EIP1109 - PRECOMPILEDCALL opcode (Remove CALL costs for precompiled contracts)

# Simple Summary

This EIP creates a specific opcode named PRECOMPILEDCALL to call Precompiled contracts without the costs of a normal CALL.

# Abstract

This EIP tries to resolve the problem of high gas consumption when calling precompiled contracts with a small gas cost. Using this opcode for calling precompiled contracts allows to define precompiled contracts whose effective cost it is less than 700.

# Motivation

Each precompiled contract has an already defined cost for calling it. It does not make sense to add the implicit extra gas cost of the CALL opcode.

As an example, SHA256 precompiled contract costs 60 and ECADD costs 500 (proposed to costs only 50 in EIP-1108 . When a precompiled contract is called, 700 gas is consumed just for the CALL opcode besides the costs of the precompiled contract.

This makes no sense, and right now it's impossible to define a precompiled contract whose effective cost for using it, is less than 700.

# Specification

If block.number >= XXXXX, define a new opcode named PRECOMPILEDCALL with code value 0xfb.

The gas cost of the OPCODE is 2 (Gbase) plus the Specific gas cost defined for each specific precompiled smart contract.

The OPCODE takes 5 words from the stack and returns 1 word to the stack.

The input stack values are:

mu_s[0] = The address of the precompiled smart contract that is called. mu_s[1] = Pointer to memory for the input parameters. mu_s[2] = Length of the input parameters in bytes. mu_s[3] = Pointer to memory where the output is stored mu_s[4] = Length of the output buffer.

The return will be 1 in case of success call and 0 in any of the next cases:

1.- mu_s[0] is an address of an undefined precompiled smart contract. 2.- The precompiled smart contract fails (as defined on each smart contract). Invalid input parameters for example.

Precompiled smart contracs, does not execute opcodes, so there is no need to pass a gas parameter as a normal CALL (0xf1). If the available gas is less that 2 plus the required gas required for the specific precompiled smart cotract, the context just STOPS executing with an "Out of Gas" error.

There is no stack check for this call.

The normal CALLs to the precompiled smart contracts continue to work with the exact same behavior.

A PRECOMPILEDCALL to a regular address or regular smart contract, is considered a call to an "undefined smart contract", so the VM MUST not execute it and the opcode must return 0x0 .

# Rationale

There was a first proposal for removing the gast consts for the CALL, but it looks that it's easier to implement and test a new opcode just for that.

The code is just the next opcode available after the STATICCALL opcode.

# Backwards Compatibility

This EIP is backwards compatible. Smart contracts that call precompiled contracts using this new opcode will cost less from now on.

Old contracts that call precompiled smart contracts with the CALL method, will continue working.

# Test Cases

Normal call to a defined precompiled contract.
Call to undefined precompiled contract.
Call to a regular contract
Call to a regular account
Call to 0x0 smart contract (Does not exists).
Call with large values for the offste pointers and lengths
Call with the exact gas remaining needed to call smart contract.
Call with the exact gas remaining minus one needed to call smart contract.

# Implementation

Not implemented yet.