[clang-tools-extra] [clang-tidy] Fix false negative in performance-inefficient-vector-ope… (PR #179484)

[Luka Aladashvili via cfe-commits]

https://github.com/llukito created https://github.com/llvm/llvm-project/pull/179484

### Summary
This change allows the `performance-inefficient-vector-operation` check to detect `push_back` or `emplace_back` calls even when the loop body contains multiple statements. Previously, the check was limited to loops with a single statement.

### Logic Changes
- Removed the `statementCountIs(1)` constraint from the AST matcher.
- Updated the matcher to check for `AppendCall` within a `compoundStmt`.

### Testing
- Added a regression test in `clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-vector-operation.cpp

>From e0d915f68f6994ee4987f230020a290e49833038 Mon Sep 17 00:00:00 2001
From: Luka Aladashvili <115102487+llukito at users.noreply.github.com>
Date: Tue, 3 Feb 2026 15:32:33 +0000
Subject: [PATCH] [clang-tidy] Fix false negative in
 performance-inefficient-vector-operation

---
 .../performance/InefficientVectorOperationCheck.cpp |  4 ++--
 .../performance/inefficient-vector-operation.cpp    | 13 +++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.cpp b/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.cpp
index 814a4f854319c..8f8bbbfd10937 100644
--- a/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/InefficientVectorOperationCheck.cpp
@@ -111,10 +111,10 @@ void InefficientVectorOperationCheck::addMatcher(
   const auto RefersToLoopVar = ignoringParenImpCasts(
       declRefExpr(to(varDecl(equalsBoundNode(LoopInitVarName)))));
 
-  // Matchers for the loop whose body has only 1 push_back/emplace_back calling
+  // Matchers for the loop whose body contains a push_back/emplace_back calling
   // statement.
   const auto HasInterestingLoopBody = hasBody(
-      anyOf(compoundStmt(statementCountIs(1), has(AppendCall)), AppendCall));
+      anyOf(compoundStmt(has(AppendCall)), AppendCall));
   const auto InInterestingCompoundStmt =
       hasParent(compoundStmt(has(TargetVarDefStmt)).bind(LoopParentName));
 
diff --git a/clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-vector-operation.cpp b/clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-vector-operation.cpp
index e1e25d76d4909..631354605e915 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-vector-operation.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/performance/inefficient-vector-operation.cpp
@@ -424,3 +424,16 @@ void f(std::vector<int>& t) {
 }
 
 } // namespace gh95596
+
+void multiple_statements_in_loop() {
+  std::vector<int> v1;
+  std::vector<int> v2;
+  // CHECK-FIXES: v1.reserve(10);
+  // CHECK-FIXES: v2.reserve(10);
+  for (int i = 0; i < 10; ++i) {
+    v1.push_back(i);
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'push_back' is called inside a loop
+    v2.push_back(i);
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'push_back' is called inside a loop
+  }
+}
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