[ARM] Allow zext in ARMCodeGenPrepare

Treat zext instructions as roots, like we do for truncs.

Differential Revision: https://reviews.llvm.org/D50759


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339868 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed