clang/lib/Sema/SemaStmtAttr.cpp

   1 //===--- SemaStmtAttr.cpp - Statement Attribute Handling ------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 //  This file implements stmt-related attribute processing.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "clang/AST/ASTContext.h"
  14 #include "clang/AST/EvaluatedExprVisitor.h"
  15 #include "clang/Basic/SourceManager.h"
  16 #include "clang/Basic/TargetInfo.h"
  17 #include "clang/Sema/DelayedDiagnostic.h"
  18 #include "clang/Sema/Lookup.h"
  19 #include "clang/Sema/ScopeInfo.h"
  20 #include "clang/Sema/SemaInternal.h"
  21 #include "llvm/ADT/StringExtras.h"
  22 #include <optional>
  23
  24 using namespace clang;
  25 using namespace sema;
  26
  27 static Attr *handleFallThroughAttr(Sema &S, Stmt *St, const ParsedAttr &A,
  28                                    SourceRange Range) {
  29   FallThroughAttr Attr(S.Context, A);
  30   if (isa<SwitchCase>(St)) {
  31     S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
  32         << A << St->getBeginLoc();
  33     SourceLocation L = S.getLocForEndOfToken(Range.getEnd());
  34     S.Diag(L, diag::note_fallthrough_insert_semi_fixit)
  35         << FixItHint::CreateInsertion(L, ";");
  36     return nullptr;
  37   }
  38   auto *FnScope = S.getCurFunction();
  39   if (FnScope->SwitchStack.empty()) {
  40     S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch);
  41     return nullptr;
  42   }
  43
  44   // If this is spelled as the standard C++17 attribute, but not in C++17, warn
  45   // about using it as an extension.
  46   if (!S.getLangOpts().CPlusPlus17 && A.isCXX11Attribute() &&
  47       !A.getScopeName())
  48     S.Diag(A.getLoc(), diag::ext_cxx17_attr) << A;
  49
  50   FnScope->setHasFallthroughStmt();
  51   return ::new (S.Context) FallThroughAttr(S.Context, A);
  52 }
  53
  54 static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A,
  55                                 SourceRange Range) {
  56   std::vector<StringRef> DiagnosticIdentifiers;
  57   for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) {
  58     StringRef RuleName;
  59
  60     if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr))
  61       return nullptr;
  62
  63     // FIXME: Warn if the rule name is unknown. This is tricky because only
  64     // clang-tidy knows about available rules.
  65     DiagnosticIdentifiers.push_back(RuleName);
  66   }
  67
  68   return ::new (S.Context) SuppressAttr(
  69       S.Context, A, DiagnosticIdentifiers.data(), DiagnosticIdentifiers.size());
  70 }
  71
  72 static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A,
  73                                 SourceRange) {
  74   IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
  75   IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
  76   IdentifierLoc *StateLoc = A.getArgAsIdent(2);
  77   Expr *ValueExpr = A.getArgAsExpr(3);
  78
  79   StringRef PragmaName =
  80       llvm::StringSwitch<StringRef>(PragmaNameLoc->Ident->getName())
  81           .Cases("unroll", "nounroll", "unroll_and_jam", "nounroll_and_jam",
  82                  PragmaNameLoc->Ident->getName())
  83           .Default("clang loop");
  84
  85   // This could be handled automatically by adding a Subjects definition in
  86   // Attr.td, but that would make the diagnostic behavior worse in this case
  87   // because the user spells this attribute as a pragma.
