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#include "crc32c.h"
/*
* Based on a posting to lkml by Austin Zhang <austin.zhang@intel.com>
*
* Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
* CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
* CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
* http://www.intel.com/products/processor/manuals/
* Intel(R) 64 and IA-32 Architectures Software Developer's Manual
* Volume 2A: Instruction Set Reference, A-M
*/
bool crc32c_intel_available = false;
#ifdef ARCH_HAVE_SSE4_2
#if BITS_PER_LONG == 64
#define REX_PRE "0x48, "
#define SCALE_F 8
#else
#define REX_PRE
#define SCALE_F 4
#endif
static bool crc32c_probed;
static uint32_t crc32c_intel_le_hw_byte(uint32_t crc, unsigned char const *data,
unsigned long length)
{
while (length--) {
__asm__ __volatile__(
".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
:"=S"(crc)
:"0"(crc), "c"(*data)
);
data++;
}
return crc;
}
/*
* Steps through buffer one byte at at time, calculates reflected
* crc using table.
*/
uint32_t crc32c_intel(unsigned char const *data, unsigned long length)
{
unsigned int iquotient = length / SCALE_F;
unsigned int iremainder = length % SCALE_F;
#if BITS_PER_LONG == 64
uint64_t *ptmp = (uint64_t *) data;
#else
uint32_t *ptmp = (uint32_t *) data;
#endif
uint32_t crc = ~0;
while (iquotient--) {
__asm__ __volatile__(
".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
:"=S"(crc)
:"0"(crc), "c"(*ptmp)
);
ptmp++;
}
if (iremainder)
crc = crc32c_intel_le_hw_byte(crc, (unsigned char *)ptmp,
iremainder);
return crc;
}
void crc32c_intel_probe(void)
{
if (!crc32c_probed) {
unsigned int eax, ebx, ecx = 0, edx;
eax = 1;
do_cpuid(&eax, &ebx, &ecx, &edx);
crc32c_intel_available = (ecx & (1 << 20)) != 0;
crc32c_probed = true;
}
}
#endif /* ARCH_HAVE_SSE4_2 */
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