257 lines
8.1 KiB
C
257 lines
8.1 KiB
C
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/* ===-- udivmodti4.c - Implement __udivmodti4 -----------------------------===
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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 __udivmodti4 for the compiler_rt library.
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*
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* ===----------------------------------------------------------------------===
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*/
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#include "int_lib.h"
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#if __x86_64
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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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tu_int
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__udivmodti4(tu_int a, tu_int b, tu_int* rem)
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{
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const unsigned n_udword_bits = sizeof(du_int) * CHAR_BIT;
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const unsigned n_utword_bits = sizeof(tu_int) * CHAR_BIT;
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utwords n;
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n.all = a;
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utwords d;
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d.all = b;
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utwords q;
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utwords 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_ctzll(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_clzll(d.s.high) - __builtin_clzll(n.s.high);
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/* 0 <= sr <= n_udword_bits - 2 or sr large */
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if (sr > n_udword_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_udword_bits - 1 */
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/* q.all = n.all << (n_utword_bits - sr); */
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q.s.low = 0;
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q.s.high = n.s.low << (n_udword_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_udword_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_ctzll(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_udword_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_udword_bits + __builtin_clzll(d.s.low)
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- __builtin_clzll(n.s.high);
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/* 2 <= sr <= n_utword_bits - 1
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* q.all = n.all << (n_utword_bits - sr);
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* r.all = n.all >> sr;
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* if (sr == n_udword_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_udword_bits) // 2 <= sr <= n_udword_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_udword_bits - sr);
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* r.s.high = n.s.high >> sr;
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* r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr);
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* }
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* else // n_udword_bits + 1 <= sr <= n_utword_bits - 1
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* {
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* q.s.low = n.s.low << (n_utword_bits - sr);
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* q.s.high = (n.s.high << (n_utword_bits - sr)) |
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* (n.s.low >> (sr - n_udword_bits));
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* r.s.high = 0;
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* r.s.low = n.s.high >> (sr - n_udword_bits);
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* }
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*/
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q.s.low = (n.s.low << (n_utword_bits - sr)) &
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((di_int)(int)(n_udword_bits - sr) >> (n_udword_bits-1));
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q.s.high = ((n.s.low << ( n_udword_bits - sr)) &
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((di_int)(int)(sr - n_udword_bits - 1) >> (n_udword_bits-1))) |
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(((n.s.high << (n_utword_bits - sr)) |
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(n.s.low >> (sr - n_udword_bits))) &
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((di_int)(int)(n_udword_bits - sr) >> (n_udword_bits-1)));
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r.s.high = (n.s.high >> sr) &
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((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1));
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r.s.low = ((n.s.high >> (sr - n_udword_bits)) &
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((di_int)(int)(n_udword_bits - sr - 1) >> (n_udword_bits-1))) |
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(((n.s.high << (n_udword_bits - sr)) |
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(n.s.low >> sr)) &
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((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1)));
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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_clzll(d.s.high) - __builtin_clzll(n.s.high);
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/*0 <= sr <= n_udword_bits - 1 or sr large */
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if (sr > n_udword_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_udword_bits */
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/* q.all = n.all << (n_utword_bits - sr); */
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q.s.low = 0;
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q.s.high = n.s.low << (n_udword_bits - sr);
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/* r.all = n.all >> sr;
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* if (sr < n_udword_bits)
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* {
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* r.s.high = n.s.high >> sr;
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* r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr);
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* }
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* else
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* {
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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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*/
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r.s.high = (n.s.high >> sr) &
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((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1));
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r.s.low = (n.s.high << (n_udword_bits - sr)) |
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((n.s.low >> sr) &
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((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1)));
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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_utword_bits - sr);
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* r.all = n.all >> sr;
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* 1 <= sr <= n_utword_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_udword_bits - 1));
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r.s.low = (r.s.low << 1) | (q.s.high >> (n_udword_bits - 1));
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q.s.high = (q.s.high << 1) | (q.s.low >> (n_udword_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 ti_int s = (ti_int)(d.all - r.all - 1) >> (n_utword_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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#endif /* __x86_64 */
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