Update modexp precompile costs (EIP-7883) (#1268)

Update the [EIP-7883 "ModExp Gas Cost
Increase"](https://eips.ethereum.org/EIPS/eip-7883) to the latest
revision:
- ethereum/EIPs#9855
- ethereum/EIPs#9969

Author: chfast

circle.yml

@@ -423,13 +423,13 @@ jobs:
           working_directory: ~/build
           command: >
             bin/evmone-statetest ~/spec-tests/fixtures/state_tests/
-            --gtest_filter='-byzantium/eip198_modexp_precompile/modexp.modexp:cancun/eip4844_blobs/blob_txs.invalid_tx_blob_count:frontier/precompiles/precompiles.precompiles:osaka/eip7594_peerdas/max_blob_per_tx.invalid_max_blobs_per_tx:osaka/eip7825_transaction_gas_limit_cap/tx_gas_limit.transaction_gas_limit_cap:osaka/eip7883_modexp_gas_increase/modexp_thresholds.vectors_from_file:osaka/eip7939_count_leading_zeros/*.*:osaka/eip7951_p256verify_precompiles/*.*:prague/eip7702_set_code_tx/set_code_txs.set_code_to_precompile'
+            --gtest_filter='-cancun/eip4844_blobs/blob_txs.invalid_tx_blob_count:frontier/precompiles/precompiles.precompiles:osaka/eip7594_peerdas/max_blob_per_tx.invalid_max_blobs_per_tx:osaka/eip7825_transaction_gas_limit_cap/tx_gas_limit.transaction_gas_limit_cap:osaka/eip7939_count_leading_zeros/*.*:osaka/eip7951_p256verify_precompiles/*.*:prague/eip7702_set_code_tx/set_code_txs.set_code_to_precompile'
       - run:
           name: "Fusaka pre-release execution spec tests (blockchain_tests)"
           working_directory: ~/build
           command: >
             bin/evmone-blockchaintest ~/spec-tests/fixtures/blockchain_tests/
-            --gtest_filter='-byzantium/eip198_modexp_precompile/modexp.modexp:cancun/eip4844_blobs/blob_txs.valid_blob_tx_combinations:frontier/precompiles/precompiles.precompiles:osaka/eip7594_peerdas/max_blob_per_tx.max_blobs_per_tx_fork_transition:osaka/eip7825_transaction_gas_limit_cap/tx_gas_limit.transaction_gas_limit_cap_at_transition:osaka/eip7883_modexp_gas_increase/modexp_thresholds.vectors_from_file:osaka/eip7918_blob_reserve_price/*.*:osaka/eip7934_block_rlp_limit/max_block_rlp_size.block_at_rlp_size_limit_boundary:osaka/eip7939_count_leading_zeros/*.*:osaka/eip7951_p256verify_precompiles/*.*:prague/eip7702_set_code_tx/set_code_txs.set_code_to_precompile'
+            --gtest_filter='-cancun/eip4844_blobs/blob_txs.valid_blob_tx_combinations:frontier/precompiles/precompiles.precompiles:osaka/eip7594_peerdas/max_blob_per_tx.max_blobs_per_tx_fork_transition:osaka/eip7825_transaction_gas_limit_cap/tx_gas_limit.transaction_gas_limit_cap_at_transition:osaka/eip7918_blob_reserve_price/*.*:osaka/eip7934_block_rlp_limit/max_block_rlp_size.block_at_rlp_size_limit_boundary:osaka/eip7939_count_leading_zeros/*.*:osaka/eip7951_p256verify_precompiles/*.*:prague/eip7702_set_code_tx/set_code_txs.set_code_to_precompile'
       - collect_coverage_gcc
       - upload_coverage:
           flags: fusaka_execution_spec_tests

test/state/precompiles.cpp

@@ -127,8 +127,7 @@ PrecompileAnalysis expmod_analyze(bytes_view input, evmc_revision rev) noexcept
         // With EIP-7823 the computation never overflows.
         assert(max_len <= MODEXP_LEN_LIMIT_EIP7823);
         const auto num_words = (max_len + 7) / 8;
-        const auto num_words_squared = num_words * num_words;
-        const auto mult_complexity = max_len <= 32 ? num_words_squared : num_words_squared * 2;
+        const auto mult_complexity = max_len <= 32 ? 16 : num_words * num_words * 2;
         return uint64_t{mult_complexity};
     };
     static constexpr auto calc_mult_complexity_eip2565 = [](uint32_t max_len) noexcept {
@@ -153,7 +152,7 @@ PrecompileAnalysis expmod_analyze(bytes_view input, evmc_revision rev) noexcept
     };
     const auto& [min_gas, final_divisor, calc_mult_complexity] = [rev]() noexcept -> Params {
         if (rev >= EVMC_OSAKA)
-            return {500, 3, calc_mult_complexity_eip7883};
+            return {500, 1, calc_mult_complexity_eip7883};
         else if (rev >= EVMC_BERLIN)
             return {200, 3, calc_mult_complexity_eip2565};
         else  // Byzantium