Improve evmasm block deduplicator performance#16684
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| /// Hash function compatible with `operator==`. Found via ADL by `boost::hash`. | ||
| friend std::size_t hash_value(AssemblyItem const& _item) | ||
| { | ||
| std::size_t hash = 0; | ||
| boost::hash_combine(hash, static_cast<int>(_item.m_type)); | ||
| if (_item.m_type == Operation) | ||
| boost::hash_combine(hash, static_cast<int>(_item.instruction())); | ||
| else if (_item.m_type == VerbatimBytecode) | ||
| boost::hash_combine(hash, *_item.m_verbatimBytecode); | ||
| else | ||
| boost::hash_combine(hash, _item.data()); | ||
| return hash; | ||
| } |
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This looks OK, I would just move it somewhere else.
Placing it between operator!= and operator< does not seem like the best choice.
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I placed it here so it's evident that the implementation follows the one of the equality operator. Where do you think it should live?
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While the whole deduplication algorithm seems somewhat fragile to me, I believe the proposed changes preserve the existing behaviour and do not introduce any new issues.
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This is mainly a refactor of the
BlockDeduplicatorand no behavior change is intended.Right now the deduplicator uses a
std::setwith a lexicographical compare over each block's body. Looking up a block is thereforeO(block_size * log N)per probe and each comparison walks both blocks assembly item by assembly item (worst case the entire block).The refactor exchanges the
setwith anunordered_setprovided a specific hash function and a specific equality function. Each block's body is hashed once viahash_rangeand equality checks useranges::equalover the same range. Lookup is thenO(block_size)amortized.To achieve this,
AssemblyItemgets ahash_valuefriend so that boost hash can load a hash via ADLBlockIteratorgets default ctor and post-increment to satisfy the range concept (needed forhash_rangeandranges::equal).Some benchmarks on my machine: