[llvm] [VPlan] Compute blend masks from minimum set of edge masks (PR #201783)

[Luke Lau via llvm-commits]

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@@ -78,8 +81,17 @@ class VPPredicator {
     return VPBB->getFirstNonPhi();
   }
 
+  using EdgeTy = std::pair<const VPBasicBlock *, const VPBasicBlock *>;
+
+  /// Compute the "furthest up" set of edges for each incoming value of \Phi.
+  MapVector<EdgeTy, VPValue *> computeBlendEdges(VPPhi *Phi);
+
+  /// Given a set of \p Edges that lead to \p VPBB, return the OR of all edges
+  /// or an equivalent block in-mask.
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lukel97 wrote:

Clarified in 5d82ee1510ee4e456ba17a14d559dfdd1d85785a

https://github.com/llvm/llvm-project/pull/201783