Re: [Qemu-devel] [PATCH 1/4] target-tilegx: Add fpu header file

[Chen Gang]

On 11/13/15 00:10, Peter Maydell wrote:
> On 12 November 2015 at 16:04, Chen Gang <address@hidden> wrote:
>> On 11/12/15 22:34, Richard Henderson wrote:
>>> On 11/08/2015 06:43 AM, Chen Gang wrote:
>>>
>>>> +#if !defined(HOST_WORDS_BIGENDIAN)
>>>> +    /* According to float(uns)sisf2 and float(uns)sidf2 in gcc tilegx.md 
>>>> */
>>>> +    uint64_t exp : 8;             /* exp, 0x9e: 31 + TILEGX_F_EXP_FZERO */
>>>> +    uint64_t uiknown0 : 2;        /* unknown */
>>>
>>> I would really rather you didn't use bitfields, because of exactly this 
>>> sort of endianness problem.  Because, really, you can't trust this layout.  
>>> But I won't press this point, because it is complicated enough already.
>>>
>>
>> Because of endianess issues, for me, I don't like bit fields either. But
>> I can not find any other simpler ways than current.
> 
>> OK, I shall remove them.
>>
>>>> +#pragma pack(pop)
>>>
>>> Huh?  What are you attempting to do here?
>>>
>>
>> It is for matching "#pragma pack(push, 1)" which is above all related
>> struct/unions in this header file.
> 
> Please don't use 'pragma pack' or bitfields. If you need to pack
> and unpack things from a target-CPU defined field use bit operations
> and/or extract32/deposit32/extract64/deposit64.
> 

OK, thanks, although it means I have to rewrite most of code, and test
them again. I shall try to send patch v2 within the next week.

Thanks.
-- 
Chen Gang (陈刚)

Open, share, and attitude like air, water, and life which God blessed