[clang-tools-extra] [clang-tidy] add check to suggest replacement of nested std::min or std::max with initializer lists (PR #85572)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-tidy

Author: Sopy (sopyb)

<details>
<summary>Changes</summary>

closes #<!-- -->25340

Identifies cases where `std::min` or `std::max` is used to find the minimum or maximum value among more than two items through repeated calls. The check replaces these calls with a single call to `std::min` or `std::max` that uses an initializer list. This makes the code slightly more efficient.

---
Full diff: https://github.com/llvm/llvm-project/pull/85572.diff


6 Files Affected:

- (modified) clang-tools-extra/clang-tidy/modernize/CMakeLists.txt (+1) 
- (added) clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.cpp (+138) 
- (added) clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.h (+58) 
- (modified) clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp (+3) 
- (modified) clang-tools-extra/docs/ReleaseNotes.rst (+6) 
- (modified) clang-tools-extra/docs/clang-tidy/checks/list.rst (+2) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/modernize/CMakeLists.txt b/clang-tools-extra/clang-tidy/modernize/CMakeLists.txt
index 6852db6c2ee311..8005d6e91c060c 100644
--- a/clang-tools-extra/clang-tidy/modernize/CMakeLists.txt
+++ b/clang-tools-extra/clang-tidy/modernize/CMakeLists.txt
@@ -16,6 +16,7 @@ add_clang_library(clangTidyModernizeModule
   MakeSharedCheck.cpp
   MakeSmartPtrCheck.cpp
   MakeUniqueCheck.cpp
+  MinMaxUseInitializerListCheck.cpp
   ModernizeTidyModule.cpp
   PassByValueCheck.cpp
   RawStringLiteralCheck.cpp
diff --git a/clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.cpp b/clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.cpp
new file mode 100644
index 00000000000000..b7dc3ff436f6e3
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.cpp
@@ -0,0 +1,138 @@
+//===--- MinMaxUseInitializerListCheck.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 "MinMaxUseInitializerListCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+
+MinMaxUseInitializerListCheck::MinMaxUseInitializerListCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      Inserter(Options.getLocalOrGlobal("IncludeStyle",
+                                        utils::IncludeSorter::IS_LLVM),
+               areDiagsSelfContained()) {}
+
+void MinMaxUseInitializerListCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IncludeStyle", Inserter.getStyle());
+}
+
+void MinMaxUseInitializerListCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      callExpr(
+          callee(functionDecl(hasName("::std::max"))),
+          hasAnyArgument(callExpr(callee(functionDecl(hasName("::std::max"))))),
+          unless(
+              hasParent(callExpr(callee(functionDecl(hasName("::std::max")))))))
+          .bind("maxCall"),
+      this);
+
+  Finder->addMatcher(
+      callExpr(
+          callee(functionDecl(hasName("::std::min"))),
+          hasAnyArgument(callExpr(callee(functionDecl(hasName("::std::min"))))),
+          unless(
+              hasParent(callExpr(callee(functionDecl(hasName("::std::min")))))))
+          .bind("minCall"),
+      this);
+}
+
+void MinMaxUseInitializerListCheck::registerPPCallbacks(
+    const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
+  Inserter.registerPreprocessor(PP);
+}
+
+void MinMaxUseInitializerListCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *MaxCall = Result.Nodes.getNodeAs<CallExpr>("maxCall");
+  const auto *MinCall = Result.Nodes.getNodeAs<CallExpr>("minCall");
+
+  const CallExpr *TopCall = MaxCall ? MaxCall : MinCall;
+  if (!TopCall) {
+    return;
+  }
+  const QualType ResultType =
+      TopCall->getDirectCallee()->getReturnType().getNonReferenceType();
+
+  const Expr *FirstArg = nullptr;
+  const Expr *LastArg = nullptr;
+  std::vector<const Expr *> Args;
+  findArgs(TopCall, &FirstArg, &LastArg, Args);
+
+  if (!FirstArg || !LastArg || Args.size() <= 2) {
+    return;
+  }
+
+  std::string ReplacementText = "{";
+  for (const Expr *Arg : Args) {
+    QualType ArgType = Arg->getType();
+    bool CastNeeded =
+        ArgType.getCanonicalType() != ResultType.getCanonicalType();
+
+    if (CastNeeded)
+      ReplacementText += "static_cast<" + ResultType.getAsString() + ">(";
+
+    ReplacementText += Lexer::getSourceText(
+        CharSourceRange::getTokenRange(Arg->getSourceRange()),
+        *Result.SourceManager, Result.Context->getLangOpts());
+
+    if (CastNeeded)
+      ReplacementText += ")";
+    ReplacementText += ", ";
+  }
+  ReplacementText = ReplacementText.substr(0, ReplacementText.size() - 2) + "}";
+
+  diag(TopCall->getBeginLoc(),
+       "do not use nested std::%0 calls, use %1 instead")
+      << TopCall->getDirectCallee()->getName() << ReplacementText
+      << FixItHint::CreateReplacement(
