fpusave
void fpusave (union savefpu *addr, uint64_t mask);
fpusave((union savefpu *)(a), m); \
fpusave(curthread->td_savefpu, npx_xcr0_mask);
fpusave(addr, npx_xcr0_mask);
fpusave(curthread->td_savefpu, 0);
fpusave(addr, 0);