[llvm] [Docs] Fix concat vectors (PR #131860)

[via llvm-commits]

https://github.com/john-stuart2 created https://github.com/llvm/llvm-project/pull/131860

GenericOpcodes.td states that the number of operands are variadic.

let InOperandList = (ins type1:$src0, variable_ops);

X86 supports up to 4 inputs. The example uses 512-bit aka AVX-512 to make it look real and show the effect of the ~many operands.

Test plan: ninja docs-llvm-html

>From 93c81188e8c2cec75e88097ce82d0c4c0d709fef Mon Sep 17 00:00:00 2001
From: John Stuart <john.stuart.science at gmail.com>
Date: Tue, 18 Mar 2025 17:10:58 +0100
Subject: [PATCH] [Docs] Fix concat vectors

GenericOpcodes.td states that the number of operands are variadic.

let InOperandList = (ins type1:$src0, variable_ops);

X86 supports up to 4 inputs. The example uses 512-bit aka AVX-512 to
make it look real and show the effect of the ~many operands.

Test plan: ninja docs-llvm-html
---
 llvm/docs/GlobalISel/GenericOpcode.rst | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/llvm/docs/GlobalISel/GenericOpcode.rst b/llvm/docs/GlobalISel/GenericOpcode.rst
index 8b76a407c34f8..57bc202deff88 100644
--- a/llvm/docs/GlobalISel/GenericOpcode.rst
+++ b/llvm/docs/GlobalISel/GenericOpcode.rst
@@ -725,7 +725,13 @@ Mixing scalable vectors and fixed vectors are not allowed.
 G_CONCAT_VECTORS
 ^^^^^^^^^^^^^^^^
 
-Concatenate two vectors to form a longer vector.
+Concatenate vectors to form a longer vector.
+
+.. code-block:: none
+
+  %4:_(<16 x i32>) = G_CONCAT_VECTORS %3:_(<4 x i32>), %2:_(<4 x i32>),
+                                      %1:_(<4 x i32>), %0:_(<4 x i32>)
+
 
 G_BUILD_VECTOR, G_BUILD_VECTOR_TRUNC
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^