compiler/glsl/ast_array_index.cpp

/*
 * Copyright © 2010 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 "ast.h"
#include "compiler/glsl_types.h"
#include "ir.h"

void
ast_array_specifier::print(void) const
{
   foreach_list_typed (ast_node, array_dimension, link, &this->array_dimensions) {
      printf("[ ");
      if (((ast_expression*)array_dimension)->oper != ast_unsized_array_dim)
         array_dimension->print();
      printf("] ");
   }
}

/**
 * If \c ir is a reference to an array for which we are tracking the max array
 * element accessed, track that the given element has been accessed.
 * Otherwise do nothing.
 *
 * This function also checks whether the array is a built-in array whose
 * maximum size is too small to accommodate the given index, and if so uses
 * loc and state to report the error.
 */
static void
update_max_array_access(ir_rvalue *ir, int idx, YYLTYPE *loc,
                        struct _mesa_glsl_parse_state *state)
{
   if (ir_dereference_variable *deref_var = ir->as_dereference_variable()) {
      ir_variable *var = deref_var->var;
      if (idx > (int)var->data.max_array_access) {
         var->data.max_array_access = idx;

         /* Check whether this access will, as a side effect, implicitly cause
          * the size of a built-in array to be too large.
          */
         check_builtin_array_max_size(var->name, idx+1, *loc, state);
      }
   } else if (ir_dereference_record *deref_record =
              ir->as_dereference_record()) {
      /* There are three possibilities we need to consider:
       *
       * - Accessing an element of an array that is a member of a named
       *   interface block (e.g. ifc.foo[i])
       *
       * - Accessing an element of an array that is a member of a named
       *   interface block array (e.g. ifc[j].foo[i]).
       *
       * - Accessing an element of an array that is a member of a named
       *   interface block array of arrays (e.g. ifc[j][k].foo[i]).
       */
      ir_dereference_variable *deref_var =
         deref_record->record->as_dereference_variable();
      if (deref_var == NULL) {
         ir_dereference_array *deref_array =
            deref_record->record->as_dereference_array();
         ir_dereference_array *deref_array_prev = NULL;
         while (deref_array != NULL) {
            deref_array_prev = deref_array;
            deref_array = deref_array->array->as_dereference_array();
         }
         if (deref_array_prev != NULL)
            deref_var = deref_array_prev->array->as_dereference_variable();
      }

      if (deref_var != NULL) {
         if (deref_var->var->is_interface_instance()) {
            unsigned field_idx = deref_record->field_idx;
            assert(field_idx < deref_var->var->get_interface_type()->length);

            int *const max_ifc_array_access =
               deref_var->var->get_max_ifc_array_access();

            assert(max_ifc_array_access != NULL);

            if (idx > max_ifc_array_access[field_idx]) {
               max_ifc_array_access[field_idx] = idx;

               /* Check whether this access will, as a side effect, implicitly
                * cause the size of a built-in array to be too large.
                */
               const char *field_name =
                  deref_record->record->type->fields.structure[field_idx].name;
               check_builtin_array_max_size(field_name, idx+1, *loc, state);
            }
         }
      }
   }
}


static int
get_implicit_array_size(struct _mesa_glsl_parse_state *state,
                        ir_rvalue *array)
{
   ir_variable *var = array->variable_referenced();

   /* Inputs in control shader are implicitly sized
    * to the maximum patch size.
    */
   if (state->stage == MESA_SHADER_TESS_CTRL &&
       var->data.mode == ir_var_shader_in) {
      return state->Const.MaxPatchVertices;
   }

   /* Non-patch inputs in evaluation shader are implicitly sized
    * to the maximum patch size.
    */
   if (state->stage == MESA_SHADER_TESS_EVAL &&
       var->data.mode == ir_var_shader_in &&
       !var->data.patch) {
      return state->Const.MaxPatchVertices;
   }

   return 0;
}


ir_rvalue *
_mesa_ast_array_index_to_hir(void *mem_ctx,
                             struct _mesa_glsl_parse_state *state,
                             ir_rvalue *array, ir_rvalue *idx,
                             YYLTYPE &loc, YYLTYPE &idx_loc)
{
   if (!array->type->is_error()
       && !array->type->is_array()
       && !array->type->is_matrix()
       && !array->type->is_vector()) {
      _mesa_glsl_error(& idx_loc, state,
                       "cannot dereference non-array / non-matrix / "
                       "non-vector");
   }

   if (!idx->type->is_error()) {
      if (!idx->type->is_integer()) {
         _mesa_glsl_error(& idx_loc, state, "array index must be integer type");
      } else if (!idx->type->is_scalar()) {
         _mesa_glsl_error(& idx_loc, state, "array index must be scalar");
      }
   }

