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/*
* Copyright © 2018 Valve Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Authors:
* Daniel Schürmann (daniel.schuermann@campus.tu-berlin.de)
*
*/
#ifndef ACO_DOMINANCE_CPP
#define ACO_DOMINANCE_CPP
#include "aco_ir.h"
/*
* Implements the algorithms for computing the dominator tree from
* "A Simple, Fast Dominance Algorithm" by Cooper, Harvey, and Kennedy.
*
* Different from the paper, our CFG allows to compute the dominator tree
* in a single pass as it is guaranteed that the dominating predecessors
* are processed before the current block.
*/
namespace aco {
void dominator_tree(Program* program)
{
program->blocks[0].logical_idom = 0;
program->blocks[0].linear_idom = 0;
for (unsigned i = 1; i < program->blocks.size(); i++) {
Block& block = program->blocks[i];
int new_logical_idom = -1;
int new_linear_idom = -1;
for (unsigned pred_idx : block.logical_preds) {
if ((int) program->blocks[pred_idx].logical_idom == -1)
continue;
if (new_logical_idom == -1) {
new_logical_idom = pred_idx;
continue;
}
while ((int) pred_idx != new_logical_idom) {
if ((int) pred_idx > new_logical_idom)
pred_idx = program->blocks[pred_idx].logical_idom;
if ((int) pred_idx < new_logical_idom)
new_logical_idom = program->blocks[new_logical_idom].logical_idom;
}
}
for (unsigned pred_idx : block.linear_preds) {
if ((int) program->blocks[pred_idx].linear_idom == -1)
continue;
if (new_linear_idom == -1) {
new_linear_idom = pred_idx;
continue;
}
while ((int) pred_idx != new_linear_idom) {
if ((int) pred_idx > new_linear_idom)
pred_idx = program->blocks[pred_idx].linear_idom;
if ((int) pred_idx < new_linear_idom)
new_linear_idom = program->blocks[new_linear_idom].linear_idom;
}
}
block.logical_idom = new_logical_idom;
block.linear_idom = new_linear_idom;
}
}
}
#endif
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