[llvm] [LangRef] Add description of toc-data global variables (PR #94828)

[Kai Luo via llvm-commits]

https://github.com/bzEq created https://github.com/llvm/llvm-project/pull/94828

Add description of `toc-data` global variable in LLVM Language Reference.

Addressed comment in https://github.com/llvm/llvm-project/pull/94593#pullrequestreview-2102796085.

>From 4d0ee177d5bba8147b5dd7f31d5151ff8ff29322 Mon Sep 17 00:00:00 2001
From: Kai Luo <lkail at cn.ibm.com>
Date: Sat, 8 Jun 2024 10:10:15 +0800
Subject: [PATCH] Add description of toc-data global variables

---
 llvm/docs/LangRef.rst | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 9fb2c048a5c86..093f9e4c62086 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -812,6 +812,9 @@ doesn't). These kinds of structs (we may call them homogeneous scalable vector
 structs) are considered sized and can be used in loads, stores, allocas, but
 not GEPs.
 
+Globals with ``toc-data`` attribute set are stored in TOC of XCOFF. Their
+alignments are the same as that of a TOC entry.
+
 Syntax::
 
       @<GlobalVarName> = [Linkage] [PreemptionSpecifier] [Visibility]