[llvm] [VPlan] Update final IV exit value via VPlan. (PR #112147)

[via llvm-commits]

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@@ -312,10 +312,12 @@ Value *VPTransformState::get(VPValue *Def, bool NeedsScalar) {
   }
 
   auto *LastInst = cast<Instruction>(get(Def, LastLane));
+  auto OldIP = Builder.saveIP();
+  // TODO: Remove once VPDerivedRecipe can be simplified, which requires
+  // vector trip count being modeled in VPlan.
   // Set the insert point after the last scalarized instruction or after the
   // last PHI, if LastInst is a PHI. This ensures the insertelement sequence
   // will directly follow the scalar definitions.
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ayalz wrote:

Retain current code?
```suggestion
  // Set the insert point after the last scalarized instruction or after the
  // last PHI, if LastInst is a PHI. This ensures the insertelement sequence
  // will directly follow the scalar definitions.
  auto OldIP = Builder.saveIP();
```

https://github.com/llvm/llvm-project/pull/112147