[mips][msa] Splat.d endianness check

Before this change, it was always the first element of a vector that got splatted since the lower 6 bits of vshf.d $wd were always zero for little endian.
Additionally, masking has been performed for vshf via which splat.d is created.

Vshf has a property where if its first operand's elements have either bit 6 or 7 set, destination element is set to zero.
Initially masked with 63 to avoid this property, which would result in generation of and.v + vshf.d in all cases.
Masking with one results in generating a single splati.d instruction when possible.

Differential Revision: https://reviews.llvm.org/D32216


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306090 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed