src/amd/compiler/aco_dominance.cpp

   1 /*
   2  * Copyright © 2018 Valve 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 DEALINGS
  21  * IN THE SOFTWARE.
  22  *
  23  * Authors:
  24  *    Daniel Schürmann (daniel.schuermann@campus.tu-berlin.de)
  25  *
  26  */
  27
  28 #ifndef ACO_DOMINANCE_CPP
  29 #define ACO_DOMINANCE_CPP
  30
  31 #include "aco_ir.h"
  32
  33 /*
  34  * Implements the algorithms for computing the dominator tree from
  35  * "A Simple, Fast Dominance Algorithm" by Cooper, Harvey, and Kennedy.
  36  *
  37  * Different from the paper, our CFG allows to compute the dominator tree
  38  * in a single pass as it is guaranteed that the dominating predecessors
  39  * are processed before the current block.
  40  */
  41
  42 namespace aco {
  43
  44 void dominator_tree(Program* program)
  45 {
  46    program->blocks[0].logical_idom = 0;
  47    program->blocks[0].linear_idom = 0;
  48
  49    for (unsigned i = 1; i < program->blocks.size(); i++) {
  50       Block& block = program->blocks[i];
  51       int new_logical_idom = -1;
  52       int new_linear_idom = -1;
  53       for (unsigned pred_idx : block.logical_preds) {
  54          if ((int) program->blocks[pred_idx].logical_idom == -1)
  55             continue;
  56
  57          if (new_logical_idom == -1) {
  58             new_logical_idom = pred_idx;
  59             continue;
  60          }
  61
  62          while ((int) pred_idx != new_logical_idom) {
  63             if ((int) pred_idx > new_logical_idom)
  64                pred_idx = program->blocks[pred_idx].logical_idom;
  65             if ((int) pred_idx < new_logical_idom)
  66                new_logical_idom = program->blocks[new_logical_idom].logical_idom;
  67          }
  68       }
  69
  70       for (unsigned pred_idx : block.linear_preds) {
  71          if ((int) program->blocks[pred_idx].linear_idom == -1)
  72             continue;
  73
  74          if (new_linear_idom == -1) {
  75             new_linear_idom = pred_idx;
  76             continue;
  77          }
  78
  79          while ((int) pred_idx != new_linear_idom) {
  80             if ((int) pred_idx > new_linear_idom)
  81                pred_idx = program->blocks[pred_idx].linear_idom;
  82             if ((int) pred_idx < new_linear_idom)
  83                new_linear_idom = program->blocks[new_linear_idom].linear_idom;
  84          }
  85       }
  86
  87       block.logical_idom = new_logical_idom;
  88       block.linear_idom = new_linear_idom;
  89    }
  90 }
  91
  92 }
  93 #endif