[llvm] [VPlan] Model FOR extract of exit value in VPlan. (PR #93395)

[via llvm-commits]

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@@ -1182,6 +1188,11 @@ class VPInstruction : public VPRecipeWithIRFlags {
     BranchOnCount,
     BranchOnCond,
     ComputeReductionResult,
+    // Takes the VPValue to extract from as first operand and the lane to
+    // extract from as second operand. The second operand must be a constant and
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ayalz wrote:

```suggestion
    // extract as second operand, counting from the end starting with 1 for last. The second operand must be a positive constant and
```

https://github.com/llvm/llvm-project/pull/93395