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aarch64: Add Linux runtime cpu feature detection using HWCAP_CPUID

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Based partially on code by Janne Grunau.

Signed-off-by: Martin Storsjö <martin@martin.st>
This commit is contained in:
Martin Storsjö 2023-05-25 15:47:15 +03:00
parent 397cb623c8
commit 493fcde50a
2 changed files with 54 additions and 0 deletions
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2
configure vendored
View File

@ -2209,6 +2209,7 @@ HAVE_LIST_PUB="
HEADERS_LIST="
arpa_inet_h
asm_hwcap_h
asm_types_h
cdio_paranoia_h
cdio_paranoia_paranoia_h
@ -6432,6 +6433,7 @@ check_headers io.h
enabled libdrm &&
check_headers linux/dma-buf.h
check_headers asm/hwcap.h
check_headers linux/perf_event.h
check_headers libcrystalhd/libcrystalhd_if.h
check_headers malloc.h

52
libavutil/aarch64/cpu.c
View File

@ -20,6 +20,56 @@
#include "libavutil/cpu_internal.h"
#include "config.h"
#if (defined(__linux__) || defined(__ANDROID__)) && HAVE_GETAUXVAL && HAVE_ASM_HWCAP_H
#include <stdint.h>
#include <asm/hwcap.h>
#include <sys/auxv.h>
#define get_cpu_feature_reg(reg, val) \
__asm__("mrs %0, " #reg : "=r" (val))
static int detect_flags(void)
{
int flags = 0;
unsigned long hwcap;
hwcap = getauxval(AT_HWCAP);
#if defined(HWCAP_CPUID)
// We can check for DOTPROD and I8MM using HWCAP_ASIMDDP and
// HWCAP2_I8MM too, avoiding to read the CPUID registers (which triggers
// a trap, handled by the kernel). However the HWCAP_* defines for these
// extensions are added much later than HWCAP_CPUID, so the userland
// headers might lack support for them even if the binary later is run
// on hardware that does support it (and where the kernel might support
// HWCAP_CPUID).
// See https://www.kernel.org/doc/html/latest/arm64/cpu-feature-registers.html
if (hwcap & HWCAP_CPUID) {
uint64_t tmp;
get_cpu_feature_reg(ID_AA64ISAR0_EL1, tmp);
if (((tmp >> 44) & 0xf) == 0x1)
flags |= AV_CPU_FLAG_DOTPROD;
get_cpu_feature_reg(ID_AA64ISAR1_EL1, tmp);
if (((tmp >> 52) & 0xf) == 0x1)
flags |= AV_CPU_FLAG_I8MM;
}
#else
(void)hwcap;
#endif
return flags;
}
#else
static int detect_flags(void)
{
return 0;
}
#endif
int ff_get_cpu_flags_aarch64(void)
{
int flags = AV_CPU_FLAG_ARMV8 * HAVE_ARMV8 |
@ -33,6 +83,8 @@ int ff_get_cpu_flags_aarch64(void)
flags |= AV_CPU_FLAG_I8MM;
#endif
flags |= detect_flags();
return flags;
}