1 //===--- SemaStmtAttr.cpp - Statement Attribute Handling ------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements stmt-related attribute processing.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "clang/AST/ASTContext.h"
14 #include "clang/AST/EvaluatedExprVisitor.h"
15 #include "clang/Basic/SourceManager.h"
16 #include "clang/Basic/TargetInfo.h"
17 #include "clang/Sema/DelayedDiagnostic.h"
18 #include "clang/Sema/Lookup.h"
19 #include "clang/Sema/ScopeInfo.h"
20 #include "clang/Sema/SemaInternal.h"
21 #include "llvm/ADT/StringExtras.h"
22
23 using namespace clang;
24 using namespace sema;
25
handleFallThroughAttr(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange Range)26 static Attr *handleFallThroughAttr(Sema &S, Stmt *St, const ParsedAttr &A,
27 SourceRange Range) {
28 FallThroughAttr Attr(S.Context, A);
29 if (isa<SwitchCase>(St)) {
30 S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
31 << A << St->getBeginLoc();
32 SourceLocation L = S.getLocForEndOfToken(Range.getEnd());
33 S.Diag(L, diag::note_fallthrough_insert_semi_fixit)
34 << FixItHint::CreateInsertion(L, ";");
35 return nullptr;
36 }
37 auto *FnScope = S.getCurFunction();
38 if (FnScope->SwitchStack.empty()) {
39 S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_outside_switch);
40 return nullptr;
41 }
42
43 // If this is spelled as the standard C++17 attribute, but not in C++17, warn
44 // about using it as an extension.
45 if (!S.getLangOpts().CPlusPlus17 && A.isCXX11Attribute() &&
46 !A.getScopeName())
47 S.Diag(A.getLoc(), diag::ext_cxx17_attr) << A;
48
49 FnScope->setHasFallthroughStmt();
50 return ::new (S.Context) FallThroughAttr(S.Context, A);
51 }
52
handleSuppressAttr(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange Range)53 static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A,
54 SourceRange Range) {
55 std::vector<StringRef> DiagnosticIdentifiers;
56 for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) {
57 StringRef RuleName;
58
59 if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr))
60 return nullptr;
61
62 // FIXME: Warn if the rule name is unknown. This is tricky because only
63 // clang-tidy knows about available rules.
64 DiagnosticIdentifiers.push_back(RuleName);
65 }
66
67 return ::new (S.Context) SuppressAttr(
68 S.Context, A, DiagnosticIdentifiers.data(), DiagnosticIdentifiers.size());
69 }
70
handleLoopHintAttr(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange)71 static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A,
72 SourceRange) {
73 IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
74 IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
75 IdentifierLoc *StateLoc = A.getArgAsIdent(2);
76 Expr *ValueExpr = A.getArgAsExpr(3);
77
78 StringRef PragmaName =
79 llvm::StringSwitch<StringRef>(PragmaNameLoc->Ident->getName())
80 .Cases("unroll", "nounroll", "unroll_and_jam", "nounroll_and_jam",
81 PragmaNameLoc->Ident->getName())
82 .Default("clang loop");
83
84 // This could be handled automatically by adding a Subjects definition in
85 // Attr.td, but that would make the diagnostic behavior worse in this case
86 // because the user spells this attribute as a pragma.
87 if (!isa<DoStmt, ForStmt, CXXForRangeStmt, WhileStmt>(St)) {
88 std::string Pragma = "#pragma " + std::string(PragmaName);
89 S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
90 return nullptr;
91 }
92
93 LoopHintAttr::OptionType Option;
94 LoopHintAttr::LoopHintState State;
95
96 auto SetHints = [&Option, &State](LoopHintAttr::OptionType O,
97 LoopHintAttr::LoopHintState S) {
98 Option = O;
99 State = S;
100 };
101
102 if (PragmaName == "nounroll") {
103 SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable);
104 } else if (PragmaName == "unroll") {
105 // #pragma unroll N
106 if (ValueExpr)
107 SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric);
108 else
109 SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable);
110 } else if (PragmaName == "nounroll_and_jam") {
111 SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable);
112 } else if (PragmaName == "unroll_and_jam") {
113 // #pragma unroll_and_jam N
114 if (ValueExpr)
115 SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric);
116 else
117 SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable);
118 } else {
119 // #pragma clang loop ...
