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<NullStmt>(St)) { 30 S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target) 31 << Attr.getSpelling() << St->getBeginLoc(); 32 if (isa<SwitchCase>(St)) { 33 SourceLocation L = S.getLocForEndOfToken(Range.getEnd()); 34 S.Diag(L, diag::note_fallthrough_insert_semi_fixit) 35 << FixItHint::CreateInsertion(L, ";"); 36 } 37 return nullptr; 38 } 39 auto *FnScope = S.getCurFunction(); 40 if (FnScope->SwitchStack.empty()) { 41 S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch); 42 return nullptr; 43 } 44 45 // If this is spelled as the standard C++17 attribute, but not in C++17, warn 46 // about using it as an extension. 47 if (!S.getLangOpts().CPlusPlus17 && A.isCXX11Attribute() && 48 !A.getScopeName()) 49 S.Diag(A.getLoc(), diag::ext_cxx17_attr) << A; 50 51 FnScope->setHasFallthroughStmt(); 52 return ::new (S.Context) FallThroughAttr(S.Context, A); 53 } 54 55 static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A, 56 SourceRange Range) { 57 if (A.getNumArgs() < 1) { 58 S.Diag(A.getLoc(), diag::err_attribute_too_few_arguments) << A << 1; 59 return nullptr; 60 } 61 62 std::vector<StringRef> DiagnosticIdentifiers; 63 for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) { 64 StringRef RuleName; 65 66 if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr)) 67 return nullptr; 68 69 // FIXME: Warn if the rule name is unknown. This is tricky because only 70 // clang-tidy knows about available rules. 71 DiagnosticIdentifiers.push_back(RuleName); 72 } 73 74 return ::new (S.Context) SuppressAttr( 75 S.Context, A, DiagnosticIdentifiers.data(), DiagnosticIdentifiers.size()); 76 } 77 78 static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A, 79 SourceRange) { 80 IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0); 81 IdentifierLoc *OptionLoc = A.getArgAsIdent(1); 82 IdentifierLoc *StateLoc = A.getArgAsIdent(2); 83 Expr *ValueExpr = A.getArgAsExpr(3); 84 85 StringRef PragmaName = 86 llvm::StringSwitch<StringRef>(PragmaNameLoc->Ident->getName()) 87 .Cases("unroll", "nounroll", "unroll_and_jam", "nounroll_and_jam", 88 PragmaNameLoc->Ident->getName()) 89 .Default("clang loop"); 90 91 if (St->getStmtClass() != Stmt::DoStmtClass && 92 St->getStmtClass() != Stmt::ForStmtClass && 93 St->getStmtClass() != Stmt::CXXForRangeStmtClass && 94 St->getStmtClass() != Stmt::WhileStmtClass) { 95 std::string Pragma = "#pragma " + std::string(PragmaName); 96 S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma; 97 return nullptr; 98 } 99 100 LoopHintAttr::OptionType Option; 101 LoopHintAttr::LoopHintState State; 102 103 auto SetHints = [&Option, &State](LoopHintAttr::OptionType O, 104 LoopHintAttr::LoopHintState S) { 105 Option = O; 106 State = S; 107 }; 108 109 if (PragmaName == "nounroll") { 110 SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable); 111 } else if (PragmaName == "unroll") { 112 // #pragma unroll N 113 if (ValueExpr) 114 SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric); 115 else 116 SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable); 117 } else if (PragmaName == "nounroll_and_jam") { 118 SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable); 119 } else if (PragmaName == "unroll_and_jam") { 120 // #pragma unroll_and_jam N 121 if (ValueExpr) 122 SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric); 123 else 124 SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable); 125 } else { 126 // #pragma clang loop ... 