Rename opcodes for clarity

Abstract

Rename the BALANCE, SHA3, NUMBER, GASLIMIT, GAS and INVALID opcodes to reflect their true meaning.

Specification

Rename the opcodes as follows:

• BALANCE (0x31) to EXTBALANCE to be in line with EXTCODESIZE, EXTCODECOPY and EXTCODEHASH
• SHA3 (0x20) to KECCAK256
• NUMBER (0x43) to BLOCKNUMBER
• GASLIMIT (0x45) to BLOCKGASLIMIT to avoid confusion with the gas limit of the transaction
• GAS (0x5a) to GASLEFT to be clear what it refers to
• INVALID (0xfe) to ABORT to clearly articulate when someone refers this opcode as opposed to "any invalid opcode"

Backwards Compatibility

This has no effect on any code. It can influence what mnemonics assemblers will use.

Implementation

Not applicable.

References

EIP-6 previously renamed SUICIDE (0xff) to SELFDESTRUCT. Renaming SHA3 was previously proposed by EIP-59.

Copyright

Copyright and related rights waived via CC0.