[clang-tidy] Add check performance-faster-string-find

Summary:
Add check performance-faster-string-find.
It replaces single character string literals to character literals in calls to string::find and friends.

Reviewers: alexfh

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D16152

llvm-svn: 260712

clang-tools-extra/clang-tidy/performance/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangTidyPerformanceModule
+  FasterStringFindCheck.cpp
   ForRangeCopyCheck.cpp
   ImplicitCastInLoopCheck.cpp
   PerformanceTidyModule.cpp

clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.cpp

@@ -0,0 +1,128 @@
+//===--- FasterStringFindCheck.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 "FasterStringFindCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace performance {
+
+namespace {
+
+static const char StringLikeClassesDelimiter[] = ";";
+
+std::vector<std::string> ParseClasses(StringRef Option) {
+  SmallVector<StringRef, 4> Classes;
+  Option.split(Classes, StringLikeClassesDelimiter);
+  std::vector<std::string> Result;
+  for (StringRef &Class : Classes) {
+    Class = Class.trim();
+    if (!Class.empty())
+      Result.push_back(Class);
+  }
+  return Result;
+}
+
+llvm::Optional<std::string> MakeCharacterLiteral(const StringLiteral *Literal) {
+  std::string Result;
+  {
+    llvm::raw_string_ostream OS(Result);
+    Literal->outputString(OS);
+  }
+  // Now replace the " with '.
+  auto pos = Result.find_first_of('"');
+  if (pos == Result.npos) return llvm::None;
+  Result[pos] = '\'';
+  pos = Result.find_last_of('"');
+  if (pos == Result.npos) return llvm::None;
+  Result[pos] = '\'';
+  return Result;
+}
+
+AST_MATCHER(StringLiteral, lengthIsOne) { return Node.getLength() == 1; }
+
+AST_MATCHER_FUNCTION(ast_matchers::internal::Matcher<Expr>,
+                     hasSubstitutedType) {
+  return hasType(qualType(anyOf(substTemplateTypeParmType(),
+                                hasDescendant(substTemplateTypeParmType()))));
+}
+
+} // namespace
+
+FasterStringFindCheck::FasterStringFindCheck(StringRef Name,
+                                             ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      StringLikeClasses(
+          ParseClasses(Options.get("StringLikeClasses", "std::basic_string"))) {
+}
+
+void FasterStringFindCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "StringLikeClasses",
+                llvm::join(StringLikeClasses.begin(), StringLikeClasses.end(),
+                           StringLikeClassesDelimiter));
+}
+
+void FasterStringFindCheck::registerMatchers(MatchFinder *Finder) {
+  if (!getLangOpts().CPlusPlus)
+    return;
+
+  const auto SingleChar =
+      expr(ignoringParenCasts(stringLiteral(lengthIsOne()).bind("literal")));
+
+  const auto StringFindFunctions =
+      anyOf(hasName("find"), hasName("rfind"), hasName("find_first_of"),
+            hasName("find_first_not_of"), hasName("find_last_of"),
+            hasName("find_last_not_of"));
+
+  llvm::Optional<ast_matchers::internal::Matcher<NamedDecl>> IsStringClass;
+
+  for (const auto &ClassName : StringLikeClasses) {
+    const auto HasName = hasName(ClassName);
+    IsStringClass = IsStringClass ? anyOf(*IsStringClass, HasName) : HasName;
+  }
+
+  if (IsStringClass) {
+    Finder->addMatcher(
+        cxxMemberCallExpr(
+            callee(functionDecl(StringFindFunctions).bind("func")),
+            anyOf(argumentCountIs(1), argumentCountIs(2)),
+            hasArgument(0, SingleChar),
+            on(expr(hasType(recordDecl(*IsStringClass)),
+                    unless(hasSubstitutedType())))),
+        this);
+  }
+}
+
+void FasterStringFindCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Literal = Result.Nodes.getNodeAs<StringLiteral>("literal");
+  const auto *FindFunc = Result.Nodes.getNodeAs<FunctionDecl>("func");
+
+  auto Replacement = MakeCharacterLiteral(Literal);
+  if (!Replacement)
+    return;
+
+  diag(Literal->getLocStart(), "%0 called with a string literal consisting of "
+                               "a single character; consider using the more "
+                               "effective overload accepting a character")
+      << FindFunc->getName()
+      << FixItHint::CreateReplacement(
+             CharSourceRange::getTokenRange(Literal->getLocStart(),
+                                            Literal->getLocEnd()),
+             *Replacement);
+}
+
+} // namespace performance
+} // namespace tidy
+} // namespace clang