127 assert(OptionLoc && OptionLoc->Ident && 128 "Attribute must have valid option info."); 129 Option = llvm::StringSwitch<LoopHintAttr::OptionType>( 130 OptionLoc->Ident->getName()) 131 .Case("vectorize", LoopHintAttr::Vectorize) 132 .Case("vectorize_width", LoopHintAttr::VectorizeWidth) 133 .Case("interleave", LoopHintAttr::Interleave) 134 .Case("vectorize_predicate", LoopHintAttr::VectorizePredicate) 135 .Case("interleave_count", LoopHintAttr::InterleaveCount) 136 .Case("unroll", LoopHintAttr::Unroll) 137 .Case("unroll_count", LoopHintAttr::UnrollCount) 138 .Case("pipeline", LoopHintAttr::PipelineDisabled) 139 .Case("pipeline_initiation_interval", 140 LoopHintAttr::PipelineInitiationInterval) 141 .Case("distribute", LoopHintAttr::Distribute) 142 .Default(LoopHintAttr::Vectorize); 143 if (Option == LoopHintAttr::VectorizeWidth) { 144 assert((ValueExpr || (StateLoc && StateLoc->Ident)) && 145 "Attribute must have a valid value expression or argument."); 146 if (ValueExpr && S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc())) 147 return nullptr; 148 if (StateLoc && StateLoc->Ident && StateLoc->Ident->isStr("scalable")) 149 State = LoopHintAttr::ScalableWidth; 150 else 151 State = LoopHintAttr::FixedWidth; 152 } else if (Option == LoopHintAttr::InterleaveCount || 153 Option == LoopHintAttr::UnrollCount || 154 Option == LoopHintAttr::PipelineInitiationInterval) { 155 assert(ValueExpr && "Attribute must have a valid value expression."); 156 if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc())) 157 return nullptr; 158 State = LoopHintAttr::Numeric; 159 } else if (Option == LoopHintAttr::Vectorize || 160 Option == LoopHintAttr::Interleave || 161 Option == LoopHintAttr::VectorizePredicate || 162 Option == LoopHintAttr::Unroll || 163 Option == LoopHintAttr::Distribute || 164 Option == LoopHintAttr::PipelineDisabled) { 165 assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument"); 166 if (StateLoc->Ident->isStr("disable")) 167 State = LoopHintAttr::Disable; 168 else if (StateLoc->Ident->isStr("assume_safety")) 169 State = LoopHintAttr::AssumeSafety; 170 else if (StateLoc->Ident->isStr("full")) 171 State = LoopHintAttr::Full; 172 else if (StateLoc->Ident->isStr("enable")) 173 State = LoopHintAttr::Enable; 174 else 175 llvm_unreachable("bad loop hint argument"); 176 } else 177 llvm_unreachable("bad loop hint"); 178 } 179 180 return LoopHintAttr::CreateImplicit(S.Context, Option, State, ValueExpr, A); 181 } 182 183 namespace { 184 class CallExprFinder : public ConstEvaluatedExprVisitor<CallExprFinder> { 185 bool FoundCallExpr = false; 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 FoundCallExpr; } 193 194 void VisitCallExpr(const CallExpr *E) { FoundCallExpr = true; } 195 void VisitAsmStmt(const AsmStmt *S) { FoundCallExpr = true; } 196 197 void Visit(const Stmt *St) { 198 if (!St) 199 return; 200 ConstEvaluatedExprVisitor<CallExprFinder>::Visit(St); 201 } 202 }; 203 } // namespace 204 205 static Attr *handleNoMergeAttr(Sema &S, Stmt *St, const ParsedAttr &A, 206 SourceRange Range) { 207 NoMergeAttr NMA(S.Context, A); 208 if (S.CheckAttrNoArgs(A)) 209 return nullptr; 210 211 CallExprFinder CEF(S, St); 212 213 if (!CEF.foundCallExpr()) { 214 S.Diag(St->getBeginLoc(), diag::warn_nomerge_attribute_ignored_in_stmt) 215 << NMA.getSpelling(); 216 return nullptr; 217 } 218 219 return ::new (S.Context) NoMergeAttr(S.Context, A); 220 } 221 222 static Attr *handleLikely(Sema &S, Stmt *St, const ParsedAttr &A, 223 SourceRange Range) { 224 225 if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName()) 226 S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range; 227 228 return ::new (S.Context) LikelyAttr(S.Context, A); 229 } 230 231 static Attr *handleUnlikely(Sema &S, Stmt *St, const ParsedAttr &A, 232 SourceRange Range) { 233 234 if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName()) 235 S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range; 236 237 return ::new (S.Context) UnlikelyAttr(S.Context, A); 238 } 239 240 static void 241 CheckForIncompatibleAttributes(Sema &S, 242 const SmallVectorImpl<const Attr *> &Attrs) { 243 // There are 6 categories of loop hints