[llvm] [GISel][Docs] Add a little bit of documentation for G_FENCE. (PR #73722)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-globalisel

Author: Craig Topper (topperc)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/73722.diff


1 Files Affected:

- (modified) llvm/docs/GlobalISel/GenericOpcode.rst (+3-2) 


``````````diff
diff --git a/llvm/docs/GlobalISel/GenericOpcode.rst b/llvm/docs/GlobalISel/GenericOpcode.rst
index 6c42ddcaff1eccf..26ff34376fb838c 100644
--- a/llvm/docs/GlobalISel/GenericOpcode.rst
+++ b/llvm/docs/GlobalISel/GenericOpcode.rst
@@ -751,9 +751,10 @@ operands.
 G_FENCE
 ^^^^^^^
 
-.. caution::
+Generic fence. The first operand is the memory ordering. The second operand is
+the syncscope.
 
-  I couldn't find any documentation on this at the time of writing.
+See the LLVM LangRef entry on the '``fence'`` instruction for more details.
 
 G_MEMCPY
 ^^^^^^^^

``````````

</details>


https://github.com/llvm/llvm-project/pull/73722