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/* ===-- udivmodti4.c - Implement __udivmodti4 -----------------------------===
*
* The LLVM Compiler Infrastructure
*
* This file is dual licensed under the MIT and the University of Illinois Open
* Source Licenses. See LICENSE.TXT for details.
*
* ===----------------------------------------------------------------------===
*
* This file implements __udivmodti4 for the compiler_rt library.
*
* ===----------------------------------------------------------------------===
*/
#include "int_lib.h"
#ifdef CRT_HAS_128BIT
/* Effects: if rem != 0, *rem = a % b
* Returns: a / b
*/
/* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */
COMPILER_RT_ABI tu_int
__udivmodti4(tu_int a, tu_int b, tu_int* rem)
{
const unsigned n_udword_bits = sizeof(du_int) * CHAR_BIT;
const unsigned n_utword_bits = sizeof(tu_int) * CHAR_BIT;
utwords n;
n.all = a;
utwords d;
d.all = b;
utwords q;
utwords r;
unsigned sr;
/* special cases, X is unknown, K != 0 */
if (n.s.high == 0)
{
if (d.s.high == 0)
{
/* 0 X
* ---
* 0 X
*/
if (rem)
*rem = n.s.low % d.s.low;
return n.s.low / d.s.low;
}
/* 0 X
* ---
* K X
*/
if (rem)
*rem = n.s.low;
return 0;
}
/* n.s.high != 0 */
if (d.s.low == 0)
{
if (d.s.high == 0)
{
/* K X
* ---
* 0 0
*/
if (rem)
*rem = n.s.high % d.s.low;
return n.s.high / d.s.low;
}
/* d.s.high != 0 */
if (n.s.low == 0)
{
/* K 0
* ---
* K 0
*/
if (rem)
{
r.s.high = n.s.high % d.s.high;
r.s.low = 0;
*rem = r.all;
}
return n.s.high / d.s.high;
}
/* K K
* ---
* K 0
*/
if ((d.s.high & (d.s.high - 1)) == 0) /* if d is a power of 2 */
{
if (rem)
{
r.s.low = n.s.low;
r.s.high = n.s.high & (d.s.high - 1);
*rem = r.all;
}
return n.s.high >> __builtin_ctzll(d.s.high);
}
/* K K
* ---
* K 0
*/
sr = __builtin_clzll(d.s.high) - __builtin_clzll(n.s.high);
/* 0 <= sr <= n_udword_bits - 2 or sr large */
if (sr > n_udword_bits - 2)
{
if (rem)
*rem = n.all;
return 0;
}
++sr;
/* 1 <= sr <= n_udword_bits - 1 */
/* q.all = n.all << (n_utword_bits - sr); */
q.s.low = 0;
q.s.high = n.s.low << (n_udword_bits - sr);
/* r.all = n.all >> sr; */
r.s.high = n.s.high >> sr;
r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr);
}
else /* d.s.low != 0 */
{
if (d.s.high == 0)
{
/* K X
* ---
* 0 K
*/
if ((d.s.low & (d.s.low - 1)) == 0) /* if d is a power of 2 */
{
if (rem)
*rem = n.s.low & (d.s.low - 1);
if (d.s.low == 1)
return n.all;
sr = __builtin_ctzll(d.s.low);
q.s.high = n.s.high >> sr;
q.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr);
return q.all;
}
/* K X
* ---
* 0 K
*/
sr = 1 + n_udword_bits + __builtin_clzll(d.s.low)
- __builtin_clzll(n.s.high);
/* 2 <= sr <= n_utword_bits - 1
* q.all = n.all << (n_utword_bits - sr);
* r.all = n.all >> sr;
*/
if (sr == n_udword_bits)
{
q.s.low = 0;
q.s.high = n.s.low;
r.s.high = 0;
r.s.low = n.s.high;
}
else if (sr < n_udword_bits) // 2 <= sr <= n_udword_bits - 1
{
q.s.low = 0;
q.s.high = n.s.low << (n_udword_bits - sr);
r.s.high = n.s.high >> sr;
r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr);
}
else // n_udword_bits + 1 <= sr <= n_utword_bits - 1
{
q.s.low = n.s.low << (n_utword_bits - sr);
q.s.high = (n.s.high << (n_utword_bits - sr)) |
(n.s.low >> (sr - n_udword_bits));
r.s.high = 0;
r.s.low = n.s.high >> (sr - n_udword_bits);
}
}
else
{
/* K X
* ---
* K K
*/
sr = __builtin_clzll(d.s.high) - __builtin_clzll(n.s.high);
/*0 <= sr <= n_udword_bits - 1 or sr large */
if (sr > n_udword_bits - 1)
{
if (rem)
*rem = n.all;
return 0;
}
++sr;
/* 1 <= sr <= n_udword_bits
* q.all = n.all << (n_utword_bits - sr);
* r.all = n.all >> sr;
*/
q.s.low = 0;
if (sr == n_udword_bits)
{
q.s.high = n.s.low;
r.s.high = 0;
r.s.low = n.s.high;
}
else
{
r.s.high = n.s.high >> sr;
r.s.low = (n.s.high << (n_udword_bits - sr)) | (n.s.low >> sr);
q.s.high = n.s.low << (n_udword_bits - sr);
}
}
}
/* Not a special case
* q and r are initialized with:
* q.all = n.all << (n_utword_bits - sr);
* r.all = n.all >> sr;
* 1 <= sr <= n_utword_bits - 1
*/
su_int carry = 0;
for (; sr > 0; --sr)
{
/* r:q = ((r:q) << 1) | carry */
r.s.high = (r.s.high << 1) | (r.s.low >> (n_udword_bits - 1));
r.s.low = (r.s.low << 1) | (q.s.high >> (n_udword_bits - 1));
q.s.high = (q.s.high << 1) | (q.s.low >> (n_udword_bits - 1));
q.s.low = (q.s.low << 1) | carry;
/* carry = 0;
* if (r.all >= d.all)
* {
* r.all -= d.all;
* carry = 1;
* }
*/
const ti_int s = (ti_int)(d.all - r.all - 1) >> (n_utword_bits - 1);
carry = s & 1;
r.all -= d.all & s;
}
q.all = (q.all << 1) | carry;
if (rem)
*rem = r.all;
return q.all;
}
#endif /* CRT_HAS_128BIT */
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