[Mesa-dev] [PATCH] gallium/util: Define ffsll on OpenBSD.

Sat Mar 21 10:10:06 PDT 2015

On 17/03/15 23:44, Emil Velikov wrote:
> On 17/03/15 01:25, Jonathan Gray wrote:
>> On Mon, Mar 16, 2015 at 08:37:28PM +0000, Emil Velikov wrote:
>>> On 26/02/15 13:49, Jose Fonseca wrote:
>>>> On 26/02/15 13:42, Jose Fonseca wrote:
>>>>> On 26/02/15 03:55, Jonathan Gray wrote:
>>>>>> On Wed, Feb 25, 2015 at 07:09:26PM -0800, Matt Turner wrote:
>>>>>>> On Wed, Feb 25, 2015 at 7:03 PM, Jonathan Gray <jsg at jsg.id.au> wrote:
>>>>>>>> On Wed, Feb 25, 2015 at 06:53:14PM -0800, Matt Turner wrote:
>>>>>>>>> On Wed, Feb 25, 2015 at 5:37 PM, Jonathan Gray <jsg at jsg.id.au> wrote:
>>>>>>>>>> If it isn't going to be configure checks could someone merge the
>>>>>>>>>> original patch in this thread?
>>>>>>>>>
>>>>>>>>> I committed
>>>>>>>>>
>>>>>>>>> commit 3492e88090d2d0c0bfbc934963b8772b45fc8880
>>>>>>>>> Author: Matt Turner <mattst88 at gmail.com>
>>>>>>>>> Date:   Fri Feb 20 18:46:43 2015 -0800
>>>>>>>>>
>>>>>>>>>      gallium/util: Use HAVE___BUILTIN_* macros.
>>>>>>>>>
>>>>>>>>>      Reviewed-by: Eric Anholt <eric at anholt.net>
>>>>>>>>>      Reviewed-by: Jose Fonseca <jfonseca at vmware.com>
>>>>>>>>>
>>>>>>>>> which switched over a bunch of preprocessor checks around __builtin*
>>>>>>>>> calls to use the macros defined by autotools.
>>>>>>>>>
>>>>>>>>> So I think cleaning it up to use __builtin_ffs* first #ifdef
>>>>>>>>> HAVE___BUILTIN_* can go forward now.
>>>>>>>>
>>>>>>>> Yes but there is no HAVE_FFSLL for constructs like
>>>>>>>>
>>>>>>>> #if !defined(HAVE_FFSLL) && defined(HAVE___BUILTIN_FFSLL)
>>>>>>>>
>>>>>>>> or is it ok to always use the builtin?
>>>>>>>
>>>>>>> I think the question is whether it's okay to always use the builtin if
>>>>>>> it's available (as opposed to libc functions). I think the answer to
>>>>>>> that is yes.
>>>>>>
>>>>>> So in that case how about the following?  Or is it going to break
>>>>>> the android scons build?
>>>>>>
>>>>>>  From cba39ba72115e57d262cb4b099c4e72106f01812 Mon Sep 17 00:00:00 2001
>>>>>> From: Jonathan Gray <jsg at jsg.id.au>
>>>>>> Date: Thu, 26 Feb 2015 14:46:45 +1100
>>>>>> Subject: [PATCH] gallium/util: use ffs* builtins if available
>>>>>>
>>>>>> Required to build on OpenBSD which doesn't have ffsll in libc.
>>>>>>
>>>>>> Signed-off-by: Jonathan Gray <jsg at jsg.id.au>
>>>>>> ---
>>>>>>   src/gallium/auxiliary/util/u_math.h | 11 ++++++++---
>>>>>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/src/gallium/auxiliary/util/u_math.h
>>>>>> b/src/gallium/auxiliary/util/u_math.h
>>>>>> index b4a65e4..5bc9b97 100644
>>>>>> --- a/src/gallium/auxiliary/util/u_math.h
>>>>>> +++ b/src/gallium/auxiliary/util/u_math.h
>>>>>> @@ -384,9 +384,6 @@ unsigned ffs( unsigned u )
>>>>>>
>>>>>>      return i;
>>>>>>   }
>>>>>> -#elif defined(__MINGW32__) || defined(PIPE_OS_ANDROID)
>>>>>> -#define ffs __builtin_ffs
>>>>>> -#define ffsll __builtin_ffsll
>>>>>
>>>>> Scons does define HAVE___BUILTIN_FFS for mingw.
>>>>>
>>>>> However `git grep '\<ffs\>` shows ffs is used directly in many other
>>>>> places.  So I suspect this change will break them.
>>>>>
>>>>>>   #endif
>>>>>>
>>>>>>   #endif /* FFS_DEFINED */
>>>>>> @@ -435,7 +432,11 @@ util_last_bit_signed(int i)
>>>>>>   static INLINE int
>>>>>>   u_bit_scan(unsigned *mask)
>>>>>>   {
>>>>>> +#if defined(HAVE___BUILTIN_FFS)
>>>>>> +   int i = __builtin_ffs(*mask) - 1;
>>>>>> +#else
>>>>>>      int i = ffs(*mask) - 1;