clang-tools-extra/clang-tidy/performance/FasterStringFindCheck.h

@@ -0,0 +1,43 @@
+//===--- FasterStringFindCheck.h - clang-tidy--------------------*- C++ -*-===//
+//
+//                     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_FASTER_STRING_FIND_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_FASTER_STRING_FIND_H
+
+#include "../ClangTidy.h"
+
+#include <string>
+#include <vector>
+
+namespace clang {
+namespace tidy {
+namespace performance {
+
+/// Optimize calls to std::string::find() and friends when the needle passed is
+/// a single character string literal.
+/// The character literal overload is more efficient.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/performance-faster-string-find.html
+class FasterStringFindCheck : public ClangTidyCheck {
+public:
+  FasterStringFindCheck(StringRef Name, ClangTidyContext *Context);
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+
+private:
+  const std::vector<std::string> StringLikeClasses;
+};
+
+} // namespace performance
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_PERFORMANCE_FASTER_STRING_FIND_H

clang-tools-extra/clang-tidy/performance/PerformanceTidyModule.cpp

@@ -11,6 +11,7 @@
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
 
+#include "FasterStringFindCheck.h"
 #include "ForRangeCopyCheck.h"
 #include "ImplicitCastInLoopCheck.h"
 #include "UnnecessaryCopyInitialization.h"
@@ -22,6 +23,8 @@ namespace performance {
 class PerformanceModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+    CheckFactories.registerCheck<FasterStringFindCheck>(
+        "performance-faster-string-find");
     CheckFactories.registerCheck<ForRangeCopyCheck>(
         "performance-for-range-copy");
     CheckFactories.registerCheck<ImplicitCastInLoopCheck>(

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -80,6 +80,7 @@ Clang-Tidy Checks
    modernize-use-default
    modernize-use-nullptr
    modernize-use-override
+   performance-faster-string-find
    performance-for-range-copy
    performance-implicit-cast-in-loop
    readability-braces-around-statements

clang-tools-extra/docs/clang-tidy/checks/performance-faster-string-find.rst

@@ -0,0 +1,22 @@
+.. title:: clang-tidy - performance-faster-string-find
+
+performance-faster-string-find
+==============================
+
+Optimize calls to std::string::find() and friends when the needle passed is
+a single character string literal.
+The character literal overload is more efficient.
+
+By default only `std::basic_string` is considered. This list can be modified by
+passing a `;` separated list of class names using the `StringLikeClasses`
+option. The methods to consired are fixed, though.
+
+Examples:
+
+.. code-block:: c++
+
+  str.find("A");
+
+  // becomes
+
+  str.find('A');

