Design the Memory Representation (Initial)

[ktemkin]

Description

LLVM’s assumption of R/W memory and registers does not fit with the memory model used by the Cairo VM. We can either take the SSA form and treat the target as an infinite-register machine, or we can emulate R/W memory directly.

For this initial design phase we want to do the bare minimum to get mostly-correct semantics as far as the LLVM IR expects. This task includes designing the assignment model and the semantics of the operations on pointers.

[iamrecursion]

To add a bit more information to this:

• Cairo VM uses write-once memory.
• The conventional way to represent R/W memory cells on top of this is to use an array.
• Arrays nested in arrays could provide something more like a conventional "memory".
• On top of that, we also need to support explicit notions of:
  • Allocation
  • Deallocation
  • Pointer arithmetic
  • And so on (anything you can do with memory in C, really)
• We also need to contend with how wide our pointers are, and other things like that. Until we define our own target this should probably match our target.