Le 24 mai 2023 10:39:59 GMT+03:00, Hao Chen <chen...@loongson.cn> a écrit :
>
>在 2023/5/20 下午5:38, Rémi Denis-Courmont 写道:
>> Le lauantaina 20. toukokuuta 2023, 10.27.19 EEST Hao Chen a écrit :
>>> From: yuanhecai <yuanhe...@loongson.cn>
>>>
>>> This patch supports the use of the "checkasm --bench" testing feature
>>> on loongarch platform.
>>>
>>> Change-Id: I42790388d057c9ade0dfa38a19d9c1fd44ca0bc3
>>> ---
>>> libavutil/loongarch/timer.h | 48 +++++++++++++++++++++++++++++++++++++
>>> libavutil/timer.h | 2 ++
>>> 2 files changed, 50 insertions(+)
>>> create mode 100644 libavutil/loongarch/timer.h
>>>
>>> diff --git a/libavutil/loongarch/timer.h b/libavutil/loongarch/timer.h
>>> new file mode 100644
>>> index 0000000000..44ed786409
>>> --- /dev/null
>>> +++ b/libavutil/loongarch/timer.h
>>> @@ -0,0 +1,48 @@
>>> +/*
>>> + * Copyright (c) 2023 Loongson Technology Corporation Limited
>>> + * Contributed by Hecai Yuan <yuanhe...@loongson.cn>
>>> + *
>>> + * This file is part of FFmpeg.
>>> + *
>>> + * FFmpeg is free software; you can redistribute it and/or
>>> + * modify it under the terms of the GNU Lesser General Public
>>> + * License as published by the Free Software Foundation; either
>>> + * version 2.1 of the License, or (at your option) any later version.
>>> + *
>>> + * FFmpeg is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>>> + * Lesser General Public License for more details.
>>> + *
>>> + * You should have received a copy of the GNU Lesser General Public
>>> + * License along with FFmpeg; if not, write to the Free Software
>>> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
>>> USA + */
>>> +
>>> +#ifndef AVUTIL_LOONGARCH_TIMER_H
>>> +#define AVUTIL_LOONGARCH_TIMER_H
>>> +
>>> +#include <stdint.h>
>>> +#include "config.h"
>>> +
>>> +#if HAVE_INLINE_ASM
>>> +
>>> +#define AV_READ_TIME read_time
>>> +
>>> +static inline uint64_t read_time(void)
>>> +{
>>> +
>>> +#if ARCH_LOONGARCH64
>>> + uint64_t a, id = 0;
>> Initial value is never used.
>>
>>> + __asm__ volatile ( "rdtime.d %0, %1" : "=r"(a), "=r"(id) :: "memory"
>>> ); + return a;
>>> +#else
>>> + uint32_t a, id = 0;
>>> + __asm__ volatile ( "rdtimel.w %0, %1" : "=r"(a), "=r"(id) :: "memory"
>>> ); + return (uint64_t)a;
>>> +#endif
>> Why do you clobber memory here?
>>
>>> +}
>>> +
>>> +#endif /* HAVE_INLINE_ASM */
>>> +
>>> +#endif /* AVUTIL_LOONGARCH_TIMER_H */
>>> diff --git a/libavutil/timer.h b/libavutil/timer.h
>>> index d3db5a27ef..861ba7e9d7 100644
>>> --- a/libavutil/timer.h
>>> +++ b/libavutil/timer.h
>>> @@ -61,6 +61,8 @@
>>> # include "riscv/timer.h"
>>> #elif ARCH_X86
>>> # include "x86/timer.h"
>>> +#elif ARCH_LOONGARCH
>>> +# include "loongarch/timer.h"
>>> #endif
>>>
>>> #if !defined(AV_READ_TIME)
>>>
>> Thanks for your advice. As described in loongarch's instruction manual,
>> the rdtime.d instruction is used as follows:
>> rdtime.d rd, rj. The rj register stores the counter ID. In this application,
>> the value of counter ID is equal to 0.
You're setting a value, zero, to a variable `id`, that is then used as output
operand. As far as the compiler is concerned, the value zero is never used and
the initialisation can be elided. The value of register %1 is unspecified.
If you meant for `id` to be an input operand, the constraints are incorrect.
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