Re: [ping][patch] Fixed-point patch 2/10

[Mark Mitchell <mark@codesourcery.com>]

Nigel Stephens wrote:
> 
> 
> Mark Mitchell wrote:
>> Fu, Chao-Ying wrote:
>>
>>  
>>> Ex 2: (A and B are negative. )
>>> A.high = 0xffffffffffffffff and A.low = 0x8000000000000000
>>> B.high = 0xffffffffffffffff and B.low = 0x0000000000000001
>>> => A > B, because A.high == B.high and
>>> (unsigned HOST_WIDE_INT) a.low > (unsigned HOST_WIDE_INT) b.low
>>>     
>>
>> Yes, I see; two's complement is set up so that after masking the sign
>> bit, you can do an unsigned compare.  Thank you for explaining.
>>   
> 
> Since double_int is already declared with low unsigned, like this:
> 
>    typedef struct
>    {
>      unsigned HOST_WIDE_INT low;
>      HOST_WIDE_INT high;
>    } double_int;
> 
> 
> Would it be more obvious to simply remove the casts altogether, e.g.

There's a comment in double-int.h that suggests that the signedness of
low/high is historical and subject to change.  So, I think the casts are
OK -- but I think omitting them is also OK.  Chao-Ying, you may decide
that as you please.

Thanks,

-- 
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713