[llvm] [GlobalISel][TableGen] MIR Pattern Variadics (PR #100563)

[Matt Arsenault via llvm-commits]

================
@@ -143,6 +143,57 @@ Semantics:
     (apply (G_FSUB $dst, $src, $tmp),
            (G_FNEG GITypeOf<"$dst">:$tmp, $src))>;
 
+GIVariadic
+~~~~~~~~~~
+
+``GIVariadic<>`` is a ``GISpecialType`` that allows for matching 1 or
+more operands remaining on an instruction.
+
+Type Parameters:
+
+* The minimum number of additional operands to match. Must be greater than zero.
+
+  * Default is 1.
+
+* The maximum number of additional operands to match. Must be strictly greater
+  than the minimum.
+
+  * 0 can be used to indicate there is no upper limit.
+  * Default is 0.
+
+Semantics:
+
+* ``GIVariadic<>`` operands can not be defs.
----------------
arsenm wrote:

```suggestion
* ``GIVariadic<>`` operands cannot be defs.
```

https://github.com/llvm/llvm-project/pull/100563