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/**
* SPDX-License-Identifier: GPL-3.0-or-later
* Copyright 2019 (C) Fabian Klötzl
*/
#include "seqcmp.h"
#include "config.h"
#include <assert.h>
#define UNLIKELY(X) __builtin_expect((X), 0)
size_t seqcmp_generic(const char *begin, const char *other, size_t length)
{
assert(begin != NULL);
assert(other != NULL);
size_t substitutions = 0;
size_t i = 0;
for (; i < length; i++) {
if (UNLIKELY(begin[i] != other[i])) {
substitutions++;
}
}
return substitutions;
}
#ifdef ENABLE_X86_SIMD
seqcmp_fn *seqcmp_select(void)
{
// As ifunc resolvers are called before any constructors run, we explicitly
// have to initialize the cpu model detector.
// https://gcc.gnu.org/onlinedocs/gcc/x86-Built-in-Functions.html
__builtin_cpu_init();
#ifdef ENABLE_AVX512
if (__builtin_cpu_supports("popcnt") &&
__builtin_cpu_supports("avx512bw") &&
__builtin_cpu_supports("avx512vl")) {
return seqcmp_avx512;
} else
#endif
if (__builtin_cpu_supports("popcnt") &&
__builtin_cpu_supports("avx2")) {
return seqcmp_avx2;
} else if (__builtin_cpu_supports("popcnt") &&
__builtin_cpu_supports("sse2")) {
return seqcmp_sse2;
} else {
return seqcmp_generic;
}
}
#if __has_attribute(ifunc) && HAVE_FUNC_ATTRIBUTE_IFUNC
size_t seqcmp(const char *begin, const char *other, size_t length)
__attribute__((ifunc("seqcmp_select")));
#else
size_t seqcmp(const char *begin, const char *other, size_t length)
{
return (seqcmp_select())(begin, other, length);
}
#endif
#else
size_t seqcmp(const char *begin, const char *other, size_t length)
{
return seqcmp_generic(begin, other, length);
}
#endif
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