It will fallback to mach_absolute_time inside libavutil/timer.h
Reviewed-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
This is much less precise than the cycle counter register, but
the cycle counter register is not available on apple platforms
(and on linux, it requires a kernel module for allowing user mode
access).
Signed-off-by: Martin Storsjö <martin@martin.st>
The ISB (instruction synchronization barrier) might be too heavy for
START/STOPTIMER use but should be more accurate in checkasm where the
timing overhead is subtracted.
