[Mesa-dev] [PATCH 3/8] glsl: Mark whole variable used for ClipDistance and TessLevel*.

[Marek Olšák]

Hi, this causes an assertion failure for some tests in the GLSL
compiler on radeonsi:

glsl/ir_set_program_inouts.cpp:129: void mark(gl_program*,
ir_variable*, int, int, gl_shader_stage): Assertion `var->data.mode ==
ir_var_shader_out' failed.

Test: piglit/bin/getuniform-03 -auto -fbo

I won't look into it right now, maybe next week. Any idea what's wrong here?

Thanks,
Marek

On Wed, Jan 4, 2017 at 12:07 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> There's no point in trying to mark partial array access for
> gl_ClipDistance, gl_TessLevelOuter, or gl_TessLevelInner - they're
> special built-in variables that control fixed function hardware,
> and will likely be used in an all-or-nothing fashion.
>
> Since these arrays only occupy 1-2 varying slots, we have to avoid
> our normal processing which increments the slot value by the array
> index.
>
> (I wrote this code before i965 switched from ir_set_program_inouts
> to nir_shader_gather_info.  It's not used by anyone today, and I'm
> not sure how valuable it is...the alternative to GLSL IR lowering
> is NIR compact arrays, at which point you should use nir_gather_info.)
>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/compiler/glsl/ir_set_program_inouts.cpp | 26 +++++++++++++++++++++++---
>  1 file changed, 23 insertions(+), 3 deletions(-)
>
> We could drop this patch.  It doesn't exactly help anybody today.
>
> diff --git a/src/compiler/glsl/ir_set_program_inouts.cpp b/src/compiler/glsl/ir_set_program_inouts.cpp
> index 66f0c1ebf08..376d9c693fa 100644
> --- a/src/compiler/glsl/ir_set_program_inouts.cpp
> +++ b/src/compiler/glsl/ir_set_program_inouts.cpp
> @@ -330,6 +330,23 @@ is_multiple_vertices(gl_shader_stage stage, ir_variable *var)
>     return false;
>  }
>
> +/**
> + * Return true if \p var is a GLSL built-in array that controls fixed-function
> + * aspects of the pipeline.  These have to be used as a whole.
> + */
> +static bool
> +is_fixed_function_array(ir_variable *var)
> +{
> +   switch (var->data.location) {
> +   case VARYING_SLOT_TESS_LEVEL_OUTER:
> +   case VARYING_SLOT_TESS_LEVEL_INNER:
> +   case VARYING_SLOT_CLIP_DIST0:
> +      return true;
> +   default:
> +      return false;
> +   }
> +}
> +
>  ir_visitor_status
>  ir_set_program_inouts_visitor::visit_enter(ir_dereference_array *ir)
>  {
> @@ -362,9 +379,12 @@ ir_set_program_inouts_visitor::visit_enter(ir_dereference_array *ir)
>     } else if (ir_dereference_variable * const deref_var =
>                ir->array->as_dereference_variable()) {
>        /* ir => foo[i], where foo is a variable. */
> -      if (is_multiple_vertices(this->shader_stage, deref_var->var)) {
> -         /* foo is a geometry or tessellation shader input, so i is
> -          * the vertex, and we're accessing the entire input.
> +      if (is_multiple_vertices(this->shader_stage, deref_var->var) ||
> +          is_fixed_function_array(deref_var->var)) {
> +         /* In the first case, foo is a geometry or tessellation shader input,
> +          * so i is the vertex, and we're accessing the entire input.  In the
> +          * second case, foo is a GLSL built-in array that controls
> +          * fixed-function hardware, which is consumed as a whole.
>            */
>           mark_whole_variable(deref_var->var);
>           /* We've now taken care of foo, but i might contain a subexpression
> --
> 2.11.0
>
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