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