[llvm] [MachineVerifier] Improve checks for G_INSERT_SUBVECTOR. (PR #109209)

[Michael Maitland via llvm-commits]

================
@@ -11,9 +11,11 @@ body:             |
     %1:_(<vscale x 2 x s32>) = G_IMPLICIT_DEF
     %2:_(<vscale x 1 x s32>) = G_IMPLICIT_DEF
 
+    ; CHECK: generic instruction must use register operands
----------------
michaelmaitland wrote:

Is this supposed to say `generic instruction must use register operands`? looks unrelated

https://github.com/llvm/llvm-project/pull/109209