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/*

 * Copyright © 2012 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.

 */

/**

 * \file lower_ubo_reference.cpp

 *

 * IR lower pass to replace dereferences of variables in a uniform

 * buffer object with usage of ir_binop_ubo_load expressions, each of

 * which can read data up to the size of a vec4.

 *

 * This relieves drivers of the responsibility to deal with tricky UBO

 * layout issues like std140 structures and row_major matrices on

 * their own.

 */

#include "ir.h"

#include "ir_builder.h"

#include "ir_rvalue_visitor.h"

#include "main/macros.h"

using namespace ir_builder;

namespace {

class lower_ubo_reference_visitor : public ir_rvalue_enter_visitor {

public:

   lower_ubo_reference_visitor(struct gl_shader *shader)

   : shader(shader)

   {

   }

   void handle_rvalue(ir_rvalue **rvalue);

   void emit_ubo_loads(ir_dereference *deref, ir_variable *base_offset,

		       unsigned int deref_offset);

   ir_expression *ubo_load(const struct glsl_type *type,

			   ir_rvalue *offset);

   void *mem_ctx;

   struct gl_shader *shader;

   struct gl_uniform_buffer_variable *ubo_var;

   unsigned uniform_block;

   bool progress;

};

/**

 * Determine the name of the interface block field

 *

 * This is the name of the specific member as it would appear in the

 * \c gl_uniform_buffer_variable::Name field in the shader's

 * \c UniformBlocks array.

 */

static const char *

interface_field_name(void *mem_ctx, char *base_name, ir_dereference *d)

{

   ir_constant *previous_index = NULL;

   while (d != NULL) {

      switch (d->ir_type) {

      case ir_type_dereference_variable: {

         ir_dereference_variable *v = (ir_dereference_variable *) d;

         if (previous_index

             && v->var->is_interface_instance()

             && v->var->type->is_array())

            return ralloc_asprintf(mem_ctx,

                                   "%s[%d]",

                                   base_name,

                                   previous_index->get_uint_component(0));

         else

            return base_name;

         break;

      }

      case ir_type_dereference_record: {

         ir_dereference_record *r = (ir_dereference_record *) d;

         d = r->record->as_dereference();

         break;

      }

      case ir_type_dereference_array: {

         ir_dereference_array *a = (ir_dereference_array *) d;

         d = a->array->as_dereference();

         previous_index = a->array_index->as_constant();

         break;

      }

      default:

         assert(!"Should not get here.");

         break;

      }

   }

   assert(!"Should not get here.");

   return NULL;

}

void

lower_ubo_reference_visitor::handle_rvalue(ir_rvalue **rvalue)

{

   if (!*rvalue)

      return;

   ir_dereference *deref = (*rvalue)->as_dereference();

   if (!deref)

      return;

   ir_variable *var = deref->variable_referenced();

   if (!var || !var->is_in_uniform_block())

      return;

   mem_ctx = ralloc_parent(*rvalue);

   const char *const field_name =

      interface_field_name(mem_ctx, (char *) var->interface_type->name, deref);

   this->uniform_block = -1;

   for (unsigned i = 0; i < shader->NumUniformBlocks; i++) {

      if (strcmp(field_name, shader->UniformBlocks[i].Name) == 0) {

         this->uniform_block = i;

         struct gl_uniform_block *block = &shader->UniformBlocks[i];

         this->ubo_var = var->is_interface_instance()

            ? &block->Uniforms[0] : &block->Uniforms[var->location];

         break;

      }

   }

   assert(this->uniform_block != (unsigned) -1);

   ir_rvalue *offset = new(mem_ctx) ir_constant(0u);

   unsigned const_offset = 0;

   bool row_major = ubo_var->RowMajor;

   /* Calculate the offset to the start of the region of the UBO

    * dereferenced by *rvalue.  This may be a variable offset if an

    * array dereference has a variable index.

    */

   while (deref) {

      switch (deref->ir_type) {

      case ir_type_dereference_variable: {

	 const_offset += ubo_var->Offset;

	 deref = NULL;

	 break;

      }

      case ir_type_dereference_array: {

	 ir_dereference_array *deref_array = (ir_dereference_array *)deref;

	 unsigned array_stride;

	 if (deref_array->array->type->is_matrix() && row_major) {

	    /* When loading a vector out of a row major matrix, the

	     * step between the columns (vectors) is the size of a

	     * float, while the step between the rows (elements of a

	     * vector) is handled below in emit_ubo_loads.

	     */

	    array_stride = 4;

         } else if (deref_array->type->is_interface()) {

            /* We're processing an array dereference of an interface instance

	     * array.  The thing being dereferenced *must* be a variable

	     * dereference because intefaces cannot be embedded an other

	     * types.  In terms of calculating the offsets for the lowering

	     * pass, we don't care about the array index.  All elements of an

	     * interface instance array will have the same offsets relative to

	     * the base of the block that backs them.

