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      1 //===--- SemaStmtAttr.cpp - Statement Attribute Handling ------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 //  This file implements stmt-related attribute processing.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "clang/Sema/SemaInternal.h"
     15 #include "clang/AST/ASTContext.h"
     16 #include "clang/Basic/SourceManager.h"
     17 #include "clang/Sema/DelayedDiagnostic.h"
     18 #include "clang/Sema/Lookup.h"
     19 #include "clang/Sema/LoopHint.h"
     20 #include "clang/Sema/ScopeInfo.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 AttributeList &A,
     27                                    SourceRange Range) {
     28   if (!isa<NullStmt>(St)) {
     29     S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
     30         << St->getLocStart();
     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   if (S.getCurFunction()->SwitchStack.empty()) {
     39     S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch);
     40     return nullptr;
     41   }
     42   return ::new (S.Context) FallThroughAttr(A.getRange(), S.Context,
     43                                            A.getAttributeSpellingListIndex());
     44 }
     45 
     46 static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const AttributeList &A,
     47                                 SourceRange) {
     48   IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
     49   IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
     50   IdentifierLoc *StateLoc = A.getArgAsIdent(2);
     51   Expr *ValueExpr = A.getArgAsExpr(3);
     52 
     53   bool PragmaUnroll = PragmaNameLoc->Ident->getName() == "unroll";
     54   bool PragmaNoUnroll = PragmaNameLoc->Ident->getName() == "nounroll";
     55   if (St->getStmtClass() != Stmt::DoStmtClass &&
     56       St->getStmtClass() != Stmt::ForStmtClass &&
     57       St->getStmtClass() != Stmt::CXXForRangeStmtClass &&
     58       St->getStmtClass() != Stmt::WhileStmtClass) {
     59     const char *Pragma =
     60         llvm::StringSwitch<const char *>(PragmaNameLoc->Ident->getName())
     61             .Case("unroll", "#pragma unroll")
     62             .Case("nounroll", "#pragma nounroll")
     63             .Default("#pragma clang loop");
     64     S.Diag(St->getLocStart(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
     65     return nullptr;
     66   }
     67 
     68   LoopHintAttr::OptionType Option;
     69   LoopHintAttr::Spelling Spelling;
     70   if (PragmaUnroll) {
     71     Option = ValueExpr ? LoopHintAttr::UnrollCount : LoopHintAttr::Unroll;
     72     Spelling = LoopHintAttr::Pragma_unroll;
     73   } else if (PragmaNoUnroll) {
     74     Option = LoopHintAttr::Unroll;
     75     Spelling = LoopHintAttr::Pragma_nounroll;
     76   } else {
     77     assert(OptionLoc && OptionLoc->Ident &&
     78            "Attribute must have valid option info.");
     79     IdentifierInfo *OptionInfo = OptionLoc->Ident;
     80     Option = llvm::StringSwitch<LoopHintAttr::OptionType>(OptionInfo->getName())
     81                  .Case("vectorize", LoopHintAttr::Vectorize)
     82                  .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
     83                  .Case("interleave", LoopHintAttr::Interleave)
     84                  .Case("interleave_count", LoopHintAttr::InterleaveCount)
     85                  .Case("unroll", LoopHintAttr::Unroll)
     86                  .Case("unroll_count", LoopHintAttr::UnrollCount)
     87                  .Default(LoopHintAttr::Vectorize);
     88     Spelling = LoopHintAttr::Pragma_clang_loop;
     89   }
     90 
     91   LoopHintAttr::LoopHintState State = LoopHintAttr::Default;
     92   if (PragmaNoUnroll) {
     93     State = LoopHintAttr::Disable;
     94   } else if (Option == LoopHintAttr::VectorizeWidth ||
     95              Option == LoopHintAttr::InterleaveCount ||
     96              Option == LoopHintAttr::UnrollCount) {
     97     assert(ValueExpr && "Attribute must have a valid value expression.");
     98     if (S.CheckLoopHintExpr(ValueExpr, St->getLocStart()))
     99       return nullptr;
    100   } else if (Option == LoopHintAttr::Vectorize ||
    101              Option == LoopHintAttr::Interleave ||
    102              Option == LoopHintAttr::Unroll) {
    103     // Default state is assumed if StateLoc is not specified, such as with
    104     // '#pragma unroll'.
    105     if (StateLoc && StateLoc->Ident) {
    106       if (StateLoc->Ident->isStr("disable"))
    107         State = LoopHintAttr::Disable;
    108       else
    109         State = LoopHintAttr::Enable;
    110     }
    111   }
    112 
    113   return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State,
    114                                       ValueExpr, A.getRange());
    115 }
    116 
    117 static void
    118 CheckForIncompatibleAttributes(Sema &S,
    119                                const SmallVectorImpl<const Attr *> &Attrs) {
    120   // There are 3 categories of loop hints attributes: vectorize, interleave,
    121   // and unroll. Each comes in two variants: a state form and a numeric form.
