[Mesa-dev] [PATCH 5/5] glsl: Update array access tracker of function parameters.

[Fabian Bieler]

On 2013-06-18 11:14, Ian Romanick wrote:
> On 06/03/2013 01:23 PM, Fabian Bieler wrote:
>> Uniform arrays are subject to beeing shrunk if higher members were not accessed.
>                                 ^^^^^^
> being
> 
>> Update the max_array_access flag so array members that were only accessed in
>> the function are not optimized away.
>>
>> This fixes Piglit test
>> spec/glsl-1.10/execution/samplers/in-parameter-array.shader_test.
>>
>> Signed-off-by: Fabian Bieler <fabianbieler at fastmail.fm>
>> ---
>>   src/glsl/ast_function.cpp | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/src/glsl/ast_function.cpp b/src/glsl/ast_function.cpp
>> index 00e0c05..9378894 100644
>> --- a/src/glsl/ast_function.cpp
>> +++ b/src/glsl/ast_function.cpp
>> @@ -322,6 +322,18 @@ generate_call(exec_list *instructions, ir_function_signature *sig,
>>           assert (!"Illegal formal parameter mode");
>>           break;
>>        }
>> +      } else if (formal->type->is_array()) {
>> +     /* Update the max_array_access field for array parameters.
>> +      * If the max_array_access of the formal parameter is zero, chances
>> +      * are we haven't parsed the function yet. Just set the array access
>> +      * to the whole array in that case.
>> +      */
> 
> What will be the size of 'u' in the following vertex shader with this change?  Will it be 3 or 16 or something else?  Does that change of the definition of foo is in a different compilation unit?
It would be 16 and it doesn't change if the function is in a different compilation unit. If we wanted it to be 3 we would have to update the array access tracker later. I thought about doing it during function inlining since currently all functions are always inlined for all drivers, but that's of course somewhat of a hack.
> 
> float foo(float [16]);
> 
> uniform float u[32];
I'm assuming you meant u[16], otherwise this doesn't compile.
> 
> void main()
> {
>     gl_Position = vec4(foo(u));
> }
> 
> float foo(float x[16])
> {
>      return x[2];
> }
> 
>> +     const unsigned max_array_access = (formal->max_array_access != 0)
>> +        ? formal->max_array_access : (formal->type->array_size() - 1);
>> +     ir_variable *var = actual->whole_variable_referenced();
>> +     if (var)
>> +        var->max_array_access =
>> +           MAX2(var->max_array_access, max_array_access);
>>         }
>>
>>         actual_iter.next();
>>
>