Add test for addrspacecasting global vars

Global variables are casted to the default address space works,
as the amdgpu target is now merged, a test can be added.

tests/auxiliary/minicore.rs

@@ -179,7 +179,14 @@ impl Add<isize> for isize {
 
 #[lang = "sync"]
 trait Sync {}
-impl Sync for u8 {}
+impl_marker_trait!(
+    Sync => [
+        char, bool,
+        isize, i8, i16, i32, i64, i128,
+        usize, u8, u16, u32, u64, u128,
+        f16, f32, f64, f128,
+    ]
+);
 
 #[lang = "drop_in_place"]
 fn drop_in_place<T>(_: *mut T) {}

tests/codegen-llvm/amdgpu-addrspacecast.rs

@@ -16,3 +16,12 @@ pub fn ref_of_local(f: fn(&i32)) {
     let i = 0;
     f(&i);
 }
+
+// CHECK-LABEL: @ref_of_global
+// CHECK: addrspacecast (ptr addrspace(1) @I to ptr)
+#[no_mangle]
+pub fn ref_of_global(f: fn(&i32)) {
+    #[no_mangle]
+    static I: i32 = 0;
+    f(&I);
+}