Function xor_2_nibbles

bitvm/src/hash/blake3_utils.rs:87–136

Calculates bitwise XOR of two nibbles (x_{nibble_x} and y_{nibble_y}), each given by their u32 variable and the index of their nibble, consumes the nibble of x (which shifts the remaining nibbles of x)

(
    stack: &mut StackTracker,
    x: &mut StackVariable,
    y: StackVariable,
    nibble_x: u8,
    nibble_y: u8,
    use_full_tables: bool,
)

/// Calculates bitwise XOR of two nibbles (x_{nibble_x} and y_{nibble_y}), each given by their u32 variable and the index of their nibble, consumes the nibble of x (which shifts the remaining nibbles of x)
fn xor_2_nibbles(
    stack: &mut StackTracker,
    x: &mut StackVariable,
    y: StackVariable,
    nibble_x: u8,
    nibble_y: u8,
    use_full_tables: bool,
) -> StackVariable {
    if !use_full_tables {
        stack.op_depth();

        stack.op_dup();

        stack.copy_var_sub_n(y, nibble_y as u32);
        stack.move_var_sub_n(x, nibble_x as u32);
        stack.op_2dup();
        stack.op_min();
        stack.to_altstack();

        stack.op_max();

        stack.op_sub();
        stack.op_1sub();

        stack.op_pick();

        stack.op_add();

        stack.from_altstack();

        stack.op_sub();

        stack.op_pick()
    } else {
        stack.op_depth();
        stack.op_dup();

        stack.copy_var_sub_n(y, nibble_y as u32);

        stack.op_sub();
        stack.op_pick();

        stack.op_add();

        stack.move_var_sub_n(x, nibble_x as u32);

        stack.op_add();
        stack.op_pick()
    }
}

/// Calculates the bitwise XOR of two u32 numbers (x, y) and cyclically shifts them to right by 7. Consumes x and leaves y on the stack.
fn xor_and_rotate_right_by_7(