[Mesa-dev] [PATCH 4/4] glsl: In later GLSL versions, sequence operator is cannot be a constant expression

[Lofstedt, Marta]

Reviewed-by: Marta Lofstedt <marta.lofstedt at intel.com>


> -----Original Message-----
> From: mesa-dev [mailto:mesa-dev-bounces at lists.freedesktop.org] On
> Behalf Of Ian Romanick
> Sent: Wednesday, October 7, 2015 11:34 PM
> To: mesa-dev at lists.freedesktop.org
> Cc: Romanick, Ian D
> Subject: [Mesa-dev] [PATCH 4/4] glsl: In later GLSL versions, sequence
> operator is cannot be a constant expression
> 
> From: Ian Romanick <ian.d.romanick at intel.com>
> 
> Fixes:
>     ES3-CTS.shaders.negative.constant_sequence
> 
>     spec/glsl-es-3.00/compiler/global-initializer/from-sequence.vert
>     spec/glsl-es-3.00/compiler/global-initializer/from-sequence.frag
> 
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
>  src/glsl/ast_to_hir.cpp | 43
> ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp index
> 6af0f80..c7444ed 100644
> --- a/src/glsl/ast_to_hir.cpp
> +++ b/src/glsl/ast_to_hir.cpp
> @@ -3311,8 +3311,49 @@ process_initializer(ir_variable *var,
> ast_declaration *decl,
>        if (new_rhs != NULL) {
>           rhs = new_rhs;
> 
> +         /* Section 4.3.3 (Constant Expressions) of the GLSL ES 3.00.4 spec
> +          * says:
> +          *
> +          *     "A constant expression is one of
> +          *
> +          *        ...
> +          *
> +          *        - an expression formed by an operator on operands that are
> +          *          all constant expressions, including getting an element of
> +          *          a constant array, or a field of a constant structure, or
> +          *          components of a constant vector.  However, the sequence
> +          *          operator ( , ) and the assignment operators ( =, +=, ...)
> +          *          are not included in the operators that can create a
> +          *          constant expression."
> +          *
> +          * Section 12.43 (Sequence operator and constant expressions) says:
> +          *
> +          *     "Should the following construct be allowed?
> +          *
> +          *         float a[2,3];
> +          *
> +          *     The expression within the brackets uses the sequence operator
> +          *     (',') and returns the integer 3 so the construct is decl aring
> +          *     a single-dimensional array of size 3.  In some languages, the
> +          *     construct declares a two-dimensional array.  It would be
> +          *     preferable to make this construct illegal to avoid confusion.
> +          *
> +          *     One possibility is to change the definition of the sequence
> +          *     operator so that it does not return a constant- expression and
> +          *     hence cannot be used to declare an array size.
> +          *
> +          *     RESOLUTION: The result of a sequence operator is not a
> +          *     constant-expression."
> +          *
> +          * Section 4.3.3 (Constant Expressions) of the GLSL 4.30.9 spec
> +          * contains language almost identical to the section 4.3.3 fomr the
> +          * GLSL ES 3.00.4 spec.  This is a new limitation for these GLSL
> +          * versions.
> +          */
>           ir_constant *constant_value = rhs->constant_expression_value();
> -         if (!constant_value) {
> +         if (!constant_value ||
> +             (state->is_version(430, 300) &&
> +              decl->initializer->has_sequence_subexpression())) {
>              const char *const variable_mode =
>                 (type->qualifier.flags.q.constant)
>                 ? "const"
> --
> 2.1.0
> 
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