[clang] [clang-tools-extra] [llvm] Add clang-tidy check to suggest replacement of conditional statement with std::min/std::max (PR #77816)

[Julian Schmidt via cfe-commits]

================
@@ -0,0 +1,188 @@
+//===--- 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 "../utils/ASTUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Preprocessor.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+namespace {
+
+// Ignore if statements that are inside macros.
+AST_MATCHER(IfStmt, isIfInMacro) {
+  return Node.getIfLoc().isMacroID() || Node.getEndLoc().isMacroID();
+}
+
+} // namespace
+
+static const llvm::StringRef AlgorithmHeader("<algorithm>");
+
+static bool minCondition(const BinaryOperator::Opcode Op, const Expr *CondLhs,
+                         const Expr *CondRhs, const Expr *AssignLhs,
+                         const Expr *AssignRhs, const ASTContext &Context) {
+  if ((Op == BO_LT || Op == BO_LE) &&
+      (tidy::utils::areStatementsIdentical(CondLhs, AssignRhs, Context) &&
+       tidy::utils::areStatementsIdentical(CondRhs, AssignLhs, Context)))
+    return true;
+
+  if ((Op == BO_GT || Op == BO_GE) &&
+      (tidy::utils::areStatementsIdentical(CondLhs, AssignLhs, Context) &&
+       tidy::utils::areStatementsIdentical(CondRhs, AssignRhs, Context)))
+    return true;
+
+  return false;
+}
+
+static bool maxCondition(const BinaryOperator::Opcode Op, const Expr *CondLhs,
+                         const Expr *CondRhs, const Expr *AssignLhs,
+                         const Expr *AssignRhs, const ASTContext &Context) {
+  if ((Op == BO_LT || Op == BO_LE) &&
+      (tidy::utils::areStatementsIdentical(CondLhs, AssignLhs, Context) &&
+       tidy::utils::areStatementsIdentical(CondRhs, AssignRhs, Context)))
+    return true;
+
+  if ((Op == BO_GT || Op == BO_GE) &&
+      (tidy::utils::areStatementsIdentical(CondLhs, AssignRhs, Context) &&
+       tidy::utils::areStatementsIdentical(CondRhs, AssignLhs, Context)))
+    return true;
+
+  return false;
+}
+
+QualType getNonTemplateAlias(QualType QT) {
+  while (true) {
+    // cast to a TypedefType
+    if (const TypedefType *TT = dyn_cast<TypedefType>(QT)) {
+      // check if the typedef is a template and if it is dependent
+      if (!TT->getDecl()->getDescribedTemplate() &&
+          !TT->getDecl()->getDeclContext()->isDependentContext())
+        return QT;
+      QT = TT->getDecl()->getUnderlyingType();
+    }
+    // cast to elaborated type
+    else if (const ElaboratedType *ET = dyn_cast<ElaboratedType>(QT)) {
+      QT = ET->getNamedType();
+    } else {
+      break;
+    }
+  }
+  return QT;
+}
+
+static std::string createReplacement(const Expr *CondLhs, const Expr *CondRhs,
+                                     const Expr *AssignLhs,
+                                     const SourceManager &Source,
+                                     const LangOptions &LO,
+                                     StringRef FunctionName,
+                                     const BinaryOperator *BO) {
+  const llvm::StringRef CondLhsStr = Lexer::getSourceText(
+      Source.getExpansionRange(CondLhs->getSourceRange()), Source, LO);
+  const llvm::StringRef CondRhsStr = Lexer::getSourceText(
+      Source.getExpansionRange(CondRhs->getSourceRange()), Source, LO);
+  const llvm::StringRef AssignLhsStr = Lexer::getSourceText(
+      Source.getExpansionRange(AssignLhs->getSourceRange()), Source, LO);
+
+  clang::QualType GlobalImplicitCastType;
+  clang::QualType LhsType = CondLhs->getType()
+                                .getCanonicalType()
+                                .getNonReferenceType()
+                                .getUnqualifiedType();
+  clang::QualType RhsType = CondRhs->getType()
+                                .getCanonicalType()
+                                .getNonReferenceType()
+                                .getUnqualifiedType();
+  if (LhsType != RhsType) {
+    GlobalImplicitCastType = getNonTemplateAlias(BO->getLHS()->getType());
+  }
+
+  return (AssignLhsStr + " = " + FunctionName +
+          (!GlobalImplicitCastType.isNull()
+               ? "<" + GlobalImplicitCastType.getAsString() + ">("
+               : "(") +
+          CondLhsStr + ", " + CondRhsStr + ");")
+      .str();
+}
+
+UseStdMinMaxCheck::UseStdMinMaxCheck(StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IncludeInserter(Options.getLocalOrGlobal("IncludeStyle",
+                                               utils::IncludeSorter::IS_LLVM),
+                      areDiagsSelfContained()) {}
+
+void UseStdMinMaxCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IncludeStyle", IncludeInserter.getStyle());
+}
+
+void UseStdMinMaxCheck::registerMatchers(MatchFinder *Finder) {
+  auto AssignOperator =
+      binaryOperator(hasOperatorName("="),
+                     hasLHS(expr(unless(isTypeDependent())).bind("AssignLhs")),
+                     hasRHS(expr(unless(isTypeDependent())).bind("AssignRhs")));
+  auto BinaryOperator =
+      binaryOperator(hasAnyOperatorName("<", ">", "<=", ">="),
+                     hasLHS(expr(unless(isTypeDependent())).bind("CondLhs")),
+                     hasRHS(expr(unless(isTypeDependent())).bind("CondRhs")))
+          .bind("binaryOp");
+  Finder->addMatcher(
+      ifStmt(stmt().bind("if"), unless(isIfInMacro()),
+             unless(hasElse(stmt())), // Ensure `if` has no `else`
+             hasCondition(BinaryOperator),
+             hasThen(
+                 anyOf(stmt(AssignOperator),
+                       compoundStmt(statementCountIs(1), has(AssignOperator)))),
+             hasParent(stmt(unless(ifStmt(hasElse(
+                 equalsBoundNode("if"))))))), // Ensure `if` has no `else if`
+      this);
+}
+
+void UseStdMinMaxCheck::registerPPCallbacks(const SourceManager &SM,
+                                            Preprocessor *PP,
+                                            Preprocessor *ModuleExpanderPP) {
+  IncludeInserter.registerPreprocessor(PP);
+}
+
+void UseStdMinMaxCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *If = Result.Nodes.getNodeAs<IfStmt>("if");
+  const auto &LO = (*Result.Context).getLangOpts();
+  const auto *CondLhs = Result.Nodes.getNodeAs<Expr>("CondLhs");
+  const auto *CondRhs = Result.Nodes.getNodeAs<Expr>("CondRhs");
+  const auto *AssignLhs = Result.Nodes.getNodeAs<Expr>("AssignLhs");
+  const auto *AssignRhs = Result.Nodes.getNodeAs<Expr>("AssignRhs");
+  const auto *BinaryOp = Result.Nodes.getNodeAs<BinaryOperator>("binaryOp");
+  const auto BinaryOpcode = BinaryOp->getOpcode();
+  const SourceLocation IfLocation = If->getIfLoc();
+  const SourceLocation ThenLocation = If->getEndLoc();
+
+  auto ReplaceAndDiagnose = [&](const llvm::StringRef FunctionName) {
+    const SourceManager &Source = (*Result.Context).getSourceManager();
----------------
5chmidti wrote:

Please remove the not needed parentheses

https://github.com/llvm/llvm-project/pull/77816