[Mesa-dev] [PATCH 1/2] glsl: Fix redeclaration rules for gl_FragCoord.

[Chris Forbes]

OK, sounds good to me.

On Fri, May 2, 2014 at 5:55 AM, Anuj Phogat <anuj.phogat at gmail.com> wrote:
> On Thu, Apr 17, 2014 at 1:05 AM, Chris Forbes <chrisf at ijw.co.nz> wrote:
>> Correct, this doesn't try to tackle the link-time cases at all.
>>
>> After sending these out, Anuj told me that he had similar patches
>> pending review. Unfortunate to duplicate effort, but it's what I get
>> for doing a bunch of random bug-stomping, I guess :)
>>
>> Hopefully we can pick the best ideas from both series.
>>
> Chris, my series got r-b Ian. It'll be extra work to decouple compiler and
> linker patches in the series and then testing. So, I'm inclined towards
> landing my series as it is. Hope that is fine with you. We can always
> improve the compiler code later if required.
>
>> On Thu, Apr 17, 2014 at 6:29 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
>>> On 04/12/2014 10:30 PM, Chris Forbes wrote:
>>>> The ARB_fragment_coord_conventions spec, section 4.3.x (Input Layout
>>>> Qualifiers) says:
>>>>
>>>>   "All redeclarations of gl_FragCoord in all fragment shaders in a
>>>>   single program must have the same set of qualifiers. Within any
>>>>   shader, the first redeclarations of gl_FragCoord must appear before
>>>>   any use of gl_FragCoord."
>>>>
>>>> Fixes piglit's tests:
>>>>    arb_fragment_coord_conventions/compiler/redeclaration-after-use
>>>>    arb_fragment_coord_conventions/compiler/redeclaration-around-use
>>>>    glsl-1.50/compiler/fragment_coord_conventions/layout-qualifiers-conflicting-case-1
>>>>    glsl-1.50/compiler/fragment_coord_conventions/layout-qualifiers-conflicting-case-2
>>>>
>>>> Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
>>>> ---
>>>>  src/glsl/ast_to_hir.cpp | 20 ++++++++++++++++++++
>>>>  1 file changed, 20 insertions(+)
>>>>
>>>> diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
>>>> index 9b9d511..d1eb3e2 100644
>>>> --- a/src/glsl/ast_to_hir.cpp
>>>> +++ b/src/glsl/ast_to_hir.cpp
>>>> @@ -2715,9 +2715,29 @@ get_variable_being_redeclared(ir_variable *var, YYLTYPE loc,
>>>>        /* Allow redeclaration of gl_FragCoord for ARB_fcc layout
>>>>         * qualifiers.
>>>>         */
>>>> +
>>>> +      if (earlier->data.how_declared != ir_var_declared_implicitly
>>>> +          && (earlier->data.origin_upper_left != var->data.origin_upper_left
>>>> +             || earlier->data.pixel_center_integer != var->data.pixel_center_integer)) {
>>>> +         _mesa_glsl_error(&loc, state,
>>>> +                          "Inconsistent redeclarations of gl_FragCoord");
>>>> +      }
>>>> +
>>>>        earlier->data.origin_upper_left = var->data.origin_upper_left;
>>>>        earlier->data.pixel_center_integer = var->data.pixel_center_integer;
>>>>
>>>> +      if (earlier->data.used &&
>>>> +          earlier->data.how_declared == ir_var_declared_implicitly) {
>>>> +         /* ARB_fragment_coord_conventions spec Section 4.3.x.1
>>>> +          * (Input Layout Qualifier) says:
>>>> +          *
>>>> +          * "Within any shader, the first redeclarations of gl_FragCoord
>>>> +          * must appear before any use of gl_FragCoord."
>>>> +          */
>>>> +         _mesa_glsl_error(&loc, state,
>>>> +                          "First redeclaration of gl_FragCoord must appear before any use");
>>>> +      }
>>>> +
>>>>        /* According to section 4.3.7 of the GLSL 1.30 spec,
>>>>         * the following built-in varaibles can be redeclared with an
>>>>         * interpolation qualifier:
>>>>
>>>
>>> It seems like this will catch multiple, inconsistent redeclarations
>>> within a single fragment shader...but the spec text quoted indicates
>>> that redeclarations in all fragment shaders being linked together into a
>>> single program need to be consistent.
>>>
>>> I don't see any code to handle that in linker*.cpp, so presumably we
>>> ought to add that as well.  Regardless, this is a good improvement!
>>>
>>> Both patches are:
>>> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
>>>
>>> Thanks, Chris.
>>>
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