Method start_patchable

cranelift/codegen/src/machinst/buffer.rs:616–620

Begin a region of patchable code. There is one requirement for the code that is emitted: It must not introduce any instructions that could be chomped (branches are an example of this). In other words, you must not call [`MachBuffer::add_cond_branch`] or [`MachBuffer::add_uncond_branch`] between calls to this method and [`MachBuffer::end_patchable`].

(&mut self)

    /// [`MachBuffer::add_uncond_branch`] between calls to this method and
    /// [`MachBuffer::end_patchable`].
    pub fn start_patchable(&mut self) -> OpenPatchRegion {
        assert!(!self.open_patchable, "Patchable regions may not be nested");
        self.open_patchable = true;
        OpenPatchRegion(usize::try_from(self.cur_offset()).unwrap())
    }

    /// End a region of patchable code, yielding a [`PatchRegion`] value that
    /// can be consumed later to produce a one-off mutable slice to the