270 lines
8.6 KiB
Zig
270 lines
8.6 KiB
Zig
const CHAR_BIT = 8;
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const du_int = c_ulonglong;
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const di_int = c_longlong;
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const si_int = c_int;
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const su_int = c_uint;
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const udwords = [2]su_int;
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const low = if (@compile_var("is_big_endian")) 1 else 0;
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const high = 1 - low;
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export fn __udivdi3(a: du_int, b: du_int) -> du_int {
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return __udivmoddi4(a, b, null);
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}
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fn du_int_to_udwords(x: du_int) -> udwords {
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// TODO ability to take address of params
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const x2 = x;
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return *(&udwords)(&x2);
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}
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export fn __udivmoddi4(a: du_int, b: du_int, maybe_rem: ?&du_int) -> du_int {
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const n_uword_bits = @sizeof(su_int) * CHAR_BIT;
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const n_udword_bits = @sizeof(du_int) * CHAR_BIT;
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var n = du_int_to_udwords(a);
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var d = du_int_to_udwords(b);
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var q: udwords = undefined;
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var r: udwords = undefined;
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var sr: c_uint = undefined;
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/* special cases, X is unknown, K != 0 */
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if (n[high] == 0) {
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if (d[high] == 0) {
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/* 0 X
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* ---
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* 0 X
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*/
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if (const rem ?= maybe_rem) {
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*rem = n[low] % d[low];
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}
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return n[low] / d[low];
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}
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/* 0 X
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* ---
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* K X
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*/
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if (const rem ?= maybe_rem) {
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*rem = n[low];
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}
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return 0;
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}
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/* n[high] != 0 */
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if (d[low] == 0) {
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if (d[high] == 0) {
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/* K X
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* ---
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* 0 0
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*/
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if (var rem ?= maybe_rem) {
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*rem = n[high] % d[low];
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}
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return n[high] / d[low];
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}
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/* d[high] != 0 */
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if (n[low] == 0) {
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/* K 0
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* ---
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* K 0
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*/
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if (var rem ?= maybe_rem) {
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r[high] = n[high] % d[high];
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r[low] = 0;
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*rem = *(&du_int)(&r[0]);
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}
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return n[high] / d[high];
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}
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/* K K
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* ---
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* K 0
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*/
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// if d is a power of 2
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if ((d[high] & (d[high] - 1)) == 0) {
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if (var rem ?= maybe_rem) {
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r[low] = n[low];
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r[high] = n[high] & (d[high] - 1);
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*rem = *(&du_int)(&r[0]);
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}
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return n[high] >> @ctz(@typeof(d[high]), d[high]);
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}
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/* K K
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* ---
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* K 0
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*/
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sr = @clz(su_int, d[high]) - @clz(su_int, n[high]);
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/* 0 <= sr <= n_uword_bits - 2 or sr large */
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if (sr > n_uword_bits - 2) {
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if (var rem ?= maybe_rem) {
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*rem = *(&du_int)(&n[0]);
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}
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return 0;
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}
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sr += 1;
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/* 1 <= sr <= n_uword_bits - 1 */
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/* q.all = n.all << (n_udword_bits - sr); */
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q[low] = 0;
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q[high] = n[low] << (n_uword_bits - sr);
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/* r.all = n.all >> sr; */
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r[high] = n[high] >> sr;
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r[low] = (n[high] << (n_uword_bits - sr)) | (n[low] >> sr);
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} else {
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/* d[low] != 0 */
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if (d[high] == 0) {
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/* K X
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* ---
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* 0 K
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*/
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/* if d is a power of 2 */
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if ((d[low] & (d[low] - 1)) == 0) {
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if (var rem ?= maybe_rem) {
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*rem = n[low] & (d[low] - 1);
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}
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if (d[low] == 1) {
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return *(&du_int)(&n[0]);
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}
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sr = @ctz(@typeof(d[low]), d[low]);
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q[high] = n[high] >> sr;
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q[low] = (n[high] << (n_uword_bits - sr)) | (n[low] >> sr);
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return *(&du_int)(&q[0]);
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}
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/* K X
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* ---
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* 0 K
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*/
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sr = 1 + n_uword_bits + @clz(su_int, d[low]) - @clz(su_int, n[high]);
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/* 2 <= sr <= n_udword_bits - 1
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* q.all = n.all << (n_udword_bits - sr);
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* r.all = n.all >> sr;
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*/
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if (sr == n_uword_bits) {
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q[low] = 0;
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q[high] = n[low];
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r[high] = 0;
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r[low] = n[high];
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} else if (sr < n_uword_bits) {
