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https://github.com/cuberite/libdeflate.git
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5729095d2d
Make test-only builds of libdeflate support an environmental variable LIBDEFLATE_DISABLE_CPU_FEATURES that contains a list of CPU features to disable like "avx512bw,avx2,sse2". This makes it possible to test all the variants of dynamically dispatched code without editing the source code. Note, this environmental variable is not a stable interface, so put the support for it behind a scary-looking option TEST_SUPPORT__DO_NOT_USE.
129 lines
3.5 KiB
C
129 lines
3.5 KiB
C
/*
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* arm/cpu_features.c - feature detection for ARM processors
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*
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* Copyright 2018 Eric Biggers
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following
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* conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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/*
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* ARM processors don't have a standard way for unprivileged programs to detect
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* processor features. But, on Linux we can read the AT_HWCAP and AT_HWCAP2
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* values from /proc/self/auxv.
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*
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* Ideally we'd use the C library function getauxval(), but it's not guaranteed
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* to be available: it was only added to glibc in 2.16, and in Android it was
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* added to API level 18 for ARM and level 21 for AArch64.
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*/
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#include "../cpu_features_common.h" /* must be included first */
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#include "cpu_features.h"
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#if ARM_CPU_FEATURES_ENABLED
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#include <errno.h>
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#include <fcntl.h>
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#include <string.h>
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#include <unistd.h>
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#define AT_HWCAP 16
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#define AT_HWCAP2 26
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volatile u32 _cpu_features = 0;
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static void scan_auxv(unsigned long *hwcap, unsigned long *hwcap2)
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{
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int fd;
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unsigned long auxbuf[32];
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int filled = 0;
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int i;
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fd = open("/proc/self/auxv", O_RDONLY);
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if (fd < 0)
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return;
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for (;;) {
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do {
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int ret = read(fd, &((char *)auxbuf)[filled],
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sizeof(auxbuf) - filled);
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if (ret <= 0) {
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if (ret < 0 && errno == EINTR)
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continue;
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goto out;
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}
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filled += ret;
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} while (filled < 2 * sizeof(long));
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i = 0;
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do {
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unsigned long type = auxbuf[i];
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unsigned long value = auxbuf[i + 1];
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if (type == AT_HWCAP)
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*hwcap = value;
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else if (type == AT_HWCAP2)
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*hwcap2 = value;
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i += 2;
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filled -= 2 * sizeof(long);
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} while (filled >= 2 * sizeof(long));
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memmove(auxbuf, &auxbuf[i], filled);
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}
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out:
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close(fd);
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}
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static const struct cpu_feature arm_cpu_feature_table[] = {
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{ARM_CPU_FEATURE_NEON, "neon"},
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{ARM_CPU_FEATURE_PMULL, "pmull"},
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};
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void setup_cpu_features(void)
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{
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u32 features = 0;
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unsigned long hwcap = 0;
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unsigned long hwcap2 = 0;
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scan_auxv(&hwcap, &hwcap2);
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#ifdef __arm__
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STATIC_ASSERT(sizeof(long) == 4);
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if (hwcap & (1 << 12)) /* HWCAP_NEON */
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features |= ARM_CPU_FEATURE_NEON;
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if (hwcap2 & (1 << 1)) /* HWCAP2_PMULL */
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features |= ARM_CPU_FEATURE_PMULL;
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#else
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STATIC_ASSERT(sizeof(long) == 8);
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if (hwcap & (1 << 1)) /* HWCAP_ASIMD */
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features |= ARM_CPU_FEATURE_NEON;
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if (hwcap & (1 << 4)) /* HWCAP_PMULL */
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features |= ARM_CPU_FEATURE_PMULL;
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#endif
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disable_cpu_features_for_testing(&features, arm_cpu_feature_table,
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ARRAY_LEN(arm_cpu_feature_table));
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_cpu_features = features | ARM_CPU_FEATURES_KNOWN;
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}
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#endif /* ARM_CPU_FEATURES_ENABLED */
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