St->getBeginLoc(), diag::err_pragma_cilk_precedes_noncilk)
        << "#pragma cilk";
      return nullptr;
    }
  
    if (St->getStmtClass() != Stmt::DoStmtClass &&
        St->getStmtClass() != Stmt::ForStmtClass &&
        St->getStmtClass() != Stmt::CXXForRangeStmtClass &&
        St->getStmtClass() != Stmt::WhileStmtClass &&
        St->getStmtClass() != Stmt::CilkForStmtClass) {
      std::string Pragma = "#pragma " + std::string(PragmaName);
      S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
      return nullptr;
    }
  
    LoopHintAttr::Spelling Spelling =
        LoopHintAttr::Spelling(A.getAttributeSpellingListIndex());
    LoopHintAttr::OptionType Option;
    LoopHintAttr::LoopHintState State;
  
    auto SetHints = [&Option, &State](LoopHintAttr::OptionType O,
                                      LoopHintAttr::LoopHintState S) {
      Option = O;
      State = S;
    };
  
    if (PragmaName == "nounroll") {
      SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable);
    } else if (PragmaName == "unroll") {
      // #pragma unroll N
      if (ValueExpr)
        SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric);
      else
        SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable);
    } else if (PragmaName == "nounroll_and_jam") {
      SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable);
    } else if (PragmaName == "unroll_and_jam") {
      // #pragma unroll_and_jam N
      if (ValueExpr)
        SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric);
      else
        SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable);
    } else if (PragmaName == "cilk") {
      Spelling = LoopHintAttr::Pragma_cilk;
      Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
                   OptionLoc->Ident->getName())
                   .Case("grainsize", LoopHintAttr::TapirGrainsize)
                   .Default(LoopHintAttr::TapirGrainsize);
      if (Option == LoopHintAttr::TapirGrainsize) {
        assert(ValueExpr && "Attribute must have a valid value expression.");
        if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
          return nullptr;
        State = LoopHintAttr::Numeric;
      } else
        llvm_unreachable("bad loop hint");
    } else {
      // #pragma clang loop ...
      assert(OptionLoc && OptionLoc->Ident &&
             "Attribute must have valid option info.");
      Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
                   OptionLoc->Ident->getName())
                   .Case("vectorize", LoopHintAttr::Vectorize)
                   .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
                   .Case("interleave", LoopHintAttr::Interleave)
                   .Case("interleave_count", LoopHintAttr::InterleaveCount)
                   .Case("unroll", LoopHintAttr::Unroll)
                   .Case("unroll_count", LoopHintAttr::UnrollCount)
                   .Case("pipeline", LoopHintAttr::PipelineDisabled)
                   .Case("pipeline_initiation_interval",
                         LoopHintAttr::PipelineInitiationInterval)
                   .Case("distribute", LoopHintAttr::Distribute)
                   .Default(LoopHintAttr::Vectorize);
      if (Option == LoopHintAttr::VectorizeWidth ||
          Option == LoopHintAttr::InterleaveCount ||
          Option == LoopHintAttr::UnrollCount ||
          Option == LoopHintAttr::PipelineInitiationInterval) {
        assert(ValueExpr && "Attribute must have a valid value expression.");
        if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
          return nullptr;
        State = LoopHintAttr::Numeric;
      } else if (Option == LoopHintAttr::Vectorize ||
                 Option == LoopHintAttr::Interleave ||
                 Option == LoopHintAttr::Unroll ||
                 Option == LoopHintAttr::Distribute ||
                 Option == LoopHintAttr::PipelineDisabled) {
        assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
        if (StateLoc->Ident->isStr("disable"))
          State = LoopHintAttr::Disable;
        else if (StateLoc->Ident->isStr("assume_safety"))
          State = LoopHintAttr::AssumeSafety;
        else if (StateLoc->Ident->isStr("full"))
          State = LoopHintAttr::Full;
        else if (StateLoc->Ident->isStr("enable"))
          State = LoopHintAttr::Enable;
        else
          llvm_unreachable("bad loop hint argument");
      } else
        llvm_unreachable("bad loop hint");
    }
  
    return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State,
                                        ValueExpr, A.getRange());
  }
  
  static void
  CheckForIncompatibleAttributes(Sema &S,
                                 const SmallVectorImpl<const Attr *> &Attrs) {
    // There are 7 categories of loop hints attributes: vectorize, interleave,
    // unroll, unroll_and_jam, pipeline, distribute, and (Tapir) grainsize. Except
    // for distribute they come in two variants: a state form and a numeric form.
    // The state form selectively defaults/enables/disables the transformation for
    // the loop (for unroll, default indicates full unrolling rather than enabling
    // the transformation). The numeric form form provides an integer hint (for
    // example, unroll count) to the transformer. The following array accumulates
    // the hints encountered while iterating through the attributes to check for
    // compatibility.
    struct {
      const LoopHintAttr *StateAttr;
      const LoopHintAttr *NumericAttr;
    } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
                     {nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
                     {nullptr, nullptr}};
  
    for (const auto *I : Attrs) {
      const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
  
      // Skip non loop hint attributes
      if (!LH)
        continue;
  
