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/*
* Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibJS/Bytecode/PassManager.h>
#include <string.h>
namespace JS::Bytecode::Passes {
void UnifySameBlocks::perform(PassPipelineExecutable& executable)
{
started();
VERIFY(executable.cfg.has_value());
VERIFY(executable.inverted_cfg.has_value());
auto cfg = executable.cfg.release_value();
auto inverted_cfg = executable.inverted_cfg.release_value();
HashMap<BasicBlock const*, BasicBlock const*> equal_blocks;
for (size_t i = 0; i < executable.executable.basic_blocks.size(); ++i) {
auto& block = executable.executable.basic_blocks[i];
auto block_bytes = block.instruction_stream();
for (auto& candidate_block : executable.executable.basic_blocks.span().slice(i + 1)) {
if (equal_blocks.contains(&*candidate_block))
continue;
// FIXME: This can probably be relaxed a bit...
if (candidate_block->size() != block.size())
continue;
auto candidate_bytes = candidate_block->instruction_stream();
// FIXME: NewBigInt's value is not correctly reflected by its encoding in memory,
// this will yield false negatives for blocks containing that
if (memcmp(candidate_bytes.data(), block_bytes.data(), candidate_block->size()) == 0)
equal_blocks.set(&*candidate_block, &block);
}
}
auto replace_blocks = [&](auto& match, auto& replacement) {
Optional<size_t> first_successor_position;
auto it = executable.executable.basic_blocks.find_if([match](auto& block) { return match == block; });
VERIFY(!it.is_end());
executable.executable.basic_blocks.remove(it.index());
if (!first_successor_position.has_value())
first_successor_position = it.index();
for (auto& block : executable.executable.basic_blocks) {
InstructionStreamIterator it { block.instruction_stream() };
while (!it.at_end()) {
auto& instruction = *it;
++it;
const_cast<Instruction&>(instruction).replace_references(*match, replacement);
}
}
return first_successor_position;
};
for (auto& entry : equal_blocks)
(void)replace_blocks(entry.key, *entry.value);
finished();
}
}
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