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moves instruction decoder into own class

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Eyck-Alexander Jentzsch 2024-07-23 11:30:33 +02:00
parent 60808c8649
commit 6ee484a771
3 changed files with 167 additions and 0 deletions
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1
CMakeLists.txt
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@ -20,6 +20,7 @@ set(LIB_SOURCES
src/iss/arch/tgc5c.cpp
src/vm/interp/vm_tgc5c.cpp
src/vm/fp_functions.cpp
src/vm/instruction_decoder.cpp
src/iss/semihosting/semihosting.cpp
)

103
src/vm/instruction_decoder.cpp Normal file
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@ -0,0 +1,103 @@
/*******************************************************************************
* Copyright (C) 2024 MINRES Technologies GmbH
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* Contributors:
* alex@minres.com - initial implementation
******************************************************************************/
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <limits>
#include <numeric>
#include <vector>
#include <vm/instruction_decoder.h>
decoder::decoder(std::vector<generic_instruction_descriptor> instr_list) {
for(auto instr : instr_list) {
root.instrs.push_back(instr);
}
populate_decoding_tree(root);
}
void decoder::populate_decoding_tree(decoding_tree_node& parent) {
// create submask
parent.submask =
std::accumulate(parent.instrs.begin(), parent.instrs.end(), std::numeric_limits<uint32_t>::max(),
[](int current_submask, const generic_instruction_descriptor& instr) { return current_submask & instr.mask; });
// put each instr according to submask&encoding into children
for(auto instr : parent.instrs) {
bool foundMatch = false;
for(auto& child : parent.children) {
// use value as identifying trait
if(child.value == (instr.value & parent.submask)) {
child.instrs.push_back(instr);
foundMatch = true;
}
}
if(!foundMatch) {
decoding_tree_node child = decoding_tree_node(instr.value & parent.submask);
child.instrs.push_back(instr);
parent.children.push_back(child);
}
}
parent.instrs.clear();
// call populate_decoding_tree for all children
if(parent.children.size() > 1)
for(auto& child : parent.children) {
populate_decoding_tree(child);
}
else {
// sort instrs by value of the mask, so we have the least restrictive mask last
std::sort(parent.children[0].instrs.begin(), parent.children[0].instrs.end(),
[](const generic_instruction_descriptor& instr1, const generic_instruction_descriptor& instr2) {
return instr1.mask > instr2.mask;
});
}
}
uint32_t decoder::decode_instr(uint32_t word) { return _decode_instr(this->root, word); }
uint32_t decoder::_decode_instr(decoding_tree_node const& node, uint32_t word) {
if(!node.children.size()) {
if(node.instrs.size() == 1)
return node.instrs[0].index;
for(auto instr : node.instrs) {
if((instr.mask & word) == instr.value)
return instr.index;
}
} else {
for(auto child : node.children) {
if(child.value == (node.submask & word)) {
return _decode_instr(child, word);
}
}
}
return std::numeric_limits<uint32_t>::max();
}

63
src/vm/instruction_decoder.h Normal file
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@ -0,0 +1,63 @@
/*******************************************************************************
* Copyright (C) 2024 MINRES Technologies GmbH
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* Contributors:
* alex@minres.com - initial implementation
******************************************************************************/
#include <cstddef>
#include <cstdint>
#include <limits>
#include <vector>
struct generic_instruction_descriptor {
uint32_t value;
uint32_t mask;
uint32_t index;
};
struct decoding_tree_node {
std::vector<generic_instruction_descriptor> instrs;
std::vector<decoding_tree_node> children;
uint32_t submask = std::numeric_limits<uint32_t>::max();
uint32_t value;
decoding_tree_node(uint32_t value)
: value(value) {}
};
class decoder {
public:
decoder(std::vector<generic_instruction_descriptor> instr_list);
uint32_t decode_instr(uint32_t word);
private:
decoding_tree_node root{decoding_tree_node(std::numeric_limits<uint32_t>::max())};
void populate_decoding_tree(decoding_tree_node& root);
uint32_t _decode_instr(decoding_tree_node const& node, uint32_t word);
};