[X86] Generate testl instruction through truncates.

Summary:
This was introduced in D42646 but ended up being reverted because the original implementation was buggy.

Depends on D42646

Reviewers: craig.topper, niravd, spatel, hfinkel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D42741

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323899 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed