Add regression test for option initialization

Author: oli-obk

tests/codegen/slice-init.rs

@@ -63,6 +63,34 @@ pub fn nonzero_integer_array() {
     opaque(&x);
 }
 
+const N: usize = 100;
+
+// FIXME: The two bytes of the u16 are the same, so we should
+// just use memset, too.
+// CHECK-LABEL: @u16_init_one_bytes
+#[no_mangle]
+pub fn u16_init_one_bytes() -> [u16; N] {
+    // CHECK-NOT: select
+    // CHECK: br
+    // CHECK-NOT: switch
+    // CHECK: icmp
+    // CHECK-NOT: call void @llvm.memset.p0
+    [const { u16::from_be_bytes([1, 1]) }; N]
+}
+
+// FIXME: undef bytes can just be initialized with the same value as the
+// defined bytes, if the defines bytes are all the same.
+// CHECK-LABEL: @option_none_init
+#[no_mangle]
+pub fn option_none_init() -> [Option<u8>; N] {
+    // CHECK-NOT: select
+    // CHECK: br label %repeat_loop_header{{.*}}
+    // CHECK-NOT: switch
+    // CHECK: icmp
+    // CHECK-NOT: call void @llvm.memset.p0
+    [None; N]
+}
+
 // Use an opaque function to prevent rustc from removing useless drops.
 #[inline(never)]
 pub fn opaque(_: impl Sized) {}