[llvm] [SLP]: Introduce and use getDataFlowCost (PR #112999)

[Matt Arsenault via llvm-commits]

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@@ -10267,8 +10302,14 @@ InstructionCost BoUpSLP::getTreeCost(ArrayRef<Value *> VectorizedVals) {
       continue;
 
     // No extract cost for vector "scalar"
-    if (isa<FixedVectorType>(EU.Scalar->getType()))
+    if (isa<FixedVectorType>(EU.Scalar->getType())) {
+      // Account for any additional costs required by CallingConvention for the
+      // type.
+      if (isa_and_nonnull<ReturnInst>(EU.User))
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arsenm wrote:

Outgoing call arguments too. But this is just the type legality cost? 

https://github.com/llvm/llvm-project/pull/112999