This is the initial check-in for adding register scavenging to PPC. (Currently,

This is the initial check-in for adding register scavenging to PPC. (Currently,
PPC-64 doesn't work.) This also lowers the spilling of the CR registers so that
it uses a register other than the default R0 register (the scavenger scrounges
for one). A significant part of this patch fixes how kill information is
handled.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47863 91177308-0d34-0410-b5e6-96231b3b80d8