  88   if (!isa<DoStmt, ForStmt, CXXForRangeStmt, WhileStmt>(St)) {
  89     std::string Pragma = "#pragma " + std::string(PragmaName);
  90     S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
  91     return nullptr;
  92   }
  93
  94   LoopHintAttr::OptionType Option;
  95   LoopHintAttr::LoopHintState State;
  96
  97   auto SetHints = [&Option, &State](LoopHintAttr::OptionType O,
  98                                     LoopHintAttr::LoopHintState S) {
  99     Option = O;
 100     State = S;
 101   };
 102
 103   if (PragmaName == "nounroll") {
 104     SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable);
 105   } else if (PragmaName == "unroll") {
 106     // #pragma unroll N
 107     if (ValueExpr)
 108       SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric);
 109     else
 110       SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable);
 111   } else if (PragmaName == "nounroll_and_jam") {
 112     SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable);
 113   } else if (PragmaName == "unroll_and_jam") {
 114     // #pragma unroll_and_jam N
 115     if (ValueExpr)
 116       SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric);
 117     else
 118       SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable);
 119   } else {
 120     // #pragma clang loop ...
 121     assert(OptionLoc && OptionLoc->Ident &&
 122            "Attribute must have valid option info.");
 123     Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
 124                  OptionLoc->Ident->getName())
 125                  .Case("vectorize", LoopHintAttr::Vectorize)
 126                  .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
 127                  .Case("interleave", LoopHintAttr::Interleave)
 128                  .Case("vectorize_predicate", LoopHintAttr::VectorizePredicate)
 129                  .Case("interleave_count", LoopHintAttr::InterleaveCount)
 130                  .Case("unroll", LoopHintAttr::Unroll)
 131                  .Case("unroll_count", LoopHintAttr::UnrollCount)
 132                  .Case("pipeline", LoopHintAttr::PipelineDisabled)
 133                  .Case("pipeline_initiation_interval",
 134                        LoopHintAttr::PipelineInitiationInterval)
 135                  .Case("distribute", LoopHintAttr::Distribute)
 136                  .Default(LoopHintAttr::Vectorize);
 137     if (Option == LoopHintAttr::VectorizeWidth) {
 138       assert((ValueExpr || (StateLoc && StateLoc->Ident)) &&
 139              "Attribute must have a valid value expression or argument.");
 140       if (ValueExpr && S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
 141         return nullptr;
 142       if (StateLoc && StateLoc->Ident && StateLoc->Ident->isStr("scalable"))
 143         State = LoopHintAttr::ScalableWidth;
 144       else
 145         State = LoopHintAttr::FixedWidth;
 146     } else if (Option == LoopHintAttr::InterleaveCount ||
 147                Option == LoopHintAttr::UnrollCount ||
 148                Option == LoopHintAttr::PipelineInitiationInterval) {
 149       assert(ValueExpr && "Attribute must have a valid value expression.");
 150       if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
 151         return nullptr;
 152       State = LoopHintAttr::Numeric;
 153     } else if (Option == LoopHintAttr::Vectorize ||
 154                Option == LoopHintAttr::Interleave ||
 155                Option == LoopHintAttr::VectorizePredicate ||
 156                Option == LoopHintAttr::Unroll ||
 157                Option == LoopHintAttr::Distribute ||
 158                Option == LoopHintAttr::PipelineDisabled) {
 159       assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
 160       if (StateLoc->Ident->isStr("disable"))
 161         State = LoopHintAttr::Disable;
 162       else if (StateLoc->Ident->isStr("assume_safety"))
 163         State = LoopHintAttr::AssumeSafety;
 164       else if (StateLoc->Ident->isStr("full"))
 165         State = LoopHintAttr::Full;
