forked from OSchip/llvm-project
63 lines
1.7 KiB
C
63 lines
1.7 KiB
C
//===-- udivsi3.c - Implement __udivsi3 -----------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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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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// This function should not call __divsi3!
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COMPILER_RT_ABI su_int __udivsi3(su_int n, su_int d) {
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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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// 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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#if defined(__ARM_EABI__)
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COMPILER_RT_ALIAS(__udivsi3, __aeabi_uidiv)
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#endif
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