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::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
CheckForIncompatibleAttributes(Sema & S,const SmallVectorImpl<const Attr * > & Attrs)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 
ProcessStmtAttribute(Sema & S,Stmt * St,const AttributeList & A,SourceRange Range)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 
ProcessStmtAttributes(Stmt * S,AttributeList * AttrList,SourceRange Range)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