 166       else if (StateLoc->Ident->isStr("enable"))
 167         State = LoopHintAttr::Enable;
 168       else
 169         llvm_unreachable("bad loop hint argument");
 170     } else
 171       llvm_unreachable("bad loop hint");
 172   }
 173
 174   return LoopHintAttr::CreateImplicit(S.Context, Option, State, ValueExpr, A);
 175 }
 176
 177 namespace {
 178 class CallExprFinder : public ConstEvaluatedExprVisitor<CallExprFinder> {
 179   bool FoundAsmStmt = false;
 180   std::vector<const CallExpr *> CallExprs;
 181
 182 public:
 183   typedef ConstEvaluatedExprVisitor<CallExprFinder> Inherited;
 184
 185   CallExprFinder(Sema &S, const Stmt *St) : Inherited(S.Context) { Visit(St); }
 186
 187   bool foundCallExpr() { return !CallExprs.empty(); }
 188   const std::vector<const CallExpr *> &getCallExprs() { return CallExprs; }
 189
 190   bool foundAsmStmt() { return FoundAsmStmt; }
 191
 192   void VisitCallExpr(const CallExpr *E) { CallExprs.push_back(E); }
 193
 194   void VisitAsmStmt(const AsmStmt *S) { FoundAsmStmt = true; }
 195
 196   void Visit(const Stmt *St) {
 197     if (!St)
 198       return;
 199     ConstEvaluatedExprVisitor<CallExprFinder>::Visit(St);
 200   }
 201 };
 202 } // namespace
 203
 204 static Attr *handleNoMergeAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 205                                SourceRange Range) {
 206   NoMergeAttr NMA(S.Context, A);
 207   CallExprFinder CEF(S, St);
 208
 209   if (!CEF.foundCallExpr() && !CEF.foundAsmStmt()) {
 210     S.Diag(St->getBeginLoc(), diag::warn_attribute_ignored_no_calls_in_stmt)
 211         << A;
 212     return nullptr;
 213   }
 214
 215   return ::new (S.Context) NoMergeAttr(S.Context, A);
 216 }
 217
 218 template <typename OtherAttr, int DiagIdx>
 219 static bool CheckStmtInlineAttr(Sema &SemaRef, const Stmt *OrigSt,
 220                                 const Stmt *CurSt,
 221                                 const AttributeCommonInfo &A) {
 222   CallExprFinder OrigCEF(SemaRef, OrigSt);
 223   CallExprFinder CEF(SemaRef, CurSt);
 224
 225   // If the call expressions lists are equal in size, we can skip
 226   // previously emitted diagnostics. However, if the statement has a pack
 227   // expansion, we have no way of telling which CallExpr is the instantiated
 228   // version of the other. In this case, we will end up re-diagnosing in the
 229   // instantiation.
 230   // ie: [[clang::always_inline]] non_dependent(), (other_call<Pack>()...)
 231   // will diagnose nondependent again.
 232   bool CanSuppressDiag =
 233       OrigSt && CEF.getCallExprs().size() == OrigCEF.getCallExprs().size();
 234
 235   if (!CEF.foundCallExpr()) {
 236     return SemaRef.Diag(CurSt->getBeginLoc(),
 237                         diag::warn_attribute_ignored_no_calls_in_stmt)
 238            << A;
 239   }
 240
 241   for (const auto &Tup :
 242        llvm::zip_longest(OrigCEF.getCallExprs(), CEF.getCallExprs())) {
 243     // If the original call expression already had a callee, we already
 244     // diagnosed this, so skip it here. We can't skip if there isn't a 1:1
 245     // relationship between the two lists of call expressions.
 246     if (!CanSuppressDiag || !(*std::get<0>(Tup))->getCalleeDecl()) {
 247       const Decl *Callee = (*std::get<1>(Tup))->getCalleeDecl();
 248       if (Callee &&
 249           (Callee->hasAttr<OtherAttr>() || Callee->hasAttr<FlattenAttr>())) {
 250         SemaRef.Diag(CurSt->getBeginLoc(),
 251                      diag::warn_function_stmt_attribute_precedence)
 252             << A << (Callee->hasAttr<OtherAttr>() ? DiagIdx : 1);
 253         SemaRef.Diag(Callee->getBeginLoc(), diag::note_conflicting_attribute);
 254       }
 255     }
 256   }
 257
 258   return false;
 259 }
 260
 261 bool Sema::CheckNoInlineAttr(const Stmt *OrigSt, const Stmt *CurSt,
 262                              const AttributeCommonInfo &A) {
 263   return CheckStmtInlineAttr<AlwaysInlineAttr, 0>(*this, OrigSt, CurSt, A);
 264 }
 265
