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use cranelift_codegen::binemit::{NullStackMapSink, NullTrapSink};
use rustc_hir::LangItem;
use rustc_session::config::EntryFnType;
use crate::prelude::*;
/// Create the `main` function which will initialize the rust runtime and call
/// users main function.
pub(crate) fn maybe_create_entry_wrapper(
tcx: TyCtxt<'_>,
module: &mut impl Module,
unwind_context: &mut UnwindContext<'_>,
) {
let (main_def_id, use_start_lang_item) = match tcx.entry_fn(LOCAL_CRATE) {
Some((def_id, entry_ty)) => (
def_id,
match entry_ty {
EntryFnType::Main => true,
EntryFnType::Start => false,
},
),
None => return,
};
let instance = Instance::mono(tcx, main_def_id).polymorphize(tcx);
if module.get_name(&*tcx.symbol_name(instance).name).is_none() {
return;
}
create_entry_fn(tcx, module, unwind_context, main_def_id, use_start_lang_item);
fn create_entry_fn(
tcx: TyCtxt<'_>,
m: &mut impl Module,
unwind_context: &mut UnwindContext<'_>,
rust_main_def_id: DefId,
use_start_lang_item: bool,
) {
let main_ret_ty = tcx.fn_sig(rust_main_def_id).output();
// Given that `main()` has no arguments,
// then its return type cannot have
// late-bound regions, since late-bound
// regions must appear in the argument
// listing.
let main_ret_ty = tcx.erase_regions(main_ret_ty.no_bound_vars().unwrap());
let cmain_sig = Signature {
params: vec![
AbiParam::new(m.target_config().pointer_type()),
AbiParam::new(m.target_config().pointer_type()),
],
returns: vec![AbiParam::new(m.target_config().pointer_type() /*isize*/)],
call_conv: CallConv::triple_default(m.isa().triple()),
};
let cmain_func_id = m.declare_function("main", Linkage::Export, &cmain_sig).unwrap();
let instance = Instance::mono(tcx, rust_main_def_id).polymorphize(tcx);
let main_name = tcx.symbol_name(instance).name.to_string();
let main_sig = get_function_sig(tcx, m.isa().triple(), instance);
let main_func_id = m.declare_function(&main_name, Linkage::Import, &main_sig).unwrap();
let mut ctx = Context::new();
ctx.func = Function::with_name_signature(ExternalName::user(0, 0), cmain_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);
let arg_argc = bcx.append_block_param(block, m.target_config().pointer_type());
let arg_argv = bcx.append_block_param(block, m.target_config().pointer_type());
let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
let call_inst = if use_start_lang_item {
let start_def_id = tcx.require_lang_item(LangItem::Start, None);
let start_instance = Instance::resolve(
tcx,
ParamEnv::reveal_all(),
start_def_id,
tcx.intern_substs(&[main_ret_ty.into()]),
)
.unwrap()
.unwrap()
.polymorphize(tcx);
let start_func_id = import_function(tcx, m, start_instance);
let main_val = bcx.ins().func_addr(m.target_config().pointer_type(), main_func_ref);
let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv])
} else {
// using user-defined start fn
bcx.ins().call(main_func_ref, &[arg_argc, arg_argv])
};
let result = bcx.inst_results(call_inst)[0];
bcx.ins().return_(&[result]);
bcx.seal_all_blocks();
bcx.finalize();
}
m.define_function(cmain_func_id, &mut ctx, &mut NullTrapSink {}, &mut NullStackMapSink {})
.unwrap();
unwind_context.add_function(cmain_func_id, &ctx, m.isa());
}
}
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