PostgreSQL Source Code: src/port/pg_crc32c_armv8_choose.c Source File

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pg_crc32c_armv8_choose.c
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1/*-------------------------------------------------------------------------
2 *
3 * pg_crc32c_armv8_choose.c
4 * Choose between ARMv8 and software CRC-32C implementation.
5 *
6 * On first call, checks if the CPU we're running on supports the ARMv8
7 * CRC Extension. If it does, use the special instructions for CRC-32C
8 * computation. Otherwise, fall back to the pure software implementation
9 * (slicing-by-8).
10 *
11 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
12 * Portions Copyright (c) 1994, Regents of the University of California
13 *
14 *
15 * IDENTIFICATION
16 * src/port/pg_crc32c_armv8_choose.c
17 *
18 *-------------------------------------------------------------------------
19 */
20
21#ifndef FRONTEND
22#include "postgres.h"
23#else
24#include "postgres_fe.h"
25#endif
26
27#if defined(HAVE_ELF_AUX_INFO) || defined(HAVE_GETAUXVAL)
28#include <sys/auxv.h>
29#if defined(__linux__) && !defined(__aarch64__) && !defined(HWCAP2_CRC32)
30#include <asm/hwcap.h>
31#endif
32#endif
33
34#if defined(__NetBSD__)
35#include <sys/sysctl.h>
36#if defined(__aarch64__)
37#include <aarch64/armreg.h>
38#endif
39#endif
40
41#include "port/pg_crc32c.h"
42
43static bool
44 pg_crc32c_armv8_available(void)
45{
46#if defined(HAVE_ELF_AUX_INFO)
47 unsigned long value;
48
49#ifdef __aarch64__
50 return elf_aux_info(AT_HWCAP, &value, sizeof(value)) == 0 &&
51 (value & HWCAP_CRC32) != 0;
52#else
53 return elf_aux_info(AT_HWCAP2, &value, sizeof(value)) == 0 &&
54 (value & HWCAP2_CRC32) != 0;
55#endif
56#elif defined(HAVE_GETAUXVAL)
57#ifdef __aarch64__
58 return (getauxval(AT_HWCAP) & HWCAP_CRC32) != 0;
59#else
60 return (getauxval(AT_HWCAP2) & HWCAP2_CRC32) != 0;
61#endif
62#elif defined(__NetBSD__)
63 /*
64 * On NetBSD we can read the Instruction Set Attribute Registers via
65 * sysctl. For doubtless-historical reasons the sysctl interface is
66 * completely different on 64-bit than 32-bit, but the underlying
67 * registers contain the same fields.
68 */
69#define ISAR0_CRC32_BITPOS 16
70#define ISAR0_CRC32_BITWIDTH 4
71#define WIDTHMASK(w) ((1 << (w)) - 1)
72#define SYSCTL_CPU_ID_MAXSIZE 64
73
74 size_t len;
75 uint64 sysctlbuf[SYSCTL_CPU_ID_MAXSIZE];
76#if defined(__aarch64__)
77 /* We assume cpu0 is representative of all the machine's CPUs. */
78 const char *path = "machdep.cpu0.cpu_id";
79 size_t expected_len = sizeof(struct aarch64_sysctl_cpu_id);
80#define ISAR0 ((struct aarch64_sysctl_cpu_id *) sysctlbuf)->ac_aa64isar0
81#else
82 const char *path = "machdep.id_isar";
83 size_t expected_len = 6 * sizeof(int);
84#define ISAR0 ((int *) sysctlbuf)[5]
85#endif
86 uint64 fld;
87
88 /* Fetch the appropriate set of register values. */
89 len = sizeof(sysctlbuf);
90 memset(sysctlbuf, 0, len);
91 if (sysctlbyname(path, sysctlbuf, &len, NULL, 0) != 0)
92 return false; /* perhaps kernel is 64-bit and we aren't? */
93 if (len != expected_len)
94 return false; /* kernel API change? */
95
96 /* Fetch the CRC32 field from ISAR0. */
97 fld = (ISAR0 >> ISAR0_CRC32_BITPOS) & WIDTHMASK(ISAR0_CRC32_BITWIDTH);
98
99 /*
100 * Current documentation defines only the field values 0 (No CRC32) and 1
101 * (CRC32B/CRC32H/CRC32W/CRC32X/CRC32CB/CRC32CH/CRC32CW/CRC32CX). Assume
102 * that any future nonzero value will be a superset of 1.
103 */
104 return (fld != 0);
105#else
106 return false;
107#endif
108}
109
110/*
111 * This gets called on the first call. It replaces the function pointer
112 * so that subsequent calls are routed directly to the chosen implementation.
113 */
114static pg_crc32c
115 pg_comp_crc32c_choose(pg_crc32c crc, const void *data, size_t len)
116{
117 if (pg_crc32c_armv8_available())
118 pg_comp_crc32c = pg_comp_crc32c_armv8;
119 else
120 pg_comp_crc32c = pg_comp_crc32c_sb8;
121
122 return pg_comp_crc32c(crc, data, len);
123}
124
125 pg_crc32c (*pg_comp_crc32c) (pg_crc32c crc, const void *data, size_t len) = pg_comp_crc32c_choose;
uint64_t uint64
Definition: c.h:539
static struct @169 value
uint32 pg_crc32c
Definition: pg_crc32c.h:38
pg_crc32c pg_comp_crc32c_sb8(pg_crc32c crc, const void *data, size_t len)
Definition: pg_crc32c_sb8.c:35
pg_crc32c pg_comp_crc32c_armv8(pg_crc32c crc, const void *data, size_t len)
pg_crc32c(* pg_comp_crc32c)(pg_crc32c crc, const void *data, size_t len)
static bool pg_crc32c_armv8_available(void)
static pg_crc32c pg_comp_crc32c_choose(pg_crc32c crc, const void *data, size_t len)
const void size_t len
const void * data
return crc

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