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72 lines
2.7 KiB
C++
72 lines
2.7 KiB
C++
#include <algorithm>
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#include "common/util/assert.h"
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#include "BasicBlocks.h"
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#include "decompiler/ObjectFile/LinkedObjectFile.h"
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#include "decompiler/Disasm/InstructionMatching.h"
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namespace decompiler {
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/*!
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* Find all basic blocks in a function.
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* All delay slot instructions are grouped with the branch instruction.
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* This is done by finding all "dividers", which are after branch delay instructions and before
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* branch destinations, then sorting them, ignoring duplicates, and creating the blocks.
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*/
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std::vector<BasicBlock> find_blocks_in_function(const LinkedObjectFile& file,
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int seg,
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const Function& func) {
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std::vector<BasicBlock> basic_blocks;
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// note - the first word of a function is the "function" type and should go in any basic block
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std::vector<int> dividers = {0, int(func.instructions.size())};
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for (int i = 0; i < int(func.instructions.size()); i++) {
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const auto& instr = func.instructions.at(i);
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const auto& instr_info = instr.get_info();
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if (instr_info.is_branch && !instr_info.is_branch_likely) {
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// make sure the delay slot of this branch is included in the function
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assert(i + func.start_word < func.end_word - 1);
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// divider after delay slot
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dividers.push_back(i + 2);
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auto label_id = instr.get_label_target();
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assert(label_id != -1);
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const auto& label = file.labels.at(label_id);
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// should only jump to within our own function
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assert(label.target_segment == seg);
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assert(label.offset / 4 > func.start_word);
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assert(label.offset / 4 < func.end_word - 1);
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dividers.push_back(label.offset / 4 - func.start_word);
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}
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// for branch likely, we treat the likely instruction as a separate block.
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if (instr_info.is_branch_likely) {
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assert(i + func.start_word < func.end_word - 1);
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// divider after branch instruction
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dividers.push_back(i + 1);
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// divider after likely delay slot.
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dividers.push_back(i + 2);
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// divider at the destination.
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auto label_id = instr.get_label_target();
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assert(label_id != -1);
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const auto& label = file.labels.at(label_id);
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// should only jump to within our own function
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assert(label.target_segment == seg);
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assert(label.offset / 4 > func.start_word);
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assert(label.offset / 4 < func.end_word - 1);
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dividers.push_back(label.offset / 4 - func.start_word);
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}
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}
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std::sort(dividers.begin(), dividers.end());
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for (size_t i = 0; i < dividers.size() - 1; i++) {
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if (dividers[i] != dividers[i + 1]) {
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basic_blocks.emplace_back(dividers[i], dividers[i + 1]);
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assert(dividers[i] >= 0);
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}
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}
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return basic_blocks;
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}
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} // namespace decompiler
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