compiler/rustc_codegen_cranelift/src/main_shim.rs

   1 use cranelift_codegen::binemit::{NullStackMapSink, NullTrapSink};
   2 use rustc_hir::LangItem;
   3 use rustc_middle::ty::subst::GenericArg;
   4 use rustc_middle::ty::AssocKind;
   5 use rustc_session::config::EntryFnType;
   6 use rustc_span::symbol::Ident;
   7
   8 use crate::prelude::*;
   9
  10 /// Create the `main` function which will initialize the rust runtime and call
  11 /// users main function.
  12 pub(crate) fn maybe_create_entry_wrapper(
  13     tcx: TyCtxt<'_>,
  14     module: &mut impl Module,
  15     unwind_context: &mut UnwindContext,
  16     is_jit: bool,
  17     is_primary_cgu: bool,
  18 ) {
  19     let (main_def_id, is_main_fn) = match tcx.entry_fn(()) {
  20         Some((def_id, entry_ty)) => (
  21             def_id,
  22             match entry_ty {
  23                 EntryFnType::Main => true,
  24                 EntryFnType::Start => false,
  25             },
  26         ),
  27         None => return,
  28     };
  29
  30     if main_def_id.is_local() {
  31         let instance = Instance::mono(tcx, main_def_id).polymorphize(tcx);
  32         if !is_jit && module.get_name(&*tcx.symbol_name(instance).name).is_none() {
  33             return;
  34         }
  35     } else if !is_primary_cgu {
  36         return;
  37     }
  38
  39     create_entry_fn(tcx, module, unwind_context, main_def_id, is_jit, is_main_fn);
  40
  41     fn create_entry_fn(
  42         tcx: TyCtxt<'_>,
  43         m: &mut impl Module,
  44         unwind_context: &mut UnwindContext,
  45         rust_main_def_id: DefId,
  46         ignore_lang_start_wrapper: bool,
  47         is_main_fn: bool,
  48     ) {
  49         let main_ret_ty = tcx.fn_sig(rust_main_def_id).output();
  50         // Given that `main()` has no arguments,
  51         // then its return type cannot have
  52         // late-bound regions, since late-bound
  53         // regions must appear in the argument
  54         // listing.
  55         let main_ret_ty = tcx.erase_regions(main_ret_ty.no_bound_vars().unwrap());
  56
  57         let cmain_sig = Signature {
  58             params: vec![
  59                 AbiParam::new(m.target_config().pointer_type()),
  60                 AbiParam::new(m.target_config().pointer_type()),
  61             ],
  62             returns: vec![AbiParam::new(m.target_config().pointer_type() /*isize*/)],
  63             call_conv: CallConv::triple_default(m.isa().triple()),
  64         };
  65
  66         let cmain_func_id = m.declare_function("main", Linkage::Export, &cmain_sig).unwrap();
  67
  68         let instance = Instance::mono(tcx, rust_main_def_id).polymorphize(tcx);
  69
  70         let main_name = tcx.symbol_name(instance).name;
  71         let main_sig = get_function_sig(tcx, m.isa().triple(), instance);
  72         let main_func_id = m.declare_function(main_name, Linkage::Import, &main_sig).unwrap();
  73
  74         let mut ctx = Context::new();
  75         ctx.func = Function::with_name_signature(ExternalName::user(0, 0), cmain_sig);
  76         {
  77             let mut func_ctx = FunctionBuilderContext::new();
  78             let mut bcx = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
  79
  80             let block = bcx.create_block();
  81             bcx.switch_to_block(block);
  82             let arg_argc = bcx.append_block_param(block, m.target_config().pointer_type());
  83             let arg_argv = bcx.append_block_param(block, m.target_config().pointer_type());
  84
  85             let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
  86
  87             let result = if is_main_fn && ignore_lang_start_wrapper {
  88                 // regular main fn, but ignoring #[lang = "start"] as we are running in the jit
  89                 // FIXME set program arguments somehow
  90                 let call_inst = bcx.ins().call(main_func_ref, &[]);
  91                 let call_results = bcx.func.dfg.inst_results(call_inst).to_owned();
  92
  93                 let termination_trait = tcx.require_lang_item(LangItem::Termination, None);
  94                 let report = tcx
  95                     .associated_items(termination_trait)
  96                     .find_by_name_and_kind(
  97                         tcx,
  98                         Ident::from_str("report"),
  99                         AssocKind::Fn,
 100                         termination_trait,
 101                     )
 102                     .unwrap();
 103                 let report = Instance::resolve(
 104                     tcx,
 105                     ParamEnv::reveal_all(),
 106                     report.def_id,
 107                     tcx.mk_substs([GenericArg::from(main_ret_ty)].iter()),
 108                 )
 109                 .unwrap()
 110                 .unwrap();
 111
 112                 let report_name = tcx.symbol_name(report).name;
 113                 let report_sig = get_function_sig(tcx, m.isa().triple(), report);
 114                 let report_func_id =
 115                     m.declare_function(report_name, Linkage::Import, &report_sig).unwrap();
 116                 let report_func_ref = m.declare_func_in_func(report_func_id, &mut bcx.func);
 117
 118                 // FIXME do proper abi handling instead of expecting the pass mode to be identical
 119                 // for returns and arguments.
 120                 let report_call_inst = bcx.ins().call(report_func_ref, &call_results);
 121                 let res = bcx.func.dfg.inst_results(report_call_inst)[0];
 122                 match m.target_config().pointer_type() {
 123                     types::I32 => res,
 124                     types::I64 => bcx.ins().sextend(types::I64, res),
 125                     _ => unimplemented!("16bit systems are not yet supported"),
 126                 }
 127             } else if is_main_fn {
 128                 let start_def_id = tcx.require_lang_item(LangItem::Start, None);
 129                 let start_instance = Instance::resolve(
 130                     tcx,
 131                     ParamEnv::reveal_all(),
 132                     start_def_id,
 133                     tcx.intern_substs(&[main_ret_ty.into()]),
 134                 )
 135                 .unwrap()
 136                 .unwrap()
 137                 .polymorphize(tcx);
 138                 let start_func_id = import_function(tcx, m, start_instance);
 139
 140                 let main_val = bcx.ins().func_addr(m.target_config().pointer_type(), main_func_ref);
 141
 142                 let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
 143                 let call_inst = bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv]);
 144                 bcx.inst_results(call_inst)[0]
 145             } else {
 146                 // using user-defined start fn
 147                 let call_inst = bcx.ins().call(main_func_ref, &[arg_argc, arg_argv]);
 148                 bcx.inst_results(call_inst)[0]
 149             };
 150
 151             bcx.ins().return_(&[result]);
 152             bcx.seal_all_blocks();
 153             bcx.finalize();
 154         }
 155         m.define_function(cmain_func_id, &mut ctx, &mut NullTrapSink {}, &mut NullStackMapSink {})
 156             .unwrap();
 157         unwind_context.add_function(cmain_func_id, &ctx, m.isa());
 158     }
 159 }