attributes: vectorize, interleave, 244 // unroll, unroll_and_jam, pipeline and distribute. Except for distribute they 245 // come in two variants: a state form and a numeric form. The state form 246 // selectively defaults/enables/disables the transformation for the loop 247 // (for unroll, default indicates full unrolling rather than enabling the 248 // transformation). The numeric form form provides an integer hint (for 249 // example, unroll count) to the transformer. The following array accumulates 250 // the hints encountered while iterating through the attributes to check for 251 // compatibility. 252 struct { 253 const LoopHintAttr *StateAttr; 254 const LoopHintAttr *NumericAttr; 255 } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}, 256 {nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}, 257 {nullptr, nullptr}}; 258 259 for (const auto *I : Attrs) { 260 const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I); 261 262 // Skip non loop hint attributes 263 if (!LH) 264 continue; 265 266 LoopHintAttr::OptionType Option = LH->getOption(); 267 enum { 268 Vectorize, 269 Interleave, 270 Unroll, 271 UnrollAndJam, 272 Distribute, 273 Pipeline, 274 VectorizePredicate 275 } Category; 276 switch (Option) { 277 case LoopHintAttr::Vectorize: 278 case LoopHintAttr::VectorizeWidth: 279 Category = Vectorize; 280 break; 281 case LoopHintAttr::Interleave: 282 case LoopHintAttr::InterleaveCount: 283 Category = Interleave; 284 break; 285 case LoopHintAttr::Unroll: 286 case LoopHintAttr::UnrollCount: 287 Category = Unroll; 288 break; 289 case LoopHintAttr::UnrollAndJam: 290 case LoopHintAttr::UnrollAndJamCount: 291 Category = UnrollAndJam; 292 break; 293 case LoopHintAttr::Distribute: 294 // Perform the check for duplicated 'distribute' hints. 295 Category = Distribute; 296 break; 297 case LoopHintAttr::PipelineDisabled: 298 case LoopHintAttr::PipelineInitiationInterval: 299 Category = Pipeline; 300 break; 301 case LoopHintAttr::VectorizePredicate: 302 Category = VectorizePredicate; 303 break; 304 }; 305 306 assert(Category < sizeof(HintAttrs) / sizeof(HintAttrs[0])); 307 auto &CategoryState = HintAttrs[Category]; 308 const LoopHintAttr *PrevAttr; 309 if (Option == LoopHintAttr::Vectorize || 310 Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll || 311 Option == LoopHintAttr::UnrollAndJam || 312 Option == LoopHintAttr::VectorizePredicate || 313 Option == LoopHintAttr::PipelineDisabled || 314 Option == LoopHintAttr::Distribute) { 315 // Enable|Disable|AssumeSafety hint. For example, vectorize(enable). 316 PrevAttr = CategoryState.StateAttr; 317 CategoryState.StateAttr = LH; 318 } else { 319 // Numeric hint. For example, vectorize_width(8). 320 PrevAttr = CategoryState.NumericAttr; 321 CategoryState.NumericAttr = LH; 322 } 323 324 PrintingPolicy Policy(S.Context.getLangOpts()); 325 SourceLocation OptionLoc = LH->getRange().getBegin(); 326 if (PrevAttr) 327 // Cannot specify same type of attribute twice. 328 S.Diag(OptionLoc, diag::err_pragma_loop_compatibility) 329 << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy) 330 << LH->getDiagnosticName(Policy); 331 332 if (CategoryState.StateAttr && CategoryState.NumericAttr && 333 (Category == Unroll || Category == UnrollAndJam || 334 CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) { 335 // Disable hints are not compatible with numeric hints of the same 336 // category. As a special case, numeric unroll hints are also not 337 // compatible with enable or full form of the unroll pragma because these 338 // directives indicate full unrolling. 339 S.Diag(OptionLoc, diag::err_pragma_loop_compatibility) 340 << /*Duplicate=*/false 341 << CategoryState.StateAttr->getDiagnosticName(Policy) 342 << CategoryState.NumericAttr->getDiagnosticName(Policy); 343 } 344 } 345 346 // C++20 [dcl.attr.likelihood]p1 The attribute-token likely shall not appear 347 // in an attribute-specifier-seq that contains the attribute-token unlikely. 