120 assert(OptionLoc && OptionLoc->Ident &&
121 "Attribute must have valid option info.");
122 Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
123 OptionLoc->Ident->getName())
124 .Case("vectorize", LoopHintAttr::Vectorize)
125 .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
126 .Case("interleave", LoopHintAttr::Interleave)
127 .Case("vectorize_predicate", LoopHintAttr::VectorizePredicate)
128 .Case("interleave_count", LoopHintAttr::InterleaveCount)
129 .Case("unroll", LoopHintAttr::Unroll)
130 .Case("unroll_count", LoopHintAttr::UnrollCount)
131 .Case("pipeline", LoopHintAttr::PipelineDisabled)
132 .Case("pipeline_initiation_interval",
133 LoopHintAttr::PipelineInitiationInterval)
134 .Case("distribute", LoopHintAttr::Distribute)
135 .Default(LoopHintAttr::Vectorize);
136 if (Option == LoopHintAttr::VectorizeWidth) {
137 assert((ValueExpr || (StateLoc && StateLoc->Ident)) &&
138 "Attribute must have a valid value expression or argument.");
139 if (ValueExpr && S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
140 return nullptr;
141 if (StateLoc && StateLoc->Ident && StateLoc->Ident->isStr("scalable"))
142 State = LoopHintAttr::ScalableWidth;
143 else
144 State = LoopHintAttr::FixedWidth;
145 } else if (Option == LoopHintAttr::InterleaveCount ||
146 Option == LoopHintAttr::UnrollCount ||
147 Option == LoopHintAttr::PipelineInitiationInterval) {
148 assert(ValueExpr && "Attribute must have a valid value expression.");
149 if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
150 return nullptr;
151 State = LoopHintAttr::Numeric;
152 } else if (Option == LoopHintAttr::Vectorize ||
153 Option == LoopHintAttr::Interleave ||
154 Option == LoopHintAttr::VectorizePredicate ||
155 Option == LoopHintAttr::Unroll ||
156 Option == LoopHintAttr::Distribute ||
157 Option == LoopHintAttr::PipelineDisabled) {
158 assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
159 if (StateLoc->Ident->isStr("disable"))
160 State = LoopHintAttr::Disable;
161 else if (StateLoc->Ident->isStr("assume_safety"))
162 State = LoopHintAttr::AssumeSafety;
163 else if (StateLoc->Ident->isStr("full"))
164 State = LoopHintAttr::Full;
165 else if (StateLoc->Ident->isStr("enable"))
166 State = LoopHintAttr::Enable;
167 else
168 llvm_unreachable("bad loop hint argument");
169 } else
170 llvm_unreachable("bad loop hint");
171 }
172
173 return LoopHintAttr::CreateImplicit(S.Context, Option, State, ValueExpr, A);
174 }
175
176 namespace {
177 class CallExprFinder : public ConstEvaluatedExprVisitor<CallExprFinder> {
178 bool FoundCallExpr = false;
179
180 public:
181 typedef ConstEvaluatedExprVisitor<CallExprFinder> Inherited;
182
CallExprFinder(Sema & S,const Stmt * St)183 CallExprFinder(Sema &S, const Stmt *St) : Inherited(S.Context) { Visit(St); }
184
foundCallExpr()185 bool foundCallExpr() { return FoundCallExpr; }
186
VisitCallExpr(const CallExpr * E)187 void VisitCallExpr(const CallExpr *E) { FoundCallExpr = true; }
VisitAsmStmt(const AsmStmt * S)188 void VisitAsmStmt(const AsmStmt *S) { FoundCallExpr = true; }
189
Visit(const Stmt * St)190 void Visit(const Stmt *St) {
191 if (!St)
192 return;
193 ConstEvaluatedExprVisitor<CallExprFinder>::Visit(St);
194 }
195 };
196 } // namespace
197
handleNoMergeAttr(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange Range)198 static Attr *handleNoMergeAttr(Sema &S, Stmt *St, const ParsedAttr &A,
199 SourceRange Range) {
200 NoMergeAttr NMA(S.Context, A);
201 CallExprFinder CEF(S, St);
202
203 if (!CEF.foundCallExpr()) {
204 S.Diag(St->getBeginLoc(), diag::warn_nomerge_attribute_ignored_in_stmt)
205 << NMA.getSpelling();
206 return nullptr;
207 }
208
209 return ::new (S.Context) NoMergeAttr(S.Context, A);
210 }
211
handleMustTailAttr(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange Range)212 static Attr *handleMustTailAttr(Sema &S, Stmt *St, const ParsedAttr &A,
213 SourceRange Range) {
214 // Validation is in Sema::ActOnAttributedStmt().
