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/Sema/SemaInternal.h" 14 #include "clang/AST/ASTContext.h" 15 #include "clang/Basic/SourceManager.h" 16 #include "clang/Sema/DelayedDiagnostic.h" 17 #include "clang/Sema/Lookup.h" 18 #include "clang/Sema/ScopeInfo.h" 19 #include "llvm/ADT/StringExtras.h" 20 21 using namespace clang; 22 using namespace sema; 23 24 static Attr *handleFallThroughAttr(Sema &S, Stmt *St, const ParsedAttr &A, 25 SourceRange Range) { 26 FallThroughAttr Attr(A.getRange(), S.Context, 27 A.getAttributeSpellingListIndex()); 28 if (!isa<NullStmt>(St)) { 29 S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target) 30 << Attr.getSpelling() << St->getBeginLoc(); 31 if (isa<SwitchCase>(St)) { 32 SourceLocation L = S.getLocForEndOfToken(Range.getEnd()); 33 S.Diag(L, diag::note_fallthrough_insert_semi_fixit) 34 << FixItHint::CreateInsertion(L, ";"); 35 } 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.getName(); 49 50 FnScope->setHasFallthroughStmt(); 51 return ::new (S.Context) auto(Attr); 52 } 53 54 static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A, 55 SourceRange Range) { 56 if (A.getNumArgs() < 1) { 57 S.Diag(A.getLoc(), diag::err_attribute_too_few_arguments) << A << 1; 58 return nullptr; 59 } 60 61 std::vector<StringRef> DiagnosticIdentifiers; 62 for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) { 63 StringRef RuleName; 64 65 if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr)) 66 return nullptr; 67 68 // FIXME: Warn if the rule name is unknown. This is tricky because only 69 // clang-tidy knows about available rules. 70 DiagnosticIdentifiers.push_back(RuleName); 71 } 72 73 return ::new (S.Context) SuppressAttr( 74 A.getRange(), S.Context, DiagnosticIdentifiers.data(), 75 DiagnosticIdentifiers.size(), A.getAttributeSpellingListIndex()); 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::Spelling Spelling = 101 LoopHintAttr::Spelling(A.getAttributeSpellingListIndex()); 102 LoopHintAttr::OptionType Option; 103 LoopHintAttr::LoopHintState State; 104 105 auto SetHints = [&Option, &State](LoopHintAttr::OptionType O, 106 LoopHintAttr::LoopHintState S) { 107 Option = O; 108 State = S; 109 }; 110 111 if (PragmaName == "nounroll") { 112 SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable); 113 } else if (PragmaName == "unroll") { 114 // #pragma unroll N 115 if (ValueExpr) 116 SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric); 117 else 118 SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable); 119 } else if (PragmaName == "nounroll_and_jam") { 120 SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable); 121 } else if (PragmaName == "unroll_and_jam") { 122 // #pragma unroll_and_jam N 123 if (ValueExpr) 124 SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric); 125 else 126 SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable); 127 } else { 128 // #pragma clang loop ... 129 assert(OptionLoc && OptionLoc->Ident && 130 "Attribute must have valid option info."); 131 Option = llvm::StringSwitch<LoopHintAttr::OptionType>( 132 OptionLoc->Ident->getName()) 133 .Case("vectorize", LoopHintAttr::Vectorize) 134 .Case("vectorize_width", LoopHintAttr::VectorizeWidth) 135 .Case("interleave", LoopHintAttr::Interleave) 136 .Case("interleave_count", LoopHintAttr::InterleaveCount) 137 .Case("unroll", LoopHintAttr::Unroll) 138 .Case("unroll_count", LoopHintAttr::UnrollCount) 139 .Case("pipeline", LoopHintAttr::PipelineDisabled) 140 .Case("pipeline_initiation_interval", 141 LoopHintAttr::PipelineInitiationInterval) 142 .Case("distribute", LoopHintAttr::Distribute) 143 .Default(LoopHintAttr::Vectorize); 