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 static Attr *handleNoInlineAttr(Sema &S, Stmt *St, const ParsedAttr &A, 219 SourceRange Range) { 220 NoInlineAttr NIA(S.Context, A); 221 if (!NIA.isClangNoInline()) { 222 S.Diag(St->getBeginLoc(), diag::warn_function_attribute_ignored_in_stmt) 223 << "[[clang::noinline]]"; 224 return nullptr; 225 } 226 227 CallExprFinder CEF(S, St); 228 if (!CEF.foundCallExpr()) { 229 S.Diag(St->getBeginLoc(), diag::warn_attribute_ignored_no_calls_in_stmt) 230 << A; 231 return nullptr; 232 } 233 234 for (const auto *CallExpr : CEF.getCallExprs()) { 235 const Decl *Decl = CallExpr->getCalleeDecl(); 236 if (Decl->hasAttr<AlwaysInlineAttr>() || Decl->hasAttr<FlattenAttr>()) 237 S.Diag(St->getBeginLoc(), diag::warn_function_stmt_attribute_precedence) 238 << A << (Decl->hasAttr<AlwaysInlineAttr>() ? 0 : 1); 239 } 240 241 return ::new (S.Context) NoInlineAttr(S.Context, A); 242 } 243 244 static Attr *handleAlwaysInlineAttr(Sema &S, Stmt *St, const ParsedAttr &A, 245 SourceRange Range) { 246 AlwaysInlineAttr AIA(S.Context, A); 247 if (!AIA.isClangAlwaysInline()) { 248 S.Diag(St->getBeginLoc(), diag::warn_function_attribute_ignored_in_stmt) 249 << "[[clang::always_inline]]"; 250 return nullptr; 251 } 252 253 CallExprFinder CEF(S, St); 254 if (!CEF.foundCallExpr()) { 255 S.Diag(St->getBeginLoc(), diag::warn_attribute_ignored_no_calls_in_stmt) 256 << A; 257 return nullptr; 258 } 259 260 for (const auto *CallExpr : CEF.getCallExprs()) { 261 const Decl *Decl = CallExpr->getCalleeDecl(); 262 if (Decl->hasAttr<NoInlineAttr>() || Decl->hasAttr<FlattenAttr>()) 263 S.Diag(St->getBeginLoc(), diag::warn_function_stmt_attribute_precedence) 264 << A << (Decl->hasAttr<NoInlineAttr>() ? 2 : 1); 265 } 266 267 return ::new (S.Context) AlwaysInlineAttr(S.Context, A); 268 } 269 270 static Attr *handleMustTailAttr(Sema &S, Stmt *St, const ParsedAttr &A, 271 SourceRange Range) { 272 // Validation is in Sema::ActOnAttributedStmt(). 273 return ::new (S.Context) MustTailAttr(S.Context, A); 274 } 275 276 static Attr *handleLikely(Sema &S, Stmt *St, const ParsedAttr &A, 277 SourceRange Range) { 278 279 if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName()) 280 S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range; 281 282 return ::new (S.Context) LikelyAttr(S.Context, A); 283 } 284 285 static Attr *handleUnlikely(Sema &S, Stmt *St, const ParsedAttr &A, 286 SourceRange Range) { 287 288 if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName()) 289 S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range; 290 291 return ::new (S.Context) UnlikelyAttr(S.Context, A); 292 } 293 294 #define WANT_STMT_MERGE_LOGIC 295 #include "clang/Sema/AttrParsedAttrImpl.inc" 296 #undef WANT_STMT_MERGE_LOGIC 297 298 static void 299 CheckForIncompatibleAttributes(Sema &S, 300 const SmallVectorImpl<const Attr *> &Attrs) { 301 // The vast majority of attributed statements will only have one attribute 302 // on them, so skip all of the checking in the common case. 303 if (Attrs.size() < 2) 304 return; 305 306 // First, check for the easy cases that are table-generated for us. 307 if (!DiagnoseMutualExclusions(S, Attrs)) 308 return; 309 310 enum CategoryType { 311 // For the following categories, they come in two variants: a state form and 312 // a numeric form. The state form may be one of default, enable, and 313 // disable. The numeric form provides an integer hint (for example, unroll 314 // count) to the transformer. 315 Vectorize, 316 Interleave, 317 UnrollAndJam, 318 Pipeline, 319 // For unroll, default indicates full unrolling rather than enabling the 320 // transformation. 