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

[Alexey Bataev via llvm-commits]

================
@@ -11019,8 +11039,6 @@ BoUpSLP::getEntryCost(const TreeEntry *E, ArrayRef<Value *> VectorizedVals,
 
   bool NeedToShuffleReuses = !E->ReuseShuffleIndices.empty();
   if (E->isGather()) {
-    if (allConstant(VL))
-      return 0;
----------------
alexey-bataev wrote:

It should return 0. TTI handles it in getArithemticInstrCost/etc. by checking operands. If the operand is constant and can be folded away, it is free, otherwise these function include the cost of the constant materialization, where required

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