Add clang-tidy check to suggest replacement of conditional statement with std::min/std::max

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

@@ -52,6 +52,7 @@ add_clang_library(clangTidyReadabilityModule
   UniqueptrDeleteReleaseCheck.cpp
   UppercaseLiteralSuffixCheck.cpp
   UseAnyOfAllOfCheck.cpp
+  UseStdMinMaxCheck.cpp
 
   LINK_LIBS
   clangTidy

clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp

@@ -55,13 +55,16 @@
 #include "UniqueptrDeleteReleaseCheck.h"
 #include "UppercaseLiteralSuffixCheck.h"
 #include "UseAnyOfAllOfCheck.h"
+#include "UseStdMinMaxCheck.h"
 
 namespace clang::tidy {
 namespace readability {
 
 class ReadabilityModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+    CheckFactories.registerCheck<UseStdMinMaxCheck>(
+        "readability-use-std-min-max");
     CheckFactories.registerCheck<AvoidConstParamsInDecls>(
         "readability-avoid-const-params-in-decls");
     CheckFactories.registerCheck<AvoidReturnWithVoidValueCheck>(

clang-tools-extra/clang-tidy/readability/UseStdMinMaxCheck.cpp

@@ -0,0 +1,97 @@
+//===--- UseStdMinMaxCheck.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 "UseStdMinMaxCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Preprocessor.h"
+#include <optional>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+void UseStdMinMaxCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      ifStmt(
+          has(binaryOperator(
+              anyOf(hasOperatorName("<"), hasOperatorName(">"),
+                    hasOperatorName("<="), hasOperatorName(">=")),
+              hasLHS(expr().bind("lhsVar1")), hasRHS(expr().bind("rhsVar1")))),
+          hasThen(stmt(binaryOperator(hasOperatorName("="),
+                                      hasLHS(expr().bind("lhsVar2")),
+                                      hasRHS(expr().bind("rhsVar2"))))))
+          .bind("ifStmt"),
+      this);
+}
+
+void UseStdMinMaxCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *lhsVar1 = Result.Nodes.getNodeAs<Expr>("lhsVar1");
+  const auto *rhsVar1 = Result.Nodes.getNodeAs<Expr>("rhsVar1");
+  const auto *lhsVar2 = Result.Nodes.getNodeAs<Expr>("lhsVar2");
+  const auto *rhsVar2 = Result.Nodes.getNodeAs<Expr>("rhsVar2");
+  const auto *ifStmt = Result.Nodes.getNodeAs<IfStmt>("ifStmt");
+  auto &Context = *Result.Context;
+
+  if (!lhsVar1 || !rhsVar1 || !lhsVar2 || !rhsVar2 || !ifStmt)
+    return;
+
+  const BinaryOperator *binaryOp = dyn_cast<BinaryOperator>(ifStmt->getCond());
+  if (!binaryOp)
+    return;
+
+  SourceLocation ifLocation = ifStmt->getIfLoc();
+  SourceLocation thenLocation = ifStmt->getEndLoc();
+  auto lhsVar1Str = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(lhsVar1->getSourceRange()),
+      Context.getSourceManager(), Context.getLangOpts());
+
+  auto lhsVar2Str = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(lhsVar2->getSourceRange()),
+      Context.getSourceManager(), Context.getLangOpts());
+
+  auto rhsVar1Str = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(rhsVar1->getSourceRange()),
+      Context.getSourceManager(), Context.getLangOpts());
+
+  auto rhsVar2Str = Lexer::getSourceText(
+      CharSourceRange::getTokenRange(rhsVar2->getSourceRange()),
+      Context.getSourceManager(), Context.getLangOpts());
+
+  if (binaryOp->getOpcode() == BO_LT) {
+    if (lhsVar1Str == lhsVar2Str && rhsVar1Str == rhsVar2Str) {
+      diag(ifStmt->getIfLoc(), "use `std::max` instead of `<`")
+          << FixItHint::CreateReplacement(SourceRange(ifLocation, thenLocation),
+                                          lhsVar2Str.str() + " = std::max(" +
+                                              lhsVar1Str.str() + ", " +
+                                              rhsVar1Str.str() + ")");
+    } else if (lhsVar1Str == rhsVar2Str && rhsVar1Str == lhsVar2Str) {
+      diag(ifStmt->getIfLoc(), "use `std::min` instead of `<`")
+          << FixItHint::CreateReplacement(SourceRange(ifLocation, thenLocation),
+                                          lhsVar2Str.str() + " = std::min(" +
+                                              lhsVar1Str.str() + ", " +
+                                              rhsVar1Str.str() + ")");
+    }
+  } else if (binaryOp->getOpcode() == BO_GT) {
+    if (lhsVar1Str == lhsVar2Str && rhsVar1Str == rhsVar2Str) {
+      diag(ifStmt->getIfLoc(), "use `std::min` instead of `>`")
+          << FixItHint::CreateReplacement(SourceRange(ifLocation, thenLocation),
+                                          lhsVar2Str.str() + " = std::min(" +
+                                              lhsVar1Str.str() + ", " +
+                                              rhsVar1Str.str() + ")");
+    } else if (lhsVar1Str == rhsVar2Str && rhsVar1Str == lhsVar2Str) {
+      diag(ifStmt->getIfLoc(), "use `std::max` instead of `>`")
+          << FixItHint::CreateReplacement(SourceRange(ifLocation, thenLocation),
+                                          lhsVar2Str.str() + " = std::max(" +
+                                              lhsVar1Str.str() + ", " +
+                                              rhsVar1Str.str() + ")");
+    }
+  }
+}
+
+} // namespace clang::tidy::readability