clang-tools-extra/test/clang-tidy/performance-faster-string-find.cpp

@@ -0,0 +1,110 @@
+// RUN: %check_clang_tidy %s performance-faster-string-find %t -- \
+// RUN:   -config="{CheckOptions: \
+// RUN:             [{key: performance-faster-string-find.StringLikeClasses, \
+// RUN:               value: 'std::basic_string; ::llvm::StringRef;'}]}" --
+
+namespace std {
+template <typename Char>
+struct basic_string {
+  int find(const Char *, int = 0) const;
+  int find(const Char *, int, int) const;
+  int rfind(const Char *) const;
+  int find_first_of(const Char *) const;
+  int find_first_not_of(const Char *) const;
+  int find_last_of(const Char *) const;
+  int find_last_not_of(const Char *) const;
+};
+
+typedef basic_string<char> string;
+typedef basic_string<wchar_t> wstring;
+}  // namespace std
+
+namespace llvm {
+struct StringRef {
+  int find(const char *) const;
+};
+}  // namespace llvm
+
+struct NotStringRef {
+  int find(const char *);
+};
+
+void StringFind() {
+  std::string Str;
+
+  Str.find("a");
+  // CHECK-MESSAGES: [[@LINE-1]]:12: warning: find called with a string literal consisting of a single character; consider using the more effective overload accepting a character [performance-faster-string-find]
+  // CHECK-FIXES: Str.find('a');
+
+  // Works with the pos argument.
+  Str.find("a", 1);
+  // CHECK-MESSAGES: [[@LINE-1]]:12: warning: find called with a string literal
+  // CHECK-FIXES: Str.find('a', 1);
+
+  // Doens't work with strings smaller or larger than 1 char.
+  Str.find("");
+  Str.find("ab");
+
+  // Doesn't do anything with the 3 argument overload.
+  Str.find("a", 1, 1);
+
+  // Other methods that can also be replaced
+  Str.rfind("a");
+  // CHECK-MESSAGES: [[@LINE-1]]:13: warning: rfind called with a string literal
+  // CHECK-FIXES: Str.rfind('a');
+  Str.find_first_of("a");
+  // CHECK-MESSAGES: [[@LINE-1]]:21: warning: find_first_of called with a string
+  // CHECK-FIXES: Str.find_first_of('a');
+  Str.find_first_not_of("a");
+  // CHECK-MESSAGES: [[@LINE-1]]:25: warning: find_first_not_of called with a
+  // CHECK-FIXES: Str.find_first_not_of('a');
+  Str.find_last_of("a");
+  // CHECK-MESSAGES: [[@LINE-1]]:20: warning: find_last_of called with a string
+  // CHECK-FIXES: Str.find_last_of('a');
+  Str.find_last_not_of("a");
+  // CHECK-MESSAGES: [[@LINE-1]]:24: warning: find_last_not_of called with a
+  // CHECK-FIXES: Str.find_last_not_of('a');
+
+  // std::wstring should work.
+  std::wstring WStr;
+  WStr.find(L"n");
+  // CHECK-MESSAGES: [[@LINE-1]]:13: warning: find called with a string literal
+  // CHECK-FIXES: Str.find(L'n');
+  // Even with unicode that fits in one wide char.
+  WStr.find(L"\x3A9");
+  // CHECK-MESSAGES: [[@LINE-1]]:13: warning: find called with a string literal
+  // CHECK-FIXES: Str.find(L'\x3A9');
+
+  // Also with other types, but only if it was specified in the options.
+  llvm::StringRef sr;
+  sr.find("x");
+  // CHECK-MESSAGES: [[@LINE-1]]:11: warning: find called with a string literal
+  // CHECK-FIXES: sr.find('x');
+  NotStringRef nsr;
+  nsr.find("x");
+}
+
+
+template <typename T>
+int FindTemplateDependant(T value) {
+  return value.find("A");
+}
+template <typename T>
+int FindTemplateNotDependant(T pos) {
+  return std::string().find("A", pos);
+  // CHECK-MESSAGES: [[@LINE-1]]:29: warning: find called with a string literal
+  // CHECK-FIXES: return std::string().find('A', pos);
+}
+
+int FindStr() {
+  return FindTemplateDependant(std::string()) + FindTemplateNotDependant(1);
+}
+
+#define STR_MACRO(str) str.find("A")
+#define POS_MACRO(pos) std::string().find("A",pos)
+
+int Macros() {
+  return STR_MACRO(std::string()) + POS_MACRO(1);
+  // CHECK-MESSAGES: [[@LINE-1]]:10: warning: find called with a string literal
+  // CHECK-MESSAGES: [[@LINE-2]]:37: warning: find called with a string literal
+}