 266 bool Sema::CheckAlwaysInlineAttr(const Stmt *OrigSt, const Stmt *CurSt,
 267                                  const AttributeCommonInfo &A) {
 268   return CheckStmtInlineAttr<NoInlineAttr, 2>(*this, OrigSt, CurSt, A);
 269 }
 270
 271 static Attr *handleNoInlineAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 272                                 SourceRange Range) {
 273   NoInlineAttr NIA(S.Context, A);
 274   if (!NIA.isClangNoInline()) {
 275     S.Diag(St->getBeginLoc(), diag::warn_function_attribute_ignored_in_stmt)
 276         << "[[clang::noinline]]";
 277     return nullptr;
 278   }
 279
 280   if (S.CheckNoInlineAttr(/*OrigSt=*/nullptr, St, A))
 281     return nullptr;
 282
 283   return ::new (S.Context) NoInlineAttr(S.Context, A);
 284 }
 285
 286 static Attr *handleAlwaysInlineAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 287                                     SourceRange Range) {
 288   AlwaysInlineAttr AIA(S.Context, A);
 289   if (!AIA.isClangAlwaysInline()) {
 290     S.Diag(St->getBeginLoc(), diag::warn_function_attribute_ignored_in_stmt)
 291         << "[[clang::always_inline]]";
 292     return nullptr;
 293   }
 294
 295   if (S.CheckAlwaysInlineAttr(/*OrigSt=*/nullptr, St, A))
 296     return nullptr;
 297
 298   return ::new (S.Context) AlwaysInlineAttr(S.Context, A);
 299 }
 300
 301 static Attr *handleMustTailAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 302                                 SourceRange Range) {
 303   // Validation is in Sema::ActOnAttributedStmt().
 304   return ::new (S.Context) MustTailAttr(S.Context, A);
 305 }
 306
 307 static Attr *handleLikely(Sema &S, Stmt *St, const ParsedAttr &A,
 308                           SourceRange Range) {
 309
 310   if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
 311     S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range;
 312
 313   return ::new (S.Context) LikelyAttr(S.Context, A);
 314 }
 315
 316 static Attr *handleUnlikely(Sema &S, Stmt *St, const ParsedAttr &A,
 317                             SourceRange Range) {
 318
 319   if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
 320     S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range;
 321
 322   return ::new (S.Context) UnlikelyAttr(S.Context, A);
 323 }
 324
 325 #define WANT_STMT_MERGE_LOGIC
 326 #include "clang/Sema/AttrParsedAttrImpl.inc"
 327 #undef WANT_STMT_MERGE_LOGIC
 328
 329 static void
 330 CheckForIncompatibleAttributes(Sema &S,
 331                                const SmallVectorImpl<const Attr *> &Attrs) {
 332   // The vast majority of attributed statements will only have one attribute
 333   // on them, so skip all of the checking in the common case.
 334   if (Attrs.size() < 2)
 335     return;
 336
 337   // First, check for the easy cases that are table-generated for us.
 338   if (!DiagnoseMutualExclusions(S, Attrs))
 339     return;
 340
 341   enum CategoryType {
 342     // For the following categories, they come in two variants: a state form and
 343     // a numeric form. The state form may be one of default, enable, and
 344     // disable. The numeric form provides an integer hint (for example, unroll
 345     // count) to the transformer.
 346     Vectorize,
 347     Interleave,
 348     UnrollAndJam,
 349     Pipeline,
 350     // For unroll, default indicates full unrolling rather than enabling the
 351     // transformation.
 352     Unroll,
 353     // The loop distribution transformation only has a state form that is
 354     // exposed by #pragma clang loop distribute (enable | disable).
 355     Distribute,
 356     // The vector predication only has a state form that is exposed by
 357     // #pragma clang loop vectorize_predicate (enable | disable).
 358     VectorizePredicate,
 359     // This serves as a indicator to how many category are listed in this enum.
 360     NumberOfCategories
 361   };
 362   // The following array accumulates the hints encountered while iterating
 363   // through the attributes to check for compatibility.
