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

[via cfe-commits]

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@@ -0,0 +1,122 @@
+//===--- 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 "../utils/DeclRefExprUtils.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::performance {
+
+using utils::decl_ref_expr::allDeclRefExprs;
+
+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, unless(hasDescendant(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())),
+
+          // only non-X&
+          unless(hasDeclaration(
+              varDecl(hasType(qualType(lValueReferenceType()))))),
+
+          hasAncestor(leafStatement.bind("leaf_statement")),
+
+          hasDeclaration(
+              varDecl(hasAncestor(functionDecl().bind("func"))).bind("decl")),
+
+          hasParent(expr(hasParent(cxxConstructExpr())).bind("use_parent")))
+          .bind("use"),
+      this);
+}
+
+const Expr *LostStdMoveCheck::getLastVarUsage(const VarDecl &Var,
+                                              const Decl &Func,
+                                              ASTContext &Context) {
+  auto Exprs = allDeclRefExprs(Var, Func, Context);
+
+  const Expr *LastExpr = nullptr;
+  for (const auto &Expr : Exprs) {
+    if (!LastExpr)
+      LastExpr = Expr;
+
+    if (LastExpr->getBeginLoc() < Expr->getBeginLoc())
+      LastExpr = Expr;
+  }
+
+  return LastExpr;
+}
+
+template <typename Node>
+void extractNodesByIdTo(ArrayRef<BoundNodes> Matches, StringRef ID,
+                        llvm::SmallPtrSet<const Node *, 16> &Nodes) {
+  for (const auto &Match : Matches)
+    Nodes.insert(Match.getNodeAs<Node>(ID));
+}
+
+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 (MatchedUseCall)
+    return;
+
+  const auto *LastUsage =
----------------
EugeneZelenko wrote:

Ditto.

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