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   if (A.getAttributeSpellingListIndex() == SuppressAttr::CXX11_gsl_suppress &&
  57       A.getNumArgs() < 1) {
  58     // Suppression attribute with GSL spelling requires at least 1 argument.
  59     S.Diag(A.getLoc(), diag::err_attribute_too_few_arguments) << A << 1;
  60     return nullptr;
  61   }
  62
  63   std::vector<StringRef> DiagnosticIdentifiers;
  64   for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) {
  65     StringRef RuleName;
  66
  67     if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr))
  68       return nullptr;
  69
  70     DiagnosticIdentifiers.push_back(RuleName);
  71   }
  72
  73   return ::new (S.Context) SuppressAttr(
  74       S.Context, A, DiagnosticIdentifiers.data(), DiagnosticIdentifiers.size());
  75 }
  76
  77 static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A,
  78                                 SourceRange) {
  79   IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
  80   IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
  81   IdentifierLoc *StateLoc = A.getArgAsIdent(2);
  82   Expr *ValueExpr = A.getArgAsExpr(3);
  83
  84   StringRef PragmaName =
  85       llvm::StringSwitch<StringRef>(PragmaNameLoc->Ident->getName())
  86           .Cases("unroll", "nounroll", "unroll_and_jam", "nounroll_and_jam",
  87                  PragmaNameLoc->Ident->getName())
  88           .Default("clang loop");
  89
  90   // This could be handled automatically by adding a Subjects definition in
  91   // Attr.td, but that would make the diagnostic behavior worse in this case
  92   // because the user spells this attribute as a pragma.
  93   if (!isa<DoStmt, ForStmt, CXXForRangeStmt, WhileStmt>(St)) {
  94     std::string Pragma = "#pragma " + std::string(PragmaName);
  95     S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
  96     return nullptr;
  97   }
  98
  99   LoopHintAttr::OptionType Option;
 100   LoopHintAttr::LoopHintState State;
 101
 102   auto SetHints = [&Option, &State](LoopHintAttr::OptionType O,
 103                                     LoopHintAttr::LoopHintState S) {
 104     Option = O;
 105     State = S;
 106   };
 107
 108   if (PragmaName == "nounroll") {
 109     SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable);
 110   } else if (PragmaName == "unroll") {
 111     // #pragma unroll N
 112     if (ValueExpr)
 113       SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric);
 114     else
 115       SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable);
 116   } else if (PragmaName == "nounroll_and_jam") {
 117     SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable);
 118   } else if (PragmaName == "unroll_and_jam") {
 119     // #pragma unroll_and_jam N
 120     if (ValueExpr)
 121       SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric);
 122     else
 123       SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable);
 124   } else {
 125     // #pragma clang loop ...
 126     assert(OptionLoc && OptionLoc->Ident &&
 127            "Attribute must have valid option info.");
 128     Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
 129                  OptionLoc->Ident->getName())
 130                  .Case("vectorize", LoopHintAttr::Vectorize)
 131                  .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
 132                  .Case("interleave", LoopHintAttr::Interleave)
 133                  .Case("vectorize_predicate", LoopHintAttr::VectorizePredicate)
 134                  .Case("interleave_count", LoopHintAttr::InterleaveCount)
 135                  .Case("unroll", LoopHintAttr::Unroll)
 136                  .Case("unroll_count", LoopHintAttr::UnrollCount)
 137                  .Case("pipeline", LoopHintAttr::PipelineDisabled)
 138                  .Case("pipeline_initiation_interval",
 139                        LoopHintAttr::PipelineInitiationInterval)
 140                  .Case("distribute", LoopHintAttr::Distribute)
 141                  .Default(LoopHintAttr::Vectorize);
 142     if (Option == LoopHintAttr::VectorizeWidth) {
 143       assert((ValueExpr || (StateLoc && StateLoc->Ident)) &&
 144              "Attribute must have a valid value expression or argument.");
 145       if (ValueExpr && S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
 146         return nullptr;
 147       if (StateLoc && StateLoc->Ident && StateLoc->Ident->isStr("scalable"))
