[Mesa-dev] [PATCH v2] mesa: fix interface matching done in validate_io

[Tapani Pälli]

On 12/15/2015 03:31 AM, Timothy Arceri wrote:
> On Mon, 2015-12-14 at 10:29 +0200, Tapani Pälli wrote:
>> Patch makes following changes for interface matching:
>>
>>     - do not try to match builtin variables
>>     - handle swizzle in input name, as example 'a.z' should
>>       match with 'a'
>>     - check that amount of inputs and outputs matches
>>
>> These changes make interface matching tests to work in:
>>     ES31-CTS.sepshaderobjs.StateInteraction
>>
>> Test does not still pass completely due to errors in rendering
>> output. IMO this is unrelated to interface matching.
>>
>> v2: add spec reference, return true on desktop since we do not
>>      have failing cases for it, inputs and outputs amount do not
>>      need to match on desktop.
>>
>> Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
> Hi Tapani,
>
> Just a general comment first.
>
> I think we should first move _mesa_validate_pipeline_io() and
>   validate_io() to src/mesa/main/pipelineobj.c I don't think it belongs
> here right?

Sure, it can be done now. Original intention was to use program 
resources and that is why it ended up being here.

>
>> ---
>>   src/mesa/main/shader_query.cpp | 54
>> ++++++++++++++++++++++++++++++++++++++----
>>   1 file changed, 50 insertions(+), 4 deletions(-)
>>
>> diff --git a/src/mesa/main/shader_query.cpp
>> b/src/mesa/main/shader_query.cpp
>> index ced10a9..bc01b97 100644
>> --- a/src/mesa/main/shader_query.cpp
>> +++ b/src/mesa/main/shader_query.cpp
>> @@ -1377,19 +1377,38 @@ validate_io(const struct gl_shader
>> *input_stage,
>>               const struct gl_shader *output_stage, bool isES)
>>   {
>>      assert(input_stage && output_stage);
>> +   unsigned inputs = 0, outputs = 0;
>> +
>> +   /* Currently no matching done for desktop. */
> I think the spec quote should be moved here as it applies to all the
> rules in the function then you can also have the comment explaining why
> validation for desktop it not done.

OK

> I've also filed a spec bug for desktop for the reasons I outlined in
> irc previously. It would be great if you could quote the bug here also.
> Something like:
>
> /* FIXME: Update once Khronos spec bug #15331 is resolved. */

Sure, will add.

>> +   if (!isES)
>> +      return true;
>>   
>>      /* For each output in a, find input in b and do any required
>> checks. */
>>      foreach_in_list(ir_instruction, out, input_stage->ir) {
>>         ir_variable *out_var = out->as_variable();
>
> It's existing code but it would also be nice to have a patch that
> renames input_stage/output_stage to producer_stage/consumer_stage this
> it what they are called in the linker code. Maybe its just me but
> getting the outputs from input_stage just looks wrong.

OK, can change this.

>
>> -      if (!out_var || out_var->data.mode != ir_var_shader_out)
>> +      if (!out_var || out_var->data.mode != ir_var_shader_out ||
>> +          is_gl_identifier(out_var->name))
>>            continue;
>>   
>> +      outputs++;
>> +
>> +      inputs = 0;
>>         foreach_in_list(ir_instruction, in, output_stage->ir) {
> Two comments here:
>
> 1. Take a look at cross_validate_outputs_to_inputs() in
> link_varyings.cpp for a way to avoid the nested loop? Although it may
> cause even more overhaed using the symbol table not sure.

I don't know if symbol table can be trusted as variables that get 
optimized away or changed in some way are still there. Only way to be 
sure is to iterate IR or use resource list. Also, symbol table gets 
destroyed after linking. My first implementation was using a hash but 
that was also bad idea because variables names do not necessarily match 
exactly.

> 2. Take a look at the same function for matching via explicit location.
> Does the CTS not test for mismatched explicit locations? Maybe we
> should create a piglit test for this as your existing code doesn't take
> into account explicit locations.

No, I haven't seen this test using explicit locations. This patch also 
makes the interface matching pass.

> I was going to suggest sharing the code between here and the linker
> however I'm about to add a bunch of rules for matching the component
> qualifier for enhanced layouts so not entirely sure if we should do
> this what do you think?

Linker will need to do much more so maybe do separately, at least for now?

>>            ir_variable *in_var = in->as_variable();
>> -         if (!in_var || in_var->data.mode != ir_var_shader_in)
>> +         if (!in_var || in_var->data.mode != ir_var_shader_in ||
>> +             is_gl_identifier(in_var->name))
>>               continue;
>>   
>> -         if (strcmp(in_var->name, out_var->name) == 0) {
>> +         inputs++;
>> +
>> +         unsigned len = strlen(in_var->name);
>> +
>> +         /* Handle input swizzle in variable name. */
>> +         const char *dot = strchr(in_var->name, '.');
>> +         if (dot)
>> +            len = dot - in_var->name;
> Hmm ... I wonder if this is also missing from the linker or maybe the
> symbol table stuff handles this.

Variable names get mangled during optimizations so symbol table should 
have the correct names left during linking.

>> +
>> +         if (strncmp(in_var->name, out_var->name, len) == 0) {
>>               /* Since we now only validate precision, we can skip
>> this step for
>>                * desktop GLSL shaders, there precision qualifier is
>> ignored.
>>                *
>> @@ -1412,7 +1431,34 @@ validate_io(const struct gl_shader
>> *input_stage,
>>            }
>>         }
>>      }
>> -   return true;
>> +
>> +   /* Amount of inputs vs outputs should match when using OpenGL ES.
>> +    *
>> +    * From OpenGL ES 3.1 spec (Interface matching):
>> +    *
>> +    *    "At an interface between program objects, the set of inputs
>> and outputs
>> +    *    are considered to match exactly if and only if:
>> +    *
>> +    *    - Every declared input variable has a matching output, as
>> described
>> +    *    above.
>> +    *
>> +    *    - There are no user-defined output variables declared
>> without a
>> +    *    matching input variable declaration.
>> +    *
>> +    *    - All matched input and output variables have identical
>> precision
>> +    *    qualification.
>> +    *
>> +    *    When the set of inputs and outputs on an interface between
>> programs
>> +    *    matches exactly, all inputs are well-defined except when
>> the
>> +    *    corresponding outputs were not written in the previous
>> shader. However,
>> +    *    any mismatch between inputs and outputs will result in a
>> validation
>> +    *    failure."
>> +    *
>> +    * OpenGL Core 4.5 spec includes same paragraph as above but
>> without last
>> +    * precision or the last 'validation failure' clause. Therefore
>> behaviour is
>> +    * more relaxed, input and output amount does not need to match
>> on desktop.
> Well they do need to match if they are all used but it doesn't seem the
> spec requires it to validated so maybe "does not need to match" -> "is
> not required by the spec to be validated".

OK, will change.

> You are also exiting for desktop at the top of the if below is not
> required.

It is 'future-proofing' if/when we will have some desktop rules here as 
well. My assumption was that we will have some but looking at how Nvidia 
driver works, I don't think they have any rules at all for this so might 
be that it will not happen.

>> +    */
>> +   return isES ? inputs == outputs : true;
>>   }
>>   
>>   /**

// Tapani