3 /// Create the `main` function which will initialize the rust runtime and call
4 /// users main function.
5 pub fn maybe_create_entry_wrapper(tcx: TyCtxt<'_>, module: &mut Module<impl Backend + 'static>) {
6 use rustc::middle::lang_items::StartFnLangItem;
7 use rustc_session::config::EntryFnType;
9 let (main_def_id, use_start_lang_item) = match tcx.entry_fn(LOCAL_CRATE) {
10 Some((def_id, entry_ty)) => (
13 EntryFnType::Main => true,
14 EntryFnType::Start => false,
20 let instance = Instance::mono(tcx, main_def_id);
21 if module.get_name(&*tcx.symbol_name(instance).name.as_str()).is_none() {
25 create_entry_fn(tcx, module, main_def_id, use_start_lang_item);
29 m: &mut Module<impl Backend + 'static>,
30 rust_main_def_id: DefId,
31 use_start_lang_item: bool,
33 let main_ret_ty = tcx.fn_sig(rust_main_def_id).output();
34 // Given that `main()` has no arguments,
35 // then its return type cannot have
36 // late-bound regions, since late-bound
37 // regions must appear in the argument
39 let main_ret_ty = tcx.erase_regions(&main_ret_ty.no_bound_vars().unwrap());
41 let cmain_sig = Signature {
43 AbiParam::new(m.target_config().pointer_type()),
44 AbiParam::new(m.target_config().pointer_type()),
46 returns: vec![AbiParam::new(
47 m.target_config().pointer_type(), /*isize*/
49 call_conv: CallConv::triple_default(m.isa().triple()),
53 .declare_function("main", Linkage::Export, &cmain_sig)
56 let instance = Instance::mono(tcx, rust_main_def_id);
58 let (main_name, main_sig) =
59 get_function_name_and_sig(tcx, m.isa().triple(), instance, false);
61 .declare_function(&main_name, Linkage::Import, &main_sig)
64 let mut ctx = Context::new();
65 ctx.func = Function::with_name_signature(ExternalName::user(0, 0), cmain_sig.clone());
67 let mut func_ctx = FunctionBuilderContext::new();
68 let mut bcx: FunctionBuilder = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
70 let block = bcx.create_block();
71 bcx.switch_to_block(block);
72 let arg_argc = bcx.append_block_param(block, m.target_config().pointer_type());
73 let arg_argv = bcx.append_block_param(block, m.target_config().pointer_type());
75 crate::atomic_shim::init_global_lock(m, &mut bcx);
77 let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
79 let call_inst = if use_start_lang_item {
80 let start_def_id = tcx.require_lang_item(StartFnLangItem, None);
81 let start_instance = Instance::resolve(
83 ParamEnv::reveal_all(),
85 tcx.intern_substs(&[main_ret_ty.into()]),
88 let start_func_id = import_function(tcx, m, start_instance);
92 .func_addr(m.target_config().pointer_type(), main_func_ref);
94 let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
95 bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv])
97 // using user-defined start fn
98 bcx.ins().call(main_func_ref, &[arg_argc, arg_argv])
101 let result = bcx.inst_results(call_inst)[0];
102 bcx.ins().return_(&[result]);
103 bcx.seal_all_blocks();
106 m.define_function(cmain_func_id, &mut ctx).unwrap();