Give global_asm symbol names

Currently global_asm already have symbol names when using v0 scheme, this
makes them obtain symbols with legacy scheme too.

Author: nbdd0121

compiler/rustc_middle/src/mir/mono.rs

@@ -122,7 +122,7 @@ impl<'tcx> MonoItem<'tcx> {
             MonoItem::Fn(instance) => tcx.symbol_name(instance),
             MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)),
             MonoItem::GlobalAsm(item_id) => {
-                SymbolName::new(tcx, &format!("global_asm_{:?}", item_id.owner_id))
+                tcx.symbol_name(Instance::mono(tcx, item_id.owner_id.to_def_id()))
             }
         }
     }

compiler/rustc_symbol_mangling/src/legacy.rs

@@ -36,6 +36,11 @@ pub(super) fn mangle<'tcx>(
                 debug!(?instance_ty);
                 break;
             }
+            DefPathData::GlobalAsm => {
+                // `global_asm!` doesn't have a type.
+                instance_ty = tcx.types.unit;
+                break;
+            }
             _ => {
                 // if we're making a symbol for something, there ought
                 // to be a value or type-def or something in there