[FFmpeg-devel] [PATCH v2] avutil: use getauxval for CPU capabilities on linux/android ARM

[Aman Karmani]

From: Aman Karmani <aman at tmm1.net>

getauxval is faster, and works when procfs is not mounted

note that support on Android was added in 4.4 (API 20)

fixes #6578

Signed-off-by: Aman Karmani <aman at tmm1.net>
---
 configure           |  1 +
 libavutil/arm/cpu.c | 24 +++++++++++++++++++++---
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index 5b19a35f59..d21cfb4cbd 100755
--- a/configure
+++ b/configure
@@ -6265,6 +6265,7 @@ check_func_headers lzo/lzo1x.h lzo1x_999_compress
 check_func_headers mach/mach_time.h mach_absolute_time
 check_func_headers stdlib.h getenv
 check_func_headers sys/stat.h lstat
+check_func_headers sys/auxv.h getauxval
 
 check_func_headers windows.h GetModuleHandle
 check_func_headers windows.h GetProcessAffinityMask
diff --git a/libavutil/arm/cpu.c b/libavutil/arm/cpu.c
index 81e85e2525..c84a655c37 100644
--- a/libavutil/arm/cpu.c
+++ b/libavutil/arm/cpu.c
@@ -38,6 +38,10 @@
 #include <string.h>
 #include "libavutil/avstring.h"
 
+#if HAVE_GETAUXVAL
+#include <sys/auxv.h>
+#endif
+
 #define AT_HWCAP        16
 
 /* Relevant HWCAP values from kernel headers */
@@ -48,6 +52,19 @@
 #define HWCAP_VFPv3     (1 << 13)
 #define HWCAP_TLS       (1 << 15)
 
+static int get_auxval(uint32_t *hwcap)
+{
+#if HAVE_GETAUXVAL
+    unsigned long ret = getauxval(AT_HWCAP);
+    if (ret == 0)
+        return -1;
+    *hwcap = ret;
+    return 0;
+#else
+    return -1;
+#endif
+}
+
 static int get_hwcap(uint32_t *hwcap)
 {
     struct { uint32_t a_type; uint32_t a_val; } auxv;
@@ -106,9 +123,10 @@ int ff_get_cpu_flags_arm(void)
     int flags = CORE_CPU_FLAGS;
     uint32_t hwcap;
 
-    if (get_hwcap(&hwcap) < 0)
-        if (get_cpuinfo(&hwcap) < 0)
-            return flags;
+    if (get_auxval(&hwcap) < 0)
+        if (get_hwcap(&hwcap) < 0)
+            if (get_cpuinfo(&hwcap) < 0)
+                return flags;
 
 #define check_cap(cap, flag) do {               \
         if (hwcap & HWCAP_ ## cap)              \
-- 
2.33.0