102 lines
4.3 KiB
C++
102 lines
4.3 KiB
C++
/*******************************************************************************
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* Copyright (C) 2024 MINRES Technologies GmbH
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* 3. Neither the name of the copyright holder nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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* Contributors:
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* alex@minres.com - initial implementation
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******************************************************************************/
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#include <algorithm>
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#include <cassert>
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#include <cstddef>
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#include <cstdint>
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#include <limits>
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#include <numeric>
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#include <vector>
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#include <vm/instruction_decoder.h>
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decoder::decoder(std::vector<generic_instruction_descriptor> instr_list) {
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for(auto instr : instr_list) {
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root.instrs.push_back(instr);
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}
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populate_decoding_tree(root);
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}
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void decoder::populate_decoding_tree(decoding_tree_node& parent) {
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// create submask
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parent.submask =
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std::accumulate(parent.instrs.begin(), parent.instrs.end(), std::numeric_limits<uint32_t>::max(),
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[](int current_submask, const generic_instruction_descriptor& instr) { return current_submask & instr.mask; });
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// put each instr according to submask&encoding into children
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for(auto instr : parent.instrs) {
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bool foundMatch = false;
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for(auto& child : parent.children) {
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// use value as identifying trait
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if(child.value == (instr.value & parent.submask)) {
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child.instrs.push_back(instr);
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foundMatch = true;
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}
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}
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if(!foundMatch) {
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decoding_tree_node child = decoding_tree_node(instr.value & parent.submask);
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child.instrs.push_back(instr);
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parent.children.push_back(child);
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}
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}
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parent.instrs.clear();
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// call populate_decoding_tree for all children
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if(parent.children.size() > 1)
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for(auto& child : parent.children) {
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populate_decoding_tree(child);
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}
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else {
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// sort instrs by value of the mask, so we have the least restrictive mask last
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std::sort(parent.children[0].instrs.begin(), parent.children[0].instrs.end(),
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[](const generic_instruction_descriptor& instr1, const generic_instruction_descriptor& instr2) {
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return instr1.mask > instr2.mask;
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});
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}
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}
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uint32_t decoder::decode_instr(uint32_t word) { return _decode_instr(this->root, word); }
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uint32_t decoder::_decode_instr(decoding_tree_node const& node, uint32_t word) {
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if(!node.instrs.empty()) {
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for(auto& instr : node.instrs) {
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if((instr.mask & word) == instr.value)
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return instr.index;
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}
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} else if(!node.children.empty()) {
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for(auto& child : node.children) {
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if(child.value == (node.submask & word)) {
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return _decode_instr(child, word);
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}
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}
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}
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return std::numeric_limits<uint32_t>::max();
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}
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