test: fix repr-transparent-aggregates test on mips64

Since #47964 was merged, 64-bit mips started passing all structures
using 64-bit chunks regardless of their contents. The
repr-transparent-aggregates tests needs updating to cope with this.

src/test/codegen/repr-transparent-aggregates-2.rs

@@ -12,6 +12,7 @@
 
 // ignore-aarch64
 // ignore-asmjs
+// ignore-mips64
 // ignore-s390x
 // ignore-wasm
 // ignore-x86

src/test/codegen/repr-transparent-aggregates-3.rs

@@ -0,0 +1,49 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: -C no-prepopulate-passes
+
+// only-mips64
+// See repr-transparent.rs
+
+#![crate_type="lib"]
+#![feature(repr_transparent)]
+
+
+#[repr(C)]
+pub struct Big([u32; 16]);
+
+#[repr(transparent)]
+pub struct BigW(Big);
+
+// CHECK: define void @test_Big(%Big* [[BIG_RET_ATTRS:.*]], [8 x i64]
+#[no_mangle]
+pub extern fn test_Big(_: Big) -> Big { loop {} }
+
+// CHECK: define void @test_BigW(%BigW* [[BIG_RET_ATTRS]], [8 x i64]
+#[no_mangle]
+pub extern fn test_BigW(_: BigW) -> BigW { loop {} }
+
+
+#[repr(C)]
+pub union BigU {
+    foo: [u32; 16],
+}
+
+#[repr(transparent)]
+pub struct BigUw(BigU);
+
+// CHECK: define void @test_BigU(%BigU* [[BIGU_RET_ATTRS:.*]], [8 x i64]
+#[no_mangle]
+pub extern fn test_BigU(_: BigU) -> BigU { loop {} }
+
+// CHECK: define void @test_BigUw(%BigUw* [[BIGU_RET_ATTRS]], [8 x i64]
+#[no_mangle]
+pub extern fn test_BigUw(_: BigUw) -> BigUw { loop {} }