[Mesa-dev] [PATCH 10/15] glsl/standalone: Optimize dead variable declarations

[Tapani Pälli]

On 09/16/2016 01:12 AM, Ian Romanick wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
>
> We didn't bother with this in the regular compiler because it doesn't
> change the generated code.  In the stand-alone compiler, this can
> clutter the output with useless variables.  It's especially bad after
> functions are inlined but the foo_retval declarations remain.
>
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
>  src/compiler/glsl/standalone.cpp | 63 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 63 insertions(+)
>
> diff --git a/src/compiler/glsl/standalone.cpp b/src/compiler/glsl/standalone.cpp
> index c4b6854..f7e1055 100644
> --- a/src/compiler/glsl/standalone.cpp
> +++ b/src/compiler/glsl/standalone.cpp
> @@ -37,6 +37,7 @@
>  #include "standalone_scaffolding.h"
>  #include "standalone.h"
>  #include "util/string_to_uint_map.h"
> +#include "util/set.h"
>
>  class add_neg_to_sub_visitor : public ir_hierarchical_visitor {
>  public:
> @@ -69,6 +70,64 @@ public:
>     }
>  };
>
> +class dead_variable_visitor : public ir_hierarchical_visitor {
> +public:
> +   dead_variable_visitor()
> +   {
> +      variables = _mesa_set_create(NULL,
> +                                   _mesa_hash_pointer,
> +                                   _mesa_key_pointer_equal);
> +   }
> +
> +   virtual ~dead_variable_visitor()
> +   {
> +      _mesa_set_destroy(variables, NULL);
> +   }
> +
> +   virtual ir_visitor_status visit(ir_variable *ir)
> +   {
> +      /* If the variable is auto or temp, add it to the set of variables that
> +       * are candidates for removal.
> +       */
> +      if (ir->data.mode != ir_var_auto && ir->data.mode != ir_var_temporary)
> +         return visit_continue;
> +
> +      _mesa_set_add(variables, ir);
> +
> +      return visit_continue;
> +   }
> +
> +   virtual ir_visitor_status visit(ir_dereference_variable *ir)
> +   {
> +      struct set_entry *entry = _mesa_set_search(variables, ir->var);
> +
> +      /* If a variable is dereferenced at all, remove it from the set of
> +       * variables that are candidates for removal.
> +       */
> +      if (entry != NULL)
> +         _mesa_set_remove(variables, entry);
> +
> +      return visit_continue;
> +   }
> +
> +   void remove_dead_variables()
> +   {
> +      struct set_entry *entry;
> +
> +      for (entry = _mesa_set_next_entry(variables, NULL);
> +           entry != NULL;
> +           entry = _mesa_set_next_entry(variables, entry)) {

please use set_foreach() macro here, with that fixed;

Reviewed-by: Tapani Pälli <tapani.palli at intel.com>

> +         ir_variable *ir = (ir_variable *) entry->key;
> +
> +         assert(ir->ir_type == ir_type_variable);
> +         ir->remove();
> +      }
> +   }
> +
> +private:
> +   set *variables;
> +};
> +
>  static const struct standalone_options *options;
>
>  static void
> @@ -471,6 +530,10 @@ standalone_compile_shader(const struct standalone_options *_options,
>           add_neg_to_sub_visitor v;
>           visit_list_elements(&v, shader->ir);
>
> +         dead_variable_visitor dv;
> +         visit_list_elements(&dv, shader->ir);
> +         dv.remove_dead_variables();
> +
>           shader->Program = rzalloc(shader, gl_program);
>           init_gl_program(shader->Program, shader->Stage);
>        }
>