payloads/libpayload/libc/libgcc.c

   1 /*
   2  *
   3  * Copyright 2015 Google Inc.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. The name of the author may not be used to endorse or promote products
  14  *    derived from this software without specific prior written permission.
  15  *
  16  * Alternatively, this software may be distributed under the terms of the
  17  * GNU General Public License ("GPL") version 2 as published by the Free
  18  * Software Foundation.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <libpayload.h>
  34
  35 /*
  36  * Provide platform-independent backend implementation for __builtin_clz() in
  37  * <libpayload.h> in case GCC does not have an assembly version for this arch.
  38  */
  39
  40 int __clzsi2(u32 a);
  41 int __clzsi2(u32 a)
  42 {
  43         static const u8 four_bit_table[] = {
  44                 [0x0] = 4, [0x1] = 3, [0x2] = 2, [0x3] = 2,
  45                 [0x4] = 1, [0x5] = 1, [0x6] = 1, [0x7] = 1,
  46                 [0x8] = 0, [0x9] = 0, [0xa] = 0, [0xb] = 0,
  47                 [0xc] = 0, [0xd] = 0, [0xe] = 0, [0xf] = 0,
  48         };
  49         int r = 0;
  50
  51         if (!(a & (0xffff << 16))) {
  52                 r += 16;
  53                 a <<= 16;
  54         }
  55
  56         if (!(a & (0xff << 24))) {
  57                 r += 8;
  58                 a <<= 8;
  59         }
  60
  61         if (!(a & (0xf << 28))) {
  62                 r += 4;
  63                 a <<= 4;
  64         }
  65
  66         return r + four_bit_table[a >> 28];
  67 }