348 const LikelyAttr *Likely = nullptr; 349 const UnlikelyAttr *Unlikely = nullptr; 350 for (const auto *I : Attrs) { 351 if (const auto *Attr = dyn_cast<LikelyAttr>(I)) { 352 if (Unlikely) { 353 S.Diag(Attr->getLocation(), diag::err_attributes_are_not_compatible) 354 << Attr << Unlikely << Attr->getRange(); 355 S.Diag(Unlikely->getLocation(), diag::note_conflicting_attribute) 356 << Unlikely->getRange(); 357 return; 358 } 359 Likely = Attr; 360 } else if (const auto *Attr = dyn_cast<UnlikelyAttr>(I)) { 361 if (Likely) { 362 S.Diag(Attr->getLocation(), diag::err_attributes_are_not_compatible) 363 << Attr << Likely << Attr->getRange(); 364 S.Diag(Likely->getLocation(), diag::note_conflicting_attribute) 365 << Likely->getRange(); 366 return; 367 } 368 Unlikely = Attr; 369 } 370 } 371 } 372 373 static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A, 374 SourceRange Range) { 375 // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's 376 // useful for OpenCL 1.x too and doesn't require HW support. 377 // opencl_unroll_hint can have 0 arguments (compiler 378 // determines unrolling factor) or 1 argument (the unroll factor provided 379 // by the user). 380 381 unsigned NumArgs = A.getNumArgs(); 382 383 if (NumArgs > 1) { 384 S.Diag(A.getLoc(), diag::err_attribute_too_many_arguments) << A << 1; 385 return nullptr; 386 } 387 388 unsigned UnrollFactor = 0; 389 390 if (NumArgs == 1) { 391 Expr *E = A.getArgAsExpr(0); 392 Optional<llvm::APSInt> ArgVal; 393 394 if (!(ArgVal = E->getIntegerConstantExpr(S.Context))) { 395 S.Diag(A.getLoc(), diag::err_attribute_argument_type) 396 << A << AANT_ArgumentIntegerConstant << E->getSourceRange(); 397 return nullptr; 398 } 399 400 int Val = ArgVal->getSExtValue(); 401 402 if (Val <= 0) { 403 S.Diag(A.getRange().getBegin(), 404 diag::err_attribute_requires_positive_integer) 405 << A << /* positive */ 0; 406 return nullptr; 407 } 408 UnrollFactor = Val; 409 } 410 411 return OpenCLUnrollHintAttr::CreateImplicit(S.Context, UnrollFactor); 412 } 413 414 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A, 415 SourceRange Range) { 416 switch (A.getKind()) { 417 case ParsedAttr::UnknownAttribute: 418 S.Diag(A.getLoc(), A.isDeclspecAttribute() 419 ? (unsigned)diag::warn_unhandled_ms_attribute_ignored 420 : (unsigned)diag::warn_unknown_attribute_ignored) 421 << A << A.getRange(); 422 return nullptr; 423 case ParsedAttr::AT_FallThrough: 424 return handleFallThroughAttr(S, St, A, Range); 425 case ParsedAttr::AT_LoopHint: 426 return handleLoopHintAttr(S, St, A, Range); 427 case ParsedAttr::AT_OpenCLUnrollHint: 428 return handleOpenCLUnrollHint(S, St, A, Range); 429 case ParsedAttr::AT_Suppress: 430 return handleSuppressAttr(S, St, A, Range); 431 case ParsedAttr::AT_NoMerge: 432 return handleNoMergeAttr(S, St, A, Range); 433 case ParsedAttr::AT_Likely: 434 return handleLikely(S, St, A, Range); 435 case ParsedAttr::AT_Unlikely: 436 return handleUnlikely(S, St, A, Range); 437 default: 438 // if we're here, then we parsed a known attribute, but didn't recognize 439 // it as a statement attribute => it is declaration attribute 440 S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt) 441 << A << St->getBeginLoc(); 442 return nullptr; 443 } 444 } 445 446 StmtResult Sema::ProcessStmtAttributes(Stmt *S, 447 const ParsedAttributesView &AttrList, 448 SourceRange Range) { 449 SmallVector<const Attr*, 8> Attrs; 450 for (const ParsedAttr &AL : AttrList) { 451 if (Attr *a = ProcessStmtAttribute(*this, S, AL, Range)) 452 Attrs.push_back(a); 453 } 454 455 CheckForIncompatibleAttributes(*this, Attrs); 456 457 if (Attrs.empty()) 458 return S; 459 460 return ActOnAttributedStmt(Range.getBegin(), Attrs, S); 461 } 462