[InstCombine] Support vector splats in transformZExtICmp

This patch adds splat support to transformZExtICmp. The test cases are vector versions of tests that failed when commenting out parts of the existing scalar code.

One test didn't vectorize optimize properly due to another bug so a TODO has been added.

Differential Revision: https://reviews.llvm.org/D37253

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312023 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed