Copy arrays in the SSA IR

[jfecher]

Problem

Arrays in noir have value semantics. When passed to a function, they should have no observable change after the function call, even if the function being called internally mutates the array that it was passed as a parameter. Currently however, arrays are essentially passed as reference in the SSA IR and any mutations would be observable.

Happy Case

We should copy each array before passing them to any function call.

This could create many excess instructions even if a function only needs to mutate a single element of the array. If these cannot be avoided, we should create an issue to optimize this in the future to avoid these unnecessary instructions by e.g. analyzing which indices are mutated by the called function before copying the array. This would let us copy only the necessary indices.

Alternatives Considered

No response

Additional Context

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Would you like to submit a PR for this Issue?

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Support Needs

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