[llvm] Remove `br i1 undef` from some `llvm/test/CodeGen` tests (#128272)

diff --git a/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll b/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
index f96ba35..c6e6df97 100644
--- a/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
+++ b/llvm/test/CodeGen/X86/tailcall-cgp-dup.ll
@@ -113,7 +113,7 @@
 ; CHECK-NEXT:  ## %bb.1: ## %someThingWithValue.exit
 ; CHECK-NEXT:    retq
 entry:
-  br i1 undef, label %if.then.i, label %if.else.i
+  br i1 poison, label %if.then.i, label %if.else.i
 
 if.then.i:                                        ; preds = %entry
   br label %someThingWithValue.exit