Function duplicate_exits_without_lineno

crates/codegen/src/ir.rs:2723–2788

(blocks: &mut Vec<Block>, predecessors: &mut Vec<u32>)

}

fn duplicate_exits_without_lineno(blocks: &mut Vec<Block>, predecessors: &mut Vec<u32>) {
    let mut current = BlockIdx(0);
    while current != BlockIdx::NULL {
        let block = &blocks[current.idx()];
        let last = match block.instructions.last() {
            Some(ins) if ins.target != BlockIdx::NULL && is_jump_instruction(ins) => ins,
            _ => {
                current = blocks[current.idx()].next;
                continue;
            }
        };

        let target = next_nonempty_block(blocks, last.target);
        if target == BlockIdx::NULL || !is_exit_without_lineno(&blocks[target.idx()]) {
            current = blocks[current.idx()].next;
            continue;
        }
        if predecessors[target.idx()] <= 1 {
            current = blocks[current.idx()].next;
            continue;
        }

        // Copy the exit block and splice it into the linked list after current
        let new_idx = BlockIdx(blocks.len() as u32);
        let mut new_block = blocks[target.idx()].clone();
        let jump_loc = last.location;
        let jump_end_loc = last.end_location;
        propagate_locations_in_block(&mut new_block, jump_loc, jump_end_loc);
        let old_next = blocks[current.idx()].next;
        new_block.next = old_next;
        blocks.push(new_block);
        blocks[current.idx()].next = new_idx;

        // Update the jump target
        let last_mut = blocks[current.idx()].instructions.last_mut().unwrap();
        last_mut.target = new_idx;
        predecessors[target.idx()] -= 1;
        predecessors.push(1);

        // Skip past the newly inserted block
        current = old_next;
    }

    current = BlockIdx(0);
    while current != BlockIdx::NULL {
        let block = &blocks[current.idx()];
        if let Some(last) = block.instructions.last()
            && block_has_fallthrough(block)
        {
            let target = next_nonempty_block(blocks, block.next);
            if target != BlockIdx::NULL
                && predecessors[target.idx()] == 1
                && is_exit_without_lineno(&blocks[target.idx()])
            {
                let last_location = last.location;
                let last_end_location = last.end_location;
                propagate_locations_in_block(
                    &mut blocks[target.idx()],