[IR] Consolidate OneNthElements IIT descriptors. NFCI (#141492)

This replaces LLVMHalfElementsVectorType and
LLVMOne{3,4,5,6,7,8}ElementsVectorType with one parameterized IIT
descriptor.

The type signature is encoded as the argument index of the vector type
to match followed by the divisor N, and inside IITDescriptor this is
stored as two 16 bit parts, similarly to LLVMVectorOfAnyPointersToElt.

This also allows us to use a foreach to declare the [de]interleave
intrinsics.

0 files changed, 0 insertions, 0 deletions