 148         State = LoopHintAttr::ScalableWidth;
 149       else
 150         State = LoopHintAttr::FixedWidth;
 151     } else if (Option == LoopHintAttr::InterleaveCount ||
 152                Option == LoopHintAttr::UnrollCount ||
 153                Option == LoopHintAttr::PipelineInitiationInterval) {
 154       assert(ValueExpr && "Attribute must have a valid value expression.");
 155       if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
 156         return nullptr;
 157       State = LoopHintAttr::Numeric;
 158     } else if (Option == LoopHintAttr::Vectorize ||
 159                Option == LoopHintAttr::Interleave ||
 160                Option == LoopHintAttr::VectorizePredicate ||
 161                Option == LoopHintAttr::Unroll ||
 162                Option == LoopHintAttr::Distribute ||
 163                Option == LoopHintAttr::PipelineDisabled) {
 164       assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
 165       if (StateLoc->Ident->isStr("disable"))
 166         State = LoopHintAttr::Disable;
 167       else if (StateLoc->Ident->isStr("assume_safety"))
 168         State = LoopHintAttr::AssumeSafety;
 169       else if (StateLoc->Ident->isStr("full"))
 170         State = LoopHintAttr::Full;
 171       else if (StateLoc->Ident->isStr("enable"))
 172         State = LoopHintAttr::Enable;
 173       else
 174         llvm_unreachable("bad loop hint argument");
 175     } else
 176       llvm_unreachable("bad loop hint");
 177   }
 178
 179   return LoopHintAttr::CreateImplicit(S.Context, Option, State, ValueExpr, A);
 180 }
 181
 182 namespace {
 183 class CallExprFinder : public ConstEvaluatedExprVisitor<CallExprFinder> {
 184   bool FoundAsmStmt = false;
 185   std::vector<const CallExpr *> CallExprs;
 186
 187 public:
 188   typedef ConstEvaluatedExprVisitor<CallExprFinder> Inherited;
 189
 190   CallExprFinder(Sema &S, const Stmt *St) : Inherited(S.Context) { Visit(St); }
 191
 192   bool foundCallExpr() { return !CallExprs.empty(); }
 193   const std::vector<const CallExpr *> &getCallExprs() { return CallExprs; }
 194
 195   bool foundAsmStmt() { return FoundAsmStmt; }
 196
 197   void VisitCallExpr(const CallExpr *E) { CallExprs.push_back(E); }
 198
 199   void VisitAsmStmt(const AsmStmt *S) { FoundAsmStmt = true; }
 200
 201   void Visit(const Stmt *St) {
 202     if (!St)
 203       return;
 204     ConstEvaluatedExprVisitor<CallExprFinder>::Visit(St);
 205   }
 206 };
 207 } // namespace
 208
 209 static Attr *handleNoMergeAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 210                                SourceRange Range) {
 211   NoMergeAttr NMA(S.Context, A);
 212   CallExprFinder CEF(S, St);
 213
 214   if (!CEF.foundCallExpr() && !CEF.foundAsmStmt()) {
 215     S.Diag(St->getBeginLoc(), diag::warn_attribute_ignored_no_calls_in_stmt)
 216         << A;
 217     return nullptr;
 218   }
 219
 220   return ::new (S.Context) NoMergeAttr(S.Context, A);
 221 }
 222
 223 template <typename OtherAttr, int DiagIdx>
 224 static bool CheckStmtInlineAttr(Sema &SemaRef, const Stmt *OrigSt,
 225                                 const Stmt *CurSt,
 226                                 const AttributeCommonInfo &A) {
 227   CallExprFinder OrigCEF(SemaRef, OrigSt);
 228   CallExprFinder CEF(SemaRef, CurSt);
 229
 230   // If the call expressions lists are equal in size, we can skip
 231   // previously emitted diagnostics. However, if the statement has a pack
 232   // expansion, we have no way of telling which CallExpr is the instantiated
 233   // version of the other. In this case, we will end up re-diagnosing in the
 234   // instantiation.
 235   // ie: [[clang::always_inline]] non_dependent(), (other_call<Pack>()...)
 236   // will diagnose nondependent again.
 237   bool CanSuppressDiag =
 238       OrigSt && CEF.getCallExprs().size() == OrigCEF.getCallExprs().size();
 239
 240   if (!CEF.foundCallExpr()) {
 241     return SemaRef.Diag(CurSt->getBeginLoc(),
 242                         diag::warn_attribute_ignored_no_calls_in_stmt)
 243            << A;
 244   }
 245
 246   for (const auto &Tup :
 247        llvm::zip_longest(OrigCEF.getCallExprs(), CEF.getCallExprs())) {
 248     // If the original call expression already had a callee, we already
 249     // diagnosed this, so skip it here. We can't skip if there isn't a 1:1
 250     // relationship between the two lists of call expressions.