      LoopHintAttr::OptionType Option = LH->getOption();
      enum {
        Vectorize,
        Interleave,
        Unroll,
        UnrollAndJam,
        Distribute,
        Pipeline,
        TapirGrainsize
      } Category;
      switch (Option) {
      case LoopHintAttr::Vectorize:
      case LoopHintAttr::VectorizeWidth:
        Category = Vectorize;
        break;
      case LoopHintAttr::Interleave:
      case LoopHintAttr::InterleaveCount:
        Category = Interleave;
        break;
      case LoopHintAttr::Unroll:
      case LoopHintAttr::UnrollCount:
        Category = Unroll;
        break;
      case LoopHintAttr::UnrollAndJam:
      case LoopHintAttr::UnrollAndJamCount:
        Category = UnrollAndJam;
        break;
      case LoopHintAttr::Distribute:
        // Perform the check for duplicated 'distribute' hints.
        Category = Distribute;
        break;
      case LoopHintAttr::PipelineDisabled:
      case LoopHintAttr::PipelineInitiationInterval:
        Category = Pipeline;
        break;
      case LoopHintAttr::TapirGrainsize:
        Category = TapirGrainsize;
        break;
      };
  
      assert(Category < sizeof(HintAttrs) / sizeof(HintAttrs[0]));
      auto &CategoryState = HintAttrs[Category];
      const LoopHintAttr *PrevAttr;
      if (Option == LoopHintAttr::Vectorize ||
          Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll ||
          Option == LoopHintAttr::UnrollAndJam ||
          Option == LoopHintAttr::PipelineDisabled ||
          Option == LoopHintAttr::Distribute) {
        // Enable|Disable|AssumeSafety hint.  For example, vectorize(enable).
        PrevAttr = CategoryState.StateAttr;
        CategoryState.StateAttr = LH;
      } else {
        // Numeric hint.  For example, vectorize_width(8).
        PrevAttr = CategoryState.NumericAttr;
        CategoryState.NumericAttr = LH;
      }
  
      PrintingPolicy Policy(S.Context.getLangOpts());
      SourceLocation OptionLoc = LH->getRange().getBegin();
      if (PrevAttr)
        // Cannot specify same type of attribute twice.
        S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
            << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
            << LH->getDiagnosticName(Policy);
  
      if (CategoryState.StateAttr && CategoryState.NumericAttr &&
          (Category == Unroll || Category == UnrollAndJam ||
           CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
        // Disable hints are not compatible with numeric hints of the same
        // category.  As a special case, numeric unroll hints are also not
        // compatible with enable or full form of the unroll pragma because these
        // directives indicate full unrolling.
        S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
            << /*Duplicate=*/false
            << CategoryState.StateAttr->getDiagnosticName(Policy)
            << CategoryState.NumericAttr->getDiagnosticName(Policy);
      }
    }
  }
  
  static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A,
                                      SourceRange Range) {
    // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's
    // useful for OpenCL 1.x too and doesn't require HW support.
    // opencl_unroll_hint can have 0 arguments (compiler
    // determines unrolling factor) or 1 argument (the unroll factor provided
    // by the user).
  
    unsigned NumArgs = A.getNumArgs();
  
    if (NumArgs > 1) {
      S.Diag(A.getLoc(), diag::err_attribute_too_many_arguments) << A << 1;
      return nullptr;
    }
  
    unsigned UnrollFactor = 0;
  
    if (NumArgs == 1) {
      Expr *E = A.getArgAsExpr(0);
      llvm::APSInt ArgVal(32);
  
      if (!E->isIntegerConstantExpr(ArgVal, S.Context)) {
        S.Diag(A.getLoc(), diag::err_attribute_argument_type)
            << A << AANT_ArgumentIntegerConstant << E->getSourceRange();
        return nullptr;
      }
  
      int Val = ArgVal.getSExtValue();
  
      if (Val <= 0) {
        S.Diag(A.getRange().getBegin(),
               diag::err_attribute_requires_positive_integer)
            << A << /* positive */ 0;
        return nullptr;
      }
      UnrollFactor = Val;
    }
  
    return OpenCLUnrollHintAttr::CreateImplicit(S.Context, UnrollFactor);
  }
  
  static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
                                    SourceRange Range) {
    switch (A.getKind()) {
    case ParsedAttr::UnknownAttribute:
      S.Diag(A.getLoc(), A.isDeclspecAttribute()
                             ? (unsigned)diag::warn_unhandled_ms_attribute_ignored
                             : (unsigned)diag::warn_unknown_attribute_ignored)
          << A.getName();
      return nullptr;
    case ParsedAttr::AT_FallThrough:
      return handleFallThroughAttr(S, St, A, Range);
    case ParsedAttr::AT_LoopHint:
      return handleLoopHintAttr(S, St, A, Range);
    case ParsedAttr::AT_OpenCLUnrollHint:
      return handleOpenCLUnrollHint(S, St, A, Range);
    case ParsedAttr::AT_Suppress:
      return handleSuppressAttr(S, St, A, Range);
    default:
      // if we're here, then we parsed a known attribute, but didn't recognize
      // it as a statement attribute => it is declaration attribute
      S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt)
          << A.getName() << St->getBeginLoc();
      return nullptr;
    }
  }
  
  StmtResult Sema::ProcessStmtAttributes(Stmt *S,
                                         const ParsedAttributesView &AttrList,
                                         SourceRange Range) {
    SmallVector<const Attr*, 8> Attrs;
    for (const ParsedAttr &AL : AttrList) {
      if (Attr *a = ProcessStmtAttribute(*this, S, AL, Range))
        Attrs.push_back(a);
    }
  
    CheckForIncompatibleAttributes(*this, Attrs);
  
    if (Attrs.empty())
      return S;
  
    return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
  }
  