[llvm] [LV] Use SCEV to compute final value of complex induction variables (PR #195059)

[Luke Lau via llvm-commits]

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@@ -1157,8 +1157,44 @@ optimizeLatchExitInductionUser(VPlan &Plan, VPValue *Op,
   return nullptr;
 }
 
+static VPValue *optimizeLatchExitIVUserViaSCEV(VPlan &Plan, VPValue *Op,
+                                               PredicatedScalarEvolution &PSE,
+                                               VPValue *ResumeTC,
+                                               const Loop *L) {
+  VPValue *Incoming;
+  if (!match(Op, m_ExtractLastLaneOfLastPart(m_VPValue(Incoming))))
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lukel97 wrote:

I think for EVL tail folding this will need something like `m_ExtractLane(m_LastActiveLane(m_HeaderMask()))`

https://github.com/llvm/llvm-project/pull/195059