321 Unroll, 322 // The loop distribution transformation only has a state form that is 323 // exposed by #pragma clang loop distribute (enable | disable). 324 Distribute, 325 // The vector predication only has a state form that is exposed by 326 // #pragma clang loop vectorize_predicate (enable | disable). 327 VectorizePredicate, 328 // This serves as a indicator to how many category are listed in this enum. 329 NumberOfCategories 330 }; 331 // The following array accumulates the hints encountered while iterating 332 // through the attributes to check for compatibility. 333 struct { 334 const LoopHintAttr *StateAttr; 335 const LoopHintAttr *NumericAttr; 336 } HintAttrs[CategoryType::NumberOfCategories] = {}; 337 338 for (const auto *I : Attrs) { 339 const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I); 340 341 // Skip non loop hint attributes 342 if (!LH) 343 continue; 344 345 CategoryType Category = CategoryType::NumberOfCategories; 346 LoopHintAttr::OptionType Option = LH->getOption(); 347 switch (Option) { 348 case LoopHintAttr::Vectorize: 349 case LoopHintAttr::VectorizeWidth: 350 Category = Vectorize; 351 break; 352 case LoopHintAttr::Interleave: 353 case LoopHintAttr::InterleaveCount: 354 Category = Interleave; 355 break; 356 case LoopHintAttr::Unroll: 357 case LoopHintAttr::UnrollCount: 358 Category = Unroll; 359 break; 360 case LoopHintAttr::UnrollAndJam: 361 case LoopHintAttr::UnrollAndJamCount: 362 Category = UnrollAndJam; 363 break; 364 case LoopHintAttr::Distribute: 365 // Perform the check for duplicated 'distribute' hints. 366 Category = Distribute; 367 break; 368 case LoopHintAttr::PipelineDisabled: 369 case LoopHintAttr::PipelineInitiationInterval: 370 Category = Pipeline; 371 break; 372 case LoopHintAttr::VectorizePredicate: 373 Category = VectorizePredicate; 374 break; 375 }; 376 377 assert(Category != NumberOfCategories && "Unhandled loop hint option"); 378 auto &CategoryState = HintAttrs[Category]; 379 const LoopHintAttr *PrevAttr; 380 if (Option == LoopHintAttr::Vectorize || 381 Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll || 382 Option == LoopHintAttr::UnrollAndJam || 383 Option == LoopHintAttr::VectorizePredicate || 384 Option == LoopHintAttr::PipelineDisabled || 385 Option == LoopHintAttr::Distribute) { 386 // Enable|Disable|AssumeSafety hint. For example, vectorize(enable). 387 PrevAttr = CategoryState.StateAttr; 388 CategoryState.StateAttr = LH; 389 } else { 390 // Numeric hint. For example, vectorize_width(8). 391 PrevAttr = CategoryState.NumericAttr; 392 CategoryState.NumericAttr = LH; 393 } 394 395 PrintingPolicy Policy(S.Context.getLangOpts()); 396 SourceLocation OptionLoc = LH->getRange().getBegin(); 397 if (PrevAttr) 398 // Cannot specify same type of attribute twice. 399 S.Diag(OptionLoc, diag::err_pragma_loop_compatibility) 400 << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy) 401 << LH->getDiagnosticName(Policy); 402 403 if (CategoryState.StateAttr && CategoryState.NumericAttr && 404 (Category == Unroll || Category == UnrollAndJam || 405 CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) { 406 // Disable hints are not compatible with numeric hints of the same 407 // category. As a special case, numeric unroll hints are also not 408 // compatible with enable or full form of the unroll pragma because these 409 // directives indicate full unrolling. 