EIP-3855 — PUSH0 Opcode

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EIP-3855: PUSH0 Opcode

Before EIP-3855, pushing zero onto the EVM stack required PUSH1 0x00 (2 bytes, 3 gas). EIP-3855 added PUSH0 (0x5f) — 1 byte, 2 gas. A trivial-looking change that saves significant bytecode size and gas across the entire ecosystem because zero is the most-pushed value.

Status

Activated in the Shanghai hard fork (April 2023). Solidity 0.8.20+ emits PUSH0 by default for chains that support it.

Neo Equivalent

NeoVM has had PUSH0 (opcode 0x10) since launch, plus PUSH1 through PUSH16 as direct integer constants. There was no need for a retrofit because the design included it from day one.

Live on Neo TestNet

Both implementations are deployed on Neo N3 TestNet (network magic 894710606).

Implementation	Contract Hash	Deploy Tx
Solidity (neo-solc)	0x52b860448a5d1ff537160a0bee8c83cdfe72fe4d	0xba96b7c4…1c0a8d
Neo C# (nccs)	0x6704d604997959ce4e098bd96ecbacef358e9ff6	0x92572481…a6c00c

Cross-implementation invocations match on zero, falseBool. Source pairs under docs/standards-mirror/deployments/eip-3855/.

EVM bytecode comparison:

Pre-EIP-3855:    60 00     PUSH1 0x00
                 [2 bytes, 3 gas]

Post-EIP-3855:   5f         PUSH0
                 [1 byte, 2 gas]

Across an entire compiled contract, this can save dozens of bytes and millions of
gas across thousands of executions. OZ's ERC-20 dropped ~50 bytes after the
PUSH0 introduction.

NeoVM bytecode (since day one):

  PUSH0 (0x10)    // push integer 0
  PUSH1 (0x11)    // push integer 1
  PUSH2 (0x12)    // push integer 2
  ...
  PUSH16 (0x20)   // push integer 16

  PUSHM1 (0x0F)   // push integer -1

  PUSHA   (0x0A)  // push address
  PUSHNULL (0x0B) // push StackItem.Null

  PUSHDATA1 (0x0C) ...  // push N bytes (N <= 255)

A Solidity-to-NeoVM compiler (like neo-devpack-solidity) emits PUSH0 directly when it
needs zero. There's no retrofit story here because the VM was designed with
small-integer constant opcodes from the start.

Compiler Note

The neo-devpack-solidity compiler maps Solidity zero literals to NeoVM PUSH0 on every emit. No version gate, no chain-version conditional — the opcode has always been available.