Instruction Types

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The Bytecode iterator returns instructions as a discriminated union (OpcodeData) representing different instruction categories and fusion patterns.

Base Instruction Type

All instruction objects share common fields:

TypeScript

interface BaseInstruction {
  pc: number              // Program counter (byte offset)
  type: InstructionType   // Discriminator for union
}

Instruction Categories

Regular Instructions

Standard single-byte opcodes (ADD, MUL, SWAP1, etc.):

interface RegularInstruction extends BaseInstruction {
  type: 'regular'
  opcode: number         // Raw opcode byte (0x00-0xFF)
}

Example:

{
  type: 'regular',
  pc: 4,
  opcode: 0x01  // ADD
}

PUSH Instructions

PUSH1 through PUSH32 with immediate data:

interface PushInstruction extends BaseInstruction {
  type: 'push'
  opcode: number         // PUSH1 (0x60) through PUSH32 (0x7F)
  value: bigint          // Pushed value
  size: number           // Push size in bytes (1-32)
}

Example:

{
  type: 'push',
  pc: 0,
  opcode: 0x60,         // PUSH1
  value: 42n,
  size: 1
}

JUMPDEST Instructions

Valid jump destinations with block metadata:

interface JumpdestInstruction extends BaseInstruction {
  type: 'jumpdest'
  pc: number
  gas_cost: number      // Gas cost from here to next terminator
  min_stack: number     // Min stack depth required for this block
  max_stack: number     // Max stack depth reached in this block
}

Example:

{
  type: 'jumpdest',
  pc: 23,
  gas_cost: 156,        // Total gas to execute block
  min_stack: 2,         // Needs 2 items on stack minimum
  max_stack: 5          // Block pushes up to 5 items total
}

JUMPDEST metadata enables efficient block-level gas estimation and stack validation without re-analyzing.

JUMP Instructions

Dynamic unconditional jump (target determined at runtime):

interface JumpInstruction extends BaseInstruction {
  type: 'jump'
  pc: number
}

Example:

{
  type: 'jump',
  pc: 45
}

jump type indicates dynamic JUMP (not fused with PUSH). Target validation occurs at runtime.

JUMPI Instructions

Dynamic conditional jump (target and condition determined at runtime):

interface JumpiInstruction extends BaseInstruction {
  type: 'jumpi'
  pc: number
}

Example:

{
  type: 'jumpi',
  pc: 67
}

PC Instructions

PC opcode returning current program counter:

interface PcInstruction extends BaseInstruction {
  type: 'pc'
  pc: number
  value: number          // Value that PC will push (equals pc field)
}

Example:

{
  type: 'pc',
  pc: 100,
  value: 100             // PC pushes its own position
}

STOP Instructions

Halts execution:

interface StopInstruction extends BaseInstruction {
  type: 'stop'
  pc: number
}

INVALID Instructions

Invalid opcodes or undefined instruction bytes:

interface InvalidInstruction extends BaseInstruction {
  type: 'invalid'
  pc: number
}

Fusion Instructions

Optimizable multi-instruction patterns detected during analysis.

Arithmetic Fusions

PUSH + ADD

interface PushAddFusion extends BaseInstruction {
  type: 'push_add_fusion'
  value: bigint          // PUSH value
  pc: number            // Position of PUSH
}

Represents: PUSH value + ADD → Add immediate value to stack top.

PUSH + MUL

interface PushMulFusion extends BaseInstruction {
  type: 'push_mul_fusion'
  value: bigint
  pc: number
}

Represents: PUSH value + MUL → Multiply stack top by immediate.

PUSH + SUB

interface PushSubFusion extends BaseInstruction {
  type: 'push_sub_fusion'
  value: bigint
  pc: number
}

Represents: PUSH value + SUB → Subtract immediate from stack top.

PUSH + DIV

interface PushDivFusion extends BaseInstruction {
  type: 'push_div_fusion'
  value: bigint
  pc: number
}

Represents: PUSH value + DIV → Divide stack top by immediate.

