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 ParsedAttr &A,
27                                    SourceRange Range) {
28   FallThroughAttr Attr(A.getRange(), S.Context,
29                        A.getAttributeSpellingListIndex());
30   if (!isa<NullStmt>(St)) {
31     S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
32         << Attr.getSpelling() << St->getBeginLoc();
33     if (isa<SwitchCase>(St)) {
34       SourceLocation L = S.getLocForEndOfToken(Range.getEnd());
35       S.Diag(L, diag::note_fallthrough_insert_semi_fixit)
36           << FixItHint::CreateInsertion(L, ";");
37     }
38     return nullptr;
39   }
40   auto *FnScope = S.getCurFunction();
41   if (FnScope->SwitchStack.empty()) {
42     S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch);
43     return nullptr;
44   }
45 
46   // If this is spelled as the standard C++17 attribute, but not in C++17, warn
47   // about using it as an extension.
48   if (!S.getLangOpts().CPlusPlus17 && A.isCXX11Attribute() &&
49       !A.getScopeName())
50     S.Diag(A.getLoc(), diag::ext_cxx17_attr) << A.getName();
51 
52   FnScope->setHasFallthroughStmt();
53   return ::new (S.Context) auto(Attr);
54 }
55 
56 static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A,
57                                 SourceRange Range) {
58   if (A.getNumArgs() < 1) {
59     S.Diag(A.getLoc(), diag::err_attribute_too_few_arguments) << A << 1;
60     return nullptr;
61   }
62 
63   std::vector<StringRef> DiagnosticIdentifiers;
64   for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) {
65     StringRef RuleName;
66 
67     if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr))
68       return nullptr;
69 
70     // FIXME: Warn if the rule name is unknown. This is tricky because only
71     // clang-tidy knows about available rules.
72     DiagnosticIdentifiers.push_back(RuleName);
73   }
74 
75   return ::new (S.Context) SuppressAttr(
76       A.getRange(), S.Context, DiagnosticIdentifiers.data(),
77       DiagnosticIdentifiers.size(), A.getAttributeSpellingListIndex());
78 }
79 
80 static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A,
81                                 SourceRange) {
82   IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
83   IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
84   IdentifierLoc *StateLoc = A.getArgAsIdent(2);
85   Expr *ValueExpr = A.getArgAsExpr(3);
86 
87   bool PragmaUnroll = PragmaNameLoc->Ident->getName() == "unroll";
88   bool PragmaNoUnroll = PragmaNameLoc->Ident->getName() == "nounroll";
89   bool PragmaUnrollAndJam = PragmaNameLoc->Ident->getName() == "unroll_and_jam";
90   bool PragmaNoUnrollAndJam =
91       PragmaNameLoc->Ident->getName() == "nounroll_and_jam";
92   if (St->getStmtClass() != Stmt::DoStmtClass &&
93       St->getStmtClass() != Stmt::ForStmtClass &&
94       St->getStmtClass() != Stmt::CXXForRangeStmtClass &&
95       St->getStmtClass() != Stmt::WhileStmtClass) {
96     const char *Pragma =
97         llvm::StringSwitch<const char *>(PragmaNameLoc->Ident->getName())
98             .Case("unroll", "#pragma unroll")
99             .Case("nounroll", "#pragma nounroll")
100             .Case("unroll_and_jam", "#pragma unroll_and_jam")
101             .Case("nounroll_and_jam", "#pragma nounroll_and_jam")
102             .Default("#pragma clang loop");
103     S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
104     return nullptr;
105   }
106 
107   LoopHintAttr::Spelling Spelling =
108       LoopHintAttr::Spelling(A.getAttributeSpellingListIndex());
109   LoopHintAttr::OptionType Option;
110   LoopHintAttr::LoopHintState State;
111   if (PragmaNoUnroll) {
112     // #pragma nounroll
113     Option = LoopHintAttr::Unroll;
114     State = LoopHintAttr::Disable;
115   } else if (PragmaUnroll) {
116     if (ValueExpr) {
117       // #pragma unroll N
118       Option = LoopHintAttr::UnrollCount;
119       State = LoopHintAttr::Numeric;
120     } else {
121       // #pragma unroll
122       Option = LoopHintAttr::Unroll;
123       State = LoopHintAttr::Enable;
124     }
125   } else if (PragmaNoUnrollAndJam) {
126     // #pragma nounroll_and_jam
127     Option = LoopHintAttr::UnrollAndJam;
128     State = LoopHintAttr::Disable;
129   } else if (PragmaUnrollAndJam) {
130     if (ValueExpr) {
131       // #pragma unroll_and_jam N
132       Option = LoopHintAttr::UnrollAndJamCount;
133       State = LoopHintAttr::Numeric;
134     } else {
135       // #pragma unroll_and_jam
136       Option = LoopHintAttr::UnrollAndJam;
137       State = LoopHintAttr::Enable;
138     }
139   } else {
140     // #pragma clang loop ...