>>>>>> +#endif
>>>>>>      *mask &= ~(1 << i);
>>>>>>      return i;
>>>>>>   }
>>>>>> @@ -444,7 +445,11 @@ u_bit_scan(unsigned *mask)
>>>>>>   static INLINE int
>>>>>>   u_bit_scan64(uint64_t *mask)
>>>>>>   {
>>>>>> +#if defined(HAVE___BUILTIN_FFSLL)
>>>>>> +   int i = __builtin_ffsll(*mask) - 1;
>>>>>> +#else
>>>>>>      int i = ffsll(*mask) - 1;
>>>>>> +#endif
>>>>>>      *mask &= ~(1llu << i);
>>>>>>      return i;
>>>>>>   }
>>>>>>
>>>>>
>>>>>
>>>>> I think the right thing long term is to provide ffs and ffsll in
>>>>> c99_compat.h or c99_math.h for all platforms.  And let the rest of the
>>>>> code just always assume it's available somehow.
>>>>>
>>>>>
>>>>> Otherwise, let's just '#define ffs __builtin_ffs' on OpenBSD too.
>>>>
>>>> In other words, the original patch on this thread
>>>>
>>>>   http://lists.freedesktop.org/archives/mesa-dev/2015-February/076071.html
>>>>
>>>> is the only patch I've seen so far that doesn't break Mingw.
>>>>
>>>> If you rather use HAVE___BUILTIN_FFSLL, then just do
>>>>
>>>> diff --git a/src/gallium/auxiliary/util/u_math.h
>>>> b/src/gallium/auxiliary/util/u_math.h
>>>> index 959f76e..d372cfd 100644
>>>> --- a/src/gallium/auxiliary/util/u_math.h
>>>> +++ b/src/gallium/auxiliary/util/u_math.h
>>>> @@ -384,7 +384,7 @@ unsigned ffs( unsigned u )
>>>>
>>>>     return i;
>>>>  }
>>>> -#elif defined(__MINGW32__) || defined(PIPE_OS_ANDROID)
>>>> +#elif defined(__MINGW32__) || defined(PIPE_OS_ANDROID) ||
>>>> defined(HAVE___BUILTIN_FFSLL)
>>>>  #define ffs __builtin_ffs
>>>>  #define ffsll __builtin_ffsll
>>>>  #endif
>>>>
>>> Jonathan
>>>
>>> Seems like this has ended up a longer discussion that anticipated :\
>>> Can you please confirm if the above works for you ?
>>>
>>> Thanks
>>> Emil
>>
>> It looks like that diff was mangled by the mail client and doesn't have
>> the newline escaped.  It also assumes a ffsll builtin implies a ffs
>> builtin is present.  So how about the following instead:
>>
>> diff --git a/src/gallium/auxiliary/util/u_math.h b/src/gallium/auxiliary/util/u_math.h
>> index 8f62cac..89c63d7 100644
>> --- a/src/gallium/auxiliary/util/u_math.h
>> +++ b/src/gallium/auxiliary/util/u_math.h
>> @@ -383,14 +383,28 @@ unsigned ffs( unsigned u )
>>  
>>     return i;
>>  }
>> -#elif defined(__MINGW32__) || defined(PIPE_OS_ANDROID)
>> +#elif defined(__MINGW32__) || defined(PIPE_OS_ANDROID) || \
>> +    defined(HAVE___BUILTIN_FFS) 
>>  #define ffs __builtin_ffs
>> -#define ffsll __builtin_ffsll
>>  #endif
>>  
>>  #endif /* FFS_DEFINED */
>>  
>>  /**
>> + * Find first bit set in long long.  Least significant bit is 1.
>> + * Return 0 if no bits set.
>> + */
>> +#ifndef FFSLL_DEFINED
>> +#define FFSLL_DEFINED 1
>> +
>> +#if defined(__MINGW32__) || defined(PIPE_OS_ANDROID) || \
>> +    defined(HAVE___BUILTIN_FFSLL)
>> +#define ffsll __builtin_ffsll
>> +#endif
>> +
>> +#endif /* FFSLL_DEFINED */
>> +
>> +/**
>>   * Find last bit set in a word.  The least significant bit is 1.
>>   * Return 0 if no bits are set.
>>   */
>>
> Looks ok to me. Afaict splitting out __builtin_ffs and __builtin_ffsll
> is a nice idea, as one does have to imply the other. Haven't seen any
> references behind the FFS_DEFINED guards, although I'd assume that is to
> prevent clashing with the one in classic mesa.
> 
> Reviewed-by: Emil Velikov <emil.l.velikov at gmail.com>
> 
Fwiw, I will be commiting this in the next few days unless there are any
objections.

-Emil