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

[Ian Romanick]

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?

float foo(float [16]);

uniform float u[32];

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();
>