Win64: Stack alignment constraints aren't applied during SET_FPREG

Stack realignment occurs after the prolog, not during, for Win64.
Because of this, don't factor in the maximum stack alignment when
establishing a frame pointer.

This fixes PR22572.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230113 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed