---
eip: 7877
title: Enhanced RETURN opcodes
description: Deprecate RETURN opcode in favor of new opcodes that allow returning data from various locations without first having to write to memory.
author: Josh Weintraub (@jhweintraub)
discussions-to: https://ethereum-magicians.org/t/eip-7877-new-m-s-t-rreturn-opcodes/22731
status: Stagnant
type: Standards Track
category: Core
created: 2025-01-31
requires: 6, 1153, 3855
---

## Abstract

This EIP specifies a series of new `RETURN` opcodes which allow the user to specify which data location to return from
instead of defaulting to returning from memory.

## Motivation

With the introduction of transient storage, many smart contracts have begun to store data using the new transient opcodes to optimize for gas usage, whereby a callback
involves returning the data previously stored transiently. However, the current `RETURN` opcode only allows for returning sequential bytes in memory. This requires
developers to incur additional gas overhead by manually writing data from transient storage to memory before returning,
incuring both an additional memory expansion and opcode cost from complicated for-loops. Similar
inefficiencies already occur when attempting to return data already placed in storage. This EIP attempts to rectify
this by allowing developers to optimize their code by deciding where to return data from directly, instead of requiring
the intermediate step of first copying the data to memory.

## Specification

This EIP introduces 3 new opcodes as well as renaming/aliasing an existing one.

```
SRETURN (0xf6)
TRETURN (0xf7)
RRETURN (0xf8)

RETURN -> MRETURN (0xf3)
```

The `MRETURN` opcode is a rename of `RETURN`, whereby sequential bytes in memory are returned. It will operate exactly as it currenty does as of the Cancun hard-fork, and its gas cost will remain the same.

`RRETURN` operates similar to `MRETURN`. It pops two items off the stack, an offset to begin reading bytes from in the
existing `RETURNDATA` buffer, and a number of bytes to return. Those bytes are used to overwrite the existing `RETURNDATA` buffer and then a return to the previous function is performed.

`SRETURN` and `TRETURN` operate similarly, except on storage and transient respectively. It pops two items off the stack,
a slot number to begin reading from, and a number of sequential slots to return from. Ex: `SRETURN(0x0, 0x40)` returns the 64 bytes of data in slots [0, 1], and `TRETURN(0x0, 0x40)` returns the data in transient storage slots [0, 1]. Since the
existing `S/TLOAD` opcodes already return 32-bytes, having the opcode return data in chunks of 32-bytes should make implementation by assembly/compiler much simpler.
If the length parameter is a zero, then only the initial slot value should be returned, so `SRETURN(0x00, 0x00)` returns the value at storage slot 0.

The cost for these opcodes should be similar to the cost of accessing data now.

```
SRETURN = (number_of_cold_slots) * 2100 + (numer_of_warm_slots * 100)
TRETURN = number_of_slots * 100

RRETURN = cost of RETURNDATACOPY without memory_expansion cost

minimum_word_size = (size + 31) / 32

static_gas = 3
dynamic_gas = 3 * minimum_word_size

overall = static_gas + dynamic_gas
```

## Rationale

Allowing for more targeted return opcodes allows for saving gas at all levels of smart contract optimization by eliminating
the intermediate steps of first writing any data to memory before returning. In events where this data may be large, this can result in significant gas savings. These opcodes can be built into the Solidity compiler directly so that all contracts
can take advantage of them. Similarly, by making return more explicit it allows for better static analysis by avoiding messy memory allocations.

There is precedent for these changes.

EIP-3855: Introducing `PUSH0` opcode to optimize away alternative methods of pushing 0 onto the stack.

EIP-6: Renaming `SUICIDE` to `SELFDESTRUCT` without changing functionality.

## Backwards Compatibility

There are no backwards compatibility concerns, as `MRETURN` will utilize the same gas cost and opcode as `RETURN` does now. Due to EOF, it is suggested that these changes be
activated in future EVM version once EOF has been fully implemented.

## Security Considerations

There are no security considerations as it is fully backwards compatible, and reduces potential attack space through simplified bytecode.

## Copyright

Copyright and related rights waived via [CC0](../LICENSE.md).