Constant arrays are duplicated

[guipublic]

Problem

In the following snippet, the tableY array is duplicated for every read done in the loop 0..6:

struct ScalarField {
    base4_slices: [u8; 63]
}

impl ScalarField {
    fn new() -> Self {
        Self { base4_slices: [0; 63] }
    }
    fn from_field(x: Field) -> Self {
        let bytes: [u8] = x.to_le_radix(4, 63);
        let mut result: Self = ScalarField { base4_slices: [0; 63] };
        for i in 0..63 {
            result.base4_slices[i] = bytes[62 - i];
        }
        result
    }
    fn get(self, idx: u64) -> u8 {
        self.base4_slices[idx]
    }
}

fn mul(scalar: ScalarField) -> Field {
    let mut tableY: [Field; 8] = [0; 8];
    for i in 0..8 {
        tableY[i] = i as Field;
    }
    let mut foo = 0;
    for i in 0..6 {
        let idx: u64 = scalar.get(i) as u64;
        foo += tableY[idx];
    }
    foo
}

fn main(x: Field) -> pub Field {
    let scalar = ScalarField::from_field(x);
    mul(scalar)
}

This generates multiple MemoryInit on ACIR side while we could use only one.

Happy Case

Array is not duplicated

Project Impact

None

Impact Context

No response

Workaround

None

Workaround Description

No response

Additional Context

No response

Would you like to submit a PR for this Issue?

Yes

Support Needs

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