Add flag to configure `noalias` on `Box<T>`

To aid making an informed decision about the aliasing
rules of box, give users an option to remove `noalias`
from box.

2 files changed, 16 insertions, 0 deletions

diff --git a/src/test/codegen/noalias-box-off.rs b/src/test/codegen/noalias-box-off.rs
new file mode 100644
index 00000000000..afd17c7c160
--- /dev/null
+++ b/src/test/codegen/noalias-box-off.rs
@@ -0,0 +1,8 @@
+// compile-flags: -O -Z box-noalias=no
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @box_should_not_have_noalias_if_disabled(
+// CHECK-NOT: noalias
+#[no_mangle]
+pub fn box_should_not_have_noalias_if_disabled(_b: Box<u8>) {}
diff --git a/src/test/codegen/noalias-box.rs b/src/test/codegen/noalias-box.rs
new file mode 100644
index 00000000000..a3d1f093d8b
--- /dev/null
+++ b/src/test/codegen/noalias-box.rs
@@ -0,0 +1,8 @@
+// compile-flags: -O
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @box_should_have_noalias_by_default(
+// CHECK: noalias
+#[no_mangle]
+pub fn box_should_have_noalias_by_default(_b: Box<u8>) {}