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

[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 getLastLaneForVF(const ElementCount &VF, unsigned Offset = 1) {
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ayalz wrote:

`Last` is no longer accurate. Plus worth asserting that `Offset` is not larger than VF.
How about adding `getPenultimateLaneForVF(VF)` instead, which together with `getLastLaneForVF(VF)` call a private `getLaneFromEnd(VF, OffsetFromEnd)`?


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