[llvm] [AArch64][CostModel] Consider the cost of const vector (PR #117539)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

Thanks for the patch, I planned adding constant vector materialization cost myself for some time. Unfortunately, SLP part of this patch is wrong.
The only place, where the constant materialization cost must be used in SLPVectorizer are `InstructionCost getBuildVectorCost(ArrayRef<Value *> VL, Value *Root)` function and `InstructionCost BoUpSLP::getGatherCost` function, all other cost estimations must be in TTI

https://github.com/llvm/llvm-project/pull/117539