[clang] [clang][AST] Adding Release Note for Attributed Type Dedupe Fix (PR #204384)

[Qiongsi Wu via cfe-commits]

https://github.com/qiongsiwu created https://github.com/llvm/llvm-project/pull/204384

https://github.com/llvm/llvm-project/pull/200961 fixed a regression that could lead to significant increase in pcm/pch sizes and load time. This PR adds a release note. 

>From acf3bf093c85d5baf8601ff575a58e7f233e1a8a Mon Sep 17 00:00:00 2001
From: Qiongsi Wu <qiongsi_wu at apple.com>
Date: Wed, 17 Jun 2026 09:57:24 -0700
Subject: [PATCH] Adding a releae note for
 https://github.com/llvm/llvm-project/pull/200961.

---
 clang/docs/ReleaseNotes.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 930f26ce8f5d8..11656d560ee34 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -724,6 +724,11 @@ Bug Fixes to Attribute Support
 - Fixed a crash when a ``section`` attribute or ``#pragma clang section`` caused a
   section type conflict with a declaration whose name is not a simple identifier,
   such as a lambda's call operator. (#GH192264)
+- Fixed a regression where attributed types (such as those carrying ``_Nonnull``/``_Nullable`` attributes)
+  were not deduplicated, because the attributes' arguments were not taken into
+  account when uniquing them. The duplications could substantially increase the
+  size of precompiled headers and modules (PCH/PCM), and the time spent loading
+  them. (#GH200961)
 
 Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^