[llvm] [TTI] Use MemIntrinsicCostAttributes for getGatherScatterOpCost (PR #168650)

[Luke Lau via llvm-commits]

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@@ -1598,8 +1603,10 @@ class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
     // For a target without strided memory operations (or for an illegal
     // operation type on one which does), assume we lower to a gather/scatter
     // operation.  (Which may in turn be scalarized.)
-    return thisT()->getGatherScatterOpCost(Opcode, DataTy, Ptr, VariableMask,
-                                           Alignment, CostKind, I);
+    unsigned IID = Opcode == Instruction::Load ? Intrinsic::masked_gather
+                                               : Intrinsic::masked_scatter;
+    return thisT()->getGatherScatterOpCost(
+        {IID, DataTy, Ptr, VariableMask, Alignment, I}, CostKind);
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lukel97 wrote:

The guide mentions it's for non-trivial constructors though, and the constructor here is trivial in that it only initialises members:

> Do not use these to call constructors with non-trivial logic or if you care that you’re calling some particular constructor. 

I think we use brace initialisation in a good few other places across LLVM. Not a strongly held opinion, but I feel like the class name here is long enough that it might warrant the more succinct syntax. 

https://github.com/llvm/llvm-project/pull/168650