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arm: detect cpu features at runtime on Linux 

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