When the CodeGenInfo is to be created for the PPC64 target machine,
a default code-model selection is converted to CodeModel::Medium
provided we are not targeting the Darwin OS. Defaults for Darwin
are unaffected.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168747 91177308-0d34-0410-b5e6-96231b3b80d8