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PEEPanEIP-3855_ PUSH0 Instruction.md

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title PEEPanEIP-3855: PUSH0 Instruction
type slide
slideOptions
theme allottedMinutes
league
15

Ipsilon

Hugo de la Cruz Romero -- github.com/hugo-dc

Alex Beregszaszi github.com/axic

--

A protocol research team focusing on the EVM. Website: ipsilon.xyz

EIP-3855: PUSH0 Instruction

  • Status: Review
  • Considered for inclusion in
    Shanghai Network Upgrade

Introduction

  • Usage of constant value 0
    • Value of zero frequently used by many instructions expecting offsets as inputs.

Introduction

  • Examples:
    • Opcodes dealing with offsets:
      • CALLDATACOPY
      • CODECOPY
      • EXTCODECOPY
      • etc.
    • CALL*: Setting zeros as return data parameters when the contract prefers using RETURNDATA* to retreive the results.

Abstract

  • New opcode PUSH0 with a cost of 2 gas (base).
  • It is introduced as the instruction number 0x5f.
Hex Name
... ...
0x5f PUSH0
0x60 PUSH1
... PUSHn
0X7f PUSH32

Motivation

  • Reduce gas usage and contract code size:
    • PUSH1 00 ~ 60 00: 400 gas for deployment, 3 gas for runtime.
    • PUSH0 ~ 5f: 200 gas for deployment, 2 gas for runtime.

Motivation

  • Reduce risk of contracts (mis)using instructions as an optimisation measure.
    • PC
    • MSIZE
    • CALLDATASIZE
    • RETURNDATASIZE
    • CODESIZE
    • CALLVALUE
    • SELFBALANCE

Example

  • EIP-2733 (Withdrawn)
    • If implemented, would have changed the behaviour of RETURNDATASIZE such that it may not be guaranteed to be zero at the beginning of the call frame.

Analysis and Findings

Analysis and Findings

  • Traced transactions in two different nodes syncing mainnet:
    • Geth Node 1: Syncing at block ~8M
    • Geth Node 2: Syncing at block ~12M

Analysis and Findings

  • Result: Histogram of Opcode usage, with special column for PUSH1 00 (PUSH0):

General Opcode Usage

![](https://storage.googleapis.com/ethereum-hackmd/upload_7419f3867b20298e665e65889561887d.png =750x580)

PUSHn Usage

![](https://storage.googleapis.com/ethereum-hackmd/upload_49e5f844744772f73602bb94e06e3d82.png =750x580)

PUSH1 00

![](https://storage.googleapis.com/ethereum-hackmd/upload_129a9d38c95bdd18d3d3270f42aba943.png =750x580)

Other commonly used constants

![](https://storage.googleapis.com/ethereum-hackmd/upload_f838cd889445229b39b874c35b6d89c5.png =650x550)

Commonly used constants

  • 0: solved by PUSH0
  • 1: largely used in loops, could be solved by INC/DEC
  • 2: mostly used by old contracts to emulate shifts
  • 31 and 32: are mostly used by the ABI en/decoder in Solidity

INC/DEC

  • INC to increase-by-one the top item, DEC to decrease
  • Useful for loops, where this is done with PUSH1 1 ADD
  • Pro: saves 2x200 gas for deployment, and at least costs half runtime
  • Con: too much of a CISC direction