Add 'compiler/rustc_codegen_cranelift/' from commit '793d26047f994e23415f8f6bb5686ff25d3dda92'

git-subtree-dir: compiler/rustc_codegen_cranelift
git-subtree-mainline: cf798c1ec6
git-subtree-split: 793d26047f

compiler/rustc_codegen_cranelift/src/main_shim.rs

@@ -0,0 +1,130 @@
+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<'_>,
+    use_jit: bool,
+) {
+    let (main_def_id, use_start_lang_item) = match tcx.entry_fn(LOCAL_CRATE) {
+        Some((def_id, entry_ty)) => (
+            def_id.to_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,
+        use_jit,
+    );
+
+    fn create_entry_fn(
+        tcx: TyCtxt<'_>,
+        m: &mut impl Module,
+        unwind_context: &mut UnwindContext<'_>,
+        rust_main_def_id: DefId,
+        use_start_lang_item: bool,
+        use_jit: 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, main_sig) =
+            get_function_name_and_sig(tcx, m.isa().triple(), instance, false);
+        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.clone());
+        {
+            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());
+
+            crate::atomic_shim::init_global_lock(m, &mut bcx, use_jit);
+
+            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 cranelift_codegen::binemit::NullTrapSink {},
+        )
+        .unwrap();
+        unwind_context.add_function(cmain_func_id, &ctx, m.isa());
+    }
+}