[llvm] [LV] Don't consider VPValues without underlying value as generating vectors (PR #150992)

[Luke Lau via llvm-commits]

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@@ -4172,7 +4172,7 @@ static bool willGenerateVectors(VPlan &Plan, ElementCount VF,
   // Set of already visited types.
   DenseSet<Type *> Visited;
   for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
-           vp_depth_first_shallow(Plan.getVectorLoopRegion()->getEntry()))) {
+           vp_depth_first_deep(Plan.getVectorPreheader()))) {
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lukel97 wrote:

My understanding was that the vector preheader is outside of the vector region? So this will traverse through vector.ph -> vector loop region -> middle.block -> scalar.ph -> etc.

https://github.com/llvm/llvm-project/pull/150992