assign_masked
assign_masked(reg_rmw(ctxt, VCPU_REGS_RBP), reg_read(ctxt, VCPU_REGS_RSP),
assign_masked(reg_rmw(ctxt, VCPU_REGS_RSP),
assign_masked(reg_rmw(ctxt, VCPU_REGS_RSP), reg_read(ctxt, VCPU_REGS_RBP),
assign_masked(reg, *reg + inc, mask);