src/lib/libgcc.c

   1 /*
   2  * This file is part of the coreboot project.
   3  *
   4  * Copyright 2015 Google Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; version 2 of the License.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #include <types.h>
  17
  18 /*
  19  * Provide platform-independent backend implementation for __builtin_clz() in
  20  * <lib.h> in case GCC does not have an assembly version for this arch.
  21  */
  22
  23 #if !IS_ENABLED(CONFIG_ARCH_X86) /* work around lack of --gc-sections on x86 */
  24 int __clzsi2(u32 a);
  25 int __clzsi2(u32 a)
  26 {
  27         static const u8 four_bit_table[] = {
  28                 [0x0] = 4, [0x1] = 3, [0x2] = 2, [0x3] = 2,
  29                 [0x4] = 1, [0x5] = 1, [0x6] = 1, [0x7] = 1,
  30                 [0x8] = 0, [0x9] = 0, [0xa] = 0, [0xb] = 0,
  31                 [0xc] = 0, [0xd] = 0, [0xe] = 0, [0xf] = 0,
  32         };
  33         int r = 0;
  34
  35         if (!(a & (0xffff << 16))) {
  36                 r += 16;
  37                 a <<= 16;
  38         }
  39
  40         if (!(a & (0xff << 24))) {
  41                 r += 8;
  42                 a <<= 8;
  43         }
  44
  45         if (!(a & (0xf << 28))) {
  46                 r += 4;
  47                 a <<= 4;
  48         }
  49
  50         return r + four_bit_table[a >> 28];
  51 }
  52 #endif