clang-tools-extra/clang-tidy/readability/UseStdMinMaxCheck.h

@@ -0,0 +1,38 @@
+//===--- UseStdMinMaxCheck.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_READABILITY_USESTDMINMAXCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_USESTDMINMAXCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::readability {
+
+/// replaces certain conditional statements with equivalent ``std::min`` or
+/// ``std::max`` expressions, improving readability and promoting the use of
+/// standard library functions.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/readability/UseStdMinMax.html
+class UseStdMinMaxCheck : public ClangTidyCheck {
+public:
+  UseStdMinMaxCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+    return LangOpts.CPlusPlus;
+  }
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  std::optional<TraversalKind> getCheckTraversalKind() const override {
+    return TK_IgnoreUnlessSpelledInSource;
+  }
+};
+
+} // namespace clang::tidy::readability
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_USESTDMINMAXCHECK_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -224,6 +224,13 @@ New checks
   Recommends the smallest possible underlying type for an ``enum`` or ``enum``
   class based on the range of its enumerators.
 
+- New :doc:`readability-use-std-min-max
+  <clang-tidy/checks/readability/use-std-min-max>` check.
+
+  Replaces certain conditional statements with equivalent ``std::min`` or
+  ``std::max`` expressions, improving readability and promoting the use of
+  standard library functions.
+
 - New :doc:`readability-reference-to-constructed-temporary
   <clang-tidy/checks/readability/reference-to-constructed-temporary>` check.
 

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

@@ -336,6 +336,7 @@ Clang-Tidy Checks
    :doc:`portability-restrict-system-includes <portability/restrict-system-includes>`, "Yes"
    :doc:`portability-simd-intrinsics <portability/simd-intrinsics>`,
    :doc:`portability-std-allocator-const <portability/std-allocator-const>`,
+   :doc:`readability-use-std-min-max <readability/use-std-min-max>`, "Yes"
    :doc:`readability-avoid-const-params-in-decls <readability/avoid-const-params-in-decls>`, "Yes"
    :doc:`readability-avoid-return-with-void-value <readability/avoid-return-with-void-value>`,
    :doc:`readability-avoid-unconditional-preprocessor-if <readability/avoid-unconditional-preprocessor-if>`,

clang-tools-extra/docs/clang-tidy/checks/readability/use-std-min-max.rst

@@ -0,0 +1,33 @@
+.. title:: clang-tidy - readability-use-std-min-max
+
+readability-use-std-min-max
+===========================
+
+Replaces certain conditional statements with equivalent ``std::min`` or ``std::max`` expressions, 
+improving readability and promoting the use of standard library functions.
+Note: While this transformation improves code clarity, it may not be
+suitable for performance-critical code. Using ``std::min`` or ``std::max`` can
+introduce additional stores, potentially impacting performance compared to
+the original if statement that only assigns when the value needs to change.
+
+Examples:
+
+Before:
+
+.. code-block:: c++
+
+  void foo(){
+    int a,b;
+    if(a < b)
+        a = b;
+    }
+
+
+After:
+
+.. code-block:: c++
+
+  void foo(){
+    a = std::max(a, b);
+
+  }

clang-tools-extra/test/clang-tidy/checkers/readability/use-std-min-max.cpp

@@ -0,0 +1,35 @@
+// RUN: %check_clang_tidy %s readability-use-std-min-max %t
+
+void foo() {
+  int value1,value2,value3;
+  short value4;
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  if (value1 < value2)
+    value1 = value2; // CHECK-FIXES: value1 = std::max(value1, value2);
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::min` instead of `<` [readability-use-std-min-max]
+  if (value1 < value2)
+    value2 = value1; // CHECK-FIXES: value2 = std::min(value1, value2);
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::min` instead of `>` [readability-use-std-min-max]
+  if (value2 > value1)
+    value2 = value1; // CHECK-FIXES: value2 = std::min(value2, value1);
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::max` instead of `>` [readability-use-std-min-max
+  if (value2 > value1)
+    value1 = value2; // CHECK-FIXES: value1 = std::max(value2, value1);
+
+  // No suggestion needed here
+  if (value1 == value2)
+    value1 = value2;
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  if(value1<value4)
+    value1=value4; // CHECK-FIXES: value1 = std::max(value1, value4);
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::min` instead of `<` [readability-use-std-min-max]
+  if(value1+value2<value3)
+    value3 = value1+value2; // CHECK-FIXES: value3 = std::min(value1+value2, value3);
+
+}