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Precompiled contracts

A precompiled smart contract is a contract with a C++ implementation in the node. When a validator processes a transaction for such a contract, it can execute this native implementation instead of TVM. This improves performance and reduces computation fees.

Config​

The list of precompiled contracts is stored in the MasterChain configuration:

precompiled_smc#b0 gas_usage:uint64 = PrecompiledSmc;
precompiled_contracts_config#c0 list:(HashmapE 256 PrecompiledSmc) = PrecompiledContractsConfig;
_ PrecompiledContractsConfig = ConfigParam 45;

The list:(HashmapE 256 PrecompiledSmc) represents a mapping of (code_hash -> precompiled_smc). A contract is considered precompiled if its code hash exists in this map.

Contract execution​

Transactions for precompiled smart contracts (those with code hashes in ConfigParam 45) follow this execution flow:

  1. Retrieve the gas_usage value from the masterchain config
  2. If the contract balance cannot cover the gas_usage cost, the compute phase fails with cskip_no_gas.
  3. Execution proceeds via one of two paths:
    • TVM execution: Used if precompiled execution is disabled or the C++ implementation is unavailable in the node version. TVM executes with the gas limits defined by the network configuration (see gas and fee parameters and Param20/Param21).
    • Native execution: Used when precompiled implementation is both enabled and available, executing the C++ code directly
  4. Compute phase values are overridden:
    • gas_used set to gas_usage
    • vm_steps, vm_init_state_hash, and vm_final_state_hash set to zero
  5. Computation fees are calculated based on gas_usage rather than actual TVM gas consumption

For precompiled contracts, the 17th element of c7 (index 16) holds the precompiled gas_usage value for the current contract as defined in ConfigParam 45; see c7. The GETPRECOMPILEDGAS opcode is currently reserved and returns null; when activated, it will return the precompiled contract gas usage; see new opcodes. Non-precompiled contracts return null for this value.

Note: Enable precompiled contract execution by running validator-engine with the --enable-precompiled-smc (experimental) flag. Both execution methods produce identical transactions, allowing validators with and without C++ implementations to coexist in the network. This enables gradual adoption when adding new entries to ConfigParam 45.

See also​

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