[llvm] [LLVM][SCEV] udiv (mul nuw a, vscale), (mul nuw b, vscale) -> udiv a, b (PR #157836)

[Ramkumar Ramachandra via llvm-commits]

================
@@ -188,3 +188,43 @@ loop:
 exit:
   ret void
 }
+
+define noundef i64 @udiv_mul_common_vscale_factor(i64 %a, i64 %b) {
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artagnon wrote:

```suggestion
define i64 @udiv_mul_common_vscale_factor(i64 %a, i64 %b) {
```

Why is noundef necessary?

https://github.com/llvm/llvm-project/pull/157836