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glsl: relax rule on varying matching for shaders older than 4.00 

Please see new code commment for full justification.

Fixes: 18004c338f ("glsl: fail when a shader's input var has not an equivalent out var in previous")

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/3648

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7184>
This commit is contained in:
Timothy Arceri 2020-10-16 19:26:51 +11:00
parent c97e82bab5
commit c54c42321e
1 changed files with 31 additions and 1 deletions
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32
src/compiler/glsl/link_varyings.cpp
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@ -875,10 +875,40 @@ cross_validate_outputs_to_inputs(struct gl_context *ctx,
/* Check for input vars with unmatched output vars in prev stage
* taking into account that interface blocks could have a matching
* output but with different name, so we ignore them.
*
* Section 4.3.4 (Inputs) of the GLSL 4.10 specifications say:
*
* "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."
*
* However it's not defined anywhere as to how we should handle
* inputs that are not written in the previous stage and it's not
* clear what "actually read" means.
*
* The GLSL 4.20 spec however is much clearer:
*
* "Only the input variables that are statically read need to
* be written by the previous stage; it is allowed to have
* superfluous declarations of input variables."
*
* It also has a table that states it is an error to statically
* read an input that is not defined in the previous stage. While
* it is not an error to not statically write to the output (it
* just needs to be defined to not be an error).
*
* The text in the GLSL 4.20 spec was an attempt to clarify the
* previous spec iterations. However given the difference in spec
* and that some applications seem to depend on not erroring when
* the input is not actually read in control flow we only apply
* this rule to GLSL 4.00 and higher. GLSL 4.00 was chosen as
* a 3.30 shader is the highest version of GLSL we have seen in
* the wild dependant on the less strict interpretation.
*/
assert(!input->data.assigned);
if (input->data.used && !input->get_interface_type() &&
!input->data.explicit_location)
!input->data.explicit_location &&
(prog->data->Version >= (prog->IsES ? 0 : 400)))
linker_error(prog,
"%s shader input `%s' "
"has no matching output in the previous stage\n",