src/compiler/glsl/opt_conditional_discard.cpp

   1 /*
   2  * Copyright © 2014 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_conditional_discard.cpp
  26  *
  27  * Replace
  28  *
  29  *    if (cond) discard;
  30  *
  31  * with
  32  *
  33  *    (discard <condition>)
  34  */
  35
  36 #include "compiler/glsl_types.h"
  37 #include "ir.h"
  38
  39 namespace {
  40
  41 class opt_conditional_discard_visitor : public ir_hierarchical_visitor {
  42 public:
  43    opt_conditional_discard_visitor()
  44    {
  45       progress = false;
  46    }
  47
  48    ir_visitor_status visit_leave(ir_if *);
  49
  50    bool progress;
  51 };
  52
  53 } /* anonymous namespace */
  54
  55 bool
  56 opt_conditional_discard(exec_list *instructions)
  57 {
  58    opt_conditional_discard_visitor v;
  59    v.run(instructions);
  60    return v.progress;
  61 }
  62
  63 ir_visitor_status
  64 opt_conditional_discard_visitor::visit_leave(ir_if *ir)
  65 {
  66    /* Look for "if (...) discard" with no else clause or extra statements. */
  67    if (ir->then_instructions.is_empty() ||
  68        !ir->then_instructions.get_head_raw()->next->is_tail_sentinel() ||
  69        !((ir_instruction *) ir->then_instructions.get_head_raw())->as_discard() ||
  70        !ir->else_instructions.is_empty())
  71       return visit_continue;
  72
  73    /* Move the condition and replace the ir_if with the ir_discard. */
  74    ir_discard *discard = (ir_discard *) ir->then_instructions.get_head_raw();
  75    if (!discard->condition)
  76       discard->condition = ir->condition;
  77    else {
  78       void *ctx = ralloc_parent(ir);
  79       discard->condition = new(ctx) ir_expression(ir_binop_logic_and,
  80                                                   ir->condition,
  81                                                   discard->condition);
  82    }
  83    ir->replace_with(discard);
  84
  85    progress = true;
  86
  87    return visit_continue;
  88 }