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Add CPU detection for FreeBSD / OpenBSD AArch64 #2162

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Add CPU detection for FreeBSD / OpenBSD AArch64 #2162

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9 changes: 9 additions & 0 deletions absl/base/config.h
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Original file line number Diff line number Diff line change
Expand Up @@ -381,6 +381,15 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
#define ABSL_HAVE_SCHED_YIELD 1
#endif

// ABSL_HAVE_ELF_AUX_INFO
//
// Checks whether the platform implements elf_aux_info(3).
#ifdef ABSL_HAVE_ELF_AUX_INFO
#error ABSL_HAVE_ELF_AUX_INFO cannot be directly set
#elif (defined(__FreeBSD__) || defined(__OpenBSD__)) && __has_include(<sys/auxv.h>)
#define ABSL_HAVE_ELF_AUX_INFO 1
#endif

// ABSL_HAVE_SEMAPHORE_H
//
// Checks whether the platform supports the <semaphore.h> header and sem_init(3)
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24 changes: 20 additions & 4 deletions absl/base/internal/cpu_detect.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -20,8 +20,11 @@

#include "absl/base/config.h"

#if defined(__aarch64__) && defined(__linux__)
#if defined(__aarch64__) && \
(defined(__linux__) || defined(ABSL_HAVE_ELF_AUX_INFO))
#if defined(__linux__)
#include <asm/hwcap.h>
#endif
#include <sys/auxv.h>
#endif

Expand Down Expand Up @@ -265,7 +268,8 @@ bool SupportsBmi2() {
return (cpu_info[1] & (1 << 8)) != 0;
}

#elif defined(__aarch64__) && defined(__linux__)
#elif defined(__aarch64__) && \
(defined(__linux__) || defined(ABSL_HAVE_ELF_AUX_INFO))

#ifndef HWCAP_CPUID
#define HWCAP_CPUID (1 << 11)
Expand All @@ -276,12 +280,18 @@ bool SupportsBmi2() {

CpuType GetCpuType() {
// MIDR_EL1 is not visible to EL0, however the access will be emulated by
// linux if AT_HWCAP has HWCAP_CPUID set.
// Linux, FreeBSD and OpenBSD if AT_HWCAP has HWCAP_CPUID set.
//
// This method will be unreliable on heterogeneous computing systems (ex:
// big.LITTLE) since the value of MIDR_EL1 will change based on the calling
// thread.
#if defined(ABSL_HAVE_ELF_AUX_INFO)
uint64_t hwcaps;
if (elf_aux_info(AT_HWCAP, &hwcaps, sizeof(hwcaps)) != 0)
return CpuType::kUnknown;
#else
uint64_t hwcaps = getauxval(AT_HWCAP);
#endif
if (hwcaps & HWCAP_CPUID) {
uint64_t midr = 0;
ABSL_INTERNAL_AARCH64_ID_REG_READ(MIDR_EL1, midr);
Expand Down Expand Up @@ -328,7 +338,13 @@ CpuType GetCpuType() {
}

bool SupportsArmCRC32PMULL() {
#if defined(HWCAP_CRC32) && defined(HWCAP_PMULL)
#if defined(ABSL_HAVE_ELF_AUX_INFO)
uint64_t hwcaps;
bool ret = false;
if (elf_aux_info(AT_HWCAP, &hwcaps, sizeof(hwcaps)) == 0)
ret = (hwcaps & HWCAP_CRC32) && (hwcaps & HWCAP_PMULL);
return ret;
#elif defined(HWCAP_CRC32) && defined(HWCAP_PMULL)
uint64_t hwcaps = getauxval(AT_HWCAP);
return (hwcaps & HWCAP_CRC32) && (hwcaps & HWCAP_PMULL);
#else
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