Resolve instance for SymFn in global/naked asm

rust-lang · bors · May 6, 2025 · Apr 20, 2025 · Apr 21, 2025 · Apr 27, 2025
commit 3a1ee645cad501e2fd766bbacea5654a795f352b
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
@@ -457,7 +457,13 @@ where
                 rustc_hir::InlineAsmOperand::SymFn { expr } => {
                     let ty = cx.tcx().typeck(item_id.owner_id).expr_ty(expr);
                     let instance = match ty.kind() {
-                        &ty::FnDef(def_id, args) => Instance::new(def_id, args),
+                        &ty::FnDef(def_id, args) => Instance::expect_resolve(
+                            cx.tcx(),
+                            ty::TypingEnv::fully_monomorphized(),
+                            def_id,
+                            args,
+                            expr.span,
+                        ),
                         _ => span_bug!(*op_sp, "asm sym is not a function"),
                     };
 

diff --git a/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs b/compiler/rustc_codegen_ssa/src/mir/naked_asm.rs
@@ -95,7 +95,9 @@ fn inline_to_global_operand<'a, 'tcx, Cx: LayoutOf<'tcx, LayoutOfResult = TyAndL
             );
 
             let instance = match mono_type.kind() {
-                &ty::FnDef(def_id, args) => Instance::new(def_id, args),
+                &ty::FnDef(def_id, args) => {
+                    Instance::expect_resolve(cx.tcx(), cx.typing_env(), def_id, args, value.span)
+                }
                 _ => bug!("asm sym is not a function"),
             };
 

diff --git a/tests/ui/asm/global-asm-mono-sym-fn.rs b/tests/ui/asm/global-asm-mono-sym-fn.rs
@@ -0,0 +1,27 @@
+// Test that we're properly monomorphizing sym args in global asm blocks
+// that point to associated items.
+
+//@ edition: 2021
+//@ needs-asm-support
+//@ only-x86_64-unknown-linux-gnu
+//@ build-pass
+
+#![no_main]
+
+use std::arch::global_asm;
+
+fn foo() {
+    loop {}
+}
+
+trait Foo {
+    fn bar();
+}
+
+impl Foo for i32 {
+    fn bar() {
+        loop {}
+    }
+}
+
+global_asm!(".global main", "main:", "call {}", sym <i32 as Foo>::bar);
diff --git a/tests/ui/asm/naked-asm-mono-sym-fn.rs b/tests/ui/asm/naked-asm-mono-sym-fn.rs
@@ -0,0 +1,35 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/140373>.
+// Test that we're properly monomorphizing sym args in naked asm blocks
+// that point to associated items.
+
+//@ edition: 2021
+//@ needs-asm-support
+//@ only-x86_64
+//@ build-pass
+
+trait T {
+    extern "C" fn t();
+}
+
+enum E<const C: usize> {}
+
+impl<const C: usize> T for E<C> {
+    extern "C" fn t() {
+        println!("Const generic: {}", C);
+    }
+}
+
+#[unsafe(naked)]
+extern "C" fn foo<U: T>() {
+    core::arch::naked_asm!(
+        "push rax",
+        "call {fn}",
+        "pop rax",
+        "ret",
+        fn = sym <U as T>::t,
+    );
+}
+
+fn main() {
+    foo::<E<42>>();
+}