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