[Mesa-dev] [PATCH 15/28] glsl: add support for packing varyings with explicit locations

[Anuj Phogat]

On Mon, Dec 28, 2015 at 9:00 PM, Timothy Arceri
<timothy.arceri at collabora.com> wrote:
> ---
>  src/glsl/lower_packed_varyings.cpp | 45 +++++++++++++++++++++++++++-----------
>  1 file changed, 32 insertions(+), 13 deletions(-)
>
> diff --git a/src/glsl/lower_packed_varyings.cpp b/src/glsl/lower_packed_varyings.cpp
> index d91aa22..2899846 100644
> --- a/src/glsl/lower_packed_varyings.cpp
> +++ b/src/glsl/lower_packed_varyings.cpp
> @@ -178,11 +178,13 @@ private:
>     void bitwise_assign_unpack(ir_rvalue *lhs, ir_rvalue *rhs);
>     unsigned lower_rvalue(ir_rvalue *rvalue, unsigned fine_location,
>                           ir_variable *unpacked_var, const char *name,
> -                         bool gs_input_toplevel, unsigned vertex_index);
> +                         bool gs_input_toplevel, unsigned vertex_index,
> +                         bool explicit_location);
>     unsigned lower_arraylike(ir_rvalue *rvalue, unsigned array_size,
>                              unsigned fine_location,
>                              ir_variable *unpacked_var, const char *name,
> -                            bool gs_input_toplevel, unsigned vertex_index);
> +                            bool gs_input_toplevel, unsigned vertex_index,
> +                            bool explicit_location);
>     ir_dereference *get_packed_varying_deref(unsigned location,
>                                              ir_variable *unpacked_var,
>                                              const char *name,
> @@ -294,7 +296,8 @@ lower_packed_varyings_visitor::run(struct gl_shader *shader)
>
>        /* Recursively pack or unpack it. */
>        this->lower_rvalue(deref, var->data.location * 4 + var->data.location_frac, var,
> -                         var->name, this->gs_input_vertices != 0, 0);
> +                         var->name, this->gs_input_vertices != 0, 0,
> +                         var->data.explicit_location);
>     }
>  }
>
> @@ -426,7 +429,8 @@ lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
>                                              ir_variable *unpacked_var,
>                                              const char *name,
>                                              bool gs_input_toplevel,
> -                                            unsigned vertex_index)
> +                                            unsigned vertex_index,
> +                                            bool explicit_location)
>  {
>     unsigned dmul = rvalue->type->is_double() ? 2 : 1;
>     /* When gs_input_toplevel is set, we should be looking at a geometry shader
> @@ -445,7 +449,7 @@ lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
>              = ralloc_asprintf(this->mem_ctx, "%s.%s", name, field_name);
>           fine_location = this->lower_rvalue(dereference_record, fine_location,
>                                              unpacked_var, deref_name, false,
> -                                            vertex_index);
> +                                            vertex_index, explicit_location);
>        }
>        return fine_location;
>     } else if (rvalue->type->is_array()) {
> @@ -454,14 +458,15 @@ lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
>         */
>        return this->lower_arraylike(rvalue, rvalue->type->array_size(),
>                                     fine_location, unpacked_var, name,
> -                                   gs_input_toplevel, vertex_index);
> +                                   gs_input_toplevel, vertex_index,
> +                                   explicit_location);
>     } else if (rvalue->type->is_matrix()) {
>        /* Matrices are packed/unpacked by considering each column vector in
>         * sequence.
>         */
>        return this->lower_arraylike(rvalue, rvalue->type->matrix_columns,
>                                     fine_location, unpacked_var, name,
> -                                   false, vertex_index);
> +                                   false, vertex_index, explicit_location);
>     } else if (rvalue->type->vector_elements * dmul +
>                fine_location % 4 > 4) {
>        /* This vector is going to be "double parked" across two varying slots,
> @@ -502,12 +507,13 @@ lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
>        if (left_components)
>           fine_location = this->lower_rvalue(left_swizzle, fine_location,
>                                              unpacked_var, left_name, false,
> -                                            vertex_index);
> +                                            vertex_index, explicit_location);
>        else
>           /* Top up the fine location to the next slot */
>           fine_location++;
>        return this->lower_rvalue(right_swizzle, fine_location, unpacked_var,
> -                                right_name, false, vertex_index);
> +                                right_name, false, vertex_index,
> +                                explicit_location);
>     } else {
>        /* No special handling is necessary; pack the rvalue into the
>         * varying.
> @@ -528,7 +534,17 @@ lower_packed_varyings_visitor::lower_rvalue(ir_rvalue *rvalue,
>        } else {
>           this->bitwise_assign_unpack(rvalue, swizzle);
>        }
> -      return fine_location + components;
> +
> +      /* Explicitly packed components are packed by interleaving arrays, so
> +       * simply bump the location by 4 to increment the location to the next
> +       * element.
> +       *
> +       * Otherwise we pack arrays elements end to end.
> +       */
Can you help me understand this comment using an example?

> +      if (explicit_location) {
> +         return fine_location + 4;
> +      } else
> +         return fine_location + components;
>     }
>  }
>
> @@ -554,7 +570,8 @@ lower_packed_varyings_visitor::lower_arraylike(ir_rvalue *rvalue,
>                                                 ir_variable *unpacked_var,
>                                                 const char *name,
>                                                 bool gs_input_toplevel,
> -                                               unsigned vertex_index)
> +                                               unsigned vertex_index,
> +                                               bool explicit_location)
>  {
>     for (unsigned i = 0; i < array_size; i++) {
>        if (i != 0)
> @@ -568,14 +585,16 @@ lower_packed_varyings_visitor::lower_arraylike(ir_rvalue *rvalue,
>            * are at the same location, but with a different vertex index.
>            */
>           (void) this->lower_rvalue(dereference_array, fine_location,
> -                                   unpacked_var, name, false, i);
> +                                   unpacked_var, name, false, i,
> +                                   explicit_location);
>        } else {
>           char *subscripted_name
>              = ralloc_asprintf(this->mem_ctx, "%s[%d]", name, i);
> +
>           fine_location =
>              this->lower_rvalue(dereference_array, fine_location,
>                                 unpacked_var, subscripted_name,
> -                               false, vertex_index);
> +                               false, vertex_index, explicit_location);
>        }
>     }
>     return fine_location;
> --
> 2.4.3
>
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