SemaStmtAttr.cpp revision 296417 
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
23using namespace clang;
24using namespace sema;
25
26static 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
46static 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::Spelling Spelling;
69  LoopHintAttr::OptionType Option;
70  LoopHintAttr::LoopHintState State;
71  if (PragmaNoUnroll) {
72    // #pragma nounroll
73    Spelling = LoopHintAttr::Pragma_nounroll;
74    Option = LoopHintAttr::Unroll;
75    State = LoopHintAttr::Disable;
76  } else if (PragmaUnroll) {
77    Spelling = LoopHintAttr::Pragma_unroll;
78    if (ValueExpr) {
79      // #pragma unroll N
80      Option = LoopHintAttr::UnrollCount;
81      State = LoopHintAttr::Numeric;
82    } else {
83      // #pragma unroll
84      Option = LoopHintAttr::Unroll;
85      State = LoopHintAttr::Enable;
86    }
87  } else {
88    // #pragma clang loop ...
89    Spelling = LoopHintAttr::Pragma_clang_loop;
90    assert(OptionLoc && OptionLoc->Ident &&
91           "Attribute must have valid option info.");
92    Option = llvm::StringSwitch<LoopHintAttr::OptionType>(
93                 OptionLoc->Ident->getName())
94                 .Case("vectorize", LoopHintAttr::Vectorize)
95                 .Case("vectorize_width", LoopHintAttr::VectorizeWidth)
96                 .Case("interleave", LoopHintAttr::Interleave)
97                 .Case("interleave_count", LoopHintAttr::InterleaveCount)
98                 .Case("unroll", LoopHintAttr::Unroll)
99                 .Case("unroll_count", LoopHintAttr::UnrollCount)
100                 .Default(LoopHintAttr::Vectorize);
101    if (Option == LoopHintAttr::VectorizeWidth ||
102        Option == LoopHintAttr::InterleaveCount ||
103        Option == LoopHintAttr::UnrollCount) {
104      assert(ValueExpr && "Attribute must have a valid value expression.");
105      if (S.CheckLoopHintExpr(ValueExpr, St->getLocStart()))
106        return nullptr;
107      State = LoopHintAttr::Numeric;
108    } else if (Option == LoopHintAttr::Vectorize ||
109               Option == LoopHintAttr::Interleave ||
110               Option == LoopHintAttr::Unroll) {
111      assert(StateLoc && StateLoc->Ident && "Loop hint must have an argument");
112      if (StateLoc->Ident->isStr("disable"))
113        State = LoopHintAttr::Disable;
114      else if (StateLoc->Ident->isStr("assume_safety"))
115        State = LoopHintAttr::AssumeSafety;
116      else if (StateLoc->Ident->isStr("full"))
117        State = LoopHintAttr::Full;
118      else if (StateLoc->Ident->isStr("enable"))
119        State = LoopHintAttr::Enable;
120      else
121        llvm_unreachable("bad loop hint argument");
122    } else
123      llvm_unreachable("bad loop hint");
124  }
125
126  return LoopHintAttr::CreateImplicit(S.Context, Spelling, Option, State,
127                                      ValueExpr, A.getRange());
128}
129
130static void
131CheckForIncompatibleAttributes(Sema &S,
132                               const SmallVectorImpl<const Attr *> &Attrs) {
133  // There are 3 categories of loop hints attributes: vectorize, interleave,
134  // and unroll. Each comes in two variants: a state form and a numeric form.
135  // The state form selectively defaults/enables/disables the transformation
136  // for the loop (for unroll, default indicates full unrolling rather than
137  // enabling the transformation).  The numeric form form provides an integer
138  // hint (for example, unroll count) to the transformer. The following array
139  // accumulates the hints encountered while iterating through the attributes
140  // to check for compatibility.