141     assert(OptionLoc && OptionLoc->Ident &&
142            "Attribute must have valid option info.");
143     Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
144                  OptionLoc->Ident->getName())
145                  .Case("vectorize", LoopHintAttr::Vectorize)
146                  .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
147                  .Case("interleave", LoopHintAttr::Interleave)
148                  .Case("interleave_count", LoopHintAttr::InterleaveCount)
149                  .Case("unroll", LoopHintAttr::Unroll)
150                  .Case("unroll_count", LoopHintAttr::UnrollCount)
151                  .Case("distribute", LoopHintAttr::Distribute)
152                  .Default(LoopHintAttr::Vectorize);
153     if (Option == LoopHintAttr::VectorizeWidth ||
154         Option == LoopHintAttr::InterleaveCount ||
155         Option == LoopHintAttr::UnrollCount) {
156       assert(ValueExpr && "Attribute must have a valid value expression.");
157       if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
158         return nullptr;
159       State = LoopHintAttr::Numeric;
160     } else if (Option == LoopHintAttr::Vectorize ||
161                Option == LoopHintAttr::Interleave ||
162                Option == LoopHintAttr::Unroll ||
163                Option == LoopHintAttr::Distribute) {
164       assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
165       if (StateLoc->Ident->isStr("disable"))
166         State = LoopHintAttr::Disable;
167       else if (StateLoc->Ident->isStr("assume_safety"))
168         State = LoopHintAttr::AssumeSafety;
169       else if (StateLoc->Ident->isStr("full"))
170         State = LoopHintAttr::Full;
171       else if (StateLoc->Ident->isStr("enable"))
172         State = LoopHintAttr::Enable;
173       else
174         llvm_unreachable("bad loop hint argument");
175     } else
176       llvm_unreachable("bad loop hint");
177   }
178 
179   return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State,
180                                       ValueExpr, A.getRange());
181 }
182 
183 static void
184 CheckForIncompatibleAttributes(Sema &S,
185                                const SmallVectorImpl<const Attr *> &Attrs) {
186   // There are 5 categories of loop hints attributes: vectorize, interleave,
187   // unroll, unroll_and_jam and distribute. Except for distribute they come
188   // in two variants: a state form and a numeric form.  The state form
189   // selectively defaults/enables/disables the transformation for the loop
190   // (for unroll, default indicates full unrolling rather than enabling the
191   // transformation). The numeric form form provides an integer hint (for
192   // example, unroll count) to the transformer. The following array accumulates
193   // the hints encountered while iterating through the attributes to check for
194   // compatibility.
195   struct {
196     const LoopHintAttr *StateAttr;
197     const LoopHintAttr *NumericAttr;
198   } HintAttrs[] = {{nullptr, nullptr},
199                    {nullptr, nullptr},
200                    {nullptr, nullptr},
201                    {nullptr, nullptr},
202                    {nullptr, nullptr}};
203 
204   for (const auto *I : Attrs) {
205     const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
206 
207     // Skip non loop hint attributes
208     if (!LH)
209       continue;
210 
211     LoopHintAttr::OptionType Option = LH->getOption();
212     enum { Vectorize, Interleave, Unroll, UnrollAndJam, Distribute } Category;
213     switch (Option) {
214     case LoopHintAttr::Vectorize:
215     case LoopHintAttr::VectorizeWidth:
216       Category = Vectorize;
217       break;
218     case LoopHintAttr::Interleave:
219     case LoopHintAttr::InterleaveCount:
220       Category = Interleave;
221       break;
222     case LoopHintAttr::Unroll:
223     case LoopHintAttr::UnrollCount:
224       Category = Unroll;
225       break;
226     case LoopHintAttr::UnrollAndJam:
227     case LoopHintAttr::UnrollAndJamCount:
228       Category = UnrollAndJam;
229       break;
230     case LoopHintAttr::Distribute:
231       // Perform the check for duplicated 'distribute' hints.
232       Category = Distribute;
233       break;
234     };
235 
236     assert(Category < sizeof(HintAttrs) / sizeof(HintAttrs[0]));
237     auto &CategoryState = HintAttrs[Category];
238     const LoopHintAttr *PrevAttr;
239     if (Option == LoopHintAttr::Vectorize ||
240         Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll ||
241         Option == LoopHintAttr::UnrollAndJam ||
242         Option == LoopHintAttr::Distribute) {
243       // Enable|Disable|AssumeSafety hint.  For example, vectorize(enable).