410 S.Diag(OptionLoc, diag::err_pragma_loop_compatibility) 411 << /*Duplicate=*/false 412 << CategoryState.StateAttr->getDiagnosticName(Policy) 413 << CategoryState.NumericAttr->getDiagnosticName(Policy); 414 } 415 } 416 } 417 418 static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A, 419 SourceRange Range) { 420 // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's 421 // useful for OpenCL 1.x too and doesn't require HW support. 422 // opencl_unroll_hint can have 0 arguments (compiler 423 // determines unrolling factor) or 1 argument (the unroll factor provided 424 // by the user). 425 unsigned UnrollFactor = 0; 426 if (A.getNumArgs() == 1) { 427 Expr *E = A.getArgAsExpr(0); 428 std::optional<llvm::APSInt> ArgVal; 429 430 if (!(ArgVal = E->getIntegerConstantExpr(S.Context))) { 431 S.Diag(A.getLoc(), diag::err_attribute_argument_type) 432 << A << AANT_ArgumentIntegerConstant << E->getSourceRange(); 433 return nullptr; 434 } 435 436 int Val = ArgVal->getSExtValue(); 437 if (Val <= 0) { 438 S.Diag(A.getRange().getBegin(), 439 diag::err_attribute_requires_positive_integer) 440 << A << /* positive */ 0; 441 return nullptr; 442 } 443 UnrollFactor = static_cast<unsigned>(Val); 444 } 445 446 return ::new (S.Context) OpenCLUnrollHintAttr(S.Context, A, UnrollFactor); 447 } 448 449 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A, 450 SourceRange Range) { 451 if (A.isInvalid() || A.getKind() == ParsedAttr::IgnoredAttribute) 452 return nullptr; 453 454 // Unknown attributes are automatically warned on. Target-specific attributes 455 // which do not apply to the current target architecture are treated as 456 // though they were unknown attributes. 457 const TargetInfo *Aux = S.Context.getAuxTargetInfo(); 458 if (A.getKind() == ParsedAttr::UnknownAttribute || 459 !(A.existsInTarget(S.Context.getTargetInfo()) || 460 (S.Context.getLangOpts().SYCLIsDevice && Aux && 461 A.existsInTarget(*Aux)))) { 462 S.Diag(A.getLoc(), A.isDeclspecAttribute() 463 ? (unsigned)diag::warn_unhandled_ms_attribute_ignored 464 : (unsigned)diag::warn_unknown_attribute_ignored) 465 << A << A.getRange(); 466 return nullptr; 467 } 468 469 if (S.checkCommonAttributeFeatures(St, A)) 470 return nullptr; 471 472 switch (A.getKind()) { 473 case ParsedAttr::AT_AlwaysInline: 474 return handleAlwaysInlineAttr(S, St, A, Range); 475 case ParsedAttr::AT_FallThrough: 476 return handleFallThroughAttr(S, St, A, Range); 477 case ParsedAttr::AT_LoopHint: 478 return handleLoopHintAttr(S, St, A, Range); 479 case ParsedAttr::AT_OpenCLUnrollHint: 480 return handleOpenCLUnrollHint(S, St, A, Range); 481 case ParsedAttr::AT_Suppress: 482 return handleSuppressAttr(S, St, A, Range); 483 case ParsedAttr::AT_NoMerge: 484 return handleNoMergeAttr(S, St, A, Range); 485 case ParsedAttr::AT_NoInline: 486 return handleNoInlineAttr(S, St, A, Range); 487 case ParsedAttr::AT_MustTail: 488 return handleMustTailAttr(S, St, A, Range); 489 case ParsedAttr::AT_Likely: 490 return handleLikely(S, St, A, Range); 491 case ParsedAttr::AT_Unlikely: 492 return handleUnlikely(S, St, A, Range); 493 default: 494 // N.B., ClangAttrEmitter.cpp emits a diagnostic helper that ensures a 495 // declaration attribute is not written on a statement, but this code is 496 // needed for attributes in Attr.td that do not list any subjects. 497 S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt) 498 << A << St->getBeginLoc(); 499 return nullptr; 500 } 501 } 502 503 void Sema::ProcessStmtAttributes(Stmt *S, const ParsedAttributes &InAttrs, 504 SmallVectorImpl<const Attr *> &OutAttrs) { 505 for (const ParsedAttr &AL : InAttrs) { 506 if (const Attr *A = ProcessStmtAttribute(*this, S, AL, InAttrs.Range)) 507 OutAttrs.push_back(A); 508 } 509 510 CheckForIncompatibleAttributes(*this, OutAttrs); 511 } 512