General purpose instructions for bytes

[kwannoel]

Part of https://gitlab.com/mukn/glow/-/issues/80.

Features

Batch 1 (Merged: #46)

• Methods for known-size bytes
  • Compat with bytes larger than EVM Word
  • Store at free memory pointer
  • Load at free memory pointer
  • Push for large bytes
• Unit tests
• Integration tests
• Invariant assertions

Batch 2 (WIP: #50)

• Call by reference methods (by storing offset, length on stack)
• Static offset methods for load, store. Glow compiler uses mstoreat, mloadat.
• Support types with have variable sizes during runtime.
  For example, given a Bytestring with a UInt64 length,
  during compile time we do not know the actual length / contents of the bytestring.
  instead we generate instructions to store the length:
  - on stack is just takes up a slot.
  - in memory it takes up 8bytes.
  And use it to decode the contents:
  - LOAD:
  Use the offset and length on stack to retrieve the entire bytestring from memory
  - STORE:
  Use length on stack to store bytestring in memory
• memcpy
• Hashing
• calldataload, calldatacopy.
• Limit memory offset to 16/24 bytes due to gas limits, rather than 32.

Batch 3

• Integrate with existing EVM-Types - Extend? Create new types?
  • Either use .box? directly to handle boxed / unboxed types
  • or use it implicitly, with a general .evm<- method for marshalling data to EVM.

Batch 4

• Handle singletons.
• Benchmark gas for methods
• Support for marshalling? (further investigation needed)