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//===-- udivsi3.c - Implement __udivsi3 -----------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements __udivsi3 for the compiler_rt library.
//
//===----------------------------------------------------------------------===//
#include "int_lib.h"
// Returns: a / b
// Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide
su_int
__udivsi3(su_int n, su_int d)
{
const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT;
su_int q;
su_int r;
unsigned sr;
// special cases
if (d == 0)
return 0; // ?!
if (n == 0)
return 0;
sr = __builtin_clz(d) - __builtin_clz(n);
// 0 <= sr <= n_uword_bits - 1 or sr large
if (sr > n_uword_bits - 1) // d > r
return 0;
if (sr == n_uword_bits - 1) // d == 1
return n;
++sr;
// 1 <= sr <= n_uword_bits - 1
// Not a special case
q = n << (n_uword_bits - sr);
r = n >> sr;
su_int carry = 0;
for (; sr > 0; --sr)
{
// r:q = ((r:q) << 1) | carry
r = (r << 1) | (q >> (n_uword_bits - 1));
q = (q << 1) | carry;
// carry = 0;
// if (r.all >= d.all)
// {
// r.all -= d.all;
// carry = 1;
// }
const si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1);
carry = s & 1;
r -= d & s;
}
q = (q << 1) | carry;
return q;
}
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