215 return ::new (S.Context) MustTailAttr(S.Context, A);
216 }
217
handleLikely(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange Range)218 static Attr *handleLikely(Sema &S, Stmt *St, const ParsedAttr &A,
219 SourceRange Range) {
220
221 if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
222 S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range;
223
224 return ::new (S.Context) LikelyAttr(S.Context, A);
225 }
226
handleUnlikely(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange Range)227 static Attr *handleUnlikely(Sema &S, Stmt *St, const ParsedAttr &A,
228 SourceRange Range) {
229
230 if (!S.getLangOpts().CPlusPlus20 && A.isCXX11Attribute() && !A.getScopeName())
231 S.Diag(A.getLoc(), diag::ext_cxx20_attr) << A << Range;
232
233 return ::new (S.Context) UnlikelyAttr(S.Context, A);
234 }
235
236 #define WANT_STMT_MERGE_LOGIC
237 #include "clang/Sema/AttrParsedAttrImpl.inc"
238 #undef WANT_STMT_MERGE_LOGIC
239
240 static void
CheckForIncompatibleAttributes(Sema & S,const SmallVectorImpl<const Attr * > & Attrs)241 CheckForIncompatibleAttributes(Sema &S,
242 const SmallVectorImpl<const Attr *> &Attrs) {
243 // The vast majority of attributed statements will only have one attribute
244 // on them, so skip all of the checking in the common case.
245 if (Attrs.size() < 2)
246 return;
247
248 // First, check for the easy cases that are table-generated for us.
249 if (!DiagnoseMutualExclusions(S, Attrs))
250 return;
251
252 // There are 6 categories of loop hints attributes: vectorize, interleave,
253 // unroll, unroll_and_jam, pipeline and distribute. Except for distribute they
254 // come in two variants: a state form and a numeric form. The state form
255 // selectively defaults/enables/disables the transformation for the loop
256 // (for unroll, default indicates full unrolling rather than enabling the
257 // transformation). The numeric form form provides an integer hint (for
258 // example, unroll count) to the transformer. The following array accumulates
259 // the hints encountered while iterating through the attributes to check for
260 // compatibility.
261 struct {
262 const LoopHintAttr *StateAttr;
263 const LoopHintAttr *NumericAttr;
264 } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
265 {nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
266 {nullptr, nullptr}};
267
268 for (const auto *I : Attrs) {
269 const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
270
271 // Skip non loop hint attributes
272 if (!LH)
273 continue;
274
275 LoopHintAttr::OptionType Option = LH->getOption();
276 enum {
277 Vectorize,
278 Interleave,
279 Unroll,
280 UnrollAndJam,
281 Distribute,
282 Pipeline,
283 VectorizePredicate
284 } Category;
285 switch (Option) {
286 case LoopHintAttr::Vectorize:
287 case LoopHintAttr::VectorizeWidth:
288 Category = Vectorize;
289 break;
290 case LoopHintAttr::Interleave:
291 case LoopHintAttr::InterleaveCount:
292 Category = Interleave;
293 break;
294 case LoopHintAttr::Unroll:
295 case LoopHintAttr::UnrollCount:
296 Category = Unroll;
297 break;
298 case LoopHintAttr::UnrollAndJam:
299 case LoopHintAttr::UnrollAndJamCount:
300 Category = UnrollAndJam;
301 break;
302 case LoopHintAttr::Distribute:
303 // Perform the check for duplicated 'distribute' hints.
304 Category = Distribute;
305 break;
306 case LoopHintAttr::PipelineDisabled:
307 case LoopHintAttr::PipelineInitiationInterval:
308 Category = Pipeline;
309 break;
310 case LoopHintAttr::VectorizePredicate:
311 Category = VectorizePredicate;
312 break;
313 };
314
315 assert(Category < sizeof(HintAttrs) / sizeof(HintAttrs[0]));
316 auto &CategoryState = HintAttrs[Category];
317 const LoopHintAttr *PrevAttr;
318 if (Option == LoopHintAttr::Vectorize ||
319 Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll ||
320 Option == LoopHintAttr::UnrollAndJam ||
321 Option == LoopHintAttr::VectorizePredicate ||
322 Option == LoopHintAttr::PipelineDisabled ||
323 Option == LoopHintAttr::Distribute) {
324 // Enable|Disable|AssumeSafety hint. For example, vectorize(enable).
325 PrevAttr = CategoryState.StateAttr;
326 CategoryState.StateAttr = LH;
327 } else {
328 // Numeric hint. For example, vectorize_width(8).
329 PrevAttr = CategoryState.NumericAttr;
330 CategoryState.NumericAttr = LH;
331 }
332
333 PrintingPolicy Policy(S.Context.getLangOpts());
334 SourceLocation OptionLoc = LH->getRange().getBegin();
335 if (PrevAttr)
336 // Cannot specify same type of attribute twice.
337 S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
338 << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
339 << LH->getDiagnosticName(Policy);
340
341 if (CategoryState.StateAttr && CategoryState.NumericAttr &&
342 (Category == Unroll || Category == UnrollAndJam ||
343 CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
344 // Disable hints are not compatible with numeric hints of the same
345 // category. As a special case, numeric unroll hints are also not
346 // compatible with enable or full form of the unroll pragma because these
347 // directives indicate full unrolling.