+             CharSourceRange::getTokenRange(
+                 FirstArg->getBeginLoc(),
+                 Lexer::getLocForEndOfToken(TopCall->getEndLoc(), 0,
+                                            Result.Context->getSourceManager(),
+                                            Result.Context->getLangOpts())
+                     .getLocWithOffset(-2)),
+             ReplacementText)
+      << Inserter.createMainFileIncludeInsertion("<algorithm>");
+}
+
+void MinMaxUseInitializerListCheck::findArgs(const CallExpr *Call,
+                                             const Expr **First,
+                                             const Expr **Last,
+                                             std::vector<const Expr *> &Args) {
+  if (!Call) {
+    return;
+  }
+
+  const FunctionDecl *Callee = Call->getDirectCallee();
+  if (!Callee) {
+    return;
+  }
+
+  for (const Expr *Arg : Call->arguments()) {
+    if (!*First)
+      *First = Arg;
+
+    const CallExpr *InnerCall = dyn_cast<CallExpr>(Arg);
+    if (InnerCall && InnerCall->getDirectCallee() &&
+        InnerCall->getDirectCallee()->getNameAsString() ==
+            Call->getDirectCallee()->getNameAsString()) {
+      findArgs(InnerCall, First, Last, Args);
+    } else
+      Args.push_back(Arg);
+
+    *Last = Arg;
+  }
+}
+
+} // namespace clang::tidy::modernize
diff --git a/clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.h b/clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.h
new file mode 100644
index 00000000000000..dc111d4ce7800e
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/modernize/MinMaxUseInitializerListCheck.h
@@ -0,0 +1,58 @@
+//===--- MinMaxUseInitializerListCheck.h - clang-tidy -----------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MINMAXUSEINITIALIZERLISTCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MINMAXUSEINITIALIZERLISTCHECK_H
+
+#include "../ClangTidyCheck.h"
+#include "../utils/IncludeInserter.h"
+
+namespace clang::tidy::modernize {
+
+/// Transforms the repeated calls to `std::min` and `std::max` into a single
+/// call using initializer lists.
+///
+/// It identifies cases where `std::min` or `std::max` is used to find the
+/// minimum or maximum value among more than two items through repeated calls.
+/// The check replaces these calls with a single call to `std::min` or
+/// `std::max` that uses an initializer list. This makes the code slightly more
+/// efficient.
+/// \n\n
+/// For example:
+///
+/// \code
+///   int a = std::max(std::max(i, j), k);
+/// \endcode
+///
+/// This code is transformed to:
+///
+/// \code
+///   int a = std::max({i, j, k});
+/// \endcode
+class MinMaxUseInitializerListCheck : public ClangTidyCheck {
+public:
+  MinMaxUseInitializerListCheck(StringRef Name, ClangTidyContext *Context);
+
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    return LangOpts.CPlusPlus11;
+  }
+  void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void registerPPCallbacks(const SourceManager &SM, Preprocessor *PP,
+                           Preprocessor *ModuleExpanderPP) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+
+private:
+  utils::IncludeInserter Inserter;
+  void findArgs(const CallExpr *call, const Expr **first, const Expr **last,
+                std::vector<const Expr *> &args);
+};
+
+} // namespace clang::tidy::modernize
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_MINMAXUSEINITIALIZERLISTCHECK_H
diff --git a/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp b/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
index e96cf274f58cfe..776558433c5baa 100644
--- a/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp
@@ -18,6 +18,7 @@
 #include "MacroToEnumCheck.h"
 #include "MakeSharedCheck.h"
 #include "MakeUniqueCheck.h"
+#include "MinMaxUseInitializerListCheck.h"
 #include "PassByValueCheck.h"
 #include "RawStringLiteralCheck.h"
 #include "RedundantVoidArgCheck.h"
@@ -68,6 +69,8 @@ class ModernizeModule : public ClangTidyModule {
     CheckFactories.registerCheck<MacroToEnumCheck>("modernize-macro-to-enum");
     CheckFactories.registerCheck<MakeSharedCheck>("modernize-make-shared");
     CheckFactories.registerCheck<MakeUniqueCheck>("modernize-make-unique");
+    CheckFactories.registerCheck<MinMaxUseInitializerListCheck>(
+        "modernize-min-max-use-initializer-list");
     CheckFactories.registerCheck<PassByValueCheck>("modernize-pass-by-value");
     CheckFactories.registerCheck<UseDesignatedInitializersCheck>(
         "modernize-use-designated-initializers");
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 44680f79de6f54..098a924a3b1527 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -110,6 +110,12 @@ New checks
   Detects error-prone Curiously Recurring Template Pattern usage, when the CRTP
   can be constructed outside itself and the derived class.
 
