[llvm] [X86] Skip unused VRegs traverse (PR #78229)

[Shengchen Kan via llvm-commits]

================
@@ -860,3 +864,63 @@ body:             |
     RET 0
 
 ...
+---
+name:            test_globalisel_unused
----------------
KanRobert wrote:

Why is the function named `*globalisel*`? It seems that there is not global isel flag in this test.

https://github.com/llvm/llvm-project/pull/78229