348 S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
349 << /*Duplicate=*/false
350 << CategoryState.StateAttr->getDiagnosticName(Policy)
351 << CategoryState.NumericAttr->getDiagnosticName(Policy);
352 }
353 }
354 }
355
handleOpenCLUnrollHint(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange Range)356 static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A,
357 SourceRange Range) {
358 // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's
359 // useful for OpenCL 1.x too and doesn't require HW support.
360 // opencl_unroll_hint can have 0 arguments (compiler
361 // determines unrolling factor) or 1 argument (the unroll factor provided
362 // by the user).
363 unsigned UnrollFactor = 0;
364 if (A.getNumArgs() == 1) {
365 Expr *E = A.getArgAsExpr(0);
366 Optional<llvm::APSInt> ArgVal;
367
368 if (!(ArgVal = E->getIntegerConstantExpr(S.Context))) {
369 S.Diag(A.getLoc(), diag::err_attribute_argument_type)
370 << A << AANT_ArgumentIntegerConstant << E->getSourceRange();
371 return nullptr;
372 }
373
374 int Val = ArgVal->getSExtValue();
375 if (Val <= 0) {
376 S.Diag(A.getRange().getBegin(),
377 diag::err_attribute_requires_positive_integer)
378 << A << /* positive */ 0;
379 return nullptr;
380 }
381 UnrollFactor = static_cast<unsigned>(Val);
382 }
383
384 return ::new (S.Context) OpenCLUnrollHintAttr(S.Context, A, UnrollFactor);
385 }
386
ProcessStmtAttribute(Sema & S,Stmt * St,const ParsedAttr & A,SourceRange Range)387 static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
388 SourceRange Range) {
389 if (A.isInvalid() || A.getKind() == ParsedAttr::IgnoredAttribute)
390 return nullptr;
391
392 // Unknown attributes are automatically warned on. Target-specific attributes
393 // which do not apply to the current target architecture are treated as
394 // though they were unknown attributes.
395 const TargetInfo *Aux = S.Context.getAuxTargetInfo();
396 if (A.getKind() == ParsedAttr::UnknownAttribute ||
397 !(A.existsInTarget(S.Context.getTargetInfo()) ||
398 (S.Context.getLangOpts().SYCLIsDevice && Aux &&
399 A.existsInTarget(*Aux)))) {
400 S.Diag(A.getLoc(), A.isDeclspecAttribute()
401 ? (unsigned)diag::warn_unhandled_ms_attribute_ignored
402 : (unsigned)diag::warn_unknown_attribute_ignored)
403 << A << A.getRange();
404 return nullptr;
405 }
406
407 if (S.checkCommonAttributeFeatures(St, A))
408 return nullptr;
409
410 switch (A.getKind()) {
411 case ParsedAttr::AT_FallThrough:
412 return handleFallThroughAttr(S, St, A, Range);
413 case ParsedAttr::AT_LoopHint:
414 return handleLoopHintAttr(S, St, A, Range);
415 case ParsedAttr::AT_OpenCLUnrollHint:
416 return handleOpenCLUnrollHint(S, St, A, Range);
417 case ParsedAttr::AT_Suppress:
418 return handleSuppressAttr(S, St, A, Range);
419 case ParsedAttr::AT_NoMerge:
420 return handleNoMergeAttr(S, St, A, Range);
421 case ParsedAttr::AT_MustTail:
422 return handleMustTailAttr(S, St, A, Range);
423 case ParsedAttr::AT_Likely:
424 return handleLikely(S, St, A, Range);
425 case ParsedAttr::AT_Unlikely:
426 return handleUnlikely(S, St, A, Range);
427 default:
428 // N.B., ClangAttrEmitter.cpp emits a diagnostic helper that ensures a
429 // declaration attribute is not written on a statement, but this code is
430 // needed for attributes in Attr.td that do not list any subjects.
431 S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt)
432 << A << St->getBeginLoc();
433 return nullptr;
434 }
435 }
436
ProcessStmtAttributes(Stmt * S,const ParsedAttributesWithRange & InAttrs,SmallVectorImpl<const Attr * > & OutAttrs)437 void Sema::ProcessStmtAttributes(Stmt *S,
438 const ParsedAttributesWithRange &InAttrs,
439 SmallVectorImpl<const Attr *> &OutAttrs) {
440 for (const ParsedAttr &AL : InAttrs) {
441 if (const Attr *A = ProcessStmtAttribute(*this, S, AL, InAttrs.Range))
442 OutAttrs.push_back(A);
443 }
444
445 CheckForIncompatibleAttributes(*this, OutAttrs);
446 }
447