[Mesa-dev] [GSoC2016] Interested in implementing "Soft" double precision floating point support

[Ian Romanick]

On 03/10/2016 03:09 PM, Dylan Baker wrote:
> Quoting Marek Olšák (2016-03-10 06:57:57)
>> On Thu, Mar 10, 2016 at 3:30 PM, tournier.elie <tournier.elie at gmail.com> wrote:
>>> First, thank you all for your answers.
>>>
>>> So if I summarize what was said, we need
>>> Ian:
>>>  - add
>>>  - negate
>>>  - absolute value
>>>  - multiply
>>>  - reciprocal
>>>  - convert to single precision
>>>  - convert from single precision
>>> Roland:
>>>  - sqrt
>>>  - comparaison (< / == / >)
>>>  - floor/ceil
>>> I will contact Pat Brown (His name appear in the contact field in [1]) to
>>> know if we need the function below for implement gpu_shader_fp64.
>>>  - pow
>>>  - exp
>>>  - log
>>>
>>> About the license
>>>
>>> Like I mentioned in the project description, there are quite a few
>>> existing C implementations of these functions.  Finding one of those
>>> that you can understand and that has a compatible license is probably
>>> the best place to start.
>>>
>>> Main Mesa code is under MIT license.
>>> If I chose to use a GNU GPL license file like Linux kernel [3], my code must
>>> be under GNU GPL and probably all the project too. Am I right?
>>>
>>> [1] https://www.opengl.org/registry/specs/ARB/gpu_shader_fp64.txt
>>> [2] http://www.mesa3d.org/license.html
>>> [3]
>>> https://github.com/torvalds/linux/blob/097f70b3c4d84ffccca15195bdfde3a37c0a7c0f/arch/arm/nwfpe/softfloat.c
>>
>> You can't use GNU GPL for this project.
>>
>> The kernel as a whole is licensed under GNU GPL, but some source files
>> aren't. The file you linked doesn't mention GNU GPL. Somebody needs to
>> verify that the file you linked can be legally re-licensed under the
>> MIT license. If not, I think you have to forget the contents of the
>> file immediately, but I'm not a lawyer.
>>
>> Marek
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> 
> Most BSD style licenses are legally compatible, as long as none of the
> developers object. One of the BSD kernels should have a softfloat
> implementation that would be license compatible.

Yes, and there are a couple C compilers that have compatible licenses.
Portable C Compiler (PCC) being one.  LLVM might also support some
devices that lack floating-point hardware.


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