Bitwise Fusions

PUSH + AND

interface PushAndFusion extends BaseInstruction {
  type: 'push_and_fusion'
  value: bigint
  pc: number
}

Represents: PUSH value + AND → Bitwise AND with immediate.

PUSH + OR

interface PushOrFusion extends BaseInstruction {
  type: 'push_or_fusion'
  value: bigint
  pc: number
}

Represents: PUSH value + OR → Bitwise OR with immediate.

PUSH + XOR

interface PushXorFusion extends BaseInstruction {
  type: 'push_xor_fusion'
  value: bigint
  pc: number
}

Represents: PUSH value + XOR → Bitwise XOR with immediate.

Memory Fusions

PUSH + MLOAD

interface PushMloadFusion extends BaseInstruction {
  type: 'push_mload_fusion'
  value: bigint          // Memory offset
  pc: number
}

Represents: PUSH offset + MLOAD → Load from immediate memory address.

PUSH + MSTORE

interface PushMstoreFusion extends BaseInstruction {
  type: 'push_mstore_fusion'
  value: bigint          // Memory offset
  pc: number
}

Represents: PUSH offset + MSTORE → Store to immediate memory address.

PUSH + MSTORE8

interface PushMstore8Fusion extends BaseInstruction {
  type: 'push_mstore8_fusion'
  value: bigint          // Memory offset
  pc: number
}

Represents: PUSH offset + MSTORE8 → Store byte to immediate memory address.

Control Flow Fusions

PUSH + JUMP

interface PushJumpFusion extends BaseInstruction {
  type: 'push_jump_fusion'
  value: bigint          // Jump target (can be validated at compile-time)
  pc: number
}

Represents: PUSH target + JUMP → Static jump to known destination.

Static jumps can be validated during bytecode analysis. If value points to invalid JUMPDEST, bytecode is malformed.

PUSH + JUMPI

interface PushJumpiFusion extends BaseInstruction {
  type: 'push_jumpi_fusion'
  value: bigint          // Jump target
  pc: number
}

Represents: PUSH target + JUMPI → Conditional jump to known destination (condition still runtime).

ISZERO + PUSH + JUMPI

interface IszeroJumpiFusion extends BaseInstruction {
  type: 'iszero_jumpi'
  target: bigint         // Jump destination
  original_length: number // Size of original 3-instruction sequence
  pc: number
}

Represents: ISZERO + PUSH target + JUMPI → Inverted conditional jump pattern. Common in Solidity:

if (!condition) { ... }

Compiles to: ISZERO + PUSH <skip_offset> + JUMPI

Advanced Stack Fusions

DUP2 + MSTORE + PUSH

interface Dup2MstorePushFusion extends BaseInstruction {
  type: 'dup2_mstore_push'
  push_value: bigint
  original_length: number
  pc: number
}

Represents: DUP2 + MSTORE + PUSH value → Common memory write pattern.

DUP3 + ADD + MSTORE

interface Dup3AddMstoreFusion extends BaseInstruction {
  type: 'dup3_add_mstore'
  original_length: number
  pc: number
}

Represents: DUP3 + ADD + MSTORE → Offset calculation + store.

SWAP1 + DUP2 + ADD

interface Swap1Dup2AddFusion extends BaseInstruction {
  type: 'swap1_dup2_add'
  original_length: number
  pc: number
}

Represents: SWAP1 + DUP2 + ADD → Stack manipulation + arithmetic.

PUSH + DUP3 + ADD

interface PushDup3AddFusion extends BaseInstruction {
  type: 'push_dup3_add'
  value: bigint
  original_length: number
  pc: number
}

Represents: PUSH value + DUP3 + ADD → Immediate addition with stack duplication.

PUSH + ADD + DUP1

interface PushAddDup1Fusion extends BaseInstruction {
  type: 'push_add_dup1'
  value: bigint
  original_length: number
  pc: number
}

Represents: PUSH value + ADD + DUP1 → Add immediate and duplicate result.

