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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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} |