 251     if (!CanSuppressDiag || !(*std::get<0>(Tup))->getCalleeDecl()) {
 252       const Decl *Callee = (*std::get<1>(Tup))->getCalleeDecl();
 253       if (Callee &&
 254           (Callee->hasAttr<OtherAttr>() || Callee->hasAttr<FlattenAttr>())) {
 255         SemaRef.Diag(CurSt->getBeginLoc(),
 256                      diag::warn_function_stmt_attribute_precedence)
 257             << A << (Callee->hasAttr<OtherAttr>() ? DiagIdx : 1);
 258         SemaRef.Diag(Callee->getBeginLoc(), diag::note_conflicting_attribute);
 259       }
 260     }
 261   }
 262
 263   return false;
 264 }
 265
 266 bool Sema::CheckNoInlineAttr(const Stmt *OrigSt, const Stmt *CurSt,
 267                              const AttributeCommonInfo &A) {
 268   return CheckStmtInlineAttr<AlwaysInlineAttr, 0>(*this, OrigSt, CurSt, A);
 269 }
 270
 271 bool Sema::CheckAlwaysInlineAttr(const Stmt *OrigSt, const Stmt *CurSt,
 272                                  const AttributeCommonInfo &A) {
 273   return CheckStmtInlineAttr<NoInlineAttr, 2>(*this, OrigSt, CurSt, A);
 274 }
 275
 276 static Attr *handleNoInlineAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 277                                 SourceRange Range) {
 278   NoInlineAttr NIA(S.Context, A);
 279   if (!NIA.isClangNoInline()) {
 280     S.Diag(St->getBeginLoc(), diag::warn_function_attribute_ignored_in_stmt)
 281         << "[[clang::noinline]]";
 282     return nullptr;
 283   }
 284
 285   if (S.CheckNoInlineAttr(/*OrigSt=*/nullptr, St, A))
 286     return nullptr;
 287
 288   return ::new (S.Context) NoInlineAttr(S.Context, A);
 289 }
 290
 291 static Attr *handleAlwaysInlineAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 292                                     SourceRange Range) {
 293   AlwaysInlineAttr AIA(S.Context, A);
 294   if (!AIA.isClangAlwaysInline()) {
 295     S.Diag(St->getBeginLoc(), diag::warn_function_attribute_ignored_in_stmt)
 296         << "[[clang::always_inline]]";
 297     return nullptr;
 298   }
 299
 300   if (S.CheckAlwaysInlineAttr(/*OrigSt=*/nullptr, St, A))
 301     return nullptr;
 302
 303   return ::new (S.Context) AlwaysInlineAttr(S.Context, A);
 304 }
 305
 306 static Attr *handleMustTailAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 307                                 SourceRange Range) {
 308   // Validation is in Sema::ActOnAttributedStmt().
 309   return ::new (S.Context) MustTailAttr(S.Context, A);
 310 }
 311
 312 static Attr *handleLikely(Sema &S, Stmt *St, const ParsedAttr &A,
 313                           SourceRange Range) {
 314
 315   if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
 316     S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range;
 317
 318   return ::new (S.Context) LikelyAttr(S.Context, A);
 319 }
 320
 321 static Attr *handleUnlikely(Sema &S, Stmt *St, const ParsedAttr &A,
 322                             SourceRange Range) {
 323
 324   if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
 325     S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range;
 326
 327   return ::new (S.Context) UnlikelyAttr(S.Context, A);
 328 }
 329
 330 CodeAlignAttr *Sema::BuildCodeAlignAttr(const AttributeCommonInfo &CI,
 331                                         Expr *E) {
 332   if (!E->isValueDependent()) {
 333     llvm::APSInt ArgVal;
 334     ExprResult Res = VerifyIntegerConstantExpression(E, &ArgVal);
 335     if (Res.isInvalid())
 336       return nullptr;
 337     E = Res.get();
 338
 339     // This attribute requires an integer argument which is a constant power of
 340     // two between 1 and 4096 inclusive.
