src/glsl/ir_if_simplification.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_function_inlining.cpp
  26  *
  27  * Moves constant branches of if statements out to the surrounding
  28  * instruction stream.
  29  */
  30
  31 #include "ir.h"
  32
  33 class ir_if_simplification_visitor : public ir_hierarchical_visitor {
  34 public:
  35    ir_if_simplification_visitor()
  36    {
  37       this->made_progress = false;
  38    }
  39
  40    ir_visitor_status visit_leave(ir_if *);
  41
  42    bool made_progress;
  43 };
  44
  45 bool
  46 do_if_simplification(exec_list *instructions)
  47 {
  48    ir_if_simplification_visitor v;
  49
  50    v.run(instructions);
  51    return v.made_progress;
  52 }
  53
  54
  55 ir_visitor_status
  56 ir_if_simplification_visitor::visit_leave(ir_if *ir)
  57 {
  58    /* FINISHME: Ideally there would be a way to note that the condition results
  59     * FINISHME: in a constant before processing both of the other subtrees.
  60     * FINISHME: This can probably be done with some flags, but it would take
  61     * FINISHME: some work to get right.
  62     */
  63    ir_constant *condition_constant = ir->condition->constant_expression_value();
  64    if (condition_constant) {
  65       /* Move the contents of the one branch of the conditional
  66        * that matters out.
  67        */
  68       if (condition_constant->value.b[0]) {
  69          foreach_iter(exec_list_iterator, then_iter, ir->then_instructions) {
  70             ir_instruction *then_ir = (ir_instruction *)then_iter.get();
  71             ir->insert_before(then_ir);
  72          }
  73       } else {
  74          foreach_iter(exec_list_iterator, else_iter, ir->else_instructions) {
  75             ir_instruction *else_ir = (ir_instruction *)else_iter.get();
  76             ir->insert_before(else_ir);
  77          }
  78       }
  79       ir->remove();
  80       this->made_progress = true;
  81    }
  82
  83    return visit_continue;
  84 }