[llvm] [X86][BreakFalseDeps] Using reverse order for undef register selection (PR #137569)

[Phoebe Wang via llvm-commits]

================
@@ -88,7 +90,8 @@ class RegisterClassInfo {
 
   /// runOnFunction - Prepare to answer questions about MF. This must be called
   /// before any other methods are used.
----------------
phoebewang wrote:

Done.

https://github.com/llvm/llvm-project/pull/137569