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Re: [Qemu-devel] [PATCH 1/6 v6] target-tilegx: Firstly add TILE-Gx with
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From: |
Chen Gang |
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Subject: |
Re: [Qemu-devel] [PATCH 1/6 v6] target-tilegx: Firstly add TILE-Gx with minimized features |
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Date: |
Sat, 21 Mar 2015 06:55:11 +0800 |
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User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 |
On 3/21/15 01:03, Richard Henderson wrote:
> On 03/18/2015 07:04 PM, Chen Gang wrote:
>> For me, I am not quite sure about it, the related functional description
>> is:
>>
>> rf[Dest] = signExtend32 ((int32_t) rf[SrcA] * (int32_t) rf[SrcB]);
>>
>> Do you mean it is equal to:
>>
>> rf[Dest] = signExtend32 (rf[SrcA] * rf[SrcB]);
>
> Yes, of course.
>
> Think about how multiplication works. Bit N of the input cannot affect any
> output bit in [N-1,0]. Thus the first sign-extend cannot affect the output.
>
OK, thanks. I shall skip the first type cast in patch v8.
--
Chen Gang
Open, share, and attitude like air, water, and life which God blessed