[Mesa-dev] [PATCH 3/5] mesa: Make the gl_constant_value's bool occupy the same space as float/int.

[Bryan Cain]

On 08/20/2011 05:10 PM, Dan McCabe wrote:
> On 08/20/2011 01:30 PM, Bryan Cain wrote:
>> On 08/20/2011 03:05 PM, Dan McCabe wrote:
>>> What are the implications for other architectures that support doubles?
>>
>> I don't see what you mean.  gl_constant_value doesn't support doubles
>> yet.
>
> "Yet" - that is the operative word.
>
> You can buy GPUs that support doubles today. Therefore, double support
> should be on our radar (it appears to be on Eric's radar, based on his
> commit comment). And we should understand what the implications are
> for our code. Clearly, I don't understand the implications; if I did,
> I wouldn't have asked. But perhaps Eric might.
>
> There are a couple of possible answers.
>
> "I don't know" - OK, but at least let's ask the question and start
> thinking about it's answer.
>
> "No impact" - I like that answer.
>
> "It affects this, and this, and this" - While not ideal, at least we
> then know what to do in the future and prepare ourselves for that future.
>
> cheers, danm

This particular commit has no impact at all.  A core assumption of
gl_constant_value is that 4 of each type in the union will fit into a
vec4, so the gl_constant_value code will need to be reworked when double
support is added.  But this commit doesn't afffect that in any way.

Bryan

>
>>
>> Bryan
>>
>>>
>>> On 08/19/2011 05:56 PM, Eric Anholt wrote:
>>>> At least for Intel, all our uniform components are of uint32_t size,
>>>> either
>>>> float or signed or unsigned int.  For uploading uniform data in the
>>>> driver,
>>>> it's much easier to upload a full dword per uniform element instead
>>>> of trying
>>>> to pick out the bool byte and then fill in the top 3 bytes of pad
>>>> with 0.
>>>> ---
>>>>    src/mesa/program/prog_parameter.h |    2 +-
>>>>    1 files changed, 1 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/src/mesa/program/prog_parameter.h
>>>> b/src/mesa/program/prog_parameter.h
>>>> index 1a5ed34..4c2773a 100644
>>>> --- a/src/mesa/program/prog_parameter.h
>>>> +++ b/src/mesa/program/prog_parameter.h
>>>> @@ -53,7 +53,7 @@
>>>>    typedef union gl_constant_value
>>>>    {
>>>>       GLfloat f;
>>>> -   GLboolean b;
>>>> +   GLint b;
>>>>       GLint i;
>>>>       GLuint u;
>>>>    } gl_constant_value;
>
>