+- New :doc:`modernize-min-max-use-initializer-list
+  <clang-tidy/checks/modernize/min-max-use-initializer-list>` check.
+
+  Replaces chained ``std::min`` and ``std::max`` calls that can be written as
+  initializer lists.
+
 - New :doc:`modernize-use-designated-initializers
   <clang-tidy/checks/modernize/use-designated-initializers>` check.
 
diff --git a/clang-tools-extra/docs/clang-tidy/checks/list.rst b/clang-tools-extra/docs/clang-tidy/checks/list.rst
index d03e7af688f007..029c339037880e 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/list.rst
@@ -274,6 +274,7 @@ Clang-Tidy Checks
    :doc:`modernize-macro-to-enum <modernize/macro-to-enum>`, "Yes"
    :doc:`modernize-make-shared <modernize/make-shared>`, "Yes"
    :doc:`modernize-make-unique <modernize/make-unique>`, "Yes"
+   :doc:`modernize-min-max-use-initializer-list <modernize/min-max-use-initializer-list>`, "Yes"
    :doc:`modernize-pass-by-value <modernize/pass-by-value>`, "Yes"
    :doc:`modernize-raw-string-literal <modernize/raw-string-literal>`, "Yes"
    :doc:`modernize-redundant-void-arg <modernize/redundant-void-arg>`, "Yes"
@@ -324,6 +325,7 @@ Clang-Tidy Checks
    :doc:`performance-inefficient-algorithm <performance/inefficient-algorithm>`, "Yes"
    :doc:`performance-inefficient-string-concatenation <performance/inefficient-string-concatenation>`,
    :doc:`performance-inefficient-vector-operation <performance/inefficient-vector-operation>`, "Yes"
+   :doc:`performance-modernize-min-max-use-initializer-list <performance/modernize-min-max-use-initializer-list>`,
    :doc:`performance-move-const-arg <performance/move-const-arg>`, "Yes"
    :doc:`performance-move-constructor-init <performance/move-constructor-init>`,
    :doc:`performance-no-automatic-move <performance/no-automatic-move>`,

``````````

</details>


https://github.com/llvm/llvm-project/pull/85572