[Mesa-dev] [PATCH v4] glsl: enforce invariant conditions for built-in variables

[Lars Hamre]

Ping.

On Tue, May 17, 2016 at 10:49 AM, Lars Hamre <chemecse at gmail.com> wrote:
> Gentle ping, if nobody has an issues I would appreciate a push.
>
> Regards,
> Lars Hamre
>
> On Mon, May 9, 2016 at 7:00 PM, Lars Hamre <chemecse at gmail.com> wrote:
>> v3/v4:
>>  - compare varying slot locations rather than names (Ilia Mirkin)
>> v2:
>>  - ES version check (Tapani Pälli)
>>
>> The conditions for which certain built-in special variables
>> can be declared invariant were not being checked.
>>
>> GLSL ES 1.00 specification, Section "Invariance and linkage" says:
>>
>> For the built-in special variables, gl_FragCoord can
>> only be declared invariant if and only if gl_Position is
>> declared invariant. Similarly gl_PointCoord can only be
>> declared invariant if and only if gl_PointSize is declared
>> invariant. It is an error to declare gl_FrontFacing as invariant.
>>
>> This fixes the following piglit tests in spec/glsl-es-1.00/linker:
>> glsl-fcoord-invariant
>> glsl-fface-invariant
>> glsl-pcoord-invariant
>>
>> Signed-off-by: Lars Hamre <chemecse at gmail.com>
>>
>> ---
>>
>> CC: Ilia Mirkin <imirkin at alum.mit.edu>
>>
>> NOTE: Someone with access will need to commit this after the
>>       review process
>>
>>  src/compiler/glsl/link_varyings.cpp | 43 +++++++++++++++++++++++++++++++++++--
>>  1 file changed, 41 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
>> index 34e82c7..c7c9f5f 100644
>> --- a/src/compiler/glsl/link_varyings.cpp
>> +++ b/src/compiler/glsl/link_varyings.cpp
>> @@ -352,13 +352,23 @@ cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
>>     glsl_symbol_table parameters;
>>     ir_variable *explicit_locations[MAX_VARYING][4] = { {NULL, NULL} };
>>
>> +   bool is_gl_position_invariant = false;
>> +   bool is_gl_point_size_invariant = false;
>> +
>>     /* Find all shader outputs in the "producer" stage.
>>      */
>>     foreach_in_list(ir_instruction, node, producer->ir) {
>>        ir_variable *const var = node->as_variable();
>>
>>        if ((var == NULL) || (var->data.mode != ir_var_shader_out))
>> -        continue;
>> +         continue;
>> +
>> +      if (prog->IsES && prog->Version < 300) {
>> +         if (var->data.location == VARYING_SLOT_POS)
>> +            is_gl_position_invariant = var->data.invariant;
>> +         if (var->data.location == VARYING_SLOT_PSIZ)
>> +            is_gl_point_size_invariant = var->data.invariant;
>> +      }
>>
>>        if (!var->data.explicit_location
>>            || var->data.location < VARYING_SLOT_VAR0)
>> @@ -442,7 +452,36 @@ cross_validate_outputs_to_inputs(struct gl_shader_program *prog,
>>        ir_variable *const input = node->as_variable();
>>
>>        if ((input == NULL) || (input->data.mode != ir_var_shader_in))
>> -        continue;
>> +         continue;
>> +
>> +      /*
>> +       * GLSL ES 1.00 specification, Section "Invariance and linkage" says:
>> +       *
>> +       *  "For the built-in special variables, gl_FragCoord can
>> +       *  only be declared invariant if and only if gl_Position is
>> +       *  declared invariant. Similarly gl_PointCoord can only be
>> +       *  declared invariant if and only if gl_PointSize is declared
>> +       *  invariant. It is an error to declare gl_FrontFacing as invariant."
>> +       */
>> +      if (prog->IsES && prog->Version < 300 && input->data.invariant) {
>> +         if (input->data.location == VARYING_SLOT_FACE) {
>> +            linker_error(prog,
>> +                         "gl_FrontFacing cannot be declared invariant");
>> +            return;
>> +         } else if (!is_gl_position_invariant &&
>> +                    input->data.location == VARYING_SLOT_POS) {
>> +            linker_error(prog,
>> +                         "gl_FragCoord cannot be declared invariant "
>> +                         "unless gl_Position is also invariant");
>> +            return;
>> +         } else if (!is_gl_point_size_invariant &&
>> +                    input->data.location == VARYING_SLOT_PNTC) {
>> +            linker_error(prog,
>> +                         "gl_PointCoord cannot be declared invariant "
>> +                         "unless gl_PointSize is also invariant");
>> +            return;
>> +         }
>> +      }
>>
>>        if (strcmp(input->name, "gl_Color") == 0 && input->data.used) {
>>           const ir_variable *const front_color =
>> --
>> 2.5.5
>>