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 }
545