feat: Implement EIP-7745 Log Value Index with LogIndexSummary

[vineetpant]

Introduction

EIP-7745 introduces Log Value Index to replace bloom filters with a more structured and efficient approach:

Benefits:

• Better Query Efficiency: Direct lookups via indices vs. probabilistic bloom filters
• Structured Data: Merkle roots enable efficient proofs and verification
• Reduced False Positives: Exact matching vs. bloom filter collisions

Key Requirement: LogIndex must accumulate from genesis

Description

This PR implements EIP-7745 (Log Value Index), replacing traditional Ethereum bloom filters with a more efficient and structured LogIndexSummary after fork activation.

• LogIndex data structures (LogMeta, LogIndexSummary, FilterMaps)
• Block creation with LogIndexSummary (tx_packer.nim)
• Block validation with LogIndexSummary verification (process_block.nim)
• SSZ hash tree root calculations for all structures
• Sparse FilterMap implementation
• Fork activation for EIP 7745
• LogIndex accumulation from genesis through all blocks

Core Implementation

1. execution_chain/core/log_index.nim : Complete LogIndex implementation including:

Data Structures:

• LogMeta: Individual log entry with address, topics, data hash, and indices
• LogIndexSummary: 256-byte structure replacing bloom filter:
• FilterMap: Sparse bitmap for efficient filtering with:
• LogIndex: Accumulated state across all blocks:

Key Functions:

• add_block_logs(): Accumulate logs from current block
• createLogIndexSummary(): Generate 256-byte summary from LogIndex state
• encodeLogIndexSummary(): Manual byte encoding (SSZ stack overflow workaround)
• calculate_filter_maps(): Create sparse bitmaps for efficient queries
• Hash tree root calculations using SSZ merkleization

2. Integration in Block Creation in execution_chain/core/tx_pool/tx_packer.nim

• Generate LogIndexSummary when packing blocks
• Encode LogIndexSummary and store in header.logsBloom field

3. Integration in Block Validation: execution_chain/core/executor/process_block.nim

• Validate LogIndexSummary when processing blocks
• Verify encoded LogIndexSummary matches header.logsBloom

4. LogIndex Accumulation

LogIndex must accumulate from genesis - each block builds upon parent's state.

• Preserve LogIndex across vmState reinit
• Added logIndex: LogIndex field to BlockRef
• Persist accumulated LogIndex state with each processed block

Following files are updated

• execution_chain/evm/state.nim
• execution_chain/core/chain/forked_chain/chain_branch.nim
• execution_chain/core/chain/forked_chain/chain_private.nim
• execution_chain/core/chain/forked_chain.nim
• execution_chain/core/chain/forked_chain/chain_serialize.nim
• execution_chain/core/tx_pool/tx_desc.nim

5. Fork Activation

• Added EIP-7745 fork configuration
• Added eip7745Time configuration field
• Added isEip7745OrLater() helper function

Unit Test Coverage

• Unit tests for LogIndex operations
• FilterMap coordinate calculations
• Hash tree root verification
• SSZ encoding/decoding
• Fork activation logic

Breaking Changes

None - implementation is backward compatible:

• Pre-EIP-7745 blocks: Traditional bloom filters in logsBloom field
• Post-EIP-7745 blocks: LogIndexSummary encoded in logsBloom field

Known Issues / Future Work

1. Code cleanup is required to remove debug statements and add more comments
2. Activation Timestamp is currently set to test value - needs production activation block/timestamp
3. Need proper reorg handling

Related

• Pureth Implementation guide: https://pureth.guide/implementations-7745/
• EIP-7745 Specification: https://eips.ethereum.org/EIPS/eip-7745
• nim-eth PR: Feat: Adjust log types  nim-eth#827
• nim-eth branch: adjust-log-types