vsk created this revision.
vsk added reviewers: aaron.ballman, alexfh.
vsk added a subscriber: cfe-commits.
Introduce a check which suggests when it might be helpful to use "emplace"
methods. The initial version only works with std::vector and push_back (e.g
`V.push_back(T(1, 2))` -> `V.emplace_back(1, 2)`). It could be extended to work
with other containers and methods.
http://reviews.llvm.org/D21185
Files:
clang-tidy/performance/CMakeLists.txt
clang-tidy/performance/EmplaceCheck.cpp
clang-tidy/performance/EmplaceCheck.h
clang-tidy/performance/PerformanceTidyModule.cpp
test/clang-tidy/performance-emplace-into-containers.cpp
Index: test/clang-tidy/performance-emplace-into-containers.cpp
===================================================================
--- /dev/null
+++ test/clang-tidy/performance-emplace-into-containers.cpp
@@ -0,0 +1,46 @@
+// RUN: %check_clang_tidy %s performance-emplace-into-containers %t -- -- -std=c++11
+
+namespace std {
+
+template <typename T>
+struct vector {
+ void push_back(const T &x);
+ void push_back(T &&x);
+
+ template <class... Args>
+ void emplace_back(Args &&... args);
+};
+
+} // std
+
+struct X {
+ int x;
+ X() : x(0) {}
+ X(int x) : x(x) {}
+ X(int x, int y) : x(x + y) {}
+ X(const X &Obj) : x(Obj.x) {}
+};
+
+void f1() {
+ std::vector<X> v1;
+
+ v1.push_back(X());
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: Avoid a copy {{.*}}
+ // CHECK-FIXES: v1.emplace_back()
+
+ v1.push_back(X(0, 0));
+ // CHECK-MESSAGES: [[@LINE-1]]:6: warning: Avoid a copy {{.*}}
+ // CHECK-FIXES: v1.emplace_back(0, 0)
+
+ v1/*a*/./*b*/push_back(/*c*/X(/*d*/0,/*e*/0/*f*/)/*g*/)/*h*/ ;
+ // CHECK-MESSAGES: [[@LINE-1]]:16: warning: Avoid a copy {{.*}}
+ // CHECK-FIXES: v1/*a*/./*b*/emplace_back(/*c*//*d*/0,/*e*/0/*f*//*g*/)/*h*/ ;
+
+ // Do not try to deal with initializer lists.
+ v1.push_back({0, 0});
+
+ // Do not try to deal with functional casts. FIXME?
+ X x{0, 0};
+ v1.push_back(X(x));
+ v1.push_back(X(0));
+}
Index: clang-tidy/performance/PerformanceTidyModule.cpp
===================================================================
--- clang-tidy/performance/PerformanceTidyModule.cpp
+++ clang-tidy/performance/PerformanceTidyModule.cpp
@@ -11,6 +11,7 @@
#include "../ClangTidyModule.h"
#include "../ClangTidyModuleRegistry.h"
+#include "EmplaceCheck.h"
#include "FasterStringFindCheck.h"
#include "ForRangeCopyCheck.h"
#include "ImplicitCastInLoopCheck.h"
@@ -24,6 +25,8 @@
class PerformanceModule : public ClangTidyModule {
public:
void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+ CheckFactories.registerCheck<EmplaceCheck>(
+ "performance-emplace-into-containers");
CheckFactories.registerCheck<FasterStringFindCheck>(
"performance-faster-string-find");
CheckFactories.registerCheck<ForRangeCopyCheck>(
Index: clang-tidy/performance/EmplaceCheck.h
===================================================================
--- /dev/null
+++ clang-tidy/performance/EmplaceCheck.h
@@ -0,0 +1,30 @@
+//===--- EmplaceCheck.h - clang-tidy --------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_EMPLACE_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_EMPLACE_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace performance {
+
+class EmplaceCheck : public ClangTidyCheck {
+public:
+ EmplaceCheck(StringRef Name, ClangTidyContext *Context);
+ void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+ void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace performance
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_EMPLACE_H
Index: clang-tidy/performance/EmplaceCheck.cpp
===================================================================
--- /dev/null
+++ clang-tidy/performance/EmplaceCheck.cpp
@@ -0,0 +1,98 @@
+//===--- EmplaceCheck.cpp - clang-tidy ------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "EmplaceCheck.h"
+#include "clang/Lex/Lexer.h"
+
+namespace clang {
+namespace tidy {
+namespace performance {
+
+using namespace ast_matchers;
+
+EmplaceCheck::EmplaceCheck(StringRef Name, ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+
+void EmplaceCheck::registerMatchers(MatchFinder *Finder) {
+ Finder->addMatcher(
+ cxxMemberCallExpr(
+ on(expr(hasType(cxxRecordDecl(hasName("std::vector"))))),
+ callee(functionDecl(hasName("push_back"))),
+ hasArgument(0, cxxConstructExpr().bind("construct_expr")))
+ .bind("call"),
+ this);
+}
+
+namespace {
+
+/// \brief Get a StringRef representing a SourceRange.
