1414c7b049
This commit adds a bunch of passes, the most interesting of which is a pass that merges blocks together, and a pass that places blocks that flow into each other next to each other, and a very simply pass that removes duplicate basic blocks. Note that this does not remove the jump at the end of each block in that pass to avoid scope creep in the passes.
62 lines
2.1 KiB
C++
62 lines
2.1 KiB
C++
/*
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* Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibJS/Bytecode/PassManager.h>
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#include <string.h>
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namespace JS::Bytecode::Passes {
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void UnifySameBlocks::perform(PassPipelineExecutable& executable)
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{
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started();
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VERIFY(executable.cfg.has_value());
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VERIFY(executable.inverted_cfg.has_value());
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auto cfg = executable.cfg.release_value();
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auto inverted_cfg = executable.inverted_cfg.release_value();
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HashMap<BasicBlock const*, BasicBlock const*> equal_blocks;
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for (size_t i = 0; i < executable.executable.basic_blocks.size(); ++i) {
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auto& block = executable.executable.basic_blocks[i];
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auto block_bytes = block.instruction_stream();
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for (auto& candidate_block : executable.executable.basic_blocks.span().slice(i + 1)) {
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// FIXME: This can probably be relaxed a bit...
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if (candidate_block->size() != block.size())
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continue;
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auto candidate_bytes = candidate_block->instruction_stream();
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if (memcmp(candidate_bytes.data(), block_bytes.data(), candidate_block->size()) == 0)
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equal_blocks.set(&*candidate_block, &block);
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}
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}
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auto replace_blocks = [&](auto& match, auto& replacement) {
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Optional<size_t> first_successor_position;
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auto it = executable.executable.basic_blocks.find_if([match](auto& block) { return match == block; });
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VERIFY(!it.is_end());
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executable.executable.basic_blocks.remove(it.index());
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if (!first_successor_position.has_value())
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first_successor_position = it.index();
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for (auto& block : executable.executable.basic_blocks) {
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InstructionStreamIterator it { block.instruction_stream() };
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while (!it.at_end()) {
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auto& instruction = *it;
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++it;
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const_cast<Instruction&>(instruction).replace_references(*match, replacement);
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}
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}
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return first_successor_position;
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};
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for (auto& entry : equal_blocks)
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(void)replace_blocks(entry.key, *entry.value);
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finished();
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}
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}
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