141  struct {
142    const LoopHintAttr *StateAttr;
143    const LoopHintAttr *NumericAttr;
144  } HintAttrs[] = {{nullptr, nullptr}, {nullptr, nullptr}, {nullptr, nullptr}};
145
146  for (const auto *I : Attrs) {
147    const LoopHintAttr *LH = dyn_cast<LoopHintAttr>(I);
148
149    // Skip non loop hint attributes
150    if (!LH)
151      continue;
152
153    LoopHintAttr::OptionType Option = LH->getOption();
154    enum { Vectorize, Interleave, Unroll } Category;
155    switch (Option) {
156    case LoopHintAttr::Vectorize:
157    case LoopHintAttr::VectorizeWidth:
158      Category = Vectorize;
159      break;
160    case LoopHintAttr::Interleave:
161    case LoopHintAttr::InterleaveCount:
162      Category = Interleave;
163      break;
164    case LoopHintAttr::Unroll:
165    case LoopHintAttr::UnrollCount:
166      Category = Unroll;
167      break;
168    };
169
170    auto &CategoryState = HintAttrs[Category];
171    const LoopHintAttr *PrevAttr;
172    if (Option == LoopHintAttr::Vectorize ||
173        Option == LoopHintAttr::Interleave || Option == LoopHintAttr::Unroll) {
174      // Enable|Disable|AssumeSafety hint.  For example, vectorize(enable).
175      PrevAttr = CategoryState.StateAttr;
176      CategoryState.StateAttr = LH;
177    } else {
178      // Numeric hint.  For example, vectorize_width(8).
179      PrevAttr = CategoryState.NumericAttr;
180      CategoryState.NumericAttr = LH;
181    }
182
183    PrintingPolicy Policy(S.Context.getLangOpts());
184    SourceLocation OptionLoc = LH->getRange().getBegin();
185    if (PrevAttr)
186      // Cannot specify same type of attribute twice.
187      S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
188          << /*Duplicate=*/true << PrevAttr->getDiagnosticName(Policy)
189          << LH->getDiagnosticName(Policy);
190
191    if (CategoryState.StateAttr && CategoryState.NumericAttr &&
192        (Category == Unroll ||
193         CategoryState.StateAttr->getState() == LoopHintAttr::Disable)) {
194      // Disable hints are not compatible with numeric hints of the same
195      // category.  As a special case, numeric unroll hints are also not
196      // compatible with enable or full form of the unroll pragma because these
197      // directives indicate full unrolling.
198      S.Diag(OptionLoc, diag::err_pragma_loop_compatibility)
199          << /*Duplicate=*/false
200          << CategoryState.StateAttr->getDiagnosticName(Policy)
201          << CategoryState.NumericAttr->getDiagnosticName(Policy);
202    }
203  }
204}
205
206static Attr *ProcessStmtAttribute(Sema &S, Stmt *St, const AttributeList &A,
207                                  SourceRange Range) {
208  switch (A.getKind()) {
209  case AttributeList::UnknownAttribute:
210    S.Diag(A.getLoc(), A.isDeclspecAttribute() ?
211           diag::warn_unhandled_ms_attribute_ignored :
212           diag::warn_unknown_attribute_ignored) << A.getName();
213    return nullptr;
214  case AttributeList::AT_FallThrough:
215    return handleFallThroughAttr(S, St, A, Range);
216  case AttributeList::AT_LoopHint:
217    return handleLoopHintAttr(S, St, A, Range);
218  default:
219    // if we're here, then we parsed a known attribute, but didn't recognize
220    // it as a statement attribute => it is declaration attribute
221    S.Diag(A.getRange().getBegin(), diag::err_attribute_invalid_on_stmt)
222        << A.getName() << St->getLocStart();
223    return nullptr;
224  }
225}
226
227StmtResult Sema::ProcessStmtAttributes(Stmt *S, AttributeList *AttrList,
228                                       SourceRange Range) {
229  SmallVector<const Attr*, 8> Attrs;
230  for (const AttributeList* l = AttrList; l; l = l->getNext()) {
231    if (Attr *a = ProcessStmtAttribute(*this, S, *l, Range))
232      Attrs.push_back(a);
233  }
234
235  CheckForIncompatibleAttributes(*this, Attrs);
236
237  if (Attrs.empty())
238    return S;
239
240  return ActOnAttributedStmt(Range.getBegin(), Attrs, S);
241}
242