    122   // The state form selectively defaults/enables/disables the transformation
    123   // for the loop (for unroll, default indicates full unrolling rather than
    124   // enabling the transformation).  The numeric form form provides an integer
    125   // hint (for example, unroll count) to the transformer. The following array
    126   // accumulates the hints encountered while iterating through the attributes
    127   // to check for compatibility.
    128   struct {
    129     const LoopHintAttr *StateAttr;
    130     const LoopHintAttr *NumericAttr;
    131   } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}};
    132 
    133   for (const auto *I : Attrs) {
    134     const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
    135 
    136     // Skip non loop hint attributes
    137     if (!LH)
    138       continue;
    139 
    140     int Option = LH->getOption();
    141     int Category;
    142     enum { Vectorize, Interleave, Unroll };
    143     switch (Option) {
    144     case LoopHintAttr::Vectorize:
    145     case LoopHintAttr::VectorizeWidth:
    146       Category = Vectorize;
    147       break;
    148     case LoopHintAttr::Interleave:
    149     case LoopHintAttr::InterleaveCount:
    150       Category = Interleave;
    151       break;
    152     case LoopHintAttr::Unroll:
    153     case LoopHintAttr::UnrollCount:
    154       Category = Unroll;
    155       break;
    156     };
    157 
    158     auto &CategoryState = HintAttrs[Category];
    159     const LoopHintAttr *PrevAttr;
    160     if (Option == LoopHintAttr::Vectorize ||
    161         Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll) {
    162       // Enable|disable hint.  For example, vectorize(enable).
    163       PrevAttr = CategoryState.StateAttr;
    164       CategoryState.StateAttr = LH;
    165     } else {
    166       // Numeric hint.  For example, vectorize_width(8).
    167       PrevAttr = CategoryState.NumericAttr;
    168       CategoryState.NumericAttr = LH;
    169     }
    170 
    171     PrintingPolicy Policy(S.Context.getLangOpts());
    172     SourceLocation OptionLoc = LH->getRange().getBegin();
    173     if (PrevAttr)
    174       // Cannot specify same type of attribute twice.
    175       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
    176           << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
    177           << LH->getDiagnosticName(Policy);
    178 
    179     if (CategoryState.StateAttr && CategoryState.NumericAttr &&
    180         (Category == Unroll ||
    181          CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
    182       // Disable hints are not compatible with numeric hints of the same
    183       // category.  As a special case, numeric unroll hints are also not
    184       // compatible with "enable" form of the unroll pragma, unroll(full).
    185       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
    186           << /*Duplicate=*/false
    187           << CategoryState.StateAttr->getDiagnosticName(Policy)
    188           << CategoryState.NumericAttr->getDiagnosticName(Policy);
    189     }
    190   }
    191 }
    192 
    193 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const AttributeList &A,
    194                                   SourceRange Range) {
    195   switch (A.getKind()) {
    196   case AttributeList::UnknownAttribute:
    197     S.Diag(A.getLoc(), A.isDeclspecAttribute() ?
    198            diag::warn_unhandled_ms_attribute_ignored :
    199            diag::warn_unknown_attribute_ignored) << A.getName();
    200     return nullptr;
    201   case AttributeList::AT_FallThrough:
    202     return handleFallThroughAttr(S, St, A, Range);
    203   case AttributeList::AT_LoopHint:
    204     return handleLoopHintAttr(S, St, A, Range);
    205   default:
    206     // if we're here, then we parsed a known attribute, but didn't recognize
    207     // it as a statement attribute => it is declaration attribute
    208     S.Diag(A.getRange().getBegin(), diag::err_attribute_invalid_on_stmt)
    209         << A.getName() << St->getLocStart();
    210     return nullptr;
    211   }
    212 }
    213 
    214 StmtResult Sema::ProcessStmtAttributes(Stmt *S, AttributeList *AttrList,
    215                                        SourceRange Range) {
    216   SmallVector<const Attr*, 8> Attrs;
    217   for (const AttributeList* l = AttrList; l; l = l->getNext()) {
    218     if (Attr *a = ProcessStmtAttribute(*this, S, *l, Range))
    219       Attrs.push_back(a);
    220   }
    221 
    222   CheckForIncompatibleAttributes(*this, Attrs);
    223 
    224   if (Attrs.empty())
    225     return S;
    226 
    227   return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
    228 }
    229