[X86][SSE] Pulled out repeated target shuffle decodes into helper functions. NFCI.

Pulled out the code used by PSHUFB/VPERMV/VPERMV3 shuffle mask decoding into common helper functions.

The helper functions handle masks coming from BROADCAST/BUILD_VECTOR and ConstantPool nodes respectively.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260032 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed