235 lines
6.6 KiB
C
235 lines
6.6 KiB
C
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/* clang-format off */
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/* ===-- udivmoddi4.c - Implement __udivmoddi4 -----------------------------===
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*
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* The LLVM Compiler Infrastructure
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*
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* This file is dual licensed under the MIT and the University of Illinois Open
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* Source Licenses. See LICENSE.TXT for details.
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*
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* ===----------------------------------------------------------------------===
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*
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* This file implements __udivmoddi4 for the compiler_rt library.
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*
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* ===----------------------------------------------------------------------===
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*/
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STATIC_YOINK("huge_compiler_rt_license");
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#include "third_party/compiler_rt/int_lib.h"
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/* Effects: if rem != 0, *rem = a % b
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* Returns: a / b
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*/
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/* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */
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COMPILER_RT_ABI du_int
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__udivmoddi4(du_int a, du_int b, du_int* rem)
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{
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const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT;
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const unsigned n_udword_bits = sizeof(du_int) * CHAR_BIT;
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udwords n;
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n.all = a;
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udwords d;
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d.all = b;
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udwords q;
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udwords r;
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unsigned sr;
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/* special cases, X is unknown, K != 0 */
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if (n.s.high == 0)
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{
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if (d.s.high == 0)
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{
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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 (rem)
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*rem = n.s.low % d.s.low;
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return n.s.low / d.s.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 (rem)
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*rem = n.s.low;
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return 0;
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}
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/* n.s.high != 0 */
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if (d.s.low == 0)
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{
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if (d.s.high == 0)
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{
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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 (rem)
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*rem = n.s.high % d.s.low;
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return n.s.high / d.s.low;
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}
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/* d.s.high != 0 */
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if (n.s.low == 0)
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{
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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 (rem)
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{
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r.s.high = n.s.high % d.s.high;
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r.s.low = 0;
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*rem = r.all;
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}
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return n.s.high / d.s.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.s.high & (d.s.high - 1)) == 0) /* if d is a power of 2 */
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{
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if (rem)
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{
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r.s.low = n.s.low;
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r.s.high = n.s.high & (d.s.high - 1);
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*rem = r.all;
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}
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return n.s.high >> __builtin_ctz(d.s.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 = __builtin_clz(d.s.high) - __builtin_clz(n.s.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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{
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if (rem)
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*rem = n.all;
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return 0;
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}
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++sr;
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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.s.low = 0;
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q.s.high = n.s.low << (n_uword_bits - sr);
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/* r.all = n.all >> sr; */
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r.s.high = n.s.high >> sr;
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r.s.low = (n.s.high << (n_uword_bits - sr)) | (n.s.low >> sr);
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}
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else /* d.s.low != 0 */
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{
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if (d.s.high == 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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if ((d.s.low & (d.s.low - 1)) == 0) /* if d is a power of 2 */
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{
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if (rem)
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*rem = n.s.low & (d.s.low - 1);
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if (d.s.low == 1)
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return n.all;
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sr = __builtin_ctz(d.s.low);
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q.s.high = n.s.high >> sr;
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q.s.low = (n.s.high << (n_uword_bits - sr)) | (n.s.low >> sr);
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return q.all;
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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 + __builtin_clz(d.s.low) - __builtin_clz(n.s.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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{
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q.s.low = 0;
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q.s.high = n.s.low;
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r.s.high = 0;
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r.s.low = n.s.high;
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}
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else if (sr < n_uword_bits) // 2 <= sr <= n_uword_bits - 1
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{
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q.s.low = 0;
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q.s.high = n.s.low << (n_uword_bits - sr);
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r.s.high = n.s.high >> sr;
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r.s.low = (n.s.high << (n_uword_bits - sr)) | (n.s.low >> sr);
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}
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else // n_uword_bits + 1 <= sr <= n_udword_bits - 1
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{
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q.s.low = n.s.low << (n_udword_bits - sr);
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q.s.high = (n.s.high << (n_udword_bits - sr)) |
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(n.s.low >> (sr - n_uword_bits));
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r.s.high = 0;
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r.s.low = n.s.high >> (sr - n_uword_bits);
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}
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}
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else
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{
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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 = __builtin_clz(d.s.high) - __builtin_clz(n.s.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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{
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if (rem)
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*rem = n.all;
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return 0;
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}
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++sr;
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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.s.low = 0;
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if (sr == n_uword_bits)
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{
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q.s.high = n.s.low;
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r.s.high = 0;
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r.s.low = n.s.high;
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}
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else
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{
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q.s.high = n.s.low << (n_uword_bits - sr);
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r.s.high = n.s.high >> sr;
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r.s.low = (n.s.high << (n_uword_bits - sr)) | (n.s.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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su_int carry = 0;
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for (; sr > 0; --sr)
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{
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/* r:q = ((r:q) << 1) | carry */
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r.s.high = (r.s.high << 1) | (r.s.low >> (n_uword_bits - 1));
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r.s.low = (r.s.low << 1) | (q.s.high >> (n_uword_bits - 1));
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q.s.high = (q.s.high << 1) | (q.s.low >> (n_uword_bits - 1));
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q.s.low = (q.s.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 di_int s = (di_int)(d.all - r.all - 1) >> (n_udword_bits - 1);
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carry = s & 1;
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r.all -= d.all & s;
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}
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q.all = (q.all << 1) | carry;
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if (rem)
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*rem = r.all;
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return q.all;
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}
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