[pulseaudio-discuss] [PATCH v3] netbsd: Stop depending upon nonstandard __WORDSIZE

[Andrey Semashev]

On 2015-12-17 15:51, Andrey Semashev wrote:
> On 2015-12-17 15:33, Pali Rohár wrote:
>> On Thursday 17 December 2015 15:10:12 Andrey Semashev wrote:
>>> On 2015-12-17 14:50, Andrey Semashev wrote:
>>>> On 2015-12-17 02:44, Kamil Rytarowski wrote:
>>>>>
>>>>> On 16.12.2015 11:02, Pali Rohár wrote:
>>>>>>
>>>>>> Hi! There is probably no portable way for checking CPU type. But
>>>>>> you do not need to know CPU type here. You need to know if CPU has
>>>>>> fast 64bit numeric operations (and use 64bit speed optimization),
>>>>>> right?
>>>>>>
>>>>>> And this could be possible by checking size of int_fast32_t type
>>>>>> (defined in stdint.h). If is same as size of int_fast64_t type then
>>>>>> you could use 64bit optimization otherwise not (= 32bit integers
>>>>>> are faster then 64bit).
>>>>>>
>>>>>> But I will let this suggestion for reviewing of other people.
>>>>>
>>>>> This sounds like a good way to go.
>>>>
>>>> I don't think it does. int_fast32_t does not have to be 64-bit if
>>>> 32-bit
>>>> integers are fast.
>>
>> Yes. I did not wrote that int_fast32_t must be 64-bit. I wrote to
>> compare size of int_fast32_t and int_fast64_t.
>
> And they will be different on x32 which, following your logic, means
> that on x32 32-bit integers are faster than 64-bit. That's not true.
>
>>>> It _may_ be larger than 32-bit if 32-bit integers are
>>>> slow (most likely - do not have the target hardware support). I don't
>>>> think this is the case for x32 or x86_64.
>>
>> On 64bi x86 sizeof(int_fast32_t) is 8 and sizeof(int_fast64_t) also 8. On
>> 32bit x86 sizeof(int_fast32_t) is only 4.
>
> On x86_64, yes:
>
> gcc -m64 -dM -E - < /dev/null | grep FAST32
> #define __INT_FAST32_MAX__ 0x7fffffffffffffffL
> #define __INT_FAST32_TYPE__ long int
> #define __UINT_FAST32_MAX__ 0xffffffffffffffffUL
> #define __UINT_FAST32_TYPE__ long unsigned int
>
> On x32, no:
>
> gcc -mx32 -dM -E - < /dev/null | grep FAST32
> #define __INT_FAST32_MAX__ 0x7fffffff
> #define __INT_FAST32_TYPE__ int
> #define __UINT_FAST32_MAX__ 0xffffffffU
> #define __UINT_FAST32_TYPE__ unsigned int
>
>>>> If integer performance is what this preprocessor check influences, I'd
>>>> suggest checking the size of size_t. Or testing for particular
>>>> architectures explicitly, with 64-bit being the default and 32-bit only
>>>> for the tested architectures (this would probably make the code more
>>>> easily maintainable in the future).
>>>
>>> I've sent this privately in error.
>>>
>>> Also, it seems size_t is 32-bit on x32, so disregard that suggestion.
>>
>> Important question is: what you want to distinguish? It is not 32 vs 64
>> bit processor right? It is if architecture has 64bit long registers? Or
>> something else?
>
> The bitness of the architecture is a rather fuzzy term, but yes, it is
> important to determine what for this check is needed. From the
> discussion I gathered that the goal is to determine the largest fast
> integer type for math.

Damn, I keep pressing Reply instead of Reply to all... Sorry again.