ArmPkg/Library/CompilerIntrinsicsLib/Arm/udivsi3.c

   1 /** @file
   2   Compiler intrinsic for 32-bit unsigned div, ported from LLVM code.
   3
   4   Copyright (c) 2008-2009, Apple Inc. All rights reserved.
   5
   6   All rights reserved. This program and the accompanying materials
   7   are licensed and made available under the terms and conditions of the BSD License
   8   which accompanies this distribution.  The full text of the license may be found at
   9   http://opensource.org/licenses/bsd-license.php
  10
  11   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15 /**
  16   University of Illinois/NCSA
  17   Open Source License
  18
  19   Copyright (c) 2003-2008 University of Illinois at Urbana-Champaign.
  20   All rights reserved.
  21
  22   Developed by:
  23
  24       LLVM Team
  25
  26       University of Illinois at Urbana-Champaign
  27
  28       http://llvm.org
  29
  30   Permission is hereby granted, free of charge, to any person obtaining a copy of
  31   this software and associated documentation files (the "Software"), to deal with
  32   the Software without restriction, including without limitation the rights to
  33   use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
  34   of the Software, and to permit persons to whom the Software is furnished to do
  35   so, subject to the following conditions:
  36
  37       * Redistributions of source code must retain the above copyright notice,
  38         this list of conditions and the following disclaimers.
  39
  40       * Redistributions in binary form must reproduce the above copyright notice,
  41         this list of conditions and the following disclaimers in the
  42         documentation and/or other materials provided with the distribution.
  43
  44       * Neither the names of the LLVM Team, University of Illinois at
  45         Urbana-Champaign, nor the names of its contributors may be used to
  46         endorse or promote products derived from this Software without specific
  47         prior written permission.
  48
  49   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  50   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  51   FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
  52   CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  53   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  54   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
  55   SOFTWARE.
  56 **/
  57
  58
  59 #include "Llvm_int_lib.h"
  60
  61
  62 // Returns: n / d
  63
  64 // Translated from Figure 3-40 of The PowerPC Compiler Writer's Guide
  65
  66 UINT32
  67 __udivsi3(UINT32 n, UINT32 d)
  68 {
  69     const unsigned n_uword_bits = sizeof(UINT32) * CHAR_BIT;
  70     UINT32 q;
  71     UINT32 r;
  72     unsigned sr;
  73
  74     // special cases
  75     if (d == 0) {
  76 //        ASSERT (FALSE);
  77         return 0; // ?!
  78         }
  79     if (n == 0)
  80         return 0;
  81
  82     sr = COUNT_LEADING_ZEROS(d) - COUNT_LEADING_ZEROS(n);
  83     // 0 <= sr <= n_uword_bits - 1 or sr large
  84     if (sr > n_uword_bits - 1)  // d > r
  85         return 0;
  86     if (sr == n_uword_bits - 1)  // d == 1
  87         return n;
  88     ++sr;
  89     // 1 <= sr <= n_uword_bits - 1
  90     // Not a special case
  91     q = n << (n_uword_bits - sr);
  92     r = n >> sr;
  93     UINT32 carry = 0;
  94     for (; sr > 0; --sr)
  95     {
  96         // r:q = ((r:q)  << 1) | carry
  97         r = (r << 1) | (q >> (n_uword_bits - 1));
  98         q = (q << 1) | carry;
  99         // carry = 0;
 100         // if (r.all >= d.all)
 101         // {
 102         //      r.all -= d.all;
 103         //      carry = 1;
 104         // }
 105         const INT32 s = (INT32)(d - r - 1) >> (n_uword_bits - 1);
 106         carry = s & 1;
 107         r -= d & s;
 108     }
 109     q = (q << 1) | carry;
 110     return q;
 111 }