Add a new test

Author: saethlin

tests/codegen/maybeuninit.rs

@@ -0,0 +1,32 @@
+//@ compile-flags: -Copt-level=3 -Cdebuginfo=0
+
+// This is a regression test for https://github.com/rust-lang/rust/issues/139355 as well as
+// regressions I introduced while implementing a solution.
+
+#![crate_type = "lib"]
+
+use std::mem::MaybeUninit;
+
+// CHECK-LABEL: @create_small_uninit_array
+#[no_mangle]
+fn create_small_uninit_array() -> [MaybeUninit<u8>; 4] {
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: ret i32 undef
+    [MaybeUninit::<u8>::uninit(); 4]
+}
+
+// CHECK-LABEL: @create_nested_uninit_array
+#[no_mangle]
+fn create_nested_uninit_array() -> [[MaybeUninit<u8>; 4]; 100] {
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: ret void
+    [[MaybeUninit::<u8>::uninit(); 4]; 100]
+}
+
+// CHECK-LABEL: @create_ptr
+#[no_mangle]
+fn create_ptr() -> MaybeUninit<&'static str> {
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: ret %{{.*}} undef
+    MaybeUninit::uninit()
+}