244       PrevAttr = CategoryState.StateAttr;
245       CategoryState.StateAttr = LH;
246     } else {
247       // Numeric hint.  For example, vectorize_width(8).
248       PrevAttr = CategoryState.NumericAttr;
249       CategoryState.NumericAttr = LH;
250     }
251 
252     PrintingPolicy Policy(S.Context.getLangOpts());
253     SourceLocation OptionLoc = LH->getRange().getBegin();
254     if (PrevAttr)
255       // Cannot specify same type of attribute twice.
256       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
257           << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
258           << LH->getDiagnosticName(Policy);
259 
260     if (CategoryState.StateAttr && CategoryState.NumericAttr &&
261         (Category == Unroll || Category == UnrollAndJam ||
262          CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
263       // Disable hints are not compatible with numeric hints of the same
264       // category.  As a special case, numeric unroll hints are also not
265       // compatible with enable or full form of the unroll pragma because these
266       // directives indicate full unrolling.
267       S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
268           << /*Duplicate=*/false
269           << CategoryState.StateAttr->getDiagnosticName(Policy)
270           << CategoryState.NumericAttr->getDiagnosticName(Policy);
271     }
272   }
273 }
274 
275 static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A,
276                                     SourceRange Range) {
277   // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's
278   // useful for OpenCL 1.x too and doesn't require HW support.
279   // opencl_unroll_hint can have 0 arguments (compiler
280   // determines unrolling factor) or 1 argument (the unroll factor provided
281   // by the user).
282 
283   unsigned NumArgs = A.getNumArgs();
284 
285   if (NumArgs > 1) {
286     S.Diag(A.getLoc(), diag::err_attribute_too_many_arguments) << A << 1;
287     return nullptr;
288   }
289 
290   unsigned UnrollFactor = 0;
291 
292   if (NumArgs == 1) {
293     Expr *E = A.getArgAsExpr(0);
294     llvm::APSInt ArgVal(32);
295 
296     if (!E->isIntegerConstantExpr(ArgVal, S.Context)) {
297       S.Diag(A.getLoc(), diag::err_attribute_argument_type)
298           << A << AANT_ArgumentIntegerConstant << E->getSourceRange();
299       return nullptr;
300     }
301 
302     int Val = ArgVal.getSExtValue();
303 
304     if (Val <= 0) {
305       S.Diag(A.getRange().getBegin(),
306              diag::err_attribute_requires_positive_integer)
307           << A << /* positive */ 0;
308       return nullptr;
309     }
310     UnrollFactor = Val;
311   }
312 
313   return OpenCLUnrollHintAttr::CreateImplicit(S.Context, UnrollFactor);
314 }
315 
316 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
317                                   SourceRange Range) {
318   switch (A.getKind()) {
319   case ParsedAttr::UnknownAttribute:
320     S.Diag(A.getLoc(), A.isDeclspecAttribute() ?
321            diag::warn_unhandled_ms_attribute_ignored :
322            diag::warn_unknown_attribute_ignored) << A.getName();
323     return nullptr;
324   case ParsedAttr::AT_FallThrough:
325     return handleFallThroughAttr(S, St, A, Range);
326   case ParsedAttr::AT_LoopHint:
327     return handleLoopHintAttr(S, St, A, Range);
328   case ParsedAttr::AT_OpenCLUnrollHint:
329     return handleOpenCLUnrollHint(S, St, A, Range);
330   case ParsedAttr::AT_Suppress:
331     return handleSuppressAttr(S, St, A, Range);
332   default:
333     // if we're here, then we parsed a known attribute, but didn't recognize
334     // it as a statement attribute => it is declaration attribute
335     S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt)
336         << A.getName() << St->getBeginLoc();
337     return nullptr;
338   }
339 }
340 
341 StmtResult Sema::ProcessStmtAttributes(Stmt *S,
342                                        const ParsedAttributesView &AttrList,
343                                        SourceRange Range) {
344   SmallVector<const Attr*, 8> Attrs;
345   for (const ParsedAttr &AL : AttrList) {
346     if (Attr *a = ProcessStmtAttribute(*this, S, AL, Range))
347       Attrs.push_back(a);
348   }
349 
350   CheckForIncompatibleAttributes(*this, Attrs);
351 
352   if (Attrs.empty())
353     return S;
354 
355   return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
356 }
357