src/glsl/ir_sub_to_add_neg.cpp

   1 /*
   2  * Copyright © 2010 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 /**
  25  * \file ir_sub_to_add_neg.cpp
  26  *
  27  * Breaks an ir_binop_sub expression down to add(op0, neg(op1))
  28  *
  29  * This simplifies expression reassociation, and for many backends
  30  * there is no subtract operation separate from adding the negation.
  31  * For backends with native subtract operations, they will probably
  32  * want to recognize add(op0, neg(op1)) or the other way around to
  33  * produce a subtract anyway.
  34  */
  35
  36 #include "ir.h"
  37
  38 class ir_sub_to_add_neg_visitor : public ir_hierarchical_visitor {
  39 public:
  40    ir_sub_to_add_neg_visitor()
  41    {
  42       this->progress = false;
  43    }
  44
  45    ir_visitor_status visit_leave(ir_expression *);
  46
  47    bool progress;
  48 };
  49
  50 bool
  51 do_sub_to_add_neg(exec_list *instructions)
  52 {
  53    ir_sub_to_add_neg_visitor v;
  54
  55    visit_list_elements(&v, instructions);
  56    return v.progress;
  57 }
  58
  59 ir_visitor_status
  60 ir_sub_to_add_neg_visitor::visit_leave(ir_expression *ir)
  61 {
  62    if (ir->operation != ir_binop_sub)
  63       return visit_continue;
  64
  65    void *mem_ctx = talloc_parent(ir);
  66
  67    ir->operation = ir_binop_add;
  68    ir->operands[1] = new(mem_ctx) ir_expression(ir_unop_neg,
  69                                                 ir->operands[1]->type,
  70                                                 ir->operands[1],
  71                                                 NULL);
  72
  73    this->progress = true;
  74
  75    return visit_continue;
  76 }