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