[llvm] [VPlan] Add VPlan-based addMinIterCheck, replace ILV for non-epilogue. (PR #153643)

[via llvm-commits]

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@@ -9363,6 +9304,28 @@ void LoopVectorizationPlanner::attachRuntimeChecks(
   }
 }
 
+void LoopVectorizationPlanner::addMinimumIterationCheck(
+    VPlan &Plan, ElementCount VF, unsigned UF,
+    ElementCount MinProfitableTripCount) const {
+  // vscale is not necessarily a power-of-2, which means we cannot guarantee
+  // an overflow to zero when updating induction variables and so an
+  // additional overflow check is required before entering the vector loop.
+  bool CheckNeededWithTailFolding =
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ayalz wrote:

```suggestion
  bool isIndvarOverflowCheckNeededForVF =
```
? Consistent with `isIndvarOverflowCheckKnownFalse()` and specific to VF; note that UF is also not necessarily a power-of-2, perhaps worth handling as well the same way?
Then maybe `indvarBumpMayOverflow` is clearer.

https://github.com/llvm/llvm-project/pull/153643