SemaStmtAttr.cpp revision 360784 
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/Sema/SemaInternal.h"
14#include "clang/AST/ASTContext.h"
15#include "clang/Basic/SourceManager.h"
16#include "clang/Sema/DelayedDiagnostic.h"
17#include "clang/Sema/Lookup.h"
18#include "clang/Sema/ScopeInfo.h"
19#include "llvm/ADT/StringExtras.h"
20
21using namespace clang;
22using namespace sema;
23
24static Attr *handleFallThroughAttr(Sema &S, Stmt *St, const ParsedAttr &A,
25                                   SourceRange Range) {
26  FallThroughAttr Attr(S.Context, A);
27  if (!isa<NullStmt>(St)) {
28    S.Diag(A.getRange().getBegin(), diag::err_fallthrough_attr_wrong_target)
29        << Attr.getSpelling() << St->getBeginLoc();
30    if (isa<SwitchCase>(St)) {
31      SourceLocation L = S.getLocForEndOfToken(Range.getEnd());
32      S.Diag(L, diag::note_fallthrough_insert_semi_fixit)
33          << FixItHint::CreateInsertion(L, ";");
34    }
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
53static Attr *handleSuppressAttr(Sema &S, Stmt *St, const ParsedAttr &A,
54                                SourceRange Range) {
55  if (A.getNumArgs() < 1) {
56    S.Diag(A.getLoc(), diag::err_attribute_too_few_arguments) << A << 1;
57    return nullptr;
58  }
59
60  std::vector<StringRef> DiagnosticIdentifiers;
61  for (unsigned I = 0, E = A.getNumArgs(); I != E; ++I) {
62    StringRef RuleName;
63
64    if (!S.checkStringLiteralArgumentAttr(A, I, RuleName, nullptr))
65      return nullptr;
66
67    // FIXME: Warn if the rule name is unknown. This is tricky because only
68    // clang-tidy knows about available rules.
69    DiagnosticIdentifiers.push_back(RuleName);
70  }
71
72  return ::new (S.Context) SuppressAttr(
73      S.Context, A, DiagnosticIdentifiers.data(), DiagnosticIdentifiers.size());
74}
75
76static Attr *handleLoopHintAttr(Sema &S, Stmt *St, const ParsedAttr &A,
77                                SourceRange) {
78  IdentifierLoc *PragmaNameLoc = A.getArgAsIdent(0);
79  IdentifierLoc *OptionLoc = A.getArgAsIdent(1);
80  IdentifierLoc *StateLoc = A.getArgAsIdent(2);
81  Expr *ValueExpr = A.getArgAsExpr(3);
82
83  StringRef PragmaName =
84      llvm::StringSwitch<StringRef>(PragmaNameLoc->Ident->getName())
85          .Cases("unroll", "nounroll", "unroll_and_jam", "nounroll_and_jam",
86                 PragmaNameLoc->Ident->getName())
87          .Default("clang loop");
88
89  if (St->getStmtClass() != Stmt::DoStmtClass &&
90      St->getStmtClass() != Stmt::ForStmtClass &&
91      St->getStmtClass() != Stmt::CXXForRangeStmtClass &&
92      St->getStmtClass() != Stmt::WhileStmtClass) {
93    std::string Pragma = "#pragma " + std::string(PragmaName);
94    S.Diag(St->getBeginLoc(), diag::err_pragma_loop_precedes_nonloop) << Pragma;
95    return nullptr;
96  }
97
98  LoopHintAttr::OptionType Option;
99  LoopHintAttr::LoopHintState State;
100
101  auto SetHints = [&Option, &State](LoopHintAttr::OptionType O,
102                                    LoopHintAttr::LoopHintState S) {
103    Option = O;
104    State = S;
105  };
106
107  if (PragmaName == "nounroll") {
108    SetHints(LoopHintAttr::Unroll, LoopHintAttr::Disable);
109  } else if (PragmaName == "unroll") {
110    // #pragma unroll N
111    if (ValueExpr)
112      SetHints(LoopHintAttr::UnrollCount, LoopHintAttr::Numeric);
113    else
114      SetHints(LoopHintAttr::Unroll, LoopHintAttr::Enable);
115  } else if (PragmaName == "nounroll_and_jam") {
116    SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Disable);
117  } else if (PragmaName == "unroll_and_jam") {
118    // #pragma unroll_and_jam N
119    if (ValueExpr)
120      SetHints(LoopHintAttr::UnrollAndJamCount, LoopHintAttr::Numeric);
121    else
122      SetHints(LoopHintAttr::UnrollAndJam, LoopHintAttr::Enable);
123  } else {
124    // #pragma clang loop ...
