From: Qi Hu <huqi@loongson.cn>
To: gaosong <gaosong@loongson.cn>,
Richard Henderson <richard.henderson@linaro.org>,
qemu-devel@nongnu.org, maobibo <maobibo@loongson.cn>,
Peter Maydell <peter.maydell@linaro.org>,
alex.bennee@linaro.org
Subject: Re: [PATCH 5/5] target/loongarch: div if x/0 set dividend to 0
Date: Tue, 20 Sep 2022 10:18:05 +0800 [thread overview]
Message-ID: <3c401d0f-a34f-bd29-03a3-dddfae94ce0a@loongson.cn> (raw)
In-Reply-To: <e8a24cfc-005c-1196-35dd-05efdef6858b@loongson.cn>
On 2022/9/19 19:45, gaosong wrote:
>
> 在 2022/9/17 下午6:12, Richard Henderson 写道:
>> On 9/17/22 11:12, gaosong wrote:
>>>
>>> 在 2022/9/17 下午4:59, Qi Hu 写道:
>>>>
>>>> On 2022/9/17 15:59, Song Gao wrote:
>>>>> div.d, div.du, div,w, div.wu, the LoongArch host if x/0 the
>>>>> result is 0.
>>>>
>>>> The message has a typo: "div,w" => "div.w"
>>>>
>>>> Also I don't know why we need to do this, since the manual say:
>>>> "When the divisor is 0, the result can be any value".
>>>>
>>> I tested on LoongArch host, the result is always 0.
>>
>> But it is legal for a different loongarch host implementation to
>> return some other value. Therefore the test itself is not correct.
>>
> I think the manual maybe not correct, the hardware engineer said that
> they need to comfirm whether the result is always 0.
>
> Thanks.
> Song Gao
Hi,
The hardware designers suggested that 0 should not be used as the
default value when "div 0" occurs. The behavior is not guaranteed in
future processors.
So I think there are some ways to solve this:
- Remove this case("div 0") from risu test.
- Keep this patch by yourself. If you want to do risu test, patch it. :-)
regards,
Qi
>> r~
>
prev parent reply other threads:[~2022-09-20 2:19 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-17 7:59 [PATCH 0/5] Fix some bugs Song Gao
2022-09-17 7:59 ` [PATCH 1/5] target/loongarch: ftint_xxx insns set the result high 32bit 0xffffffff Song Gao
2022-09-17 7:59 ` [PATCH 2/5] target/loongarch: bstrins.w need set dest register EXT_SIGN Song Gao
2022-09-17 8:41 ` Qi Hu
2022-09-17 9:16 ` gaosong
2022-09-17 10:56 ` Qi Hu
2022-09-17 7:59 ` [PATCH 3/5] target/loongarch: Fix fnm{sub/add}_{s/d} set wrong flags Song Gao
2022-09-17 7:59 ` [PATCH 4/5] target/loongarch: flogb_{s/d} add set float_flag_divbyzero Song Gao
2022-09-17 7:59 ` [PATCH 5/5] target/loongarch: div if x/0 set dividend to 0 Song Gao
2022-09-17 8:59 ` Qi Hu
2022-09-17 9:12 ` gaosong
2022-09-17 10:12 ` Richard Henderson
2022-09-19 11:45 ` gaosong
2022-09-20 2:18 ` Qi Hu [this message]
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