This adds back-end support for the anyregcc calling convention
for use with patchpoints.
Since all registers are considered call-saved with anyregcc
(except for 0 and 1 which may still be clobbered by PLT stubs
and the like), this required adding support for saving and
restoring vector registers in prologue/epilogue code for the
first time. This is not used by any other calling convention.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@326612 91177308-0d34-0410-b5e6-96231b3b80d8
