src/glsl/opt_flatten_nested_if_blocks.cpp

   1 /*
   2  * Copyright © 2013 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_flatten_nested_if_blocks.cpp
  26  *
  27  * Flattens nested if blocks such as:
  28  *
  29  * if (x) {
  30  *    if (y) {
  31  *       ...
  32  *    }
  33  * }
  34  *
  35  * into a single if block with a combined condition:
  36  *
  37  * if (x && y) {
  38  *    ...
  39  * }
  40  */
  41
  42 #include "ir.h"
  43 #include "ir_builder.h"
  44
  45 using namespace ir_builder;
  46
  47 namespace {
  48
  49 class nested_if_flattener : public ir_hierarchical_visitor {
  50 public:
  51    nested_if_flattener()
  52    {
  53       progress = false;
  54    }
  55
  56    ir_visitor_status visit_leave(ir_if *);
  57    ir_visitor_status visit_enter(ir_assignment *);
  58
  59    bool progress;
  60 };
  61
  62 } /* unnamed namespace */
  63
  64 /* We only care about the top level "if" instructions, so don't
  65  * descend into expressions.
  66  */
  67 ir_visitor_status
  68 nested_if_flattener::visit_enter(ir_assignment *ir)
  69 {
  70    (void) ir;
  71    return visit_continue_with_parent;
  72 }
  73
  74 bool
  75 opt_flatten_nested_if_blocks(exec_list *instructions)
  76 {
  77    nested_if_flattener v;
  78
  79    v.run(instructions);
  80    return v.progress;
  81 }
  82
  83
  84 ir_visitor_status
  85 nested_if_flattener::visit_leave(ir_if *ir)
  86 {
  87    /* Only handle a single ir_if within the then clause of an ir_if.  No extra
  88     * instructions, no else clauses, nothing.
  89     */
  90    if (ir->then_instructions.is_empty() || !ir->else_instructions.is_empty())
  91       return visit_continue;
  92
  93    ir_if *inner = ((ir_instruction *) ir->then_instructions.head)->as_if();
  94    if (!inner || !inner->next->is_tail_sentinel() ||
  95        !inner->else_instructions.is_empty())
  96       return visit_continue;
  97
  98    ir->condition = logic_and(ir->condition, inner->condition);
  99    inner->then_instructions.move_nodes_to(&ir->then_instructions);
 100
 101    progress = true;
 102    return visit_continue;
 103 }