Add VirtRegMap::hasKnownPreference().

Virtual registers with a known preferred register are prioritized by
RAGreedy. This function makes the condition explicit without depending
on getRegAllocPref().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169179 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed