greenplumn pg_crc32c_sse42 源码
greenplumn pg_crc32c_sse42 代码
文件路径：/src/port/pg_crc32c_sse42.c
/*-------------------------------------------------------------------------
*
* pg_crc32c_sse42.c
* Compute CRC-32C checksum using Intel SSE 4.2 instructions.
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/port/pg_crc32c_sse42.c
*
*-------------------------------------------------------------------------
*/
#include "c.h"
#include "port/pg_crc32c.h"
#include <nmmintrin.h>
pg_crc32c
pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len)
{
const unsigned char *p = data;
const unsigned char *pend = p + len;
/*
* Process eight bytes of data at a time.
*
* NB: We do unaligned accesses here. The Intel architecture allows that,
* and performance testing didn't show any performance gain from aligning
* the begin address.
*/
#ifdef __x86_64__
while (p + 8 <= pend)
{
crc = (uint32) _mm_crc32_u64(crc, *((const uint64 *) p));
p += 8;
}
/* Process remaining full four bytes if any */
if (p + 4 <= pend)
{
crc = _mm_crc32_u32(crc, *((const unsigned int *) p));
p += 4;
}
#else
/*
* Process four bytes at a time. (The eight byte instruction is not
* available on the 32-bit x86 architecture).
*/
while (p + 4 <= pend)
{
crc = _mm_crc32_u32(crc, *((const unsigned int *) p));
p += 4;
}
#endif /* __x86_64__ */
/* Process any remaining bytes one at a time. */
while (p < pend)
{
crc = _mm_crc32_u8(crc, *p);
p++;
}
return crc;
}
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