MLOAD + SWAP1 + DUP2

interface MloadSwap1Dup2Fusion extends BaseInstruction {
  type: 'mload_swap1_dup2'
  original_length: number
  pc: number
}

Represents: MLOAD + SWAP1 + DUP2 → Memory load with stack rearrangement.

Multi-Instruction Fusions

MULTI_PUSH

interface MultiPushFusion extends BaseInstruction {
  type: 'multi_push'
  count: number          // Number of consecutive PUSHes (2-3)
  values: [bigint, bigint, bigint] // Values (unused entries are 0)
  original_length: number
  pc: number
}

Represents: Multiple consecutive PUSH instructions (2 or 3). Example:

PUSH1 0x01
PUSH1 0x02
PUSH1 0x03

→ { type: 'multi_push', count: 3, values: [1n, 2n, 3n] }

MULTI_POP

interface MultiPopFusion extends BaseInstruction {
  type: 'multi_pop'
  count: number          // Number of consecutive POPs (2-3)
  original_length: number
  pc: number
}

Represents: Multiple consecutive POP instructions (2 or 3).

Solidity-Specific Patterns

FUNCTION_DISPATCH

interface FunctionDispatchFusion extends BaseInstruction {
  type: 'function_dispatch'
  selector: number       // 4-byte function selector
  target: bigint         // Jump destination for this function
  original_length: number
  pc: number
}

Represents: PUSH4 selector + EQ + PUSH target + JUMPI → Function selector matching. Solidity pattern:

function myFunc() external { ... }

Generates function dispatch checking msg.sig == 0x12345678.

Detect all functions by collecting function_dispatch patterns. Extract function selectors for ABI reconstruction.

CALLVALUE_CHECK

interface CallvalueCheckFusion extends BaseInstruction {
  type: 'callvalue_check'
  original_length: number
  pc: number
}

Represents: CALLVALUE + DUP1 + ISZERO → Check if ETH sent (non-payable modifier). Solidity pattern:

function nonPayable() external { ... } // no `payable` modifier

Compiler inserts check: revert if msg.value > 0.

PUSH0 + PUSH0 + REVERT

interface Push0RevertFusion extends BaseInstruction {
  type: 'push0_revert'
  original_length: number
  pc: number
}

Represents: PUSH0 + PUSH0 + REVERT → Empty revert (no error message). Solidity pattern:

revert();

Or failed require() with no message.

Union Type Definition

Complete TypeScript union:

type OpcodeData =
  | RegularInstruction
  | PushInstruction
  | JumpdestInstruction
  | JumpInstruction
  | JumpiInstruction
  | PcInstruction
  | StopInstruction
  | InvalidInstruction
  // Arithmetic fusions
  | PushAddFusion
  | PushMulFusion
  | PushSubFusion
  | PushDivFusion
  // Bitwise fusions
  | PushAndFusion
  | PushOrFusion
  | PushXorFusion
  // Memory fusions
  | PushMloadFusion
  | PushMstoreFusion
  | PushMstore8Fusion
  // Control flow fusions
  | PushJumpFusion
  | PushJumpiFusion
  | IszeroJumpiFusion
  // Stack fusions
  | Dup2MstorePushFusion
  | Dup3AddMstoreFusion
  | Swap1Dup2AddFusion
  | PushDup3AddFusion
  | PushAddDup1Fusion
  | MloadSwap1Dup2Fusion
  // Multi-instruction fusions
  | MultiPushFusion
  | MultiPopFusion
  // Solidity patterns
  | FunctionDispatchFusion
  | CallvalueCheckFusion
  | Push0RevertFusion

