clang/lib/Sema/SemaStmtAttr.cpp

   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 }