| //===--- UnnecessaryValueParamCheck.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 "UnnecessaryValueParamCheck.h" |
| |
| #include "../utils/DeclRefExprUtils.h" |
| #include "../utils/FixItHintUtils.h" |
| #include "../utils/Matchers.h" |
| #include "../utils/OptionsUtils.h" |
| #include "../utils/TypeTraits.h" |
| #include "clang/Frontend/CompilerInstance.h" |
| #include "clang/Lex/Lexer.h" |
| #include "clang/Lex/Preprocessor.h" |
| |
| using namespace clang::ast_matchers; |
| |
| namespace clang { |
| namespace tidy { |
| namespace performance { |
| |
| namespace { |
| |
| std::string paramNameOrIndex(StringRef Name, size_t Index) { |
| return (Name.empty() ? llvm::Twine('#') + llvm::Twine(Index + 1) |
| : llvm::Twine('\'') + Name + llvm::Twine('\'')) |
| .str(); |
| } |
| |
| bool isReferencedOutsideOfCallExpr(const FunctionDecl &Function, |
| ASTContext &Context) { |
| auto Matches = match(declRefExpr(to(functionDecl(equalsNode(&Function))), |
| unless(hasAncestor(callExpr()))), |
| Context); |
| return !Matches.empty(); |
| } |
| |
| bool hasLoopStmtAncestor(const DeclRefExpr &DeclRef, const Decl &Decl, |
| ASTContext &Context) { |
| auto Matches = match( |
| traverse(TK_AsIs, |
| decl(forEachDescendant(declRefExpr( |
| equalsNode(&DeclRef), |
| unless(hasAncestor(stmt(anyOf(forStmt(), cxxForRangeStmt(), |
| whileStmt(), doStmt())))))))), |
| Decl, Context); |
| return Matches.empty(); |
| } |
| |
| bool isExplicitTemplateSpecialization(const FunctionDecl &Function) { |
| if (const auto *SpecializationInfo = Function.getTemplateSpecializationInfo()) |
| if (SpecializationInfo->getTemplateSpecializationKind() == |
| TSK_ExplicitSpecialization) |
| return true; |
| if (const auto *Method = llvm::dyn_cast<CXXMethodDecl>(&Function)) |
| if (Method->getTemplatedKind() == FunctionDecl::TK_MemberSpecialization && |
| Method->getMemberSpecializationInfo()->isExplicitSpecialization()) |
| return true; |
| return false; |
| } |
| |
| } // namespace |
| |
| UnnecessaryValueParamCheck::UnnecessaryValueParamCheck( |
| StringRef Name, ClangTidyContext *Context) |
| : ClangTidyCheck(Name, Context), |
| Inserter(Options.getLocalOrGlobal("IncludeStyle", |
| utils::IncludeSorter::IS_LLVM)), |
| AllowedTypes( |
| utils::options::parseStringList(Options.get("AllowedTypes", ""))) {} |
| |
| void UnnecessaryValueParamCheck::registerMatchers(MatchFinder *Finder) { |
| const auto ExpensiveValueParamDecl = parmVarDecl( |
| hasType(qualType( |
| hasCanonicalType(matchers::isExpensiveToCopy()), |
| unless(anyOf(hasCanonicalType(referenceType()), |
| hasDeclaration(namedDecl( |
| matchers::matchesAnyListedName(AllowedTypes))))))), |
| decl().bind("param")); |
| Finder->addMatcher( |
| traverse( |
| TK_AsIs, |
| functionDecl(hasBody(stmt()), isDefinition(), unless(isImplicit()), |
| unless(cxxMethodDecl(anyOf(isOverride(), isFinal()))), |
| has(typeLoc(forEach(ExpensiveValueParamDecl))), |
| unless(isInstantiated()), decl().bind("functionDecl"))), |
| this); |
| } |
| |
| void UnnecessaryValueParamCheck::check(const MatchFinder::MatchResult &Result) { |
| const auto *Param = Result.Nodes.getNodeAs<ParmVarDecl>("param"); |
| const auto *Function = Result.Nodes.getNodeAs<FunctionDecl>("functionDecl"); |
| |
| TraversalKindScope RAII(*Result.Context, TK_AsIs); |
| |
| FunctionParmMutationAnalyzer &Analyzer = |
| MutationAnalyzers.try_emplace(Function, *Function, *Result.Context) |
| .first->second; |
| if (Analyzer.isMutated(Param)) |
| return; |
| |
| const bool IsConstQualified = |
| Param->getType().getCanonicalType().isConstQualified(); |
| |
| // If the parameter is non-const, check if it has a move constructor and is |
| // only referenced once to copy-construct another object or whether it has a |
| // move assignment operator and is only referenced once when copy-assigned. |
| // In this case wrap DeclRefExpr with std::move() to avoid the unnecessary |
| // copy. |
| if (!IsConstQualified) { |
| auto AllDeclRefExprs = utils::decl_ref_expr::allDeclRefExprs( |