144 if (Option == LoopHintAttr::VectorizeWidth || 145 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::Unroll || 155 Option == LoopHintAttr::Distribute || 156 Option == LoopHintAttr::PipelineDisabled) { 157 assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument"); 158 if (StateLoc->Ident->isStr("disable")) 159 State = LoopHintAttr::Disable; 160 else if (StateLoc->Ident->isStr("assume_safety")) 161 State = LoopHintAttr::AssumeSafety; 162 else if (StateLoc->Ident->isStr("full")) 163 State = LoopHintAttr::Full; 164 else if (StateLoc->Ident->isStr("enable")) 165 State = LoopHintAttr::Enable; 166 else 167 llvm_unreachable("bad loop hint argument"); 168 } else 169 llvm_unreachable("bad loop hint"); 170 } 171 172 return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State, 173 ValueExpr, A.getRange()); 174 } 175 176 static void 177 CheckForIncompatibleAttributes(Sema &S, 178 const SmallVectorImpl<const Attr *> &Attrs) { 179 // There are 6 categories of loop hints attributes: vectorize, interleave, 180 // unroll, unroll_and_jam, pipeline and distribute. Except for distribute they 181 // come in two variants: a state form and a numeric form. The state form 182 // selectively defaults/enables/disables the transformation for the loop 183 // (for unroll, default indicates full unrolling rather than enabling the 184 // transformation). The numeric form form provides an integer hint (for 185 // example, unroll count) to the transformer. The following array accumulates 186 // the hints encountered while iterating through the attributes to check for 187 // compatibility. 188 struct { 189 const LoopHintAttr *StateAttr; 190 const LoopHintAttr *NumericAttr; 191 } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}, 192 {nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}}; 193 194 for (const auto *I : Attrs) { 195 const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I); 196 197 // Skip non loop hint attributes 198 if (!LH) 199 continue; 200 201 LoopHintAttr::OptionType Option = LH->getOption(); 202 enum { 203 Vectorize, 204 Interleave, 205 Unroll, 206 UnrollAndJam, 207 Distribute, 208 Pipeline 209 } Category; 210 switch (Option) { 211 case LoopHintAttr::Vectorize: 212 case LoopHintAttr::VectorizeWidth: 213 Category = Vectorize; 214 break; 215 case LoopHintAttr::Interleave: 216 case LoopHintAttr::InterleaveCount: 217 Category = Interleave; 218 break; 219 case LoopHintAttr::Unroll: 220 case LoopHintAttr::UnrollCount: 221 Category = Unroll; 222 break; 223 case LoopHintAttr::UnrollAndJam: 224 case LoopHintAttr::UnrollAndJamCount: 225 Category = UnrollAndJam; 226 break; 227 case LoopHintAttr::Distribute: 228 // Perform the check for duplicated 'distribute' hints. 229 Category = Distribute; 230 break; 231 case LoopHintAttr::PipelineDisabled: 232 case LoopHintAttr::PipelineInitiationInterval: 233 Category = Pipeline; 234 break; 235 }; 236 237 assert(Category < sizeof(HintAttrs) / sizeof(HintAttrs[0])); 238 auto &CategoryState = HintAttrs[Category]; 239 const LoopHintAttr *PrevAttr; 240 if (Option == LoopHintAttr::Vectorize || 241 Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll || 242 Option == LoopHintAttr::UnrollAndJam || 243 Option == LoopHintAttr::PipelineDisabled || 244 Option == LoopHintAttr::Distribute) { 245 // Enable|Disable|AssumeSafety hint. For example, vectorize(enable). 246 PrevAttr = CategoryState.StateAttr; 247 CategoryState.StateAttr = LH; 248 } else { 249 // Numeric hint. For example, vectorize_width(8). 