[Mesa-dev] [PATCH 1/3] util: Cope with LONG_BIT not being defined on Windows.

[Roland Scheidegger]

Am 09.08.2015 um 20:08 schrieb Jose Fonseca:
> On 09/08/15 17:47, Matt Turner wrote:
>> On Sun, Aug 9, 2015 at 3:57 AM, Jose Fonseca <jfonseca at vmware.com> wrote:
>>> Neither MSVC nor MinGW defines LONG_BIT.  For MSVC this was not a
>>> problem as
>>> it doesn't define __x86_64__ macro (it's GCC specific.)
>>>
>>> However on Windows long type is guaranteed to be 32bits.
>>>
>>> Also add an #error, as GCC will just warn, not throw any error, when no
>>> value is returned.
>>>
>>> Trivial.
>>> ---
>>>   src/util/rounding.h | 8 ++++++--
>>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/src/util/rounding.h b/src/util/rounding.h
>>> index b0c9918..ec31b47 100644
>>> --- a/src/util/rounding.h
>>> +++ b/src/util/rounding.h
>>> @@ -96,8 +96,10 @@ _mesa_lroundevenf(float x)
>>>   #ifdef __x86_64__
>>>   #if LONG_BIT == 64
>>>      return _mm_cvtss_si64(_mm_load_ss(&x));
>>> -#elif LONG_BIT == 32
>>> +#elif LONG_BIT == 32 || defined(_WIN32)
>>
>> Not clear to me that you want to do this, since on x86-32 using SSE
>> intrinsics will force a few memory transfers to and from the x87 FPU.
> 
> Our Windows builds use SSE math for x86. (ie., -fpmath=sse for GCC, no
> option required for MSVC, as it's the standard.)  So no x87 should be
> ever used.
> 
> (Probably it should make sense to use -msse2 and -fpmath=sse on all
> 32bits x86.)
> 
>>
>>>      return _mm_cvtss_si32(_mm_load_ss(&x));
>>> +#else
>>> +#error "Unsupported or undefined LONG_BIT"
>>
>> MSVC... sigh.
> 
> The problem was actually with MinGW, not MSVC.  As the commit
> description said, MSVC was fine (because it doesn't define __x86_64__).
> 
> AFAICT, LONG_BIT is not standard C.  So I don't think that MSVC or MinGW
> is at fault.
> 
> Jose

Apparently it's not even always defined on linux...
I wonder if soething like
#if LONG_MAX == 0x7FFFFFFFL would be more portable...

Roland