The new flag -aarch64-insert-extract-base-cost can be used to
set the value of AArch64Subtarget::getVectorInsertExtractBaseCost(),
for the purposes of experimentation.
Differential Revision: https://reviews.llvm.org/D124835
If we are inserting into or extracting from a scalable vector we do
not know the number of elements at runtime, so we can only let the
index wrap for fixed-length vectors.
Tests added here:
Analysis/CostModel/AArch64/sve-insert-extract.ll
Differential Revision: https://reviews.llvm.org/D117099