[llvm] [LV][VPlan] Prevent calculate cost for skiped instructions in precomputeCosts(). (PR #127966)

[Florian Hahn via llvm-commits]

================
@@ -75,12 +76,12 @@ loop:
   %select = phi i32 [ 0, %entry ], [ %select.next, %loop ]
   %iv.widen = zext i32 %iv to i64
   %exitcond = icmp eq i64 %n, %iv.widen
-  %select.i = select i1 %exitcond, i32 0, i32 0
+  %select.i = select i1 %exitcond, i32 0, i32 2
   %select.next = or i32 %select.i, %select
   %iv.next = add i32 %iv, 1
   br i1 %exitcond, label %exit, label %loop
 
 exit:
-  %spec.select.i.lcssa = phi i32 [ %select.next, %loop ]
+  store i32 %select.next, ptr %f, align 4
   ret void
----------------
fhahn wrote:

```suggestion
  ret i32%select.next
```

Simpler to just return the result?

https://github.com/llvm/llvm-project/pull/127966