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67 lines
1.8 KiB
C
67 lines
1.8 KiB
C
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/* ===-- udivsi3.c - Implement __udivsi3 -----------------------------------===
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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 __udivsi3 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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/* Returns: a / b */
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/* Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide */
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ARM_EABI_FNALIAS(uidiv, udivsi3)
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/* This function should not call __divsi3! */
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COMPILER_RT_ABI su_int
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__udivsi3(su_int n, su_int d)
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{
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const unsigned n_uword_bits = sizeof(su_int) * CHAR_BIT;
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su_int q;
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su_int r;
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unsigned sr;
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/* special cases */
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if (d == 0)
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return 0; /* ?! */
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if (n == 0)
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return 0;
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sr = __builtin_clz(d) - __builtin_clz(n);
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/* 0 <= sr <= n_uword_bits - 1 or sr large */
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if (sr > n_uword_bits - 1) /* d > r */
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return 0;
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if (sr == n_uword_bits - 1) /* d == 1 */
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return n;
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++sr;
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/* 1 <= sr <= n_uword_bits - 1 */
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/* Not a special case */
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q = n << (n_uword_bits - sr);
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r = n >> sr;
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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 = (r << 1) | (q >> (n_uword_bits - 1));
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q = (q << 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 si_int s = (si_int)(d - r - 1) >> (n_uword_bits - 1);
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carry = s & 1;
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r -= d & s;
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}
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q = (q << 1) | carry;
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return q;
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}
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