   /* If the array index is a constant expression and the array has a
    * declared size, ensure that the access is in-bounds.  If the array
    * index is not a constant expression, ensure that the array has a
    * declared size.
    */
   ir_constant *const const_index = idx->constant_expression_value(mem_ctx);
   if (const_index != NULL && idx->type->is_integer()) {
      const int idx = const_index->value.i[0];
      const char *type_name = "error";
      unsigned bound = 0;

      /* From page 24 (page 30 of the PDF) of the GLSL 1.50 spec:
       *
       *    "It is illegal to declare an array with a size, and then
       *    later (in the same shader) index the same array with an
       *    integral constant expression greater than or equal to the
       *    declared size. It is also illegal to index an array with a
       *    negative constant expression."
       */
      if (array->type->is_matrix()) {
         if (array->type->row_type()->vector_elements <= idx) {
            type_name = "matrix";
            bound = array->type->row_type()->vector_elements;
         }
      } else if (array->type->is_vector()) {
         if (array->type->vector_elements <= idx) {
            type_name = "vector";
            bound = array->type->vector_elements;
         }
      } else {
         /* glsl_type::array_size() returns -1 for non-array types.  This means
          * that we don't need to verify that the type is an array before
          * doing the bounds checking.
          */
         if ((array->type->array_size() > 0)
             && (array->type->array_size() <= idx)) {
            type_name = "array";
            bound = array->type->array_size();
         }
      }

      if (bound > 0) {
         _mesa_glsl_error(& loc, state, "%s index must be < %u",
                          type_name, bound);
      } else if (idx < 0) {
         _mesa_glsl_error(& loc, state, "%s index must be >= 0", type_name);
      }

      if (array->type->is_array())
         update_max_array_access(array, idx, &loc, state);
   } else if (const_index == NULL && array->type->is_array()) {
      if (array->type->is_unsized_array()) {
         int implicit_size = get_implicit_array_size(state, array);
         if (implicit_size) {
            ir_variable *v = array->whole_variable_referenced();
            if (v != NULL)
               v->data.max_array_access = implicit_size - 1;
         }
         else if (state->stage == MESA_SHADER_TESS_CTRL &&
                  array->variable_referenced()->data.mode == ir_var_shader_out &&
                  !array->variable_referenced()->data.patch) {
            /* Tessellation control shader output non-patch arrays are
             * initially unsized. Despite that, they are allowed to be
             * indexed with a non-constant expression (typically
             * "gl_InvocationID"). The array size will be determined
             * by the linker.
             */
         }
         else if (array->variable_referenced()->data.mode !=
                  ir_var_shader_storage) {
            _mesa_glsl_error(&loc, state, "unsized array index must be constant");
         } else {
            /* Unsized array non-constant indexing on SSBO is allowed only for
             * the last member of the SSBO definition.
             */
            ir_variable *var = array->variable_referenced();
            const glsl_type *iface_type = var->get_interface_type();
            int field_index = iface_type->field_index(var->name);
            /* Field index can be < 0 for instance arrays */
            if (field_index >= 0 &&
                field_index != (int) iface_type->length - 1) {
               _mesa_glsl_error(&loc, state, "Indirect access on unsized "
                                "array is limited to the last member of "
                                "SSBO.");
            }
         }
      } else if (array->type->without_array()->is_interface()
                 && ((array->variable_referenced()->data.mode == ir_var_uniform
                      && !state->is_version(400, 320)
                      && !state->ARB_gpu_shader5_enable
                      && !state->EXT_gpu_shader5_enable
                      && !state->OES_gpu_shader5_enable) ||
                     (array->variable_referenced()->data.mode == ir_var_shader_storage
                      && !state->is_version(400, 0)
                      && !state->ARB_gpu_shader5_enable))) {
         /* Page 50 in section 4.3.9 of the OpenGL ES 3.10 spec says:
          *
          *     "All indices used to index a uniform or shader storage block
          *     array must be constant integral expressions."
          *
          * But OES_gpu_shader5 (and ESSL 3.20) relax this to allow indexing
          * on uniform blocks but not shader storage blocks.
          *
          */
         _mesa_glsl_error(&loc, state, "%s block array index must be constant",
                          array->variable_referenced()->data.mode
                          == ir_var_uniform ? "uniform" : "shader storage");
      } else {
         /* whole_variable_referenced can return NULL if the array is a
          * member of a structure.  In this case it is safe to not update
          * the max_array_access field because it is never used for fields
          * of structures.
          */
         ir_variable *v = array->whole_variable_referenced();
         if (v != NULL)
            v->data.max_array_access = array->type->array_size() - 1;
      }

