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arm: detect cpu features at runtime on Linux

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This allows compiling optimised functions for features not enabled
in the core build and selecting these at runtime if the system has
the necessary support.

Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Mans Rullgard 2012-12-05 02:11:22 +00:00
parent b326755989
commit b57c1da81e
2 changed files with 86 additions and 1 deletions
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4
configure vendored
View File

@ -3161,7 +3161,9 @@ EOF
enabled vfp && check_insn vfp 'fadds s0, s0, s0'
enabled vfpv3 && check_insn vfpv3 'vmov.f32 s0, #1.0'
map 'enabled_any ${v}_external ${v}_inline || disable $v' $ARCH_EXT_LIST_ARM
[ $target_os = linux ] ||
map 'enabled_any ${v}_external ${v}_inline || disable $v' \
$ARCH_EXT_LIST_ARM
check_inline_asm asm_mod_q '"add r0, %Q0, %R0" :: "r"((long long)0)'
check_inline_asm asm_mod_y '"vmul.i32 d0, d0, %y0" :: "x"(0)'

83
libavutil/arm/cpu.c
View File

@ -19,6 +19,87 @@
#include "libavutil/cpu.h"
#include "config.h"
#define CORE_FLAG(f) \
(AV_CPU_FLAG_ ## f * (HAVE_ ## f ## _EXTERNAL || HAVE_ ## f ## _INLINE))
#define CORE_CPU_FLAGS \
(CORE_FLAG(ARMV5TE) | \
CORE_FLAG(ARMV6) | \
CORE_FLAG(ARMV6T2) | \
CORE_FLAG(VFP) | \
CORE_FLAG(VFPV3) | \
CORE_FLAG(NEON))
#if defined __linux__ || defined __ANDROID__
#include <stdint.h>
#include <stdio.h>
#define AT_HWCAP 16
/* Relevant HWCAP values from kernel headers */
#define HWCAP_VFP (1 << 6)
#define HWCAP_EDSP (1 << 7)
#define HWCAP_THUMBEE (1 << 11)
#define HWCAP_NEON (1 << 12)
#define HWCAP_VFPv3 (1 << 13)
#define HWCAP_TLS (1 << 15)
static int get_hwcap(uint32_t *hwcap)
{
struct { uint32_t a_type; uint32_t a_val; } auxv;
FILE *f = fopen("/proc/self/auxv", "r");
int err = -1;
if (!f)
return -1;
while (fread(&auxv, sizeof(auxv), 1, f) > 0) {
if (auxv.a_type == AT_HWCAP) {
*hwcap = auxv.a_val;
err = 0;
break;
}
}
fclose(f);
return err;
}
int ff_get_cpu_flags_arm(void)
{
int flags = CORE_CPU_FLAGS;
uint32_t hwcap;
if (get_hwcap(&hwcap) < 0)
return flags;
#define check_cap(cap, flag) do { \
if (hwcap & HWCAP_ ## cap) \
flags |= AV_CPU_FLAG_ ## flag; \
} while (0)
/* No flags explicitly indicate v6 or v6T2 so check others which
imply support. */
check_cap(EDSP, ARMV5TE);
check_cap(TLS, ARMV6);
check_cap(THUMBEE, ARMV6T2);
check_cap(VFP, VFP);
check_cap(VFPv3, VFPV3);
check_cap(NEON, NEON);
/* The v6 checks above are not reliable so let higher flags
trickle down. */
if (flags & (AV_CPU_FLAG_VFPV3 | AV_CPU_FLAG_NEON))
flags |= AV_CPU_FLAG_ARMV6T2;
if (flags & AV_CPU_FLAG_ARMV6T2)
flags |= AV_CPU_FLAG_ARMV6;
return flags;
}
#else
int ff_get_cpu_flags_arm(void)
{
return AV_CPU_FLAG_ARMV5TE * HAVE_ARMV5TE |
@ -28,3 +109,5 @@ int ff_get_cpu_flags_arm(void)
AV_CPU_FLAG_VFPV3 * HAVE_VFPV3 |
AV_CPU_FLAG_NEON * HAVE_NEON;
}
#endif