[llvm] [SLP]Represent SLP graph as a tree (PR #126771)

[Luke Lau via llvm-commits]

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@@ -18178,11 +18343,9 @@ void BoUpSLP::computeMinimumValueSizes() {
 
   // Ensure the roots of the vectorizable tree don't form a cycle.
   if (VectorizableTree[NodeIdx]->isGather() ||
-      (NodeIdx == 0 && !VectorizableTree[NodeIdx]->UserTreeIndices.empty()) ||
-      (NodeIdx != 0 && any_of(VectorizableTree[NodeIdx]->UserTreeIndices,
-                              [NodeIdx](const EdgeInfo &EI) {
-                                return EI.UserTE->Idx > NodeIdx;
-                              })))
+      (NodeIdx == 0 && VectorizableTree[NodeIdx]->UserTreeIndex) ||
+      (NodeIdx != 0 &&
+       VectorizableTree[NodeIdx]->UserTreeIndex.UserTE->Idx > NodeIdx))
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lukel97 wrote:

Can a cycle still occur now? Can this be made into an assert

https://github.com/llvm/llvm-project/pull/126771