 364   struct {
 365     const LoopHintAttr *StateAttr;
 366     const LoopHintAttr *NumericAttr;
 367   } HintAttrs[CategoryType::NumberOfCategories] = {};
 368
 369   for (const auto *I : Attrs) {
 370     const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
 371
 372     // Skip non loop hint attributes
 373     if (!LH)
 374       continue;
 375
 376     CategoryType Category = CategoryType::NumberOfCategories;
 377     LoopHintAttr::OptionType Option = LH->getOption();
 378     switch (Option) {
 379     case LoopHintAttr::Vectorize:
 380     case LoopHintAttr::VectorizeWidth:
 381       Category = Vectorize;
 382       break;
 383     case LoopHintAttr::Interleave:
 384     case LoopHintAttr::InterleaveCount:
 385       Category = Interleave;
 386       break;
 387     case LoopHintAttr::Unroll:
 388     case LoopHintAttr::UnrollCount:
 389       Category = Unroll;
 390       break;
 391     case LoopHintAttr::UnrollAndJam:
 392     case LoopHintAttr::UnrollAndJamCount:
 393       Category = UnrollAndJam;
 394       break;
 395     case LoopHintAttr::Distribute:
 396       // Perform the check for duplicated 'distribute' hints.
 397       Category = Distribute;
 398       break;
 399     case LoopHintAttr::PipelineDisabled:
 400     case LoopHintAttr::PipelineInitiationInterval:
 401       Category = Pipeline;
 402       break;
 403     case LoopHintAttr::VectorizePredicate:
 404       Category = VectorizePredicate;
 405       break;
 406     };
 407
 408     assert(Category != NumberOfCategories && "Unhandled loop hint option");
 409     auto &CategoryState = HintAttrs[Category];
 410     const LoopHintAttr *PrevAttr;
 411     if (Option == LoopHintAttr::Vectorize ||
 412         Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll ||
 413         Option == LoopHintAttr::UnrollAndJam ||
 414         Option == LoopHintAttr::VectorizePredicate ||
 415         Option == LoopHintAttr::PipelineDisabled ||
 416         Option == LoopHintAttr::Distribute) {
 417       // Enable|Disable|AssumeSafety hint.  For example, vectorize(enable).
 418       PrevAttr = CategoryState.StateAttr;
 419       CategoryState.StateAttr = LH;
 420     } else {
 421       // Numeric hint.  For example, vectorize_width(8).
 422       PrevAttr = CategoryState.NumericAttr;
 423       CategoryState.NumericAttr = LH;
 424     }
 425
 426     PrintingPolicy Policy(S.Context.getLangOpts());
 427     SourceLocation OptionLoc = LH->getRange().getBegin();
 428     if (PrevAttr)
 429       // Cannot specify same type of attribute twice.
 430       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
 431           << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
 432           << LH->getDiagnosticName(Policy);
 433
 434     if (CategoryState.StateAttr && CategoryState.NumericAttr &&
 435         (Category == Unroll || Category == UnrollAndJam ||
 436          CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
 437       // Disable hints are not compatible with numeric hints of the same
 438       // category.  As a special case, numeric unroll hints are also not
 439       // compatible with enable or full form of the unroll pragma because these
 440       // directives indicate full unrolling.
 441       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
 442           << /*Duplicate=*/false
 443           << CategoryState.StateAttr->getDiagnosticName(Policy)
 444           << CategoryState.NumericAttr->getDiagnosticName(Policy);
 445     }
 446   }
 447 }
 448
 449 static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A,
 450                                     SourceRange Range) {
 451   // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's
 452   // useful for OpenCL 1.x too and doesn't require HW support.
 453   // opencl_unroll_hint can have 0 arguments (compiler
 454   // determines unrolling factor) or 1 argument (the unroll factor provided
 455   // by the user).