125    assert(OptionLoc && OptionLoc->Ident &&
126           "Attribute must have valid option info.");
127    Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
128                 OptionLoc->Ident->getName())
129                 .Case("vectorize", LoopHintAttr::Vectorize)
130                 .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
131                 .Case("interleave", LoopHintAttr::Interleave)
132                 .Case("vectorize_predicate", LoopHintAttr::VectorizePredicate)
133                 .Case("interleave_count", LoopHintAttr::InterleaveCount)
134                 .Case("unroll", LoopHintAttr::Unroll)
135                 .Case("unroll_count", LoopHintAttr::UnrollCount)
136                 .Case("pipeline", LoopHintAttr::PipelineDisabled)
137                 .Case("pipeline_initiation_interval",
138                       LoopHintAttr::PipelineInitiationInterval)
139                 .Case("distribute", LoopHintAttr::Distribute)
140                 .Default(LoopHintAttr::Vectorize);
141    if (Option == LoopHintAttr::VectorizeWidth ||
142        Option == LoopHintAttr::InterleaveCount ||
143        Option == LoopHintAttr::UnrollCount ||
144        Option == LoopHintAttr::PipelineInitiationInterval) {
145      assert(ValueExpr && "Attribute must have a valid value expression.");
146      if (S.CheckLoopHintExpr(ValueExpr, St->getBeginLoc()))
147        return nullptr;
148      State = LoopHintAttr::Numeric;
149    } else if (Option == LoopHintAttr::Vectorize ||
150               Option == LoopHintAttr::Interleave ||
151               Option == LoopHintAttr::VectorizePredicate ||
152               Option == LoopHintAttr::Unroll ||
153               Option == LoopHintAttr::Distribute ||
154               Option == LoopHintAttr::PipelineDisabled) {
155      assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
156      if (StateLoc->Ident->isStr("disable"))
157        State = LoopHintAttr::Disable;
158      else if (StateLoc->Ident->isStr("assume_safety"))
159        State = LoopHintAttr::AssumeSafety;
160      else if (StateLoc->Ident->isStr("full"))
161        State = LoopHintAttr::Full;
162      else if (StateLoc->Ident->isStr("enable"))
163        State = LoopHintAttr::Enable;
164      else
165        llvm_unreachable("bad loop hint argument");
166    } else
167      llvm_unreachable("bad loop hint");
168  }
169
170  return LoopHintAttr::CreateImplicit(S.Context, Option, State, ValueExpr, A);
171}
172
173static void
174CheckForIncompatibleAttributes(Sema &S,
175                               const SmallVectorImpl<const Attr *> &Attrs) {
176  // There are 6 categories of loop hints attributes: vectorize, interleave,
177  // unroll, unroll_and_jam, pipeline and distribute. Except for distribute they
178  // come in two variants: a state form and a numeric form.  The state form
179  // selectively defaults/enables/disables the transformation for the loop
180  // (for unroll, default indicates full unrolling rather than enabling the
181  // transformation). The numeric form form provides an integer hint (for
182  // example, unroll count) to the transformer. The following array accumulates
183  // the hints encountered while iterating through the attributes to check for
184  // compatibility.
185  struct {
186    const LoopHintAttr *StateAttr;
187    const LoopHintAttr *NumericAttr;
188  } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
189                   {nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr},
190                   {nullptr, nullptr}};
191
192  for (const auto *I : Attrs) {
193    const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
194
195    // Skip non loop hint attributes
196    if (!LH)
197      continue;
198
199    LoopHintAttr::OptionType Option = LH->getOption();
200    enum {
201      Vectorize,
202      Interleave,
203      Unroll,
204      UnrollAndJam,
205      Distribute,
206      Pipeline,
207      VectorizePredicate
208    } Category;
209    switch (Option) {
210    case LoopHintAttr::Vectorize:
211    case LoopHintAttr::VectorizeWidth:
212      Category = Vectorize;
213      break;
214    case LoopHintAttr::Interleave:
215    case LoopHintAttr::InterleaveCount:
216      Category = Interleave;
217      break;
218    case LoopHintAttr::Unroll:
219    case LoopHintAttr::UnrollCount:
220      Category = Unroll;
221      break;
222    case LoopHintAttr::UnrollAndJam:
223    case LoopHintAttr::UnrollAndJamCount:
224      Category = UnrollAndJam;
225      break;
226    case LoopHintAttr::Distribute:
227      // Perform the check for duplicated 'distribute' hints.
228      Category = Distribute;
229      break;
230    case LoopHintAttr::PipelineDisabled:
231    case LoopHintAttr::PipelineInitiationInterval:
232      Category = Pipeline;
233      break;
234    case LoopHintAttr::VectorizePredicate:
235      Category = VectorizePredicate;
236      break;
237    };
238
239    assert(Category < sizeof(HintAttrs) / sizeof(HintAttrs[0]));
240    auto &CategoryState = HintAttrs[Category];
241    const LoopHintAttr *PrevAttr;
242    if (Option == LoopHintAttr::Vectorize ||
243        Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll ||
244        Option == LoopHintAttr::UnrollAndJam ||
245        Option == LoopHintAttr::VectorizePredicate ||
246        Option == LoopHintAttr::PipelineDisabled ||
247        Option == LoopHintAttr::Distribute) {
248      // Enable|Disable|AssumeSafety hint.  For example, vectorize(enable).