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// 2 <= sr <= n_uword_bits - 1
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q[low] = 0;
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q[high] = n[low] << (n_uword_bits - sr);
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r[high] = n[high] >> sr;
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r[low] = (n[high] << (n_uword_bits - sr)) | (n[low] >> sr);
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} else {
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// n_uword_bits + 1 <= sr <= n_udword_bits - 1
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q[low] = n[low] << (n_udword_bits - sr);
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q[high] = (n[high] << (n_udword_bits - sr)) |
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(n[low] >> (sr - n_uword_bits));
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r[high] = 0;
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r[low] = n[high] >> (sr - n_uword_bits);
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}
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} else {
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/* K X
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* ---
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* K K
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*/
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sr = @clz(su_int, d[high]) - @clz(su_int, n[high]);
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/* 0 <= sr <= n_uword_bits - 1 or sr large */
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if (sr > n_uword_bits - 1) {
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if (var rem ?= maybe_rem) {
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*rem = *(&du_int)(&n[0]);
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}
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return 0;
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}
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sr += 1;
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/* 1 <= sr <= n_uword_bits */
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/* q.all = n.all << (n_udword_bits - sr); */
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q[low] = 0;
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if (sr == n_uword_bits) {
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q[high] = n[low];
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r[high] = 0;
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r[low] = n[high];
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} else {
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q[high] = n[low] << (n_uword_bits - sr);
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r[high] = n[high] >> sr;
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r[low] = (n[high] << (n_uword_bits - sr)) | (n[low] >> sr);
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}
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}
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}
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/* Not a special case
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* q and r are initialized with:
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* q.all = n.all << (n_udword_bits - sr);
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* r.all = n.all >> sr;
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* 1 <= sr <= n_udword_bits - 1
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*/
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var carry: su_int = 0;
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while (sr > 0) {
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/* r:q = ((r:q) << 1) | carry */
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r[high] = (r[high] << 1) | (r[low] >> (n_uword_bits - 1));
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r[low] = (r[low] << 1) | (q[high] >> (n_uword_bits - 1));
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q[high] = (q[high] << 1) | (q[low] >> (n_uword_bits - 1));
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q[low] = (q[low] << 1) | carry;
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/* carry = 0;
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* if (r.all >= d.all)
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* {
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* r.all -= d.all;
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* carry = 1;
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* }
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*/
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const s: di_int = (di_int)(*(&du_int)(&d[0]) - *(&du_int)(&r[0]) - 1) >> (n_udword_bits - 1);
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carry = su_int(s & 1);
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*(&du_int)(&r[0]) -= *(&du_int)(&d[0]) & c_ulonglong(s);
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sr -= 1;
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}
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*(&du_int)(&q[0]) = (*(&du_int)(&q[0]) << 1) | carry;
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if (var rem ?= maybe_rem) {
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*rem = *(&du_int)(&r[0]);
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}
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return *(&du_int)(&q[0]);
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}
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export fn __umoddi3(a: du_int, b: du_int) -> du_int {
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var r: du_int = undefined;
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__udivmoddi4(a, b, &r);
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return r;
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}
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#attribute("test")
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fn test_umoddi3() {
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test_one_umoddi3(0, 1, 0);
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test_one_umoddi3(2, 1, 0);
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test_one_umoddi3(0x8000000000000000, 1, 0x0);
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test_one_umoddi3(0x8000000000000000, 2, 0x0);
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test_one_umoddi3(0xFFFFFFFFFFFFFFFF, 2, 0x1);
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}
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fn test_one_umoddi3(a: du_int, b: du_int, expected_r: du_int) {
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const r = __umoddi3(a, b);
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assert(r == expected_r);
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}
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#attribute("test")
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fn test_udivmoddi4() {
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const cases = [][4]du_int {
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[]du_int{0x0000000000000000, 0x0000000000000001, 0x0000000000000000, 0x0000000000000000},
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[]du_int{0x0000000080000000, 0x0000000100000001, 0x0000000000000000, 0x0000000080000000},
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[]du_int{0x7FFFFFFF00000001, 0x0000000000000001, 0x7FFFFFFF00000001, 0x0000000000000000},
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[]du_int{0x7FFFFFFF7FFFFFFF, 0xFFFFFFFFFFFFFFFF, 0x0000000000000000, 0x7FFFFFFF7FFFFFFF},
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[]du_int{0x8000000000000002, 0xFFFFFFFFFFFFFFFE, 0x0000000000000000, 0x8000000000000002},
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[]du_int{0x80000000FFFFFFFD, 0xFFFFFFFFFFFFFFFD, 0x0000000000000000, 0x80000000FFFFFFFD},
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[]du_int{0xFFFFFFFD00000010, 0xFFFFFFFF80000000, 0x0000000000000000, 0xFFFFFFFD00000010},
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[]du_int{0xFFFFFFFDFFFFFFFF, 0xFFFFFFFF7FFFFFFF, 0x0000000000000000, 0xFFFFFFFDFFFFFFFF},
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[]du_int{0xFFFFFFFE0747AE14, 0xFFFFFFFF0747AE14, 0x0000000000000000, 0xFFFFFFFE0747AE14},
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[]du_int{0xFFFFFFFF00000001, 0xFFFFFFFF078644FA, 0x0000000000000000, 0xFFFFFFFF00000001},
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[]du_int{0xFFFFFFFF80000000, 0xFFFFFFFF00000010, 0x0000000000000001, 0x000000007FFFFFF0},
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[]du_int{0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0x0000000000000001, 0x0000000000000000},
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};
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for (cases) |case| {
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test_one_udivmoddi4(case[0], case[1], case[2], case[3]);
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}
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}
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fn test_one_udivmoddi4(a: du_int, b: du_int, expected_q: du_int, expected_r: du_int) {
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var r: du_int = undefined;
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const q = __udivmoddi4(a, b, &r);
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assert(q == expected_q);
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assert(r == expected_r);
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}
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fn assert(b: bool) {
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if (!b) unreachable{};
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}
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