Function define_leaf

cranelift/object/tests/basic.rs:340–360

Define a leaf function that just returns. With `preserve_frame_pointers` on, this is enough to make cranelift emit a System V FDE for it.

(module: &mut ObjectModule, name: &str)

    /// Define a leaf function that just returns. With `preserve_frame_pointers`
    /// on, this is enough to make cranelift emit a System V FDE for it.
    fn define_leaf(module: &mut ObjectModule, name: &str) -> FuncId {
        let sig = Signature {
            params: vec![],
            returns: vec![],
            call_conv: CallConv::SystemV,
        };
        let func_id = module.declare_function(name, Linkage::Local, &sig).unwrap();
        let mut ctx = Context::new();
        ctx.func = Function::with_name_signature(UserFuncName::user(0, func_id.as_u32()), sig);
        let mut func_ctx = FunctionBuilderContext::new();
        {
            let mut bcx = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
            let block = bcx.create_block();
            bcx.switch_to_block(block);
            bcx.ins().return_(&[]);
            bcx.seal_all_blocks();
            bcx.finalize();
        }
        module.define_function(func_id, &mut ctx).unwrap();
        func_id
    }

    /// Iterate the entries in `.eh_frame` bytes, returning `(cie_count, fde_count)`.
    fn count_entries(data: &[u8]) -> (usize, usize) {