[clang-tools-extra] [clang-tidy] Add check performance-lost-std-move (PR #139525)

[via cfe-commits]

================
@@ -0,0 +1,180 @@
+//===--- LostStdMoveCheck.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 "LostStdMoveCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::performance {
+
+template <typename Node>
+void extractNodesByIdTo(ArrayRef<BoundNodes> Matches, StringRef ID,
+                        llvm::SmallPtrSet<const Node*, 16>& Nodes) {
+  for (const BoundNodes& Match : Matches)
+    Nodes.insert(Match.getNodeAs<Node>(ID));
+}
+
+static llvm::SmallPtrSet<const DeclRefExpr*, 16> allDeclRefExprsHonourLambda(
+    const VarDecl& VarDecl, const Decl& Decl, ASTContext& Context) {
+  auto Matches = match(
+      decl(forEachDescendant(
+          declRefExpr(to(varDecl(equalsNode(&VarDecl))),
+
+                      unless(hasAncestor(lambdaExpr(hasAnyCapture(lambdaCapture(
+                          capturesVar(varDecl(equalsNode(&VarDecl))))))))
+
+                          )
+              .bind("declRef"))),
+      Decl, Context);
+  llvm::SmallPtrSet<const DeclRefExpr*, 16> DeclRefs;
+  extractNodesByIdTo(Matches, "declRef", DeclRefs);
+  return DeclRefs;
+}
+
+static const Expr* getLastVarUsage(const VarDecl& Var, const Decl& Func,
+                                   ASTContext& Context) {
+  auto Exprs = allDeclRefExprsHonourLambda(Var, Func, Context);
+
+  const Expr* LastExpr = nullptr;
+  for (const clang::DeclRefExpr* Expr : Exprs) {
+    if (!LastExpr) LastExpr = Expr;
+
+    if (LastExpr->getBeginLoc() < Expr->getBeginLoc()) LastExpr = Expr;
+  }
+
+  return LastExpr;
+}
+
+AST_MATCHER(CXXRecordDecl, hasTrivialMoveConstructor) {
+  return Node.hasDefinition() && Node.hasTrivialMoveConstructor();
+}
+
+void LostStdMoveCheck::registerMatchers(MatchFinder* Finder) {
+  auto ReturnParent =
+      hasParent(expr(hasParent(cxxConstructExpr(hasParent(returnStmt())))));
+
+  auto OutermostExpr = expr(unless(hasParent(expr())));
+  auto LeafStatement = stmt(OutermostExpr);
+
+  Finder->addMatcher(
+      declRefExpr(
+          // not "return x;"
+          unless(ReturnParent),
+
+          unless(hasType(namedDecl(hasName("::std::string_view")))),
+
+          // non-trivial type
+          hasType(hasCanonicalType(hasDeclaration(cxxRecordDecl()))),
+
+          // non-trivial X(X&&)
+          unless(hasType(hasCanonicalType(
+              hasDeclaration(cxxRecordDecl(hasTrivialMoveConstructor()))))),
+
+          // Not in a cycle
+          unless(hasAncestor(forStmt())),
+
+          unless(hasAncestor(doStmt())),
+
+          unless(hasAncestor(whileStmt())),
+
+	  // Not in a body of lambda
+          unless(hasAncestor(compoundStmt(hasAncestor(lambdaExpr())))),
+
+          // only non-X&
+          unless(hasDeclaration(
+              varDecl(hasType(qualType(lValueReferenceType()))))),
+
+          hasAncestor(LeafStatement.bind("leaf_statement")),
+
+          hasDeclaration(
+              varDecl(hasAncestor(functionDecl().bind("func"))).bind("decl")),
+
+          anyOf(
+
+              // f(x)
+              hasParent(expr(hasParent(cxxConstructExpr())).bind("use_parent")),
+
+              // f((x))
+              hasParent(parenExpr(hasParent(
+                  expr(hasParent(cxxConstructExpr())).bind("use_parent"))))
+
+                  )
+
+              )
+          .bind("use"),
+      this);
+}
+
+void LostStdMoveCheck::check(const MatchFinder::MatchResult& Result) {
+  const auto* MatchedDecl = Result.Nodes.getNodeAs<VarDecl>("decl");
+  const auto* MatchedFunc = Result.Nodes.getNodeAs<FunctionDecl>("func");
+  const auto* MatchedUse = Result.Nodes.getNodeAs<Expr>("use");
+  const auto* MatchedUseCall = Result.Nodes.getNodeAs<CallExpr>("use_parent");
+  const auto* MatchedLeafStatement =
+      Result.Nodes.getNodeAs<Stmt>("leaf_statement");
+
+  if (!MatchedDecl->hasLocalStorage()) return;
----------------
EugeneZelenko wrote:

Should be two lines as next statement.

https://github.com/llvm/llvm-project/pull/139525