[clang] [clang][docs] Clarify the tail padding considered by `__datasizeof` (PR #125981)

[A. Jiang via cfe-commits]

https://github.com/frederick-vs-ja created https://github.com/llvm/llvm-project/pull/125981

Some tail padding are not reusable due to the ABI specification, and `__datasizeof` intentionally doesn't consider them.

Closes #125863.

>From 0577594d4ecbbae6e61e087ce16609469d5f459c Mon Sep 17 00:00:00 2001
From: "A. Jiang" <de34 at live.cn>
Date: Thu, 6 Feb 2025 10:20:49 +0800
Subject: [PATCH] [clang][docs] Clarify the tail padding considered by
 `__datasizeof`

---
 clang/docs/LanguageExtensions.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index dd7513ceaa4e4bf..a779064e84cb404 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -432,7 +432,7 @@ __datasizeof
 ------------
 
 ``__datasizeof`` behaves like ``sizeof``, except that it returns the size of the
-type ignoring tail padding.
+type ignoring reusable tail padding according to the ABI.
 
 _BitInt, _ExtInt
 ----------------