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

[Florian Hahn via llvm-commits]

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@@ -167,8 +167,8 @@ class VPLane {
 
   static VPLane getFirstLane() { return VPLane(0, VPLane::Kind::First); }
 
-  static VPLane getLastLaneForVF(const ElementCount &VF) {
-    unsigned LaneOffset = VF.getKnownMinValue() - 1;
+  static VPLane getLaneFromEnd(const ElementCount &VF, unsigned Offset) {
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fhahn wrote:

 It might be worth supporting any lane w.r.t. to he constraints that it is <= VF in the vector case or <= UF for the scalar case. Added an assert for now. This also avoids explicitly checking the lane and delegating to multiple helper functions.

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