Deduplicate function name generation

src/abi.rs

@@ -153,16 +153,37 @@ fn ty_fn_sig<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, ty: Ty<'tcx>) -> ty::FnSig<'
     tcx.normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), &sig)
 }
 
+fn get_function_name_and_sig<'a, 'tcx>(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    inst: Instance<'tcx>,
+) -> (String, Signature) {
+    assert!(!inst.substs.needs_infer() && !inst.substs.has_param_types());
+    let fn_ty = inst.ty(tcx);
+    let sig = cton_sig_from_fn_ty(tcx, fn_ty);
+    let def_path_based_names =
+        ::rustc_mir::monomorphize::item::DefPathBasedNames::new(tcx, false, false);
+    let mut name = String::new();
+    def_path_based_names.push_instance_as_string(inst, &mut name);
+    (name, sig)
+}
+
+impl<'a, 'tcx: 'a> CodegenCx<'a, 'tcx, CurrentBackend> {
+    pub fn predefine_function(&mut self, inst: Instance<'tcx>) -> (FuncId, Function) {
+        let (name, sig) = crate::abi::get_function_name_and_sig(self.tcx, inst);
+        let func_id = self
+            .module
+            .declare_function(&name, Linkage::Export, &sig)
+            .unwrap();
+        let func =
+            Function::with_name_signature(ExternalName::user(0, func_id.index() as u32), sig);
+        (func_id, func)
+    }
+}
+
 impl<'a, 'tcx: 'a> FunctionCx<'a, 'tcx> {
     /// Instance must be monomorphized
     pub fn get_function_ref(&mut self, inst: Instance<'tcx>) -> FuncRef {
-        assert!(!inst.substs.needs_infer() && !inst.substs.has_param_types());
+        let (name, sig) = get_function_name_and_sig(self.tcx, inst);
-        let fn_ty = inst.ty(self.tcx);
-        let sig = cton_sig_from_fn_ty(self.tcx, fn_ty);
-        let def_path_based_names =
-            ::rustc_mir::monomorphize::item::DefPathBasedNames::new(self.tcx, false, false);
-        let mut name = String::new();
-        def_path_based_names.push_instance_as_string(inst, &mut name);
         let func_id = self
             .module
             .declare_function(&name, Linkage::Import, &sig)

src/base.rs

@@ -27,42 +27,25 @@ pub fn trans_mono_item<'a, 'tcx: 'a>(
                     ty::ParamEnv::reveal_all(),
                     &fn_ty,
                 );
-                let sig = cton_sig_from_fn_ty(tcx, fn_ty);
 
-                let func_id = {
+                let (func_id, mut func) = cx.predefine_function(inst);
-                    // WARNING: keep in sync with FunctionCx::get_function_ref
-                    let def_path_based_names =
-                        ::rustc_mir::monomorphize::item::DefPathBasedNames::new(
-                            cx.tcx, false, false,
-                        );
-                    let mut name = String::new();
-                    def_path_based_names.push_instance_as_string(inst, &mut name);
-                    cx.module
-                        .declare_function(&name, Linkage::Export, &sig)
-                        .unwrap()
-                };
 
-                let mut f = Function::with_name_signature(
+                let comments = trans_fn(cx, &mut func, inst);
-                    ExternalName::user(0, func_id.index() as u32),
-                    sig,
-                );
-
-                let comments = trans_fn(cx, &mut f, inst);
 
                 let mut writer = crate::pretty_clif::CommentWriter(comments);
                 let mut cton = String::new();
-                ::cranelift::codegen::write::decorate_function(&mut writer, &mut cton, &f, None)
+                ::cranelift::codegen::write::decorate_function(&mut writer, &mut cton, &func, None)
                     .unwrap();
                 tcx.sess.warn(&cton);
 
                 let flags = settings::Flags::new(settings::builder());
-                match ::cranelift::codegen::verify_function(&f, &flags) {
+                match ::cranelift::codegen::verify_function(&func, &flags) {
                     Ok(_) => {}
                     Err(err) => {
                         tcx.sess.err(&format!("{:?}", err));
                         let pretty_error =
                             ::cranelift::codegen::print_errors::pretty_verifier_error(
-                                &f,
+                                &func,
                                 None,
                                 Some(Box::new(writer)),
                                 &err,
@@ -72,7 +55,7 @@ pub fn trans_mono_item<'a, 'tcx: 'a>(
                     }
                 }
 
-                context.func = f;
+                context.func = func;
                 // TODO: cranelift doesn't yet support some of the things needed
                 if false {
                     cx.module.define_function(func_id, context).unwrap();