[X86][SSE] Simplify combineVectorTruncationWithPACKSS to reduce code duplication

Simplify combineVectorTruncationWithPACKSS to just a SIGN_EXTEND_INREG followed by using the existing truncateVectorWithPACK instead of duplicating code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@334193 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed