src/compiler/glsl/opt_flip_matrices.cpp

/*
 * Copyright © 2013 Intel Corporation
 *
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 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
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 * 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
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/**
 * \file opt_flip_matrices.cpp
 *
 * Convert (matrix * vector) operations to (vector * matrixTranspose),
 * which can be done using dot products rather than multiplies and adds.
 * On some hardware, this is more efficient.
 *
 * This currently only does the conversion for built-in matrices which
 * already have transposed equivalents.  Namely, gl_ModelViewProjectionMatrix
 * and gl_TextureMatrix.
 */
#include "ir.h"
#include "ir_optimization.h"
#include "main/macros.h"

namespace {
class matrix_flipper : public ir_hierarchical_visitor {
public:
   matrix_flipper(exec_list *instructions)
   {
      progress = false;
      mvp_transpose = NULL;
      texmat_transpose = NULL;

      foreach_in_list(ir_instruction, ir, instructions) {
         ir_variable *var = ir->as_variable();
         if (!var)
            continue;
         if (strcmp(var->name, "gl_ModelViewProjectionMatrixTranspose") == 0)
            mvp_transpose = var;
         if (strcmp(var->name, "gl_TextureMatrixTranspose") == 0)
            texmat_transpose = var;
      }
   }

   ir_visitor_status visit_enter(ir_expression *ir);

   bool progress;

private:
   ir_variable *mvp_transpose;
   ir_variable *texmat_transpose;
};
}

ir_visitor_status
matrix_flipper::visit_enter(ir_expression *ir)
{
   if (ir->operation != ir_binop_mul ||
       !ir->operands[0]->type->is_matrix() ||
       !ir->operands[1]->type->is_vector())
      return visit_continue;

   ir_variable *mat_var = ir->operands[0]->variable_referenced();
   if (!mat_var)
      return visit_continue;

   if (mvp_transpose &&
       strcmp(mat_var->name, "gl_ModelViewProjectionMatrix") == 0) {
#ifndef NDEBUG
      ir_dereference_variable *deref = ir->operands[0]->as_dereference_variable();
      assert(deref && deref->var == mat_var);
#endif

      void *mem_ctx = ralloc_parent(ir);

      ir->operands[0] = ir->operands[1];
      ir->operands[1] = new(mem_ctx) ir_dereference_variable(mvp_transpose);

      progress = true;
   } else if (texmat_transpose &&
              strcmp(mat_var->name, "gl_TextureMatrix") == 0) {
      ir_dereference_array *array_ref = ir->operands[0]->as_dereference_array();
      assert(array_ref != NULL);
      ir_dereference_variable *var_ref = array_ref->array->as_dereference_variable();
      assert(var_ref && var_ref->var == mat_var);

      ir->operands[0] = ir->operands[1];
      ir->operands[1] = array_ref;

      var_ref->var = texmat_transpose;

      texmat_transpose->data.max_array_access =
         MAX2(texmat_transpose->data.max_array_access, mat_var->data.max_array_access);

      progress = true;
   }

   return visit_continue;
}

bool
opt_flip_matrices(struct exec_list *instructions)
{
   matrix_flipper v(instructions);

   visit_list_elements(&v, instructions);

   return v.progress;
}