crc/crc32c-intel.c

   1 #include <inttypes.h>
   2
   3 /*
   4  * Based on a posting to lkml by Austin Zhang <austin.zhang@intel.com>
   5  *
   6  * Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
   7  * CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
   8  * CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
   9  * http://www.intel.com/products/processor/manuals/
  10  * Intel(R) 64 and IA-32 Architectures Software Developer's Manual
  11  * Volume 2A: Instruction Set Reference, A-M
  12  */
  13
  14 #if BITS_PER_LONG == 64
  15 #define REX_PRE "0x48, "
  16 #define SCALE_F 8
  17 #else
  18 #define REX_PRE
  19 #define SCALE_F 4
  20 #endif
  21
  22 uint32_t crc32c_intel_le_hw_byte(uint32_t crc, unsigned char const *data,
  23                                  unsigned long length)
  24 {
  25         while (length--) {
  26                 __asm__ __volatile__(
  27                         ".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
  28                         :"=S"(crc)
  29                         :"0"(crc), "c"(*data)
  30                 );
  31                 data++;
  32         }
  33
  34         return crc;
  35 }
  36
  37 /*
  38  * Steps through buffer one byte at at time, calculates reflected
  39  * crc using table.
  40  */
  41 uint32_t crc32c_intel(unsigned char const *data, unsigned long length)
  42 {
  43         unsigned int iquotient = length / SCALE_F;
  44         unsigned int iremainder = length % SCALE_F;
  45 #if BITS_PER_LONG == 64
  46         uint64_t *ptmp = (uint64_t *) data;
  47 #else
  48         uint32_t *ptmp = (uint32_t *) data;
  49 #endif
  50         uint32_t crc = ~0;
  51
  52         while (iquotient--) {
  53                 __asm__ __volatile__(
  54                         ".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
  55                         :"=S"(crc)
  56                         :"0"(crc), "c"(*ptmp)
  57                 );
  58                 ptmp++;
  59         }
  60
  61         if (iremainder)
  62                 crc = crc32c_intel_le_hw_byte(crc, (unsigned char *)ptmp,
  63                                  iremainder);
  64
  65         return crc;
  66 }