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   int ValueInt = 1;
92   LoopHintAttr::LoopHintState State = LoopHintAttr::Default;
93   if (PragmaNoUnroll) {
94     State = LoopHintAttr::Disable;
95   } else if (Option == LoopHintAttr::VectorizeWidth ||
96              Option == LoopHintAttr::InterleaveCount ||
97              Option == LoopHintAttr::UnrollCount) {
98     // FIXME: We should support template parameters for the loop hint value.
99     // See bug report #19610.
100     llvm::APSInt ValueAPS;
101     if (!ValueExpr || !ValueExpr->isIntegerConstantExpr(ValueAPS, S.Context) ||
102         (ValueInt = ValueAPS.getSExtValue()) < 1) {
103       S.Diag(A.getLoc(), diag::err_pragma_loop_invalid_value);
104       return nullptr;
105     }
106   } else if (Option == LoopHintAttr::Vectorize ||
107              Option == LoopHintAttr::Interleave ||
108              Option == LoopHintAttr::Unroll) {
109     // Default state is assumed if StateLoc is not specified, such as with
110     // '#pragma unroll'.
111     if (StateLoc && StateLoc->Ident) {
112       if (StateLoc->Ident->isStr("disable"))
113         State = LoopHintAttr::Disable;
114       else
115         State = LoopHintAttr::Enable;
116     }
117   }
118 
119   return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State,
120                                       ValueInt, A.getRange());
121 }
122 
123 static void
124 CheckForIncompatibleAttributes(Sema &S,
125                                const SmallVectorImpl<const Attr *> &Attrs) {
126   // There are 3 categories of loop hints attributes: vectorize, interleave,
127   // and unroll. Each comes in two variants: a state form and a numeric form.
128   // The state form selectively defaults/enables/disables the transformation
129   // for the loop (for unroll, default indicates full unrolling rather than
130   // enabling the transformation).  The numeric form form provides an integer
131   // hint (for example, unroll count) to the transformer. The following array
132   // accumulates the hints encountered while iterating through the attributes
133   // to check for compatibility.
134   struct {
135     const LoopHintAttr *StateAttr;
136     const LoopHintAttr *NumericAttr;
137   } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}};
138 
139   for (const auto *I : Attrs) {
140     const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
141 
142     // Skip non loop hint attributes
143     if (!LH)
144       continue;
145 
146     int Option = LH->getOption();
147     int Category;
148     enum { Vectorize, Interleave, Unroll };
149     switch (Option) {
150     case LoopHintAttr::Vectorize:
151     case LoopHintAttr::VectorizeWidth:
152       Category = Vectorize;
153       break;
154     case LoopHintAttr::Interleave:
155     case LoopHintAttr::InterleaveCount:
156       Category = Interleave;
157       break;
158     case LoopHintAttr::Unroll:
159     case LoopHintAttr::UnrollCount:
160       Category = Unroll;
161       break;
162     };
163 
164     auto &CategoryState = HintAttrs[Category];
165     const LoopHintAttr *PrevAttr;
166     if (Option == LoopHintAttr::Vectorize ||
167         Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll) {
168       // Enable|disable hint.  For example, vectorize(enable).
169       PrevAttr = CategoryState.StateAttr;
170       CategoryState.StateAttr = LH;
171     } else {
172       // Numeric hint.  For example, vectorize_width(8).
173       PrevAttr = CategoryState.NumericAttr;
174       CategoryState.NumericAttr = LH;
175     }
176 
177     PrintingPolicy Policy(S.Context.getLangOpts());
178     SourceLocation OptionLoc = LH->getRange().getBegin();
179     if (PrevAttr)
180       // Cannot specify same type of attribute twice.
181       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
182           << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
183           << LH->getDiagnosticName(Policy);
184 
185     if (CategoryState.StateAttr && CategoryState.NumericAttr &&
186         (Category == Unroll ||
187          CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
188       // Disable hints are not compatible with numeric hints of the same
189       // category.  As a special case, numeric unroll hints are also not
190       // compatible with "enable" form of the unroll pragma, unroll(full).
191       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
192           << /*Duplicate=*/false
193           << CategoryState.StateAttr->getDiagnosticName(Policy)
194           << CategoryState.NumericAttr->getDiagnosticName(Policy);
195     }
196   }
197 }
198 
199 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const AttributeList &A,
200                                   SourceRange Range) {
201   switch (A.getKind()) {
202   case AttributeList::UnknownAttribute:
203     S.Diag(A.getLoc(), A.isDeclspecAttribute() ?
204            diag::warn_unhandled_ms_attribute_ignored :
205            diag::warn_unknown_attribute_ignored) << A.getName();
206     return nullptr;
207   case AttributeList::AT_FallThrough:
208     return handleFallThroughAttr(S, St, A, Range);
209   case AttributeList::AT_LoopHint:
210     return handleLoopHintAttr(S, St, A, Range);
211   default:
212     // if we're here, then we parsed a known attribute, but didn't recognize
213     // it as a statement attribute => it is declaration attribute
214     S.Diag(A.getRange().getBegin(), diag::err_attribute_invalid_on_stmt)
215         << A.getName() << St->getLocStart();
216     return nullptr;
217   }
218 }
219 
220 StmtResult Sema::ProcessStmtAttributes(Stmt *S, AttributeList *AttrList,
221                                        SourceRange Range) {
222   SmallVector<const Attr*, 8> Attrs;
223   for (const AttributeList* l = AttrList; l; l = l->getNext()) {
224     if (Attr *a = ProcessStmtAttribute(*this, S, *l, Range))
225       Attrs.push_back(a);
226   }
227 
228   CheckForIncompatibleAttributes(*this, Attrs);
229 
230   if (Attrs.empty())
231     return S;
232 
233   return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
234 }
235