             */

            assert(deref_array->array->as_dereference_variable());

            deref = deref_array->array->as_dereference();

            break;

	 } else {

	    array_stride = deref_array->type->std140_size(row_major);

	    array_stride = glsl_align(array_stride, 16);

	 }

	 ir_constant *const_index = deref_array->array_index->as_constant();

	 if (const_index) {

	    const_offset += array_stride * const_index->value.i[0];

	 } else {

	    offset = add(offset,

			 mul(deref_array->array_index,

			     new(mem_ctx) ir_constant(array_stride)));

	 }

	 deref = deref_array->array->as_dereference();

	 break;

      }

      case ir_type_dereference_record: {

	 ir_dereference_record *deref_record = (ir_dereference_record *)deref;

	 const glsl_type *struct_type = deref_record->record->type;

	 unsigned intra_struct_offset = 0;

	 unsigned max_field_align = 16;

	 for (unsigned int i = 0; i < struct_type->length; i++) {

	    const glsl_type *type = struct_type->fields.structure[i].type;

	    unsigned field_align = type->std140_base_alignment(row_major);

	    max_field_align = MAX2(field_align, max_field_align);

	    intra_struct_offset = glsl_align(intra_struct_offset, field_align);

	    if (strcmp(struct_type->fields.structure[i].name,

		       deref_record->field) == 0)

	       break;

	    intra_struct_offset += type->std140_size(row_major);

	 }

	 const_offset = glsl_align(const_offset, max_field_align);

	 const_offset += intra_struct_offset;

	 deref = deref_record->record->as_dereference();

	 break;

      }

      default:

	 assert(!"not reached");

	 deref = NULL;

	 break;

      }

   }

   /* Now that we've calculated the offset to the start of the

    * dereference, walk over the type and emit loads into a temporary.

    */

   const glsl_type *type = (*rvalue)->type;

   ir_variable *load_var = new(mem_ctx) ir_variable(type,

						    "ubo_load_temp",

						    ir_var_temporary);

   base_ir->insert_before(load_var);

   ir_variable *load_offset = new(mem_ctx) ir_variable(glsl_type::uint_type,

						       "ubo_load_temp_offset",

						       ir_var_temporary);

   base_ir->insert_before(load_offset);

   base_ir->insert_before(assign(load_offset, offset));

   deref = new(mem_ctx) ir_dereference_variable(load_var);

   emit_ubo_loads(deref, load_offset, const_offset);

   *rvalue = deref;

   progress = true;

}

ir_expression *

lower_ubo_reference_visitor::ubo_load(const glsl_type *type,

				      ir_rvalue *offset)

{

   return new(mem_ctx)

      ir_expression(ir_binop_ubo_load,

		    type,

		    new(mem_ctx) ir_constant(this->uniform_block),

		    offset);

}

/**

 * Takes LHS and emits a series of assignments into its components

 * from the UBO variable at variable_offset + deref_offset.

 *

 * Recursively calls itself to break the deref down to the point that

 * the ir_binop_ubo_load expressions generated are contiguous scalars

 * or vectors.

 */

void

lower_ubo_reference_visitor::emit_ubo_loads(ir_dereference *deref,

					    ir_variable *base_offset,

					    unsigned int deref_offset)

{

   if (deref->type->is_record()) {

      unsigned int field_offset = 0;

      for (unsigned i = 0; i < deref->type->length; i++) {

	 const struct glsl_struct_field *field =

	    &deref->type->fields.structure[i];

	 ir_dereference *field_deref =

	    new(mem_ctx) ir_dereference_record(deref->clone(mem_ctx, NULL),

					       field->name);

	 field_offset =

	    glsl_align(field_offset,

		       field->type->std140_base_alignment(ubo_var->RowMajor));

	 emit_ubo_loads(field_deref, base_offset, deref_offset + field_offset);

	 field_offset += field->type->std140_size(ubo_var->RowMajor);

      }

      return;

   }

   if (deref->type->is_array()) {

      unsigned array_stride =

	 glsl_align(deref->type->fields.array->std140_size(ubo_var->RowMajor),

		    16);

      for (unsigned i = 0; i < deref->type->length; i++) {

	 ir_constant *element = new(mem_ctx) ir_constant(i);

	 ir_dereference *element_deref =

	    new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),

					      element);

	 emit_ubo_loads(element_deref, base_offset,

			deref_offset + i * array_stride);

      }

      return;

   }

   if (deref->type->is_matrix()) {

      for (unsigned i = 0; i < deref->type->matrix_columns; i++) {

	 ir_constant *col = new(mem_ctx) ir_constant(i);

	 ir_dereference *col_deref =

	    new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),

					      col);

	 /* std140 always rounds the stride of arrays (and matrices)

	  * to a vec4, so matrices are always 16 between columns/rows.

	  */

	 emit_ubo_loads(col_deref, base_offset, deref_offset + i * 16);

      }

      return;

   }

   assert(deref->type->is_scalar() ||

	  deref->type->is_vector());

   if (!ubo_var->RowMajor) {

      ir_rvalue *offset = add(base_offset,

			      new(mem_ctx) ir_constant(deref_offset));

      base_ir->insert_before(assign(deref->clone(mem_ctx, NULL),

				    ubo_load(deref->type, offset)));

   } else {

      /* We're dereffing a column out of a row-major matrix, so we

       * gather the vector from each stored row.

      */

      assert(deref->type->base_type == GLSL_TYPE_FLOAT);

      /* Matrices, row_major or not, are stored as if they were

       * arrays of vectors of the appropriate size in std140.

       * Arrays have their strides rounded up to a vec4, so the

       * matrix stride is always 16.

       */

      unsigned matrix_stride = 16;

      for (unsigned i = 0; i < deref->type->vector_elements; i++) {

	 ir_rvalue *chan_offset =

	    add(base_offset,

		new(mem_ctx) ir_constant(deref_offset + i * matrix_stride));

	 base_ir->insert_before(assign(deref->clone(mem_ctx, NULL),

				       ubo_load(glsl_type::float_type,

						chan_offset),

				       (1U << i)));

      }

   }

}

} /* unnamed namespace */

void

lower_ubo_reference(struct gl_shader *shader, exec_list *instructions)

{

   lower_ubo_reference_visitor v(shader);

   /* Loop over the instructions lowering references, because we take

    * a deref of a UBO array using a UBO dereference as the index will

    * produce a collection of instructions all of which have cloned

    * UBO dereferences for that array index.

    */

   do {

      v.progress = false;

      visit_list_elements(&v, instructions);

   } while (v.progress);

}