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//===--- InefficientAlgorithmCheck.cpp - clang-tidy------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "InefficientAlgorithmCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
using namespace clang::ast_matchers;
namespace clang::tidy::performance {
static bool areTypesCompatible(QualType Left, QualType Right) {
if (const auto *LeftRefType = Left->getAs<ReferenceType>())
Left = LeftRefType->getPointeeType();
if (const auto *RightRefType = Right->getAs<ReferenceType>())
Right = RightRefType->getPointeeType();
return Left->getCanonicalTypeUnqualified() ==
Right->getCanonicalTypeUnqualified();
}
void InefficientAlgorithmCheck::registerMatchers(MatchFinder *Finder) {
const auto Algorithms =
hasAnyName("::std::find", "::std::count", "::std::equal_range",
"::std::lower_bound", "::std::upper_bound");
const auto ContainerMatcher = classTemplateSpecializationDecl(hasAnyName(
"::std::set", "::std::map", "::std::multiset", "::std::multimap",
"::std::unordered_set", "::std::unordered_map",
"::std::unordered_multiset", "::std::unordered_multimap"));
const auto Matcher =
callExpr(
callee(functionDecl(Algorithms)),
hasArgument(
0, cxxMemberCallExpr(
callee(cxxMethodDecl(hasName("begin"))),
on(declRefExpr(
hasDeclaration(decl().bind("IneffContObj")),
anyOf(hasType(ContainerMatcher.bind("IneffCont")),
hasType(pointsTo(
ContainerMatcher.bind("IneffContPtr")))))
.bind("IneffContExpr")))),
hasArgument(
1, cxxMemberCallExpr(callee(cxxMethodDecl(hasName("end"))),
on(declRefExpr(hasDeclaration(
equalsBoundNode("IneffContObj")))))),
hasArgument(2, expr().bind("AlgParam")))
.bind("IneffAlg");
Finder->addMatcher(Matcher, this);
}
void InefficientAlgorithmCheck::check(const MatchFinder::MatchResult &Result) {
const auto *AlgCall = Result.Nodes.getNodeAs<CallExpr>("IneffAlg");
const auto *IneffCont =
Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("IneffCont");
bool PtrToContainer = false;
if (!IneffCont) {
IneffCont =
Result.Nodes.getNodeAs<ClassTemplateSpecializationDecl>("IneffContPtr");
PtrToContainer = true;
}
const llvm::StringRef IneffContName = IneffCont->getName();
const bool Unordered = IneffContName.contains("unordered");
const bool Maplike = IneffContName.contains("map");
// Store if the key type of the container is compatible with the value
// that is searched for.
QualType ValueType = AlgCall->getArg(2)->getType();
QualType KeyType =
IneffCont->getTemplateArgs()[0].getAsType().getCanonicalType();
const bool CompatibleTypes = areTypesCompatible(KeyType, ValueType);
// Check if the comparison type for the algorithm and the container matches.
if (AlgCall->getNumArgs() == 4 && !Unordered) {
const Expr *Arg = AlgCall->getArg(3);
const QualType AlgCmp =
Arg->getType().getUnqualifiedType().getCanonicalType();
const unsigned CmpPosition = IneffContName.contains("map") ? 2 : 1;
const QualType ContainerCmp = IneffCont->getTemplateArgs()[CmpPosition]
.getAsType()
.getUnqualifiedType()
.getCanonicalType();
if (AlgCmp != ContainerCmp) {
diag(Arg->getBeginLoc(),
"different comparers used in the algorithm and the container");
return;
}
}
const auto *AlgDecl = AlgCall->getDirectCallee();
if (!AlgDecl)
return;
if (Unordered && AlgDecl->getName().find("bound") != llvm::StringRef::npos)
return;
const auto *AlgParam = Result.Nodes.getNodeAs<Expr>("AlgParam");
const auto *IneffContExpr = Result.Nodes.getNodeAs<Expr>("IneffContExpr");
FixItHint Hint;
SourceManager &SM = *Result.SourceManager;
LangOptions LangOpts = getLangOpts();
CharSourceRange CallRange =
CharSourceRange::getTokenRange(AlgCall->getSourceRange());
// FIXME: Create a common utility to extract a file range that the given token
// sequence is exactly spelled at (without macro argument expansions etc.).
// We can't use Lexer::makeFileCharRange here, because for
//
// #define F(x) x
// x(a b c);
//
// it will return "x(a b c)", when given the range "a"-"c". It makes sense for
// removals, but not for replacements.
//
// This code is over-simplified, but works for many real cases.
if (SM.isMacroArgExpansion(CallRange.getBegin()) &&
SM.isMacroArgExpansion(CallRange.getEnd())) {
CallRange.setBegin(SM.getSpellingLoc(CallRange.getBegin()));
CallRange.setEnd(SM.getSpellingLoc(CallRange.getEnd()));
}
if (!CallRange.getBegin().isMacroID() && !Maplike && CompatibleTypes) {
StringRef ContainerText = Lexer::getSourceText(
CharSourceRange::getTokenRange(IneffContExpr->getSourceRange()), SM,
LangOpts);
StringRef ParamText = Lexer::getSourceText(
CharSourceRange::getTokenRange(AlgParam->getSourceRange()), SM,
LangOpts);
std::string ReplacementText =
(llvm::Twine(ContainerText) + (PtrToContainer ? "->" : ".") +
AlgDecl->getName() + "(" + ParamText + ")")
.str();
Hint = FixItHint::CreateReplacement(CallRange, ReplacementText);
}
diag(AlgCall->getBeginLoc(),
"this STL algorithm call should be replaced with a container method")
<< Hint;
}
} // namespace clang::tidy::performance
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