 456   unsigned UnrollFactor = 0;
 457   if (A.getNumArgs() == 1) {
 458     Expr *E = A.getArgAsExpr(0);
 459     std::optional<llvm::APSInt> ArgVal;
 460
 461     if (!(ArgVal = E->getIntegerConstantExpr(S.Context))) {
 462       S.Diag(A.getLoc(), diag::err_attribute_argument_type)
 463           << A << AANT_ArgumentIntegerConstant << E->getSourceRange();
 464       return nullptr;
 465     }
 466
 467     int Val = ArgVal->getSExtValue();
 468     if (Val <= 0) {
 469       S.Diag(A.getRange().getBegin(),
 470              diag::err_attribute_requires_positive_integer)
 471           << A << /* positive */ 0;
 472       return nullptr;
 473     }
 474     UnrollFactor = static_cast<unsigned>(Val);
 475   }
 476
 477   return ::new (S.Context) OpenCLUnrollHintAttr(S.Context, A, UnrollFactor);
 478 }
 479
 480 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
 481                                   SourceRange Range) {
 482   if (A.isInvalid() || A.getKind() == ParsedAttr::IgnoredAttribute)
 483     return nullptr;
 484
 485   // Unknown attributes are automatically warned on. Target-specific attributes
 486   // which do not apply to the current target architecture are treated as
 487   // though they were unknown attributes.
 488   const TargetInfo *Aux = S.Context.getAuxTargetInfo();
 489   if (A.getKind() == ParsedAttr::UnknownAttribute ||
 490       !(A.existsInTarget(S.Context.getTargetInfo()) ||
 491         (S.Context.getLangOpts().SYCLIsDevice && Aux &&
 492          A.existsInTarget(*Aux)))) {
 493     S.Diag(A.getLoc(), A.isRegularKeywordAttribute()
 494                            ? (unsigned)diag::err_keyword_not_supported_on_target
 495                        : A.isDeclspecAttribute()
 496                            ? (unsigned)diag::warn_unhandled_ms_attribute_ignored
 497                            : (unsigned)diag::warn_unknown_attribute_ignored)
 498         << A << A.getRange();
 499     return nullptr;
 500   }
 501
 502   if (S.checkCommonAttributeFeatures(St, A))
 503     return nullptr;
 504
 505   switch (A.getKind()) {
 506   case ParsedAttr::AT_AlwaysInline:
 507     return handleAlwaysInlineAttr(S, St, A, Range);
 508   case ParsedAttr::AT_FallThrough:
 509     return handleFallThroughAttr(S, St, A, Range);
 510   case ParsedAttr::AT_LoopHint:
 511     return handleLoopHintAttr(S, St, A, Range);
 512   case ParsedAttr::AT_OpenCLUnrollHint:
 513     return handleOpenCLUnrollHint(S, St, A, Range);
 514   case ParsedAttr::AT_Suppress:
 515     return handleSuppressAttr(S, St, A, Range);
 516   case ParsedAttr::AT_NoMerge:
 517     return handleNoMergeAttr(S, St, A, Range);
 518   case ParsedAttr::AT_NoInline:
 519     return handleNoInlineAttr(S, St, A, Range);
 520   case ParsedAttr::AT_MustTail:
 521     return handleMustTailAttr(S, St, A, Range);
 522   case ParsedAttr::AT_Likely:
 523     return handleLikely(S, St, A, Range);
 524   case ParsedAttr::AT_Unlikely:
 525     return handleUnlikely(S, St, A, Range);
 526   default:
 527     // N.B., ClangAttrEmitter.cpp emits a diagnostic helper that ensures a
 528     // declaration attribute is not written on a statement, but this code is
 529     // needed for attributes in Attr.td that do not list any subjects.
 530     S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt)
 531         << A << A.isRegularKeywordAttribute() << St->getBeginLoc();
 532     return nullptr;
 533   }
 534 }
 535
 536 void Sema::ProcessStmtAttributes(Stmt *S, const ParsedAttributes &InAttrs,
 537                                  SmallVectorImpl<const Attr *> &OutAttrs) {
 538   for (const ParsedAttr &AL : InAttrs) {
 539     if (const Attr *A = ProcessStmtAttribute(*this, S, AL, InAttrs.Range))
 540       OutAttrs.push_back(A);
 541   }
 542
 543   CheckForIncompatibleAttributes(*this, OutAttrs);
 544 }