Method bind_label

cranelift/codegen/src/machinst/buffer.rs:726–748

Bind a label to the current offset. A label can only be bound once.

(&mut self, label: MachLabel, ctrl_plane: &mut ControlPlane)

    /// Bind a label to the current offset. A label can only be bound once.
    pub fn bind_label(&mut self, label: MachLabel, ctrl_plane: &mut ControlPlane) {
        trace!(
            "MachBuffer: bind label {:?} at offset {}",
            label,
            self.cur_offset()
        );
        debug_assert_eq!(self.label_offsets[label.0 as usize], UNKNOWN_LABEL_OFFSET);
        debug_assert_eq!(self.label_aliases[label.0 as usize], UNKNOWN_LABEL);
        let offset = self.cur_offset();
        self.label_offsets[label.0 as usize] = offset;
        self.lazily_clear_labels_at_tail();
        self.labels_at_tail.push(label);

        // Invariants hold: bound offset of label is <= cur_offset (in fact it
        // is equal). If the `labels_at_tail` list was complete and precise
        // before, it is still, because we have bound this label to the current
        // offset and added it to the list (which contains all labels at the
        // current offset).

        self.optimize_branches(ctrl_plane);

        // Post-invariant: by `optimize_branches()` (see argument there).
    }

    /// Lazily clear `labels_at_tail` if the tail offset has moved beyond the
    /// offset that it applies to.