Type Guards

Use TypeScript discriminated union for type-safe handling:

function analyzeInstruction(inst: OpcodeData) {
  switch (inst.type) {
    case 'push':
      console.log(`PUSH ${inst.value}`);
      break;

    case 'jumpdest':
      console.log(`JUMPDEST: gas=${inst.gas_cost}, stack=[${inst.min_stack}, ${inst.max_stack}]`);
      break;

    case 'push_jump_fusion':
      console.log(`Static jump to ${inst.value}`);
      break;

    case 'function_dispatch':
      console.log(`Function ${inst.selector.toString(16)}`);
      break;

    case 'regular':
      console.log(`Opcode 0x${inst.opcode.toString(16)}`);
      break;

    default:
      // TypeScript ensures exhaustiveness
      const _exhaustive: never = inst;
  }
}

Pattern Detection

Detect specific patterns during iteration:

// Find all static jumps
const staticJumps: bigint[] = [];
for (const inst of code.scan({ detectFusions: true })) {
  if (inst.type === 'push_jump_fusion') {
    staticJumps.push(inst.value);
  }
}

// Extract function selectors
const functions: Map<number, bigint> = new Map();
for (const inst of code.scan({ detectFusions: true })) {
  if (inst.type === 'function_dispatch') {
    functions.set(inst.selector, inst.target);
  }
}

// Detect non-payable functions
let hasCallvalueCheck = false;
for (const inst of code.scan({ detectFusions: true })) {
  if (inst.type === 'callvalue_check') {
    hasCallvalueCheck = true;
    break;
  }
}

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​Base Instruction Type

​Instruction Categories

​Regular Instructions

​PUSH Instructions

​JUMPDEST Instructions

​JUMP Instructions

​JUMPI Instructions

​PC Instructions

​STOP Instructions

​INVALID Instructions

​Fusion Instructions

​Arithmetic Fusions

​PUSH + ADD

​PUSH + MUL

​PUSH + SUB

​PUSH + DIV

​Bitwise Fusions

​PUSH + AND

​PUSH + OR

​PUSH + XOR

​Memory Fusions

​PUSH + MLOAD

​PUSH + MSTORE

​PUSH + MSTORE8

​Control Flow Fusions

​PUSH + JUMP

​PUSH + JUMPI

​ISZERO + PUSH + JUMPI

​Advanced Stack Fusions

​DUP2 + MSTORE + PUSH

​DUP3 + ADD + MSTORE

​SWAP1 + DUP2 + ADD

​PUSH + DUP3 + ADD

​PUSH + ADD + DUP1

​MLOAD + SWAP1 + DUP2

​Multi-Instruction Fusions

​MULTI_PUSH

​MULTI_POP

​Solidity-Specific Patterns

​FUNCTION_DISPATCH

​CALLVALUE_CHECK

​PUSH0 + PUSH0 + REVERT

​Union Type Definition

​Type Guards

​Pattern Detection

​See Also

Base Instruction Type

Instruction Categories

Regular Instructions

PUSH Instructions

JUMPDEST Instructions

JUMP Instructions

JUMPI Instructions

PC Instructions

STOP Instructions

INVALID Instructions

Fusion Instructions

Arithmetic Fusions

PUSH + ADD

PUSH + MUL

PUSH + SUB

PUSH + DIV

Bitwise Fusions

PUSH + AND

PUSH + OR

PUSH + XOR

Memory Fusions

PUSH + MLOAD

PUSH + MSTORE

PUSH + MSTORE8

Control Flow Fusions

PUSH + JUMP

PUSH + JUMPI

ISZERO + PUSH + JUMPI

Advanced Stack Fusions

DUP2 + MSTORE + PUSH

DUP3 + ADD + MSTORE

SWAP1 + DUP2 + ADD

PUSH + DUP3 + ADD

PUSH + ADD + DUP1

MLOAD + SWAP1 + DUP2

Multi-Instruction Fusions

MULTI_PUSH

MULTI_POP

Solidity-Specific Patterns

FUNCTION_DISPATCH

CALLVALUE_CHECK

PUSH0 + PUSH0 + REVERT

Union Type Definition

Type Guards

Pattern Detection

See Also