| *Param, *Function, *Result.Context); |
| if (AllDeclRefExprs.size() == 1) { |
| auto CanonicalType = Param->getType().getCanonicalType(); |
| const auto &DeclRefExpr = **AllDeclRefExprs.begin(); |
| |
| if (!hasLoopStmtAncestor(DeclRefExpr, *Function, *Result.Context) && |
| ((utils::type_traits::hasNonTrivialMoveConstructor(CanonicalType) && |
| utils::decl_ref_expr::isCopyConstructorArgument( |
| DeclRefExpr, *Function, *Result.Context)) || |
| (utils::type_traits::hasNonTrivialMoveAssignment(CanonicalType) && |
| utils::decl_ref_expr::isCopyAssignmentArgument( |
| DeclRefExpr, *Function, *Result.Context)))) { |
| handleMoveFix(*Param, DeclRefExpr, *Result.Context); |
| return; |
| } |
| } |
| } |
| |
| const size_t Index = std::find(Function->parameters().begin(), |
| Function->parameters().end(), Param) - |
| Function->parameters().begin(); |
| |
| auto Diag = |
| diag(Param->getLocation(), |
| "the %select{|const qualified }0parameter %1 is copied for each " |
| "invocation%select{ but only used as a const reference|}0; consider " |
| "making it a %select{const |}0reference") |
| << IsConstQualified << paramNameOrIndex(Param->getName(), Index); |
| // Do not propose fixes when: |
| // 1. the ParmVarDecl is in a macro, since we cannot place them correctly |
| // 2. the function is virtual as it might break overrides |
| // 3. the function is referenced outside of a call expression within the |
| // compilation unit as the signature change could introduce build errors. |
| // 4. the function is an explicit template specialization. |
| const auto *Method = llvm::dyn_cast<CXXMethodDecl>(Function); |
| if (Param->getBeginLoc().isMacroID() || (Method && Method->isVirtual()) || |
| isReferencedOutsideOfCallExpr(*Function, *Result.Context) || |
| isExplicitTemplateSpecialization(*Function)) |
| return; |
| for (const auto *FunctionDecl = Function; FunctionDecl != nullptr; |
| FunctionDecl = FunctionDecl->getPreviousDecl()) { |
| const auto &CurrentParam = *FunctionDecl->getParamDecl(Index); |
| Diag << utils::fixit::changeVarDeclToReference(CurrentParam, |
| *Result.Context); |
| // The parameter of each declaration needs to be checked individually as to |
| // whether it is const or not as constness can differ between definition and |
| // declaration. |
| if (!CurrentParam.getType().getCanonicalType().isConstQualified()) { |
| if (llvm::Optional<FixItHint> Fix = utils::fixit::addQualifierToVarDecl( |
| CurrentParam, *Result.Context, DeclSpec::TQ::TQ_const)) |
| Diag << *Fix; |
| } |
| } |
| } |
| |
| void UnnecessaryValueParamCheck::registerPPCallbacks( |
| const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) { |
| Inserter.registerPreprocessor(PP); |
| } |
| |
| void UnnecessaryValueParamCheck::storeOptions( |
| ClangTidyOptions::OptionMap &Opts) { |
| Options.store(Opts, "IncludeStyle", Inserter.getStyle()); |
| Options.store(Opts, "AllowedTypes", |
| utils::options::serializeStringList(AllowedTypes)); |
| } |
| |
| void UnnecessaryValueParamCheck::onEndOfTranslationUnit() { |
| MutationAnalyzers.clear(); |
| } |
| |
| void UnnecessaryValueParamCheck::handleMoveFix(const ParmVarDecl &Var, |
| const DeclRefExpr &CopyArgument, |
| const ASTContext &Context) { |
| auto Diag = diag(CopyArgument.getBeginLoc(), |
| "parameter %0 is passed by value and only copied once; " |
| "consider moving it to avoid unnecessary copies") |
| << &Var; |
| // Do not propose fixes in macros since we cannot place them correctly. |
| if (CopyArgument.getBeginLoc().isMacroID()) |
| return; |
| const auto &SM = Context.getSourceManager(); |
| auto EndLoc = Lexer::getLocForEndOfToken(CopyArgument.getLocation(), 0, SM, |
| Context.getLangOpts()); |
| Diag << FixItHint::CreateInsertion(CopyArgument.getBeginLoc(), "std::move(") |
| << FixItHint::CreateInsertion(EndLoc, ")") |
| << Inserter.createIncludeInsertion( |
| SM.getFileID(CopyArgument.getBeginLoc()), "<utility>"); |
| } |
| |
| } // namespace performance |
| } // namespace tidy |
| } // namespace clang |
