[Docs] Fix concat vectors

[john-stuart2]

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

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[john-stuart2]

@arsenm

[llvmbot]

@llvm/pr-subscribers-llvm-globalisel

Author: None (john-stuart2)

Changes

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

---

Full diff: https://github.com/llvm/llvm-project/pull/131860.diff

1 Files Affected:

• (modified) llvm/docs/GlobalISel/GenericOpcode.rst (+7-1)

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
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[arsenm]

Suggested change

	%4:_(<16 x i32>) = G_CONCAT_VECTORS %3:_(<4 x i32>), %2:_(<4 x i32>),
	%1:_(<4 x i32>), %0:_(<4 x i32>)
	%4:_(<16 x i32>) = G_CONCAT_VECTORS %0:_(<4 x i32>), %1:_(<4 x i32>),
	%2:_(<4 x i32>), %3:_(<4 x i32>)

Better use in order numbers to avoid confusing about the element indexing

[john-stuart2]

Thanks! I have no commit privileges. Could you merge the PR for me after CI is happy? Thanks!

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