BN_swap_ct
int BN_swap_ct(BN_ULONG swap, BIGNUM *a, BIGNUM *b, size_t nwords);
if (!BN_swap_ct(word & mask, x1, x2, group->field.top))
if (!BN_swap_ct(word & mask, z1, z2, group->field.top))
if (!BN_swap_ct(word & mask, x1, x2, group->field.top))
if (!BN_swap_ct(word & mask, z1, z2, group->field.top))
if (!BN_swap_ct(c, &(a)->X, &(b)->X, w) || \
!BN_swap_ct(c, &(a)->Y, &(b)->Y, w) || \
!BN_swap_ct(c, &(a)->Z, &(b)->Z, w)) \
if (!BN_swap_ct(kbit, k, lambda, group_top + 2))