forked from OSchip/llvm-project
242 lines
7.6 KiB
C
242 lines
7.6 KiB
C
//===-- 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 distributed under the University of Illinois Open Source
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// License. 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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#if __x86_64
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#include "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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// 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.high == 0)
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{
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if (d.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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if (rem)
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*rem = n.low % d.low;
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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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if (rem)
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*rem = n.low;
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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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{
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if (d.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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if (rem)
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*rem = n.high % d.low;
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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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{
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// K 0
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// ---
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// K 0
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if (rem)
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{
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r.high = n.high % d.high;
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r.low = 0;
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*rem = r.all;
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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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if ((d.high & (d.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.low = n.low;
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r.high = n.high & (d.high - 1);
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*rem = r.all;
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}
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return n.high >> __builtin_ctzll(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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sr = __builtin_clzll(d.high) - __builtin_clzll(n.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.low = 0;
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q.high = n.low << (n_udword_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_udword_bits - sr)) | (n.low >> sr);
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}
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else // d.low != 0
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{
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if (d.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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if ((d.low & (d.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.low & (d.low - 1);
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if (d.low == 1)
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return n.all;
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unsigned sr = __builtin_ctzll(d.low);
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q.high = n.high >> sr;
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q.low = (n.high << (n_udword_bits - sr)) | (n.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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sr = 1 + n_udword_bits + __builtin_clzll(d.low)
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- __builtin_clzll(n.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.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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// }
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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.low = 0;
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// q.high = n.low << (n_udword_bits - sr);
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// r.high = n.high >> sr;
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// r.low = (n.high << (n_udword_bits - sr)) | (n.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.low = n.low << (n_utword_bits - sr);
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// q.high = (n.high << (n_utword_bits - sr)) |
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// (n.low >> (sr - n_udword_bits));
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// r.high = 0;
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// r.low = n.high >> (sr - n_udword_bits);
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// }
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q.low = (n.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.high = ((n.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.high << (n_utword_bits - sr)) |
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(n.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.high = (n.high >> sr) &
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((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1));
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r.low = ((n.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.high << (n_udword_bits - sr)) |
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(n.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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sr = __builtin_clzll(d.high) - __builtin_clzll(n.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.low = 0;
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q.high = n.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.high = n.high >> sr;
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// r.low = (n.high << (n_udword_bits - sr)) | (n.low >> sr);
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// }
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// else
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// {
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// r.high = 0;
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// r.low = n.high;
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// }
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r.high = (n.high >> sr) &
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((di_int)(int)(sr - n_udword_bits) >> (n_udword_bits-1));
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r.low = (n.high << (n_udword_bits - sr)) |
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((n.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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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.high = (r.high << 1) | (r.low >> (n_udword_bits - 1));
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r.low = (r.low << 1) | (q.high >> (n_udword_bits - 1));
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q.high = (q.high << 1) | (q.low >> (n_udword_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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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
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