forked from OSchip/llvm-project
62 lines
1.6 KiB
C
62 lines
1.6 KiB
C
//===-- 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 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 __udivsi3 for the compiler_rt library.
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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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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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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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