249      PrevAttr = CategoryState.StateAttr;
250      CategoryState.StateAttr = LH;
251    } else {
252      // Numeric hint.  For example, vectorize_width(8).
253      PrevAttr = CategoryState.NumericAttr;
254      CategoryState.NumericAttr = LH;
255    }
256
257    PrintingPolicy Policy(S.Context.getLangOpts());
258    SourceLocation OptionLoc = LH->getRange().getBegin();
259    if (PrevAttr)
260      // Cannot specify same type of attribute twice.
261      S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
262          << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
263          << LH->getDiagnosticName(Policy);
264
265    if (CategoryState.StateAttr && CategoryState.NumericAttr &&
266        (Category == Unroll || Category == UnrollAndJam ||
267         CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
268      // Disable hints are not compatible with numeric hints of the same
269      // category.  As a special case, numeric unroll hints are also not
270      // compatible with enable or full form of the unroll pragma because these
271      // directives indicate full unrolling.
272      S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
273          << /*Duplicate=*/false
274          << CategoryState.StateAttr->getDiagnosticName(Policy)
275          << CategoryState.NumericAttr->getDiagnosticName(Policy);
276    }
277  }
278}
279
280static Attr *handleOpenCLUnrollHint(Sema &S, Stmt *St, const ParsedAttr &A,
281                                    SourceRange Range) {
282  // Although the feature was introduced only in OpenCL C v2.0 s6.11.5, it's
283  // useful for OpenCL 1.x too and doesn't require HW support.
284  // opencl_unroll_hint can have 0 arguments (compiler
285  // determines unrolling factor) or 1 argument (the unroll factor provided
286  // by the user).
287
288  unsigned NumArgs = A.getNumArgs();
289
290  if (NumArgs > 1) {
291    S.Diag(A.getLoc(), diag::err_attribute_too_many_arguments) << A << 1;
292    return nullptr;
293  }
294
295  unsigned UnrollFactor = 0;
296
297  if (NumArgs == 1) {
298    Expr *E = A.getArgAsExpr(0);
299    llvm::APSInt ArgVal(32);
300
301    if (!E->isIntegerConstantExpr(ArgVal, S.Context)) {
302      S.Diag(A.getLoc(), diag::err_attribute_argument_type)
303          << A << AANT_ArgumentIntegerConstant << E->getSourceRange();
304      return nullptr;
305    }
306
307    int Val = ArgVal.getSExtValue();
308
309    if (Val <= 0) {
310      S.Diag(A.getRange().getBegin(),
311             diag::err_attribute_requires_positive_integer)
312          << A << /* positive */ 0;
313      return nullptr;
314    }
315    UnrollFactor = Val;
316  }
317
318  return OpenCLUnrollHintAttr::CreateImplicit(S.Context, UnrollFactor);
319}
320
321static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const ParsedAttr &A,
322                                  SourceRange Range) {
323  switch (A.getKind()) {
324  case ParsedAttr::UnknownAttribute:
325    S.Diag(A.getLoc(), A.isDeclspecAttribute()
326                           ? (unsigned)diag::warn_unhandled_ms_attribute_ignored
327                           : (unsigned)diag::warn_unknown_attribute_ignored)
328        << A;
329    return nullptr;
330  case ParsedAttr::AT_FallThrough:
331    return handleFallThroughAttr(S, St, A, Range);
332  case ParsedAttr::AT_LoopHint:
333    return handleLoopHintAttr(S, St, A, Range);
334  case ParsedAttr::AT_OpenCLUnrollHint:
335    return handleOpenCLUnrollHint(S, St, A, Range);
336  case ParsedAttr::AT_Suppress:
337    return handleSuppressAttr(S, St, A, Range);
338  default:
339    // if we're here, then we parsed a known attribute, but didn't recognize
340    // it as a statement attribute => it is declaration attribute
341    S.Diag(A.getRange().getBegin(), diag::err_decl_attribute_invalid_on_stmt)
342        << A << St->getBeginLoc();
343    return nullptr;
344  }
345}
346
347StmtResult Sema::ProcessStmtAttributes(Stmt *S,
348                                       const ParsedAttributesView &AttrList,
349                                       SourceRange Range) {
350  SmallVector<const Attr*, 8> Attrs;
351  for (const ParsedAttr &AL : AttrList) {
352    if (Attr *a = ProcessStmtAttribute(*this, S, AL, Range))
353      Attrs.push_back(a);
354  }
355
356  CheckForIncompatibleAttributes(*this, Attrs);
357
358  if (Attrs.empty())
359    return S;
360
361  return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
362}
363