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

[Matt Arsenault via llvm-commits]

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@@ -306,6 +306,14 @@ bool GCNTTIImpl::hasBranchDivergence(const Function *F) const {
   return !F || !ST->isSingleLaneExecution(*F);
 }
 
+InstructionCost GCNTTIImpl::getDataFlowCost(Type *DataType,
+                                            bool IsCallingConv) {
+  if (isTypeLegal(DataType) || IsCallingConv)
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arsenm wrote:

```suggestion
  if (IsCallingConv  || isTypeLegal(DataType))
```

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