+StringRef getAsString(const SourceManager &SM, const LangOptions &LO,
+ SourceRange SR) {
+ // Return a null string if \p SR is invalid: this filters out non-paren
+ // based constructors (e.g default constructors).
+ if (SR.isInvalid())
+ return {};
+ return Lexer::getSourceText(Lexer::getAsCharRange(SR, SM, LO), SM, LO);
+}
+
+/// \brief Return the precise end location for the given token.
+///
+/// Use the offset to the last character in the token, instead of the offset
+/// to the first character after the token.
+SourceLocation getPreciseTokenEnd(const SourceManager &SM,
+ const LangOptions &LO, SourceLocation Loc) {
+ unsigned TokLen = Lexer::MeasureTokenLength(SM.getSpellingLoc(Loc), SM, LO);
+ return Loc.getLocWithOffset(TokLen - 1);
+}
+
+/// \brief Return the range containing the given token.
+SourceRange getPreciseTokenRange(const SourceManager &SM, const LangOptions &LO,
+ SourceLocation Loc) {
+ return {Loc, getPreciseTokenEnd(SM, LO, Loc)};
+}
+
+} // end anonymous namespace
+
+void EmplaceCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto *Call = Result.Nodes.getNodeAs<CXXMemberCallExpr>("call");
+ const auto *CE = Result.Nodes.getNodeAs<CXXConstructExpr>("construct_expr");
+
+ // Don't try to forward initializer lists.
+ if (CE->isListInitialization() || CE->isStdInitListInitialization())
+ return;
+
+ const SourceManager &SM = *Result.SourceManager;
+ const LangOptions &LO = Result.Context->getLangOpts();
+
+ StringRef ArgsStr;
+ if (!CE->getNumArgs()) {
+ ArgsStr = "";
+ } else {
+ SourceRange ArgsR = CE->getParenOrBraceRange();
+
+ // Skip just past the left parenthesis in '(', ..., ')'.
+ ArgsR.setBegin(Lexer::getLocForEndOfToken(ArgsR.getBegin(), 0, SM, LO));
+
+ ArgsStr = getAsString(SM, LO, ArgsR);
+ if (!ArgsStr.data())
+ return;
+ }
+
+ SourceLocation CalleeStartLoc = Call->getExprLoc();
+ SourceRange CalleeR = getPreciseTokenRange(SM, LO, CalleeStartLoc);
+ SourceRange ConstructR = CE->getSourceRange();
+
+ diag(CalleeStartLoc, "Avoid a copy by using an emplace method")
+ << FixItHint::CreateReplacement(CalleeR, "emplace_back")
+ << FixItHint::CreateReplacement(ConstructR, ArgsStr);
+}
+
+} // namespace performance
+} // namespace tidy
+} // namespace clang
Index: clang-tidy/performance/CMakeLists.txt
===================================================================
--- clang-tidy/performance/CMakeLists.txt
+++ clang-tidy/performance/CMakeLists.txt
@@ -1,6 +1,7 @@
set(LLVM_LINK_COMPONENTS support)
add_clang_library(clangTidyPerformanceModule
+ EmplaceCheck.cpp
FasterStringFindCheck.cpp
ForRangeCopyCheck.cpp
ImplicitCastInLoopCheck.cpp
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