[llvm] [VPlan] Implement VPWidenCastRecipe::computeCost(). (NFCI) (PR #111339)

[Florian Hahn via llvm-commits]

================
@@ -1429,6 +1429,49 @@ void VPWidenCastRecipe::execute(VPTransformState &State) {
   State.addMetadata(Cast, cast_or_null<Instruction>(getUnderlyingValue()));
 }
 
+InstructionCost VPWidenCastRecipe::computeCost(ElementCount VF,
+                                               VPCostContext &Ctx) const {
+  auto *SrcTy = cast<VectorType>(
+      ToVectorTy(Ctx.Types.inferScalarType(getOperand(0)), VF));
+  auto *DestTy = cast<VectorType>(ToVectorTy(getResultType(), VF));
+  // Computes the CastContextHint from a VPWidenMemoryRecipe instruction.
+  auto ComputeCCH = [&](VPWidenMemoryRecipe *R) -> TTI::CastContextHint {
+    assert((isa<VPWidenLoadRecipe>(R) || isa<VPWidenStoreRecipe>(R)) &&
+           "Expected a load or a store!");
+
+    if (VF.isScalar())
----------------
fhahn wrote:

This seems to be missing handling of VPInterleaveRecipe and VPReplicateRecipe?

And returning normal for live ins (the !Loop->contains() case in the legacy cost model)

https://github.com/llvm/llvm-project/pull/111339