 341     if (ArgVal < CodeAlignAttr::MinimumAlignment ||
 342         ArgVal > CodeAlignAttr::MaximumAlignment || !ArgVal.isPowerOf2()) {
 343       if (std::optional<int64_t> Value = ArgVal.trySExtValue())
 344         Diag(CI.getLoc(), diag::err_attribute_power_of_two_in_range)
 345             << CI << CodeAlignAttr::MinimumAlignment
 346             << CodeAlignAttr::MaximumAlignment << Value.value();
 347       else
 348         Diag(CI.getLoc(), diag::err_attribute_power_of_two_in_range)
 349             << CI << CodeAlignAttr::MinimumAlignment
 350             << CodeAlignAttr::MaximumAlignment << E;
 351       return nullptr;
 352     }
 353   }
 354   return new (Context) CodeAlignAttr(Context, CI, E);
 355 }
 356
 357 static Attr *handleCodeAlignAttr(Sema &S, Stmt *St, const ParsedAttr &A) {
 358
 359   Expr *E = A.getArgAsExpr(0);
 360   return S.BuildCodeAlignAttr(A, E);
 361 }
 362
 363 // Diagnose non-identical duplicates as a 'conflicting' loop attributes
 364 // and suppress duplicate errors in cases where the two match.
 365 template <typename LoopAttrT>
 366 static void CheckForDuplicateLoopAttrs(Sema &S, ArrayRef<const Attr *> Attrs) {
 367   auto FindFunc = [](const Attr *A) { return isa<const LoopAttrT>(A); };
 368   const auto *FirstItr = std::find_if(Attrs.begin(), Attrs.end(), FindFunc);
 369
 370   if (FirstItr == Attrs.end()) // no attributes found
 371     return;
 372
 373   const auto *LastFoundItr = FirstItr;
 374   std::optional<llvm::APSInt> FirstValue;
 375
 376   const auto *CAFA =
 377       dyn_cast<ConstantExpr>(cast<LoopAttrT>(*FirstItr)->getAlignment());
 378   // Return early if first alignment expression is dependent (since we don't
 379   // know what the effective size will be), and skip the loop entirely.
 380   if (!CAFA)
 381     return;
 382
 383   while (Attrs.end() != (LastFoundItr = std::find_if(LastFoundItr + 1,
 384                                                      Attrs.end(), FindFunc))) {
 385     const auto *CASA =
 386         dyn_cast<ConstantExpr>(cast<LoopAttrT>(*LastFoundItr)->getAlignment());
 387     // If the value is dependent, we can not test anything.
 388     if (!CASA)
 389       return;
 390     // Test the attribute values.
 391     llvm::APSInt SecondValue = CASA->getResultAsAPSInt();
 392     if (!FirstValue)
 393       FirstValue = CAFA->getResultAsAPSInt();
 394
 395     if (FirstValue != SecondValue) {
 396       S.Diag((*LastFoundItr)->getLocation(), diag::err_loop_attr_conflict)
 397           << *FirstItr;
 398       S.Diag((*FirstItr)->getLocation(), diag::note_previous_attribute);
 399     }
 400     return;
 401   }
 402 }
 403
 404 static Attr *handleMSConstexprAttr(Sema &S, Stmt *St, const ParsedAttr &A,
 405                                    SourceRange Range) {
 406   if (!S.getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2022_3)) {
 407     S.Diag(A.getLoc(), diag::warn_unknown_attribute_ignored)
 408         << A << A.getRange();
 409     return nullptr;
 410   }
 411   return ::new (S.Context) MSConstexprAttr(S.Context, A);
 412 }
 413
 414 #define WANT_STMT_MERGE_LOGIC
 415 #include "clang/Sema/AttrParsedAttrImpl.inc"
 416 #undef WANT_STMT_MERGE_LOGIC
 417
 418 static void
 419 CheckForIncompatibleAttributes(Sema &S,
 420                                const SmallVectorImpl<const Attr *> &Attrs) {
 421   // The vast majority of attributed statements will only have one attribute
 422   // on them, so skip all of the checking in the common case.
 423   if (Attrs.size() < 2)
 424     return;
 425
 426   // First, check for the easy cases that are table-generated for us.
 427   if (!DiagnoseMutualExclusions(S, Attrs))
 428     return;
 429
 430   enum CategoryType {
 431     // For the following categories, they come in two variants: a state form and
 432     // a numeric form. The state form may be one of default, enable, and
 433     // disable. The numeric form provides an integer hint (for example, unroll
 434     // count) to the transformer.
 435     Vectorize,
 436     Interleave,
 437     UnrollAndJam,
 438     Pipeline,
 439     // For unroll, default indicates full unrolling rather than enabling the
 440     // transformation.
 441     Unroll,
 442     // The loop distribution transformation only has a state form that is
 443     // exposed by #pragma clang loop distribute (enable | disable).
 444     Distribute,
 445     // The vector predication only has a state form that is exposed by
 446     // #pragma clang loop vectorize_predicate (enable | disable).
 447     VectorizePredicate,
 448     // This serves as a indicator to how many category are listed in this enum.
