🏆 Advanced Techniques: Bitwise & Assembly

Discover expert-level gas optimization with Yul assembly

Write efficient smart contracts that save money

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🔬 Advanced Gas Techniques

Elite gas optimization requires advanced techniques. Inline assembly gives direct EVM opcode access—Uniswap V3's sqrt calculation uses assembly for 50% gas reduction, but one mistake loses user funds (no safety checks). Calldata optimization—using calldata instead of memory for read-only parameters—saves 1,000+ gas by avoiding memory copies. Bitmaps pack 256 boolean flags into one storage slot (90%+ savings)—Uniswap's token airdrop used bitmaps to track claims for 10M+ users. Minimal proxies (EIP-1167) deploy 200-byte clones instead of full contracts (99% cheaper)—Gnosis Safe creates wallet instances this way. These techniques separate amateur from expert optimization.

🎮 Interactive: Advanced Technique Explorer

Select a technique to see code examples, gas savings, real-world usage, and safety considerations.

⚙️

Inline Assembly

50-70% savingsHigh Risk

Direct EVM opcodes bypass Solidity safety checks

💻 Code Example

// Save 200+ gas per call
function getBalance(address user) returns (uint) {
  // Solidity: ~500 gas
  return balances[user];
  
  // Assembly: ~300 gas
  assembly {
    mstore(0x00, user)
    mstore(0x20, balances.slot)
    let hash := keccak256(0x00, 0x40)
    let value := sload(hash)
    mstore(0x00, value)
    return(0x00, 0x20)
  }
}

🏭 Production Use Cases

Uniswap V3 uses assembly for sqrt math (50% gas reduction). OpenSea Seaport uses assembly for order validation.

⚠️ Safety Considerations

No overflow checks, no type safety. One mistake = funds lost. Only use for hot paths after extensive testing.

🛠️ Gas Profiling Tools

Hardhat Gas Reporter: Automatic gas reporting for tests. npx hardhat test --gas-reporter shows function costs in table format.

Foundry Gas Snapshots: forge snapshot creates baseline. forge snapshot --diff shows before/after changes. Commit snapshots to git.

Tenderly Debugger: Visual transaction traces with gas costs per opcode. See exactly which line costs the most.

eth-gas-reporter: CI integration, tracks gas over time, alerts on regressions. Essential for production contracts.

📊 Optimization Checklist

Pack storage variables

Group uint128, uint64, uint32 together. Order by size.

Cache storage reads

Read storage once into memory. Especially in loops.

Optimize loops

Cache length, use ++i, wrap in unchecked.

Use calldata for arrays

External functions with read-only array parameters.

Profile with tools

Measure before and after. Track gas in CI.

Consider bitmaps for flags

256 booleans = 1 storage slot. Huge savings.

💡 When NOT to Optimize

•
Security over gas: Don't sacrifice safety for 100 gas. Exploits cost infinitely more.
•
Readability matters: Complex optimizations need extensive comments. Future you will thank you.
•
Measure first: Profile to find hot spots. 90% of gas in 10% of code. Optimize that 10%.
•
L2s change math: On Arbitrum/Optimism, calldata is expensive. Optimization priorities differ.