The save area is twice as big and there is no struct return slot. The
stack pointer is always 16-byte aligned (after adding the bias).
Also eliminate the stack adjustment instructions around calls when the
function has a reserved stack frame.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179083 91177308-0d34-0410-b5e6-96231b3b80d8