 449     NumberOfCategories
 450   };
 451   // The following array accumulates the hints encountered while iterating
 452   // through the attributes to check for compatibility.
 453   struct {
 454     const LoopHintAttr *StateAttr;
 455     const LoopHintAttr *NumericAttr;
 456   } HintAttrs[CategoryType::NumberOfCategories] = {};
 457
 458   for (const auto *I : Attrs) {
 459     const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
 460
 461     // Skip non loop hint attributes
 462     if (!LH)
 463       continue;
 464
 465     CategoryType Category = CategoryType::NumberOfCategories;
 466     LoopHintAttr::OptionType Option = LH->getOption();
 467     switch (Option) {
 468     case LoopHintAttr::Vectorize:
 469     case LoopHintAttr::VectorizeWidth:
 470       Category = Vectorize;
 471       break;
 472     case LoopHintAttr::Interleave:
 473     case LoopHintAttr::InterleaveCount:
 474       Category = Interleave;
 475       break;
 476     case LoopHintAttr::Unroll:
 477     case LoopHintAttr::UnrollCount:
 478       Category = Unroll;
 479       break;
 480     case LoopHintAttr::UnrollAndJam:
 481     case LoopHintAttr::UnrollAndJamCount:
 482       Category = UnrollAndJam;
 483       break;
 484     case LoopHintAttr::Distribute:
 485       // Perform the check for duplicated 'distribute' hints.
 486       Category = Distribute;
 487       break;
 488     case LoopHintAttr::PipelineDisabled:
 489     case LoopHintAttr::PipelineInitiationInterval:
 490       Category = Pipeline;
 491       break;
 492     case LoopHintAttr::VectorizePredicate:
 493       Category = VectorizePredicate;
 494       break;
 495     };
 496
 497     assert(Category != NumberOfCategories && "Unhandled loop hint option");
 498     auto &CategoryState = HintAttrs[Category];
 499     const LoopHintAttr *PrevAttr;
 500     if (Option == LoopHintAttr::Vectorize ||
 501         Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll ||
 502         Option == LoopHintAttr::UnrollAndJam ||
 503         Option == LoopHintAttr::VectorizePredicate ||
 504         Option == LoopHintAttr::PipelineDisabled ||
 505         Option == LoopHintAttr::Distribute) {
 506       // Enable|Disable|AssumeSafety hint.  For example, vectorize(enable).
 507       PrevAttr = CategoryState.StateAttr;
 508       CategoryState.StateAttr = LH;
 509     } else {
 510       // Numeric hint.  For example, vectorize_width(8).
 511       PrevAttr = CategoryState.NumericAttr;
 512       CategoryState.NumericAttr = LH;
 513     }
 514
 515     PrintingPolicy Policy(S.Context.getLangOpts());
 516     SourceLocation OptionLoc = LH->getRange().getBegin();
 517     if (PrevAttr)
 518       // Cannot specify same type of attribute twice.
 519       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
 520           << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
 521           << LH->getDiagnosticName(Policy);
 522
 523     if (CategoryState.StateAttr && CategoryState.NumericAttr &&
 524         (Category == Unroll || Category == UnrollAndJam ||
 525          CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
 526       // Disable hints are not compatible with numeric hints of the same
 527       // category.  As a special case, numeric unroll hints are also not
 528       // compatible with enable or full form of the unroll pragma because these
 529       // directives indicate full unrolling.
 530       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
 531           << /*Duplicate=*/false
 532           << CategoryState.StateAttr->getDiagnosticName(Policy)
 533           << CategoryState.NumericAttr->getDiagnosticName(Policy);
 534     }
 535   }
 536 }
 537
 538 static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A,
 539                                     SourceRange Range) {
 540   // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's
 541   // useful for OpenCL 1.x too and doesn't require HW support.
 542   // opencl_unroll_hint can have 0 arguments (compiler
 543   // determines unrolling factor) or 1 argument (the unroll factor provided
 544   // by the user).
