src/lib/libgcc.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <types.h>
   4
   5 /*
   6  * Provide platform-independent backend implementation for __builtin_clz() in
   7  * <lib.h> in case GCC does not have an assembly version for this arch.
   8  */
   9
  10 /*
  11  * FIXME
  12  * work around lack of --gc-sections on x86
  13  * defined in rv32 libgcc.a
  14  */
  15
  16 #if !ENV_X86 && !ENV_RISCV
  17 int __clzsi2(u32 a);
  18 int __clzsi2(u32 a)
  19 {
  20         static const u8 four_bit_table[] = {
  21                 [0x0] = 4, [0x1] = 3, [0x2] = 2, [0x3] = 2,
  22                 [0x4] = 1, [0x5] = 1, [0x6] = 1, [0x7] = 1,
  23                 [0x8] = 0, [0x9] = 0, [0xa] = 0, [0xb] = 0,
  24                 [0xc] = 0, [0xd] = 0, [0xe] = 0, [0xf] = 0,
  25         };
  26         int r = 0;
  27
  28         if (!(a & (0xffffU << 16))) {
  29                 r += 16;
  30                 a <<= 16;
  31         }
  32
  33         if (!(a & (0xffU << 24))) {
  34                 r += 8;
  35                 a <<= 8;
  36         }
  37
  38         if (!(a & (0xfU << 28))) {
  39                 r += 4;
  40                 a <<= 4;
  41         }
  42
  43         return r + four_bit_table[a >> 28];
  44 }
  45 #endif