[llvm] [Docs] Clarify that `reassoc` isn't just for reassociation (PR #133168)

[Chris B via llvm-commits]

https://github.com/llvm-beanz created https://github.com/llvm/llvm-project/pull/133168

The `reassoc` fast-math flag allows a much wider array of algebraic transformations than just strictly reassociations. In some cases it does commutations, or distributions.

While it might make sense to fix the flag naming at some point, in the meantime we should at least have the docs be accurate to avoid confusion.

>From 9a9dc62aea85796960a44e5e9d7c9f2b4bad1dfa Mon Sep 17 00:00:00 2001
From: Chris Bieneman <chris.bieneman at me.com>
Date: Wed, 26 Mar 2025 16:55:18 -0500
Subject: [PATCH] [Docs] Clarify that `reassoc` isn't just for reassociation

The `reassoc` fast-math flag allows a much wider array of algebraic
transformations than just strictly reassociations. In some cases it does
commutations, or distributions.

While it might make sense to fix the flag naming at some point, in the
meantime we should at least have the docs be accurate to avoid
confusion.
---
 llvm/docs/LangRef.rst | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 655ec4389456c..c505aff34da31 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -3971,8 +3971,9 @@ output, given the original flags.
    for places where this can apply to LLVM's intrinsic math functions.
 
 ``reassoc``
-   Allow reassociation transformations for floating-point instructions.
-   This may dramatically change results in floating-point.
+   Allow algebraically equivalent transformations for floating-point
+   instructions such as reassociation transformations. This may dramatically
+   change results in floating-point.
 
 .. _uselistorder: