clang-tools  12.0.0git
InefficientAlgorithmCheck.cpp
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1 //===--- InefficientAlgorithmCheck.cpp - clang-tidy------------------------===//
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 
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/Lex/Lexer.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace performance {
19 
20 static bool areTypesCompatible(QualType Left, QualType Right) {
21  if (const auto *LeftRefType = Left->getAs<ReferenceType>())
22  Left = LeftRefType->getPointeeType();
23  if (const auto *RightRefType = Right->getAs<ReferenceType>())
24  Right = RightRefType->getPointeeType();
25  return Left->getCanonicalTypeUnqualified() ==
26  Right->getCanonicalTypeUnqualified();
27 }
28 
29 void InefficientAlgorithmCheck::registerMatchers(MatchFinder *Finder) {
30  const auto Algorithms =
31  hasAnyName("::std::find", "::std::count", "::std::equal_range",
32  "::std::lower_bound", "::std::upper_bound");
33  const auto ContainerMatcher = classTemplateSpecializationDecl(hasAnyName(
34  "::std::set", "::std::map", "::std::multiset", "::std::multimap",
35  "::std::unordered_set", "::std::unordered_map",
36  "::std::unordered_multiset", "::std::unordered_multimap"));
37 
38  const auto Matcher = traverse(
39  ast_type_traits::TK_AsIs,
40  callExpr(
41  callee(functionDecl(Algorithms)),
42  hasArgument(
43  0, cxxConstructExpr(has(ignoringParenImpCasts(cxxMemberCallExpr(
44  callee(cxxMethodDecl(hasName("begin"))),
45  on(declRefExpr(
46  hasDeclaration(decl().bind("IneffContObj")),
47  anyOf(hasType(ContainerMatcher.bind("IneffCont")),
48  hasType(pointsTo(
49  ContainerMatcher.bind("IneffContPtr")))))
50  .bind("IneffContExpr"))))))),
51  hasArgument(
52  1, cxxConstructExpr(has(ignoringParenImpCasts(cxxMemberCallExpr(
53  callee(cxxMethodDecl(hasName("end"))),
54  on(declRefExpr(
55  hasDeclaration(equalsBoundNode("IneffContObj"))))))))),
56  hasArgument(2, expr().bind("AlgParam")),
57  unless(isInTemplateInstantiation()))
58  .bind("IneffAlg"));
59 
60  Finder->addMatcher(Matcher, this);
61 }
62 
63 void InefficientAlgorithmCheck::check(const MatchFinder::MatchResult &Result) {
64  const auto *AlgCall = Result.Nodes.getNodeAs<CallExpr>("IneffAlg");
65  const auto *IneffCont =
66  Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("IneffCont");
67  bool PtrToContainer = false;
68  if (!IneffCont) {
69  IneffCont =
70  Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("IneffContPtr");
71  PtrToContainer = true;
72  }
73  const llvm::StringRef IneffContName = IneffCont->getName();
74  const bool Unordered =
75  IneffContName.find("unordered") != llvm::StringRef::npos;
76  const bool Maplike = IneffContName.find("map") != llvm::StringRef::npos;
77 
78  // Store if the key type of the container is compatible with the value
79  // that is searched for.
80  QualType ValueType = AlgCall->getArg(2)->getType();
81  QualType KeyType =
82  IneffCont->getTemplateArgs()[0].getAsType().getCanonicalType();
83  const bool CompatibleTypes = areTypesCompatible(KeyType, ValueType);
84 
85  // Check if the comparison type for the algorithm and the container matches.
86  if (AlgCall->getNumArgs() == 4 && !Unordered) {
87  const Expr *Arg = AlgCall->getArg(3);
88  const QualType AlgCmp =
89  Arg->getType().getUnqualifiedType().getCanonicalType();
90  const unsigned CmpPosition =
91  (IneffContName.find("map") == llvm::StringRef::npos) ? 1 : 2;
92  const QualType ContainerCmp = IneffCont->getTemplateArgs()[CmpPosition]
93  .getAsType()
94  .getUnqualifiedType()
95  .getCanonicalType();
96  if (AlgCmp != ContainerCmp) {
97  diag(Arg->getBeginLoc(),
98  "different comparers used in the algorithm and the container");
99  return;
100  }
101  }
102 
103  const auto *AlgDecl = AlgCall->getDirectCallee();
104  if (!AlgDecl)
105  return;
106 
107  if (Unordered && AlgDecl->getName().find("bound") != llvm::StringRef::npos)
108  return;
109 
110  const auto *AlgParam = Result.Nodes.getNodeAs<Expr>("AlgParam");
111  const auto *IneffContExpr = Result.Nodes.getNodeAs<Expr>("IneffContExpr");
112  FixItHint Hint;
113 
114  SourceManager &SM = *Result.SourceManager;
115  LangOptions LangOpts = getLangOpts();
116 
117  CharSourceRange CallRange =
118  CharSourceRange::getTokenRange(AlgCall->getSourceRange());
119 
120  // FIXME: Create a common utility to extract a file range that the given token
121  // sequence is exactly spelled at (without macro argument expansions etc.).
122  // We can't use Lexer::makeFileCharRange here, because for
123  //
124  // #define F(x) x
125  // x(a b c);
126  //
127  // it will return "x(a b c)", when given the range "a"-"c". It makes sense for
128  // removals, but not for replacements.
129  //
130  // This code is over-simplified, but works for many real cases.
131  if (SM.isMacroArgExpansion(CallRange.getBegin()) &&
132  SM.isMacroArgExpansion(CallRange.getEnd())) {
133  CallRange.setBegin(SM.getSpellingLoc(CallRange.getBegin()));
134  CallRange.setEnd(SM.getSpellingLoc(CallRange.getEnd()));
135  }
136 
137  if (!CallRange.getBegin().isMacroID() && !Maplike && CompatibleTypes) {
138  StringRef ContainerText = Lexer::getSourceText(
139  CharSourceRange::getTokenRange(IneffContExpr->getSourceRange()), SM,
140  LangOpts);
141  StringRef ParamText = Lexer::getSourceText(
142  CharSourceRange::getTokenRange(AlgParam->getSourceRange()), SM,
143  LangOpts);
144  std::string ReplacementText =
145  (llvm::Twine(ContainerText) + (PtrToContainer ? "->" : ".") +
146  AlgDecl->getName() + "(" + ParamText + ")")
147  .str();
148  Hint = FixItHint::CreateReplacement(CallRange, ReplacementText);
149  }
150 
151  diag(AlgCall->getBeginLoc(),
152  "this STL algorithm call should be replaced with a container method")
153  << Hint;
154 }
155 
156 } // namespace performance
157 } // namespace tidy
158 } // namespace clang
static bool areTypesCompatible(QualType Left, QualType Right)
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//