src/glsl/opt_redundant_jumps.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 opt_redundant_jumps.cpp
  26  * Remove certain types of redundant jumps
  27  */
  28
  29 #include "ir.h"
  30
  31 class redundant_jumps_visitor : public ir_hierarchical_visitor {
  32 public:
  33    redundant_jumps_visitor()
  34    {
  35       this->progress = false;
  36    }
  37
  38    virtual ir_visitor_status visit_leave(ir_if *);
  39    virtual ir_visitor_status visit_leave(ir_loop *);
  40
  41    bool progress;
  42 };
  43
  44
  45 ir_visitor_status
  46 redundant_jumps_visitor::visit_leave(ir_if *ir)
  47 {
  48    /* If the last instruction in both branches is a 'break' or a 'continue',
  49     * pull it out of the branches and insert it after the if-statment.  Note
  50     * that both must be the same type (either 'break' or 'continue').
  51     */
  52    ir_instruction *const last_then =
  53       (ir_instruction *) ir->then_instructions.get_tail();
  54    ir_instruction *const last_else =
  55       (ir_instruction *) ir->else_instructions.get_tail();
  56
  57    if ((last_then == NULL) || (last_else == NULL))
  58       return visit_continue;
  59
  60    if ((last_then->ir_type != ir_type_loop_jump)
  61        || (last_else->ir_type != ir_type_loop_jump))
  62       return visit_continue;
  63
  64    ir_loop_jump *const then_jump = (ir_loop_jump *) last_then;
  65    ir_loop_jump *const else_jump = (ir_loop_jump *) last_else;
  66
  67    if (then_jump->mode != else_jump->mode)
  68       return visit_continue;
  69
  70    then_jump->remove();
  71    else_jump->remove();
  72    this->progress = true;
  73
  74    ir->insert_after(then_jump);
  75
  76    /* If both branchs of the if-statement are now empty, remove the
  77     * if-statement.
  78     */
  79    if (ir->then_instructions.is_empty() && ir->else_instructions.is_empty())
  80       ir->remove();
  81
  82    return visit_continue;
  83 }
  84
  85
  86 ir_visitor_status
  87 redundant_jumps_visitor::visit_leave(ir_loop *ir)
  88 {
  89    /* If the last instruction of a loop body is a 'continue', remove it.
  90     */
  91    ir_instruction *const last =
  92       (ir_instruction *) ir->body_instructions.get_tail();
  93
  94    if (last && (last->ir_type == ir_type_loop_jump)
  95        && (((ir_loop_jump *) last)->mode == ir_loop_jump::jump_continue)) {
  96       last->remove();
  97       this->progress = true;
  98    }
  99
 100    return visit_continue;
 101 }
 102
 103
 104 bool
 105 optimize_redundant_jumps(exec_list *instructions)
 106 {
 107    redundant_jumps_visitor v;
 108
 109    v.run(instructions);
 110    return v.progress;
 111 }