2 files changed, 61 insertions, 1 deletions
diff --git a/src/test/codegen/deduced-param-attrs.rs b/src/test/codegen/deduced-param-attrs.rs
new file mode 100644
index 00000000000..153046eef3c
--- /dev/null
+++ b/src/test/codegen/deduced-param-attrs.rs
@@ -0,0 +1,60 @@
+// compile-flags: -O
+
+#![crate_type = "lib"]
+#![allow(incomplete_features)]
+#![feature(unsized_locals, unsized_fn_params)]
+
+use std::cell::Cell;
+use std::hint;
+
+// Check to make sure that we can deduce the `readonly` attribute from function bodies for
+// parameters passed indirectly.
+
+pub struct BigStruct {
+    blah: [i32; 1024],
+}
+
+pub struct BigCellContainer {
+    blah: [Cell<i32>; 1024],
+}
+
+// The by-value parameter for this big struct can be marked readonly.
+//
+// CHECK: @use_big_struct_immutably({{.*}} readonly {{.*}} %big_struct)
+#[no_mangle]
+pub fn use_big_struct_immutably(big_struct: BigStruct) {
+    hint::black_box(&big_struct);
+}
+
+// The by-value parameter for this big struct can't be marked readonly, because we mutate it.
+//
+// CHECK-NOT: @use_big_struct_mutably({{.*}} readonly {{.*}} %big_struct)
+#[no_mangle]
+pub fn use_big_struct_mutably(mut big_struct: BigStruct) {
+    big_struct.blah[987] = 654;
+    hint::black_box(&big_struct);
+}
+
+// The by-value parameter for this big struct can't be marked readonly, because it contains
+// UnsafeCell.
+//
+// CHECK-NOT: @use_big_cell_container({{.*}} readonly {{.*}} %big_cell_container)
+#[no_mangle]
+pub fn use_big_cell_container(big_cell_container: BigCellContainer) {
+    hint::black_box(&big_cell_container);
+}
+
+// Make sure that we don't mistakenly mark a big struct as `readonly` when passed through a generic
+// type parameter if it contains UnsafeCell.
+//
+// CHECK-NOT: @use_something({{.*}} readonly {{.*}} %something)
+#[no_mangle]
+#[inline(never)]
+pub fn use_something<T>(something: T) {
+    hint::black_box(&something);
+}
+
+#[no_mangle]
+pub fn forward_big_cell_container(big_cell_container: BigCellContainer) {
+    use_something(big_cell_container)
+}
diff --git a/src/test/codegen/function-arguments.rs b/src/test/codegen/function-arguments.rs
index bc650ebf5ee..44fee952307 100644
--- a/src/test/codegen/function-arguments.rs
+++ b/src/test/codegen/function-arguments.rs
@@ -127,7 +127,7 @@ pub fn mutable_notunpin_borrow(_: &mut NotUnpin) {
 pub fn notunpin_borrow(_: &NotUnpin) {
 }
 
-// CHECK: @indirect_struct({{%S\*|ptr}} noalias nocapture noundef dereferenceable(32) %_1)
+// CHECK: @indirect_struct({{%S\*|ptr}} noalias nocapture noundef readonly dereferenceable(32) %_1)
 #[no_mangle]
 pub fn indirect_struct(_: S) {
 }