MCOPY spec

[curryrasul]

Issue Link

Closes #510

[curryrasul]

It's not directly related to MCOPY, but I'm working on this, and looking through RETURNDATACOPY, which we discussed before @ChihChengLiang
It is said, that RETURNDATACOPY copies from memory to memory:

zkevm-specs/specs/tables.md

Lines 276 to 279 in 4f272c2

	- Copy from caller/callee memory to callee/caller memory.
	- `CALLDATACOPY` (not root call): copy from caller's memory to callee's
	- `RETURN` (not create), `REVERT`, `CALLOP` (precompile return): copy from callee's memory to caller's
	- `RETURNDATACOPY`, `MCOPY`: copy memory within current context

I read about RETURNDATACOPY, it's said that it copies from so-called return data buffer, that acts like a temporary place, where's the return value from contract-call is stored.
Is it still memory? Or maybe it doesn't belong to memory , stack or storage?

[zemse]

I read about RETURNDATACOPY, it's said that it copies from so-called return data buffer, that acts like a temporary place, where's the return value from contract-call is stored.
Is it still memory? Or maybe it doesn't belong to memory , stack or storage?

I was confused about returndata not present in CopyDataType, but it seems returndatacopy copies from the memory of child call's memory to the current call's memory. So this memory to memory copy of returndatacopy makes sense to me now and mcopy is pretty much similar apart from it is a memory to memory copy for the same call.