src/compiler/glsl/link_uniform_block_active_visitor.cpp

/*
 * Copyright © 2013 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

#include "link_uniform_block_active_visitor.h"
#include "program.h"
#include "linker_util.h"

static link_uniform_block_active *
process_block(void *mem_ctx, struct hash_table *ht, ir_variable *var)
{
   const hash_entry *const existing_block =
      _mesa_hash_table_search(ht, var->get_interface_type()->name);

   const glsl_type *const block_type = var->is_interface_instance()
      ? var->type : var->get_interface_type();


   /* If a block with this block-name has not previously been seen, add it.
    * If a block with this block-name has been seen, it must be identical to
    * the block currently being examined.
    */
   if (existing_block == NULL) {
      link_uniform_block_active *const b =
         rzalloc(mem_ctx, struct link_uniform_block_active);

      b->type = block_type;
      b->has_instance_name = var->is_interface_instance();
      b->is_shader_storage = var->data.mode == ir_var_shader_storage;

      if (var->data.explicit_binding) {
         b->has_binding = true;
         b->binding = var->data.binding;
      } else {
         b->has_binding = false;
         b->binding = 0;
      }

      _mesa_hash_table_insert(ht, var->get_interface_type()->name, (void *) b);
      return b;
   } else {
      link_uniform_block_active *const b =
         (link_uniform_block_active *) existing_block->data;

      if (b->type != block_type
          || b->has_instance_name != var->is_interface_instance())
         return NULL;
      else
         return b;
   }

   assert(!"Should not get here.");
   return NULL;
}

/* For arrays of arrays this function will give us a middle ground between
 * detecting inactive uniform blocks and structuring them in a way that makes
 * it easy to calculate the offset for indirect indexing.
 *
 * For example given the shader:
 *
 *   uniform ArraysOfArraysBlock
 *   {
 *      vec4 a;
 *   } i[3][4][5];
 *
 *   void main()
 *   {
 *      vec4 b = i[0][1][1].a;
 *      gl_Position = i[2][2][3].a + b;
 *   }
 *
 * There are only 2 active blocks above but for the sake of indirect indexing
 * and not over complicating the code we will end up with a count of 8.  Here
 * each dimension has 2 different indices counted so we end up with 2*2*2
 */
static struct uniform_block_array_elements **
process_arrays(void *mem_ctx, ir_dereference_array *ir,
               struct link_uniform_block_active *block)
{
   if (ir) {
      struct uniform_block_array_elements **ub_array_ptr =
         process_arrays(mem_ctx, ir->array->as_dereference_array(), block);
      if (*ub_array_ptr == NULL) {
         *ub_array_ptr = rzalloc(mem_ctx, struct uniform_block_array_elements);
         (*ub_array_ptr)->ir = ir;
      }

      struct uniform_block_array_elements *ub_array = *ub_array_ptr;
      ir_constant *c = ir->array_index->as_constant();
      if (c) {
         /* Index is a constant, so mark just that element used, if not
          * already.
          */
         const unsigned idx = c->get_uint_component(0);

         unsigned i;
         for (i = 0; i < ub_array->num_array_elements; i++) {
            if (ub_array->array_elements[i] == idx)
               break;
         }

         assert(i <= ub_array->num_array_elements);

         if (i == ub_array->num_array_elements) {
            ub_array->array_elements = reralloc(mem_ctx,
                                                ub_array->array_elements,
                                                unsigned,
                                                ub_array->num_array_elements + 1);

            ub_array->array_elements[ub_array->num_array_elements] = idx;

            ub_array->num_array_elements++;
         }
      } else {
         /* The array index is not a constant, so mark the entire array used. */
         assert(ir->array->type->is_array());
         if (ub_array->num_array_elements < ir->array->type->length) {
            ub_array->num_array_elements = ir->array->type->length;
            ub_array->array_elements = reralloc(mem_ctx,
                                                ub_array->array_elements,
                                                unsigned,
                                                ub_array->num_array_elements);

            for (unsigned i = 0; i < ub_array->num_array_elements; i++) {
               ub_array->array_elements[i] = i;
            }
         }
      }

      return &ub_array->array;
   } else {
      return &block->array;
   }
}

ir_visitor_status
link_uniform_block_active_visitor::visit(ir_variable *var)
{
   if (!var->is_in_buffer_block())
      return visit_continue;

