New opcode: cycle

[jasonpaulos]

Summary

Introduce a new opcode for stack manipulation:

• cycle n m: rotates the top n elements of the stack m places (i.e., so top of the stack now contains the element that was m elements down, and the element that was at the top of the stack has n-m elements above it). Fails if there are fewer than n elements on the stack or if m > n. cycle n 0 and cycle n n are both no-ops unless there are fewer than n elements on the stack.

In general, this would make stack manipulate easier and more efficient, since it essentially is a general form cover and uncover that can move multiple elements at a time.

Specifically, this opcode would make it easier for PyTeal to spill multiple local slots to the stack, then "cover" them, before invoking a recursive subroutine call.

Urgency

Nice to have for AVM 1.1.

[algoanne]

revisit this after the frame pointer work is complete (#4304 ) because this may become obsolete.

[algoanne]

no longer useful given the frame pointer work.