[Mesa-dev] [PATCH v2] glsl/linker: Allow unused in blocks which are not declated on previous stage

[Timothy Arceri]

Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>

On 24/08/18 18:25, Alejandro Piñeiro wrote:
> CCing Timothy just in case he still thinks that the original comment
> should remain as it is. In any case, it looks to me, so:
> 
> Reviewed-by: Alejandro Piñeiro <apinheiro at igalia.com>
> 
> 
> On 23/08/18 12:12, vadym.shovkoplias wrote:
>>  From Section 4.3.4 (Inputs) of the GLSL 1.50 spec:
>>
>>      "Only the input variables that are actually read need to be written
>>       by the previous stage; it is allowed to have superfluous
>>       declarations of input variables."
>>
>> Fixes:
>>      * interstage-multiple-shader-objects.shader_test
>>
>> v2:
>>    Update comment in ir.h since the usage of "used" field
>>    has been extended.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101247
>> Signed-off-by: Vadym Shovkoplias <vadym.shovkoplias at globallogic.com>
>> ---
>>   src/compiler/glsl/ir.h                      | 4 ++--
>>   src/compiler/glsl/link_interface_blocks.cpp | 8 +++++++-
>>   2 files changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/src/compiler/glsl/ir.h b/src/compiler/glsl/ir.h
>> index 67b38f48ef..d05d1998a5 100644
>> --- a/src/compiler/glsl/ir.h
>> +++ b/src/compiler/glsl/ir.h
>> @@ -667,8 +667,8 @@ public:
>>          * variable has been used.  For example, it is an error to redeclare a
>>          * variable as invariant after it has been used.
>>          *
>> -       * This is only maintained in the ast_to_hir.cpp path, not in
>> -       * Mesa's fixed function or ARB program paths.
>> +       * This is maintained in the ast_to_hir.cpp path and during linking,
>> +       * but not in Mesa's fixed function or ARB program paths.
>>          */
>>         unsigned used:1;
>>   
>> diff --git a/src/compiler/glsl/link_interface_blocks.cpp b/src/compiler/glsl/link_interface_blocks.cpp
>> index e5eca9460e..801fbcd5d9 100644
>> --- a/src/compiler/glsl/link_interface_blocks.cpp
>> +++ b/src/compiler/glsl/link_interface_blocks.cpp
>> @@ -417,9 +417,15 @@ validate_interstage_inout_blocks(struct gl_shader_program *prog,
>>          * write to any of the pre-defined outputs (e.g. if the vertex shader
>>          * does not write to gl_Position, etc), which is allowed and results in
>>          * undefined behavior.
>> +       *
>> +       * From Section 4.3.4 (Inputs) of the GLSL 1.50 spec:
>> +       *
>> +       *    "Only the input variables that are actually read need to be written
>> +       *     by the previous stage; it is allowed to have superfluous
>> +       *     declarations of input variables."
>>          */
>>         if (producer_def == NULL &&
>> -          !is_builtin_gl_in_block(var, consumer->Stage)) {
>> +          !is_builtin_gl_in_block(var, consumer->Stage) && var->data.used) {
>>            linker_error(prog, "Input block `%s' is not an output of "
>>                         "the previous stage\n", var->get_interface_type()->name);
>>            return;
>