      /* From page 23 (29 of the PDF) of the GLSL 1.30 spec:
       *
       *    "Samplers aggregated into arrays within a shader (using square
       *    brackets [ ]) can only be indexed with integral constant
       *    expressions [...]."
       *
       * This restriction was added in GLSL 1.30.  Shaders using earlier
       * version of the language should not be rejected by the compiler
       * front-end for using this construct.  This allows useful things such
       * as using a loop counter as the index to an array of samplers.  If the
       * loop in unrolled, the code should compile correctly.  Instead, emit a
       * warning.
       *
       * In GLSL 4.00 / ARB_gpu_shader5, this requirement is relaxed again to allow
       * indexing with dynamically uniform expressions. Note that these are not
       * required to be uniforms or expressions based on them, but merely that the
       * values must not diverge between shader invocations run together. If the
       * values *do* diverge, then the behavior of the operation requiring a
       * dynamically uniform expression is undefined.
       *
       * From section 4.1.7 of the ARB_bindless_texture spec:
       *
       *    "Samplers aggregated into arrays within a shader (using square
       *    brackets []) can be indexed with arbitrary integer expressions."
       */
      if (array->type->without_array()->is_sampler()) {
         if (!state->is_version(400, 320) &&
             !state->ARB_gpu_shader5_enable &&
             !state->EXT_gpu_shader5_enable &&
             !state->OES_gpu_shader5_enable &&
             !state->has_bindless()) {
            if (state->is_version(130, 300))
               _mesa_glsl_error(&loc, state,
                                "sampler arrays indexed with non-constant "
                                "expressions are forbidden in GLSL %s "
                                "and later",
                                state->es_shader ? "ES 3.00" : "1.30");
            else if (state->es_shader)
               _mesa_glsl_warning(&loc, state,
                                  "sampler arrays indexed with non-constant "
                                  "expressions will be forbidden in GLSL "
                                  "3.00 and later");
            else
               _mesa_glsl_warning(&loc, state,
                                  "sampler arrays indexed with non-constant "
                                  "expressions will be forbidden in GLSL "
                                  "1.30 and later");
         }
      }

      /* From page 27 of the GLSL ES 3.1 specification:
       *
       * "When aggregated into arrays within a shader, images can only be
       *  indexed with a constant integral expression."
       *
       * On the other hand the desktop GL specification extension allows
       * non-constant indexing of image arrays, but behavior is left undefined
       * in cases where the indexing expression is not dynamically uniform.
       */
      if (state->es_shader && array->type->without_array()->is_image()) {
         _mesa_glsl_error(&loc, state,
                          "image arrays indexed with non-constant "
                          "expressions are forbidden in GLSL ES.");
      }
   }

   /* After performing all of the error checking, generate the IR for the
    * expression.
    */
   if (array->type->is_array()
       || array->type->is_matrix()
       || array->type->is_vector()) {
      return new(mem_ctx) ir_dereference_array(array, idx);
   } else if (array->type->is_error()) {
      return array;
   } else {
      ir_rvalue *result = new(mem_ctx) ir_dereference_array(array, idx);
      result->type = glsl_type::error_type;

      return result;
   }
}