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/*
* CRC-32 algorithms implemented with the z/Architecture
* Vector Extension Facility.
*
* Copyright IBM Corp. 2015
* Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
*
*/
#include "wt_internal.h"
#include <sys/types.h>
#include <endian.h>
#if defined(HAVE_CRC32_HARDWARE)
#include <sys/auxv.h>
/* RHEL 7 has kernel support, but does not define this constant in the lib c headers. */
#ifndef HWCAP_S390_VX
#define HWCAP_S390_VX 2048
#endif
#include "crc32-s390x.h"
#include "slicing-consts.h"
#define VX_MIN_LEN 64
#define VX_ALIGNMENT 16UL
#define VX_ALIGN_MASK (VX_ALIGNMENT - 1)
/* Prototypes for functions in assembly files */
unsigned int __wt_crc32c_le_vgfm_16(unsigned int crc, const unsigned char *buf, size_t size);
/* Pure C implementations of CRC, one byte at a time */
unsigned int __wt_crc32c_le(unsigned int crc, const unsigned char *buf, size_t len){
crc = htole32(crc);
while (len--)
crc = crc32ctable_le[0][((crc >> 24) ^ *buf++) & 0xFF] ^ (crc << 8);
crc = le32toh(crc);
return crc;
}
/*
* DEFINE_CRC32_VX() - Define a CRC-32 function using the vector extension
*
* Creates a function to perform a particular CRC-32 computation. Depending
* on the message buffer, the hardware-accelerated or software implementation
* is used. Note that the message buffer is aligned to improve fetch
* operations of VECTOR LOAD MULTIPLE instructions.
*
*/
#define DEFINE_CRC32_VX(___fname, ___crc32_vx, ___crc32_sw) \
unsigned int ___fname(unsigned int crc, \
const unsigned char *data, \
size_t datalen) \
{ \
unsigned long prealign, aligned, remaining; \
\
if ((unsigned long)data & VX_ALIGN_MASK) { \
prealign = VX_ALIGNMENT - \
((unsigned long)data & VX_ALIGN_MASK); \
datalen -= prealign; \
crc = ___crc32_sw(crc, data, prealign); \
data = data + prealign; \
} \
\
if (datalen < VX_MIN_LEN) \
return ___crc32_sw(crc, data, datalen); \
\
aligned = datalen & ~VX_ALIGN_MASK; \
remaining = datalen & VX_ALIGN_MASK; \
\
crc = ___crc32_vx(crc, data, aligned); \
data = data + aligned; \
\
if (remaining) \
crc = ___crc32_sw(crc, data, remaining); \
\
return crc; \
}
/* Main CRC-32 functions */
DEFINE_CRC32_VX(__wt_crc32c_le_vx, __wt_crc32c_le_vgfm_16, __wt_crc32c_le)
/*
* __wt_checksum_hw --
* WiredTiger: return a checksum for a chunk of memory.
*/
static uint32_t
__wt_checksum_hw(const void *chunk, size_t len)
{
return (~__wt_crc32c_le_vx(0xffffffff, chunk, len));
}
#endif
/*
* __wt_checksum_init --
* WiredTiger: detect CRC hardware and set the checksum function.
*/
void
__wt_checksum_init(void)
{
#if defined(HAVE_CRC32_HARDWARE)
unsigned long caps = getauxval(AT_HWCAP);
if (caps & HWCAP_S390_VX)
__wt_process.checksum = __wt_checksum_hw;
else
__wt_process.checksum = __wt_checksum_sw;
#else /* !HAVE_CRC32_HARDWARE */
__wt_process.checksum = __wt_checksum_sw;
#endif
}
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