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 
handleFallThroughAttr(Sema & S,Stmt * St,const AttributeList & A,SourceRange Range)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 
handleLoopHintAttr(Sema & S,Stmt * St,const AttributeList & A,SourceRange)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::Spelling Spelling;
69   LoopHintAttr::OptionType Option;
70   LoopHintAttr::LoopHintState State;
71   if (PragmaNoUnroll) {
72     // #pragma nounroll
73     Spelling = LoopHintAttr::Pragma_nounroll;
74     Option = LoopHintAttr::Unroll;
75     State = LoopHintAttr::Disable;
76   } else if (PragmaUnroll) {
77     Spelling = LoopHintAttr::Pragma_unroll;
78     if (ValueExpr) {
79       // #pragma unroll N
80       Option = LoopHintAttr::UnrollCount;
81       State = LoopHintAttr::Numeric;
82     } else {
83       // #pragma unroll
84       Option = LoopHintAttr::Unroll;
85       State = LoopHintAttr::Enable;
86     }
87   } else {
88     // #pragma clang loop ...
89     Spelling = LoopHintAttr::Pragma_clang_loop;
90     assert(OptionLoc && OptionLoc->Ident &&
91            "Attribute must have valid option info.");
92     Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
93                  OptionLoc->Ident->getName())
94                  .Case("vectorize", LoopHintAttr::Vectorize)
95                  .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
96                  .Case("interleave", LoopHintAttr::Interleave)
97                  .Case("interleave_count", LoopHintAttr::InterleaveCount)
98                  .Case("unroll", LoopHintAttr::Unroll)
99                  .Case("unroll_count", LoopHintAttr::UnrollCount)
100                  .Default(LoopHintAttr::Vectorize);
101     if (Option == LoopHintAttr::VectorizeWidth ||
102         Option == LoopHintAttr::InterleaveCount ||
103         Option == LoopHintAttr::UnrollCount) {
104       assert(ValueExpr && "Attribute must have a valid value expression.");
105       if (S.CheckLoopHintExpr(ValueExpr, St->getLocStart()))
106         return nullptr;
107       State = LoopHintAttr::Numeric;
108     } else if (Option == LoopHintAttr::Vectorize ||
109                Option == LoopHintAttr::Interleave ||
110                Option == LoopHintAttr::Unroll) {
111       assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
112       if (StateLoc->Ident->isStr("disable"))
113         State = LoopHintAttr::Disable;
114       else if (StateLoc->Ident->isStr("assume_safety"))
115         State = LoopHintAttr::AssumeSafety;
116       else if (StateLoc->Ident->isStr("full"))
117         State = LoopHintAttr::Full;
118       else if (StateLoc->Ident->isStr("enable"))
119         State = LoopHintAttr::Enable;
120       else
121         llvm_unreachable("bad loop hint argument");
122     } else
123       llvm_unreachable("bad loop hint");
124   }
125 
126   return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State,
127                                       ValueExpr, A.getRange());
128 }
129 
130 static void
CheckForIncompatibleAttributes(Sema & S,const SmallVectorImpl<const Attr * > & Attrs)131 CheckForIncompatibleAttributes(Sema &S,
132                                const SmallVectorImpl<const Attr *> &Attrs) {
133   // There are 3 categories of loop hints attributes: vectorize, interleave,
134   // and unroll. Each comes in two variants: a state form and a numeric form.
135   // The state form selectively defaults/enables/disables the transformation
136   // for the loop (for unroll, default indicates full unrolling rather than
137   // enabling the transformation).  The numeric form form provides an integer
138   // hint (for example, unroll count) to the transformer. The following array
139   // accumulates the hints encountered while iterating through the attributes
140   // to check for compatibility.
141   struct {
142     const LoopHintAttr *StateAttr;
143     const LoopHintAttr *NumericAttr;
144   } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}};
145 
146   for (const auto *I : Attrs) {
147     const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
148 
149     // Skip non loop hint attributes
150     if (!LH)
151       continue;
152 
153     int Option = LH->getOption();
154     int Category;
155     enum { Vectorize, Interleave, Unroll };
156     switch (Option) {
157     case LoopHintAttr::Vectorize:
158     case LoopHintAttr::VectorizeWidth:
159       Category = Vectorize;
160       break;
161     case LoopHintAttr::Interleave:
162     case LoopHintAttr::InterleaveCount:
163       Category = Interleave;
164       break;
165     case LoopHintAttr::Unroll:
166     case LoopHintAttr::UnrollCount:
167       Category = Unroll;
168       break;
169     };
170 
171     auto &CategoryState = HintAttrs[Category];
172     const LoopHintAttr *PrevAttr;
173     if (Option == LoopHintAttr::Vectorize ||
174         Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll) {
175       // Enable|Disable|AssumeSafety hint.  For example, vectorize(enable).
176       PrevAttr = CategoryState.StateAttr;
177       CategoryState.StateAttr = LH;
178     } else {
179       // Numeric hint.  For example, vectorize_width(8).
180       PrevAttr = CategoryState.NumericAttr;
181       CategoryState.NumericAttr = LH;
182     }
183 
184     PrintingPolicy Policy(S.Context.getLangOpts());
185     SourceLocation OptionLoc = LH->getRange().getBegin();
186     if (PrevAttr)
187       // Cannot specify same type of attribute twice.
188       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
189           << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
190           << LH->getDiagnosticName(Policy);
191 
192     if (CategoryState.StateAttr && CategoryState.NumericAttr &&
193         (Category == Unroll ||
194          CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
195       // Disable hints are not compatible with numeric hints of the same
196       // category.  As a special case, numeric unroll hints are also not
197       // compatible with enable or full form of the unroll pragma because these
198       // directives indicate full unrolling.
199       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
200           << /*Duplicate=*/false
201           << CategoryState.StateAttr->getDiagnosticName(Policy)
202           << CategoryState.NumericAttr->getDiagnosticName(Policy);
203     }
204   }
205 }
206 
ProcessStmtAttribute(Sema & S,Stmt * St,const AttributeList & A,SourceRange Range)207 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const AttributeList &A,
208                                   SourceRange Range) {
209   switch (A.getKind()) {
210   case AttributeList::UnknownAttribute:
211     S.Diag(A.getLoc(), A.isDeclspecAttribute() ?
212            diag::warn_unhandled_ms_attribute_ignored :
213            diag::warn_unknown_attribute_ignored) << A.getName();
214     return nullptr;
215   case AttributeList::AT_FallThrough:
216     return handleFallThroughAttr(S, St, A, Range);
217   case AttributeList::AT_LoopHint:
218     return handleLoopHintAttr(S, St, A, Range);
219   default:
220     // if we're here, then we parsed a known attribute, but didn't recognize
221     // it as a statement attribute => it is declaration attribute
222     S.Diag(A.getRange().getBegin(), diag::err_attribute_invalid_on_stmt)
223         << A.getName() << St->getLocStart();
224     return nullptr;
225   }
226 }
227 
ProcessStmtAttributes(Stmt * S,AttributeList * AttrList,SourceRange Range)228 StmtResult Sema::ProcessStmtAttributes(Stmt *S, AttributeList *AttrList,
229                                        SourceRange Range) {
230   SmallVector<const Attr*, 8> Attrs;
231   for (const AttributeList* l = AttrList; l; l = l->getNext()) {
232     if (Attr *a = ProcessStmtAttribute(*this, S, *l, Range))
233       Attrs.push_back(a);
234   }
235 
236   CheckForIncompatibleAttributes(*this, Attrs);
237 
238   if (Attrs.empty())
239     return S;
240 
241   return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
242 }
243