forked from OSchip/llvm-project
108 lines
4.1 KiB
C++
108 lines
4.1 KiB
C++
//===--- ForRangeCopyCheck.cpp - clang-tidy--------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "ForRangeCopyCheck.h"
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#include "../utils/DeclRefExprUtils.h"
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#include "../utils/FixItHintUtils.h"
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#include "../utils/TypeTraits.h"
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#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
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using namespace clang::ast_matchers;
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namespace clang {
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namespace tidy {
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namespace performance {
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ForRangeCopyCheck::ForRangeCopyCheck(StringRef Name, ClangTidyContext *Context)
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: ClangTidyCheck(Name, Context),
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WarnOnAllAutoCopies(Options.get("WarnOnAllAutoCopies", 0)) {}
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void ForRangeCopyCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
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Options.store(Opts, "WarnOnAllAutoCopies", WarnOnAllAutoCopies);
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}
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void ForRangeCopyCheck::registerMatchers(MatchFinder *Finder) {
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// Match loop variables that are not references or pointers or are already
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// initialized through MaterializeTemporaryExpr which indicates a type
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// conversion.
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auto LoopVar = varDecl(
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hasType(hasCanonicalType(unless(anyOf(referenceType(), pointerType())))),
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unless(hasInitializer(expr(hasDescendant(materializeTemporaryExpr())))));
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Finder->addMatcher(cxxForRangeStmt(hasLoopVariable(LoopVar.bind("loopVar")))
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.bind("forRange"),
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this);
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}
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void ForRangeCopyCheck::check(const MatchFinder::MatchResult &Result) {
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const auto *Var = Result.Nodes.getNodeAs<VarDecl>("loopVar");
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// Ignore code in macros since we can't place the fixes correctly.
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if (Var->getBeginLoc().isMacroID())
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return;
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if (handleConstValueCopy(*Var, *Result.Context))
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return;
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const auto *ForRange = Result.Nodes.getNodeAs<CXXForRangeStmt>("forRange");
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handleCopyIsOnlyConstReferenced(*Var, *ForRange, *Result.Context);
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}
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bool ForRangeCopyCheck::handleConstValueCopy(const VarDecl &LoopVar,
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ASTContext &Context) {
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if (WarnOnAllAutoCopies) {
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// For aggressive check just test that loop variable has auto type.
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if (!isa<AutoType>(LoopVar.getType()))
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return false;
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} else if (!LoopVar.getType().isConstQualified()) {
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return false;
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}
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llvm::Optional<bool> Expensive =
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utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
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if (!Expensive || !*Expensive)
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return false;
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auto Diagnostic =
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diag(LoopVar.getLocation(),
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"the loop variable's type is not a reference type; this creates a "
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"copy in each iteration; consider making this a reference")
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<< utils::fixit::changeVarDeclToReference(LoopVar, Context);
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if (!LoopVar.getType().isConstQualified())
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Diagnostic << utils::fixit::changeVarDeclToConst(LoopVar);
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return true;
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}
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bool ForRangeCopyCheck::handleCopyIsOnlyConstReferenced(
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const VarDecl &LoopVar, const CXXForRangeStmt &ForRange,
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ASTContext &Context) {
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llvm::Optional<bool> Expensive =
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utils::type_traits::isExpensiveToCopy(LoopVar.getType(), Context);
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if (LoopVar.getType().isConstQualified() || !Expensive || !*Expensive)
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return false;
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// We omit the case where the loop variable is not used in the loop body. E.g.
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//
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// for (auto _ : benchmark_state) {
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// }
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//
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// Because the fix (changing to `const auto &`) will introduce an unused
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// compiler warning which can't be suppressed.
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// Since this case is very rare, it is safe to ignore it.
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if (!ExprMutationAnalyzer(*ForRange.getBody(), Context).isMutated(&LoopVar) &&
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!utils::decl_ref_expr::allDeclRefExprs(LoopVar, *ForRange.getBody(),
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Context)
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.empty()) {
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diag(LoopVar.getLocation(),
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"loop variable is copied but only used as const reference; consider "
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"making it a const reference")
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<< utils::fixit::changeVarDeclToConst(LoopVar)
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<< utils::fixit::changeVarDeclToReference(LoopVar, Context);
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return true;
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}
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return false;
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}
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} // namespace performance
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} // namespace tidy
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} // namespace clang
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