250 PrevAttr = CategoryState.NumericAttr; 251 CategoryState.NumericAttr = LH; 252 } 253 254 PrintingPolicy Policy(S.Context.getLangOpts()); 255 SourceLocation OptionLoc = LH->getRange().getBegin(); 256 if (PrevAttr) 257 // Cannot specify same type of attribute twice. 258 S.Diag(OptionLoc, diag::err_pragma_loop_compatibility) 259 << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy) 260 << LH->getDiagnosticName(Policy); 261 262 if (CategoryState.StateAttr && CategoryState.NumericAttr && 263 (Category == Unroll || Category == UnrollAndJam || 264 CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) { 265 // Disable hints are not compatible with numeric hints of the same 266 // category. As a special case, numeric unroll hints are also not 267 // compatible with enable or full form of the unroll pragma because these 268 // directives indicate full unrolling. 269 S.Diag(OptionLoc, diag::err_pragma_loop_compatibility) 270 << /*Duplicate=*/false 271 << CategoryState.StateAttr->getDiagnosticName(Policy) 272 << CategoryState.NumericAttr->getDiagnosticName(Policy); 273 } 274 } 275 } 276 277 static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A, 278 SourceRange Range) { 279 // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's 280 // useful for OpenCL 1.x too and doesn't require HW support. 281 // opencl_unroll_hint can have 0 arguments (compiler 282 // determines unrolling factor) or 1 argument (the unroll factor provided 283 // by the user). 284 285 unsigned NumArgs = A.getNumArgs(); 286 287 if (NumArgs > 1) { 288 S.Diag(A.getLoc(), diag::err_attribute_too_many_arguments) << A << 1; 289 return nullptr; 290 } 291 292 unsigned UnrollFactor = 0; 293 294 if (NumArgs == 1) { 295 Expr *E = A.getArgAsExpr(0); 296 llvm::APSInt ArgVal(32); 297 298 if (!E->isIntegerConstantExpr(ArgVal, S.Context)) { 299 S.Diag(A.getLoc(), diag::err_attribute_argument_type) 300 << A << AANT_ArgumentIntegerConstant << E->getSourceRange(); 301 return nullptr; 302 } 303 304 int Val = ArgVal.getSExtValue(); 305 306 if (Val <= 0) { 307 S.Diag(A.getRange().getBegin(), 308 diag::err_attribute_requires_positive_integer) 309 << A << /* positive */ 0; 310 return nullptr; 311 } 312 UnrollFactor = Val; 313 } 314 315 return OpenCLUnrollHintAttr::CreateImplicit(S.Context, UnrollFactor); 316 } 317 318 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A, 319 SourceRange Range) { 320 switch (A.getKind()) { 321 case ParsedAttr::UnknownAttribute: 322 S.Diag(A.getLoc(), A.isDeclspecAttribute() 323 ? (unsigned)diag::warn_unhandled_ms_attribute_ignored 324 : (unsigned)diag::warn_unknown_attribute_ignored) 325 << A.getName(); 326 return nullptr; 327 case ParsedAttr::AT_FallThrough: 328 return handleFallThroughAttr(S, St, A, Range); 329 case ParsedAttr::AT_LoopHint: 330 return handleLoopHintAttr(S, St, A, Range); 331 case ParsedAttr::AT_OpenCLUnrollHint: 332 return handleOpenCLUnrollHint(S, St, A, Range); 333 case ParsedAttr::AT_Suppress: 334 return handleSuppressAttr(S, St, A, Range); 335 default: 336 // if we're here, then we parsed a known attribute, but didn't recognize 337 // it as a statement attribute => it is declaration attribute 338 S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt) 339 << A.getName() << St->getBeginLoc(); 340 return nullptr; 341 } 342 } 343 344 StmtResult Sema::ProcessStmtAttributes(Stmt *S, 345 const ParsedAttributesView &AttrList, 346 SourceRange Range) { 347 SmallVector<const Attr*, 8> Attrs; 348 for (const ParsedAttr &AL : AttrList) { 349 if (Attr *a = ProcessStmtAttribute(*this, S, AL, Range)) 350 Attrs.push_back(a); 351 } 352 353 CheckForIncompatibleAttributes(*this, Attrs); 354 355 if (Attrs.empty()) 356 return S; 357 358 return ActOnAttributedStmt(Range.getBegin(), Attrs, S); 359 } 360