[llvm] [TableGen] Fix concatenation of subreg and artificial subregs (PR #114391)

[Sander de Smalen via llvm-commits]

================
@@ -411,6 +410,9 @@ CodeGenRegister::computeSubRegs(CodeGenRegBank &RegBank) {
         Parts.push_back(getSubRegIndex(SR->ExplicitSubRegs[j]));
     }
 
+    if (Parts.size() < 2)
+      continue;
----------------
sdesmalen-arm wrote:

Good point @jayfoad!

https://github.com/llvm/llvm-project/pull/114391