compiler/rustc_codegen_cranelift/src/main_shim.rs

   1 use cranelift_frontend::{FunctionBuilder, FunctionBuilderContext};
   2 use rustc_hir::LangItem;
   3 use rustc_middle::ty::AssocKind;
   4 use rustc_middle::ty::GenericArg;
   5 use rustc_session::config::{sigpipe, 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, sigpipe)) = match tcx.entry_fn(()) {
  20         Some((def_id, entry_ty)) => (
  21             def_id,
  22             match entry_ty {
  23                 EntryFnType::Main { sigpipe } => (true, sigpipe),
  24                 EntryFnType::Start => (false, sigpipe::DEFAULT),
  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 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, sigpipe);
  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         sigpipe: u8,
  49     ) {
  50         let main_ret_ty = tcx.fn_sig(rust_main_def_id).no_bound_vars().unwrap().output();
  51         // Given that `main()` has no arguments,
  52         // then its return type cannot have
  53         // late-bound regions, since late-bound
  54         // regions must appear in the argument
  55         // listing.
  56         let main_ret_ty = tcx.normalize_erasing_regions(
  57             ty::ParamEnv::reveal_all(),
  58             main_ret_ty.no_bound_vars().unwrap(),
  59         );
  60
  61         let cmain_sig = Signature {
  62             params: vec![
  63                 AbiParam::new(m.target_config().pointer_type()),
  64                 AbiParam::new(m.target_config().pointer_type()),
  65             ],
  66             returns: vec![AbiParam::new(m.target_config().pointer_type() /*isize*/)],
  67             call_conv: crate::conv_to_call_conv(
  68                 tcx.sess,
  69                 tcx.sess.target.options.entry_abi,
  70                 m.target_config().default_call_conv,
  71             ),
  72         };
  73
  74         let entry_name = tcx.sess.target.options.entry_name.as_ref();
  75         let cmain_func_id = match m.declare_function(entry_name, Linkage::Export, &cmain_sig) {
  76             Ok(func_id) => func_id,
  77             Err(err) => {
  78                 tcx.dcx()
  79                     .fatal(format!("entry symbol `{entry_name}` declared multiple times: {err}"));
  80             }
  81         };
  82
  83         let instance = Instance::mono(tcx, rust_main_def_id).polymorphize(tcx);
  84
  85         let main_name = tcx.symbol_name(instance).name;
  86         let main_sig = get_function_sig(tcx, m.target_config().default_call_conv, instance);
  87         let main_func_id = m.declare_function(main_name, Linkage::Import, &main_sig).unwrap();
  88
  89         let mut ctx = Context::new();
  90         ctx.func.signature = cmain_sig;
  91         {
  92             let mut func_ctx = FunctionBuilderContext::new();
  93             let mut bcx = FunctionBuilder::new(&mut ctx.func, &mut func_ctx);
  94
  95             let block = bcx.create_block();
  96             bcx.switch_to_block(block);
  97             let arg_argc = bcx.append_block_param(block, m.target_config().pointer_type());
  98             let arg_argv = bcx.append_block_param(block, m.target_config().pointer_type());
  99             let arg_sigpipe = bcx.ins().iconst(types::I8, sigpipe as i64);
 100
 101             let main_func_ref = m.declare_func_in_func(main_func_id, &mut bcx.func);
 102
 103             let result = if is_main_fn && ignore_lang_start_wrapper {
 104                 // regular main fn, but ignoring #[lang = "start"] as we are running in the jit
 105                 // FIXME set program arguments somehow
 106                 let call_inst = bcx.ins().call(main_func_ref, &[]);
 107                 let call_results = bcx.func.dfg.inst_results(call_inst).to_owned();
 108
 109                 let termination_trait = tcx.require_lang_item(LangItem::Termination, None);
 110                 let report = tcx
 111                     .associated_items(termination_trait)
 112                     .find_by_name_and_kind(
 113                         tcx,
 114                         Ident::from_str("report"),
 115                         AssocKind::Fn,
 116                         termination_trait,
 117                     )
 118                     .unwrap();
 119                 let report = Instance::expect_resolve(
 120                     tcx,
 121                     ParamEnv::reveal_all(),
 122                     report.def_id,
 123                     tcx.mk_args(&[GenericArg::from(main_ret_ty)]),
 124                 )
 125                 .polymorphize(tcx);
 126
 127                 let report_name = tcx.symbol_name(report).name;
 128                 let report_sig = get_function_sig(tcx, m.target_config().default_call_conv, report);
 129                 let report_func_id =
 130                     m.declare_function(report_name, Linkage::Import, &report_sig).unwrap();
 131                 let report_func_ref = m.declare_func_in_func(report_func_id, &mut bcx.func);
 132
 133                 // FIXME do proper abi handling instead of expecting the pass mode to be identical
 134                 // for returns and arguments.
 135                 let report_call_inst = bcx.ins().call(report_func_ref, &call_results);
 136                 let res = bcx.func.dfg.inst_results(report_call_inst)[0];
 137                 match m.target_config().pointer_type() {
 138                     types::I32 => res,
 139                     types::I64 => bcx.ins().sextend(types::I64, res),
 140                     _ => unimplemented!("16bit systems are not yet supported"),
 141                 }
 142             } else if is_main_fn {
 143                 let start_def_id = tcx.require_lang_item(LangItem::Start, None);
 144                 let start_instance = Instance::expect_resolve(
 145                     tcx,
 146                     ParamEnv::reveal_all(),
 147                     start_def_id,
 148                     tcx.mk_args(&[main_ret_ty.into()]),
 149                 )
 150                 .polymorphize(tcx);
 151                 let start_func_id = import_function(tcx, m, start_instance);
 152
 153                 let main_val = bcx.ins().func_addr(m.target_config().pointer_type(), main_func_ref);
 154
 155                 let func_ref = m.declare_func_in_func(start_func_id, &mut bcx.func);
 156                 let call_inst =
 157                     bcx.ins().call(func_ref, &[main_val, arg_argc, arg_argv, arg_sigpipe]);
 158                 bcx.inst_results(call_inst)[0]
 159             } else {
 160                 // using user-defined start fn
 161                 let call_inst = bcx.ins().call(main_func_ref, &[arg_argc, arg_argv]);
 162                 bcx.inst_results(call_inst)[0]
 163             };
 164
 165             bcx.ins().return_(&[result]);
 166             bcx.seal_all_blocks();
 167             bcx.finalize();
 168         }
 169
 170         if let Err(err) = m.define_function(cmain_func_id, &mut ctx) {
 171             tcx.dcx().fatal(format!("entry symbol `{entry_name}` defined multiple times: {err}"));
 172         }
 173
 174         unwind_context.add_function(cmain_func_id, &ctx, m.isa());
 175     }
 176 }