65 lines
1.6 KiB
C
65 lines
1.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* pg_crc32c_sse42_choose.c
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* Choose between Intel SSE 4.2 and software CRC-32C implementation.
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*
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* On first call, checks if the CPU we're running on supports Intel SSE
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* 4.2. If it does, use the special SSE instructions for CRC-32C
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* computation. Otherwise, fall back to the pure software implementation
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* (slicing-by-8).
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*
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* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/port/pg_crc32c_sse42_choose.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "c.h"
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#ifdef HAVE__GET_CPUID
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#include <cpuid.h>
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#endif
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#ifdef HAVE__CPUID
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#include <intrin.h>
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#endif
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#include "port/pg_crc32c.h"
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static bool
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pg_crc32c_sse42_available(void)
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{
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unsigned int exx[4] = {0, 0, 0, 0};
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#if defined(HAVE__GET_CPUID)
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__get_cpuid(1, &exx[0], &exx[1], &exx[2], &exx[3]);
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#elif defined(HAVE__CPUID)
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__cpuid(exx, 1);
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#else
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#error cpuid instruction not available
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#endif
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return (exx[2] & (1 << 20)) != 0; /* SSE 4.2 */
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}
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/*
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* This gets called on the first call. It replaces the function pointer
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* so that subsequent calls are routed directly to the chosen implementation.
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*/
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static pg_crc32c
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pg_comp_crc32c_choose(pg_crc32c crc, const void *data, size_t len)
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{
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if (pg_crc32c_sse42_available())
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pg_comp_crc32c = pg_comp_crc32c_sse42;
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else
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pg_comp_crc32c = pg_comp_crc32c_sb8;
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return pg_comp_crc32c(crc, data, len);
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}
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pg_crc32c (*pg_comp_crc32c) (pg_crc32c crc, const void *data, size_t len) = pg_comp_crc32c_choose;
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