   /* Section 2.11.6 (Uniform Variables) of the OpenGL ES 3.0.3 spec says:
    *
    *     "All members of a named uniform block declared with a shared or
    *     std140 layout qualifier are considered active, even if they are not
    *     referenced in any shader in the program. The uniform block itself is
    *     also considered active, even if no member of the block is
    *     referenced."
    */
   if (var->get_interface_type_packing() == GLSL_INTERFACE_PACKING_PACKED)
      return visit_continue;

   /* Process the block.  Bail if there was an error. */
   link_uniform_block_active *const b =
      process_block(this->mem_ctx, this->ht, var);
   if (b == NULL) {
      linker_error(this->prog,
                   "uniform block `%s' has mismatching definitions",
                   var->get_interface_type()->name);
      this->success = false;
      return visit_stop;
   }

   assert(b->array == NULL);
   assert(b->type != NULL);
   assert(!b->type->is_array() || b->has_instance_name);

   /* For uniform block arrays declared with a shared or std140 layout
    * qualifier, mark all its instances as used.
    */
   const glsl_type *type = b->type;
   struct uniform_block_array_elements **ub_array = &b->array;
   while (type->is_array()) {
      assert(b->type->length > 0);

      *ub_array = rzalloc(this->mem_ctx, struct uniform_block_array_elements);
      (*ub_array)->num_array_elements = type->length;
      (*ub_array)->array_elements = reralloc(this->mem_ctx,
                                             (*ub_array)->array_elements,
                                             unsigned,
                                             (*ub_array)->num_array_elements);

      for (unsigned i = 0; i < (*ub_array)->num_array_elements; i++) {
         (*ub_array)->array_elements[i] = i;
      }
      ub_array = &(*ub_array)->array;
      type = type->fields.array;
   }

   return visit_continue;
}

ir_visitor_status
link_uniform_block_active_visitor::visit_enter(ir_dereference_array *ir)
{
   /* cycle through arrays of arrays */
   ir_dereference_array *base_ir = ir;
   while (base_ir->array->ir_type == ir_type_dereference_array)
      base_ir = base_ir->array->as_dereference_array();

   ir_dereference_variable *const d =
      base_ir->array->as_dereference_variable();
   ir_variable *const var = (d == NULL) ? NULL : d->var;

   /* If the r-value being dereferenced is not a variable (e.g., a field of a
    * structure) or is not a uniform block instance, continue.
    *
    * WARNING: It is not enough for the variable to be part of uniform block.
    * It must represent the entire block.  Arrays (or matrices) inside blocks
    * that lack an instance name are handled by the ir_dereference_variable
    * function.
    */
   if (var == NULL
       || !var->is_in_buffer_block()
       || !var->is_interface_instance())
      return visit_continue;

   /* Process the block.  Bail if there was an error. */
   link_uniform_block_active *const b =
      process_block(this->mem_ctx, this->ht, var);
   if (b == NULL) {
      linker_error(prog,
                   "uniform block `%s' has mismatching definitions",
                   var->get_interface_type()->name);
      this->success = false;
      return visit_stop;
   }

   /* Block arrays must be declared with an instance name.
    */
   assert(b->has_instance_name);
   assert(b->type != NULL);

   /* If the block array was declared with a shared or std140 layout
    * qualifier, all its instances have been already marked as used in
    * link_uniform_block_active_visitor::visit(ir_variable *).
    */
   if (var->get_interface_type_packing() == GLSL_INTERFACE_PACKING_PACKED) {
      b->var = var;
      process_arrays(this->mem_ctx, ir, b);
   }

   return visit_continue_with_parent;
}

ir_visitor_status
link_uniform_block_active_visitor::visit(ir_dereference_variable *ir)
{
   ir_variable *var = ir->var;

   if (!var->is_in_buffer_block())
      return visit_continue;

   assert(!var->is_interface_instance() || !var->type->is_array());

   /* Process the block.  Bail if there was an error. */
   link_uniform_block_active *const b =
      process_block(this->mem_ctx, this->ht, var);
   if (b == NULL) {
      linker_error(this->prog,
                   "uniform block `%s' has mismatching definitions",
                   var->get_interface_type()->name);
      this->success = false;
      return visit_stop;
   }

   assert(b->array == NULL);
   assert(b->type != NULL);

   return visit_continue;
}