 545   unsigned UnrollFactor = 0;
 546   if (A.getNumArgs() == 1) {
 547     Expr *E = A.getArgAsExpr(0);
 548     std::optional<llvm::APSInt> ArgVal;
 549
 550     if (!(ArgVal = E->getIntegerConstantExpr(S.Context))) {
 551       S.Diag(A.getLoc(), diag::err_attribute_argument_type)
 552           << A << AANT_ArgumentIntegerConstant << E->getSourceRange();
 553       return nullptr;
 554     }
 555
 556     int Val = ArgVal->getSExtValue();
 557     if (Val <= 0) {
 558       S.Diag(A.getRange().getBegin(),
 559              diag::err_attribute_requires_positive_integer)
 560           << A << /* positive */ 0;
 561       return nullptr;
 562     }
 563     UnrollFactor = static_cast<unsigned>(Val);
 564   }
 565
 566   return ::new (S.Context) OpenCLUnrollHintAttr(S.Context, A, UnrollFactor);
 567 }
 568
 569 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
 570                                   SourceRange Range) {
 571   if (A.isInvalid() || A.getKind() == ParsedAttr::IgnoredAttribute)
 572     return nullptr;
 573
 574   // Unknown attributes are automatically warned on. Target-specific attributes
 575   // which do not apply to the current target architecture are treated as
 576   // though they were unknown attributes.
 577   const TargetInfo *Aux = S.Context.getAuxTargetInfo();
 578   if (A.getKind() == ParsedAttr::UnknownAttribute ||
 579       !(A.existsInTarget(S.Context.getTargetInfo()) ||
 580         (S.Context.getLangOpts().SYCLIsDevice && Aux &&
 581          A.existsInTarget(*Aux)))) {
 582     S.Diag(A.getLoc(), A.isRegularKeywordAttribute()
 583                            ? (unsigned)diag::err_keyword_not_supported_on_target
 584                        : A.isDeclspecAttribute()
 585                            ? (unsigned)diag::warn_unhandled_ms_attribute_ignored
 586                            : (unsigned)diag::warn_unknown_attribute_ignored)
 587         << A << A.getRange();
 588     return nullptr;
 589   }
 590
 591   if (S.checkCommonAttributeFeatures(St, A))
 592     return nullptr;
 593
 594   switch (A.getKind()) {
 595   case ParsedAttr::AT_AlwaysInline:
 596     return handleAlwaysInlineAttr(S, St, A, Range);
 597   case ParsedAttr::AT_FallThrough:
 598     return handleFallThroughAttr(S, St, A, Range);
 599   case ParsedAttr::AT_LoopHint:
 600     return handleLoopHintAttr(S, St, A, Range);
 601   case ParsedAttr::AT_OpenCLUnrollHint:
 602     return handleOpenCLUnrollHint(S, St, A, Range);
 603   case ParsedAttr::AT_Suppress:
 604     return handleSuppressAttr(S, St, A, Range);
 605   case ParsedAttr::AT_NoMerge:
 606     return handleNoMergeAttr(S, St, A, Range);
 607   case ParsedAttr::AT_NoInline:
 608     return handleNoInlineAttr(S, St, A, Range);
 609   case ParsedAttr::AT_MustTail:
 610     return handleMustTailAttr(S, St, A, Range);
 611   case ParsedAttr::AT_Likely:
 612     return handleLikely(S, St, A, Range);
 613   case ParsedAttr::AT_Unlikely:
 614     return handleUnlikely(S, St, A, Range);
 615   case ParsedAttr::AT_CodeAlign:
 616     return handleCodeAlignAttr(S, St, A);
 617   case ParsedAttr::AT_MSConstexpr:
 618     return handleMSConstexprAttr(S, St, A, Range);
 619   default:
 620     // N.B., ClangAttrEmitter.cpp emits a diagnostic helper that ensures a
 621     // declaration attribute is not written on a statement, but this code is
 622     // needed for attributes in Attr.td that do not list any subjects.
 623     S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt)
 624         << A << A.isRegularKeywordAttribute() << St->getBeginLoc();
 625     return nullptr;
 626   }
 627 }
 628
 629 void Sema::ProcessStmtAttributes(Stmt *S, const ParsedAttributes &InAttrs,
 630                                  SmallVectorImpl<const Attr *> &OutAttrs) {
 631   for (const ParsedAttr &AL : InAttrs) {
 632     if (const Attr *A = ProcessStmtAttribute(*this, S, AL, InAttrs.Range))
 633       OutAttrs.push_back(A);
 634   }
 635
 636   CheckForIncompatibleAttributes(*this, OutAttrs);
 637   CheckForDuplicateLoopAttrs<CodeAlignAttr>(*this, OutAttrs);
 638 }
 639
 640 bool Sema::CheckRebuiltStmtAttributes(ArrayRef<const Attr *> Attrs) {
 641   CheckForDuplicateLoopAttrs<CodeAlignAttr>(*this, Attrs);
 642   return false;
 643 }